The kernel's command-line parameters

The following is a consolidated list of the kernel parameters as implemented by the __setup(), early_param(), core_param() and module_param() macros and sorted into English Dictionary order (defined as ignoring all punctuation and sorting digits before letters in a case insensitive manner), and with descriptions where known.

The kernel parses parameters from the kernel command line up to "--"; if it doesn't recognize a parameter and it doesn't contain a '.', the parameter gets passed to init: parameters with '=' go into init's environment, others are passed as command line arguments to init. Everything after "--" is passed as an argument to init.

Module parameters can be specified in two ways: via the kernel command line with a module name prefix, or via modprobe, e.g.:

(kernel command line) usbcore.blinkenlights=1
(modprobe command line) modprobe usbcore blinkenlights=1

Parameters for modules which are built into the kernel need to be specified on the kernel command line. modprobe looks through the kernel command line (/proc/cmdline) and collects module parameters when it loads a module, so the kernel command line can be used for loadable modules too.

Hyphens (dashes) and underscores are equivalent in parameter names, so:

log_buf_len=1M print-fatal-signals=1

can also be entered as:

log-buf-len=1M print_fatal_signals=1

Double-quotes can be used to protect spaces in values, e.g.:

param="spaces in here"

cpu lists:

Some kernel parameters take a list of CPUs as a value, e.g. isolcpus, nohz_full, irqaffinity, rcu_nocbs. The format of this list is:

<cpu number>,...,<cpu number>


<cpu number>-<cpu number> (must be a positive range in ascending order)

or a mixture

<cpu number>,...,<cpu number>-<cpu number>

Note that for the special case of a range one can split the range into equal sized groups and for each group use some amount from the beginning of that group:

<cpu number>-<cpu number>:<used size>/<group size>

For example one can add to the command line following parameter:


where the final item represents CPUs 100,101,125,126,150,151,...

The value "N" can be used to represent the numerically last CPU on the system, i.e "foo_cpus=16-N" would be equivalent to "16-31" on a 32 core system.

Keep in mind that "N" is dynamic, so if system changes cause the bitmap width to change, such as less cores in the CPU list, then N and any ranges using N will also change. Use the same on a small 4 core system, and "16-N" becomes "16-3" and now the same boot input will be flagged as invalid (start > end).

The special case-tolerant group name "all" has a meaning of selecting all CPUs, so that "nohz_full=all" is the equivalent of "nohz_full=0-N".

The semantics of "N" and "all" is supported on a level of bitmaps and holds for all users of bitmap_parselist().

This document may not be entirely up to date and comprehensive. The command "modinfo -p ${modulename}" shows a current list of all parameters of a loadable module. Loadable modules, after being loaded into the running kernel, also reveal their parameters in /sys/module/${modulename}/parameters/. Some of these parameters may be changed at runtime by the command echo -n ${value} > /sys/module/${modulename}/parameters/${parm}.

The parameters listed below are only valid if certain kernel build options were enabled and if respective hardware is present. This list should be kept in alphabetical order. The text in square brackets at the beginning of each description states the restrictions within which a parameter is applicable:

ACPI    ACPI support is enabled.
AGP     AGP (Accelerated Graphics Port) is enabled.
ALSA    ALSA sound support is enabled.
APIC    APIC support is enabled.
APM     Advanced Power Management support is enabled.
APPARMOR AppArmor support is enabled.
ARM     ARM architecture is enabled.
ARM64   ARM64 architecture is enabled.
AX25    Appropriate AX.25 support is enabled.
CLK     Common clock infrastructure is enabled.
CMA     Contiguous Memory Area support is enabled.
DRM     Direct Rendering Management support is enabled.
DYNAMIC_DEBUG Build in debug messages and enable them at runtime
EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
EFI     EFI Partitioning (GPT) is enabled
EVM     Extended Verification Module
FB      The frame buffer device is enabled.
FTRACE  Function tracing enabled.
GCOV    GCOV profiling is enabled.
HW      Appropriate hardware is enabled.
HYPER_V HYPERV support is enabled.
IA-64   IA-64 architecture is enabled.
IMA     Integrity measurement architecture is enabled.
IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
IPV6    IPv6 support is enabled.
ISAPNP  ISA PnP code is enabled.
ISDN    Appropriate ISDN support is enabled.
ISOL    CPU Isolation is enabled.
JOY     Appropriate joystick support is enabled.
KGDB    Kernel debugger support is enabled.
KVM     Kernel Virtual Machine support is enabled.
LIBATA  Libata driver is enabled
LOONGARCH LoongArch architecture is enabled.
LOOP    Loopback device support is enabled.
LP      Printer support is enabled.
M68k    M68k architecture is enabled.
                These options have more detailed description inside of
MDA     MDA console support is enabled.
MIPS    MIPS architecture is enabled.
MOUSE   Appropriate mouse support is enabled.
MSI     Message Signaled Interrupts (PCI).
MTD     MTD (Memory Technology Device) support is enabled.
NET     Appropriate network support is enabled.
NFS     Appropriate NFS support is enabled.
NUMA    NUMA support is enabled.
OF      Devicetree is enabled.
PARISC  The PA-RISC architecture is enabled.
PCI     PCI bus support is enabled.
PCIE    PCI Express support is enabled.
PCMCIA  The PCMCIA subsystem is enabled.
PNP     Plug & Play support is enabled.
PPC     PowerPC architecture is enabled.
PPT     Parallel port support is enabled.
PS2     Appropriate PS/2 support is enabled.
PV_OPS  A paravirtualized kernel is enabled.
RAM     RAM disk support is enabled.
RDT     Intel Resource Director Technology.
RISCV   RISCV architecture is enabled.
S390    S390 architecture is enabled.
SCSI    Appropriate SCSI support is enabled.
                A lot of drivers have their options described inside
                the Documentation/scsi/ sub-directory.
SECURITY Different security models are enabled.
SELINUX SELinux support is enabled.
SERIAL  Serial support is enabled.
SH      SuperH architecture is enabled.
SMP     The kernel is an SMP kernel.
SPARC   Sparc architecture is enabled.
SUSPEND System suspend states are enabled.
SWSUSP  Software suspend (hibernation) is enabled.
TPM     TPM drivers are enabled.
UMS     USB Mass Storage support is enabled.
USB     USB support is enabled.
USBHID  USB Human Interface Device support is enabled.
V4L     Video For Linux support is enabled.
VGA     The VGA console has been enabled.
VMMIO   Driver for memory mapped virtio devices is enabled.
VT      Virtual terminal support is enabled.
WDT     Watchdog support is enabled.
X86-32  X86-32, aka i386 architecture is enabled.
X86-64  X86-64 architecture is enabled.
                More X86-64 boot options can be found in
X86     Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
X86_UV  SGI UV support is enabled.
XEN     Xen support is enabled
XTENSA  xtensa architecture is enabled.

In addition, the following text indicates that the option:

BOOT    Is a boot loader parameter.
BUGS=   Relates to possible processor bugs on the said processor.
KNL     Is a kernel start-up parameter.

Parameters denoted with BOOT are actually interpreted by the boot loader, and have no meaning to the kernel directly. Do not modify the syntax of boot loader parameters without extreme need or coordination with <The Linux/x86 Boot Protocol>.

There are also arch-specific kernel-parameters not documented here. See for example <AMD64 Specific Boot Options>.

Note that ALL kernel parameters listed below are CASE SENSITIVE, and that a trailing = on the name of any parameter states that that parameter will be entered as an environment variable, whereas its absence indicates that it will appear as a kernel argument readable via /proc/cmdline by programs running once the system is up.

The number of kernel parameters is not limited, but the length of the complete command line (parameters including spaces etc.) is limited to a fixed number of characters. This limit depends on the architecture and is between 256 and 4096 characters. It is defined in the file ./include/uapi/asm-generic/setup.h as COMMAND_LINE_SIZE.

Finally, the [KMG] suffix is commonly described after a number of kernel parameter values. These 'K', 'M', and 'G' letters represent the _binary_ multipliers 'Kilo', 'Mega', and 'Giga', equaling 2^10, 2^20, and 2^30 bytes respectively. Such letter suffixes can also be entirely omitted:

        acpi=           [HW,ACPI,X86,ARM64,RISCV64]
                        Advanced Configuration and Power Interface
                        Format: { force | on | off | strict | noirq | rsdt |
                                  copy_dsdt }
                        force -- enable ACPI if default was off
                        on -- enable ACPI but allow fallback to DT [arm64,riscv64]
                        off -- disable ACPI if default was on
                        noirq -- do not use ACPI for IRQ routing
                        strict -- Be less tolerant of platforms that are not
                                strictly ACPI specification compliant.
                        rsdt -- prefer RSDT over (default) XSDT
                        copy_dsdt -- copy DSDT to memory
                        For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or
                        "acpi=force" are available

                        See also Documentation/power/runtime_pm.rst, pci=noacpi

        acpi_apic_instance=     [ACPI, IOAPIC]
                        Format: <int>
                        2: use 2nd APIC table, if available
                        1,0: use 1st APIC table
                        default: 0

        acpi_backlight= [HW,ACPI]
                        { vendor | video | native | none }
                        If set to vendor, prefer vendor-specific driver
                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
                        of the ACPI video.ko driver.
                        If set to video, use the ACPI video.ko driver.
                        If set to native, use the device's native backlight mode.
                        If set to none, disable the ACPI backlight interface.

                        force FADT to use 32 bit addresses rather than the
                        64 bit X_* addresses. Some firmware have broken 64
                        bit addresses for force ACPI ignore these and use
                        the older legacy 32 bit addresses.

        acpica_no_return_repair [HW, ACPI]
                        Disable AML predefined validation mechanism
                        This mechanism can repair the evaluation result to make
                        the return objects more ACPI specification compliant.
                        This option is useful for developers to identify the
                        root cause of an AML interpreter issue when the issue
                        has something to do with the repair mechanism.

        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
                        Format: <int>
                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
                        debug output.  Bits in debug_layer correspond to a
                        _COMPONENT in an ACPI source file, e.g.,
                            #define _COMPONENT ACPI_EVENTS
                        Bits in debug_level correspond to a level in
                        ACPI_DEBUG_PRINT statements, e.g.,
                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
                        The debug_level mask defaults to "info".  See
                        Documentation/firmware-guide/acpi/debug.rst for more information about
                        debug layers and levels.

                        Enable processor driver info messages:
                        Enable AML "Debug" output, i.e., stores to the Debug
                        object while interpreting AML:
                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
                        Enable all messages related to ACPI hardware:
                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff

                        Some values produce so much output that the system is
                        unusable.  The "log_buf_len" parameter may be useful
                        if you need to capture more output.

        acpi_enforce_resources= [ACPI]
                        { strict | lax | no }
                        Check for resource conflicts between native drivers
                        and ACPI OperationRegions (SystemIO and SystemMemory
                        only). IO ports and memory declared in ACPI might be
                        used by the ACPI subsystem in arbitrary AML code and
                        can interfere with legacy drivers.
                        strict (default): access to resources claimed by ACPI
                        is denied; legacy drivers trying to access reserved
                        resources will fail to bind to device using them.
                        lax: access to resources claimed by ACPI is allowed;
                        legacy drivers trying to access reserved resources
                        will bind successfully but a warning message is logged.
                        no: ACPI OperationRegions are not marked as reserved,
                        no further checks are performed.

        acpi_force_table_verification   [HW,ACPI]
                        Enable table checksum verification during early stage.
                        By default, this is disabled due to x86 early mapping
                        size limitation.

        acpi_irq_balance [HW,ACPI]
                        ACPI will balance active IRQs
                        default in APIC mode

        acpi_irq_nobalance [HW,ACPI]
                        ACPI will not move active IRQs (default)
                        default in PIC mode

        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
                        Format: <irq>,<irq>...

        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
                        use by PCI
                        Format: <irq>,<irq>...

        acpi_mask_gpe=  [HW,ACPI]
                        Due to the existence of _Lxx/_Exx, some GPEs triggered
                        by unsupported hardware/firmware features can result in
                        GPE floodings that cannot be automatically disabled by
                        the GPE dispatcher.
                        This facility can be used to prevent such uncontrolled
                        GPE floodings.
                        Format: <byte> or <bitmap-list>

        acpi_no_auto_serialize  [HW,ACPI]
                        Disable auto-serialization of AML methods
                        AML control methods that contain the opcodes to create
                        named objects will be marked as "Serialized" by the
                        auto-serialization feature.
                        This feature is enabled by default.
                        This option allows to turn off the feature.

        acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump

        acpi_no_static_ssdt     [HW,ACPI]
                        Disable installation of static SSDTs at early boot time
                        By default, SSDTs contained in the RSDT/XSDT will be
                        installed automatically and they will appear under
                        This option turns off this feature.
                        Note that specifying this option does not affect
                        dynamic table installation which will install SSDT
                        tables to /sys/firmware/acpi/tables/dynamic.

        acpi_no_watchdog        [HW,ACPI,WDT]
                        Ignore the ACPI-based watchdog interface (WDAT) and let
                        a native driver control the watchdog device instead.

        acpi_rsdp=      [ACPI,EFI,KEXEC]
                        Pass the RSDP address to the kernel, mostly used
                        on machines running EFI runtime service to boot the
                        second kernel for kdump.

        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
                        Format: To spoof as Windows 98: ="Microsoft Windows"

        acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
                        of 2 which is mandated by ACPI 6) as the supported ACPI
                        specification revision (when using this switch, it may
                        be necessary to carry out a cold reboot _twice_ in a
                        row to make it take effect on the platform firmware).

        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
                        acpi_osi="string1"      # add string1
                        acpi_osi="!string2"     # remove string2
                        acpi_osi=!*             # remove all strings
                        acpi_osi=!              # disable all built-in OS vendor
                        acpi_osi=!!             # enable all built-in OS vendor
                        acpi_osi=               # disable all strings

                        'acpi_osi=!' can be used in combination with single or
                        multiple 'acpi_osi="string1"' to support specific OS
                        vendor string(s).  Note that such command can only
                        affect the default state of the OS vendor strings, thus
                        it cannot affect the default state of the feature group
                        strings and the current state of the OS vendor strings,
                        specifying it multiple times through kernel command line
                        is meaningless.  This command is useful when one do not
                        care about the state of the feature group strings which
                        should be controlled by the OSPM.
                          1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
                             to 'acpi_osi="Windows 2000" acpi_osi=!', they all
                             can make '_OSI("Windows 2000")' TRUE.

                        'acpi_osi=' cannot be used in combination with other
                        'acpi_osi=' command lines, the _OSI method will not
                        exist in the ACPI namespace.  NOTE that such command can
                        only affect the _OSI support state, thus specifying it
                        multiple times through kernel command line is also
                          1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'

                        'acpi_osi=!*' can be used in combination with single or
                        multiple 'acpi_osi="string1"' to support specific
                        string(s).  Note that such command can affect the
                        current state of both the OS vendor strings and the
                        feature group strings, thus specifying it multiple times
                        through kernel command line is meaningful.  But it may
                        still not able to affect the final state of a string if
                        there are quirks related to this string.  This command
                        is useful when one want to control the state of the
                        feature group strings to debug BIOS issues related to
                        the OSPM features.
                          1. 'acpi_osi="Module Device" acpi_osi=!*' can make
                             '_OSI("Module Device")' FALSE.
                          2. 'acpi_osi=!* acpi_osi="Module Device"' can make
                             '_OSI("Module Device")' TRUE.
                          3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
                             equivalent to
                             'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
                             'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
                             they all will make '_OSI("Windows 2000")' TRUE.

        acpi_pm_good    [X86]
                        Override the pmtimer bug detection: force the kernel
                        to assume that this machine's pmtimer latches its value
                        and always returns good values.

        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
                        Format: { level | edge | high | low }

        acpi_skip_timer_override [HW,ACPI]
                        Recognize and ignore IRQ0/pin2 Interrupt Override.
                        For broken nForce2 BIOS resulting in XT-PIC timer.

        acpi_sleep=     [HW,ACPI] Sleep options
                        Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
                                  s4_nohwsig, old_ordering, nonvs,
                                  sci_force_enable, nobl }
                        See Documentation/power/video.rst for information on
                        s3_bios and s3_mode.
                        s3_beep is for debugging; it makes the PC's speaker beep
                        as soon as the kernel's real-mode entry point is called.
                        s4_hwsig causes the kernel to check the ACPI hardware
                        signature during resume from hibernation, and gracefully
                        refuse to resume if it has changed. This complies with
                        the ACPI specification but not with reality, since
                        Windows does not do this and many laptops do change it
                        on docking. So the default behaviour is to allow resume
                        and simply warn when the signature changes, unless the
                        s4_hwsig option is enabled.
                        s4_nohwsig prevents ACPI hardware signature from being
                        used (or even warned about) during resume.
                        old_ordering causes the ACPI 1.0 ordering of the _PTS
                        control method, with respect to putting devices into
                        low power states, to be enforced (the ACPI 2.0 ordering
                        of _PTS is used by default).
                        nonvs prevents the kernel from saving/restoring the
                        ACPI NVS memory during suspend/hibernation and resume.
                        sci_force_enable causes the kernel to set SCI_EN directly
                        on resume from S1/S3 (which is against the ACPI spec,
                        but some broken systems don't work without it).
                        nobl causes the internal blacklist of systems known to
                        behave incorrectly in some ways with respect to system
                        suspend and resume to be ignored (use wisely).

        acpi_use_timer_override [HW,ACPI]
                        Use timer override. For some broken Nvidia NF5 boards
                        that require a timer override, but don't have HPET

        add_efi_memmap  [EFI; X86] Include EFI memory map in
                        kernel's map of available physical RAM.

        agp=            [AGP]
                        { off | try_unsupported }
                        off: disable AGP support
                        try_unsupported: try to drive unsupported chipsets
                                (may crash computer or cause data corruption)

        ALSA            [HW,ALSA]
                        See Documentation/sound/alsa-configuration.rst

        alignment=      [KNL,ARM]
                        Allow the default userspace alignment fault handler
                        behaviour to be specified.  Bit 0 enables warnings,
                        bit 1 enables fixups, and bit 2 sends a segfault.

        align_va_addr=  [X86-64]
                        Align virtual addresses by clearing slice [14:12] when
                        allocating a VMA at process creation time. This option
                        gives you up to 3% performance improvement on AMD F15h
                        machines (where it is enabled by default) for a
                        CPU-intensive style benchmark, and it can vary highly in
                        a microbenchmark depending on workload and compiler.

                        32: only for 32-bit processes
                        64: only for 64-bit processes
                        on: enable for both 32- and 64-bit processes
                        off: disable for both 32- and 64-bit processes

        alloc_snapshot  [FTRACE]
                        Allocate the ftrace snapshot buffer on boot up when the
                        main buffer is allocated. This is handy if debugging
                        and you need to use tracing_snapshot() on boot up, and
                        do not want to use tracing_snapshot_alloc() as it needs
                        to be done where GFP_KERNEL allocations are allowed.

        allow_mismatched_32bit_el0 [ARM64]
                        Allow execve() of 32-bit applications and setting of the
                        PER_LINUX32 personality on systems where only a strict
                        subset of the CPUs support 32-bit EL0. When this
                        parameter is present, the set of CPUs supporting 32-bit
                        EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
                        and hot-unplug operations may be restricted.

                        See Documentation/arch/arm64/asymmetric-32bit.rst for more

        amd_iommu=      [HW,X86-64]
                        Pass parameters to the AMD IOMMU driver in the system.
                        Possible values are:
                        fullflush - Deprecated, equivalent to iommu.strict=1
                        off       - do not initialize any AMD IOMMU found in
                                    the system
                        force_isolation - Force device isolation for all
                                          devices. The IOMMU driver is not
                                          allowed anymore to lift isolation
                                          requirements as needed. This option
                                          does not override iommu=pt
                        force_enable - Force enable the IOMMU on platforms known
                                       to be buggy with IOMMU enabled. Use this
                                       option with care.
                        pgtbl_v1     - Use v1 page table for DMA-API (Default).
                        pgtbl_v2     - Use v2 page table for DMA-API.
                        irtcachedis  - Disable Interrupt Remapping Table (IRT) caching.

        amd_iommu_dump= [HW,X86-64]
                        Enable AMD IOMMU driver option to dump the ACPI table
                        for AMD IOMMU. With this option enabled, AMD IOMMU
                        driver will print ACPI tables for AMD IOMMU during
                        IOMMU initialization.

        amd_iommu_intr= [HW,X86-64]
                        Specifies one of the following AMD IOMMU interrupt
                        remapping modes:
                        legacy     - Use legacy interrupt remapping mode.
                        vapic      - Use virtual APIC mode, which allows IOMMU
                                     to inject interrupts directly into guest.
                                     This mode requires kvm-amd.avic=1.
                                     (Default when IOMMU HW support is present.)

        amd_pstate=     [X86]
                          Do not enable amd_pstate as the default
                          scaling driver for the supported processors
                          Use amd_pstate with passive mode as a scaling driver.
                          In this mode autonomous selection is disabled.
                          Driver requests a desired performance level and platform
                          tries to match the same performance level if it is
                          satisfied by guaranteed performance level.
                          Use amd_pstate_epp driver instance as the scaling driver,
                          driver provides a hint to the hardware if software wants
                          to bias toward performance (0x0) or energy efficiency (0xff)
                          to the CPPC firmware. then CPPC power algorithm will
                          calculate the runtime workload and adjust the realtime cores
                          Activate guided autonomous mode. Driver requests minimum and
                          maximum performance level and the platform autonomously
                          selects a performance level in this range and appropriate
                          to the current workload.     [HW,JOY] Amiga joystick support
                        Map of devices attached to JOY0DAT and JOY1DAT
                        Format: <a>,<b>
                        See also Documentation/input/joydev/joystick.rst     [HW,JOY] Analog joystick and gamepad support
                        Specifies type or capabilities of an analog joystick
                        connected to one of 16 gameports
                        Format: <type1>,<type2>,..<type16>

        apc=            [HW,SPARC]
                        Power management functions (SPARCstation-4/5 + deriv.)
                        Format: noidle
                        Disable APC CPU standby support. SPARCstation-Fox does
                        not play well with APC CPU idle - disable it if you have
                        APC and your system crashes randomly.

        apic=           [APIC,X86] Advanced Programmable Interrupt Controller
                        Change the output verbosity while booting
                        Format: { quiet (default) | verbose | debug }
                        Change the amount of debugging information output
                        when initialising the APIC and IO-APIC components.
                        For X86-32, this can also be used to specify an APIC
                        driver name.
                        Format: apic=driver_name
                        Examples: apic=bigsmp

        apic_extnmi=    [APIC,X86] External NMI delivery setting
                        Format: { bsp (default) | all | none }
                        bsp:  External NMI is delivered only to CPU 0
                        all:  External NMIs are broadcast to all CPUs as a
                              backup of CPU 0
                        none: External NMI is masked for all CPUs. This is
                              useful so that a dump capture kernel won't be
                              shot down by NMI

        autoconf=       [IPV6]
                        See Documentation/networking/ipv6.rst.

        apm=            [APM] Advanced Power Management
                        See header of arch/x86/kernel/apm_32.c.

        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
                        Format: { "0" | "1" }
                        See security/apparmor/Kconfig help text
                        0 -- disable.
                        1 -- enable.
                        Default value is set via kernel config option.

        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
                        Format: <io>,<irq>,<nodeID>

        arm64.nobti     [ARM64] Unconditionally disable Branch Target
                        Identification support

        arm64.nomops    [ARM64] Unconditionally disable Memory Copy and Memory
                        Set instructions support

        arm64.nomte     [ARM64] Unconditionally disable Memory Tagging Extension

        arm64.nopauth   [ARM64] Unconditionally disable Pointer Authentication

        arm64.nosme     [ARM64] Unconditionally disable Scalable Matrix
                        Extension support

        arm64.nosve     [ARM64] Unconditionally disable Scalable Vector
                        Extension support

        ataflop=        [HW,M68k]

        atarimouse=     [HW,MOUSE] Atari Mouse

        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
                        EzKey and similar keyboards

        atkbd.reset=    [HW] Reset keyboard during initialization

        atkbd.set=      [HW] Select keyboard code set
                        Format: <int> (2 = AT (default), 3 = PS/2)

        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar

        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
                        Format: <bool> (0 = real, 1 = synthetic (default))

        atkbd.softrepeat= [HW]
                        Use software keyboard repeat

        audit=          [KNL] Enable the audit sub-system
                        Format: { "0" | "1" | "off" | "on" }
                        0 | off - kernel audit is disabled and can not be
                            enabled until the next reboot
                        unset - kernel audit is initialized but disabled and
                            will be fully enabled by the userspace auditd.
                        1 | on - kernel audit is initialized and partially
                            enabled, storing at most audit_backlog_limit
                            messages in RAM until it is fully enabled by the
                            userspace auditd.
                        Default: unset

        audit_backlog_limit= [KNL] Set the audit queue size limit.
                        Format: <int> (must be >=0)
                        Default: 64

        bau=            [X86_UV] Enable the BAU on SGI UV.  The default
                        behavior is to disable the BAU (i.e. bau=0).
                        Format: { "0" | "1" }
                        0 - Disable the BAU.
                        1 - Enable the BAU.
                        unset - Disable the BAU.

        baycom_epp=     [HW,AX25]
                        Format: <io>,<mode>

        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
                        Format: <io>,<mode>
                        See header of drivers/net/hamradio/baycom_par.c.

        baycom_ser_fdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
                        Format: <io>,<irq>,<mode>[,<baud>]
                        See header of drivers/net/hamradio/baycom_ser_fdx.c.

        baycom_ser_hdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
                        Format: <io>,<irq>,<mode>
                        See header of drivers/net/hamradio/baycom_ser_hdx.c.

        bert_disable    [ACPI]
                        Disable BERT OS support on buggy BIOSes.

        bgrt_disable    [ACPI][X86]
                        Disable BGRT to avoid flickering OEM logo.

        blkdevparts=    Manual partition parsing of block device(s) for
                        embedded devices based on command line input.
                        See Documentation/block/cmdline-partition.rst

        boot_delay=     Milliseconds to delay each printk during boot.
                        Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
                        and you may also have to specify "lpj=".  Boot_delay
                        values larger than 10 seconds (10000) are assumed
                        erroneous and ignored.
                        Format: integer

        bootconfig      [KNL]
                        Extended command line options can be added to an initrd
                        and this will cause the kernel to look for it.

                        See Documentation/admin-guide/bootconfig.rst

        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)     Most important insmod options are available as
                        kernel args too.
        bttv.pll=       See Documentation/admin-guide/media/bttv.rst

        bulk_remove=off [PPC]  This parameter disables the use of the pSeries
                        firmware feature for flushing multiple hpte entries
                        at a time.

        c101=           [NET] Moxa C101 synchronous serial card

        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
                        Sometimes CPU hardware bugs make them report the cache
                        size incorrectly. The kernel will attempt work arounds
                        to fix known problems, but for some CPUs it is not
                        possible to determine what the correct size should be.
                        This option provides an override for these situations.

                        [NET] Specifies amount of time (in seconds) that
                        the kernel should wait for a network carrier. By default
                        it waits 120 seconds.

        ca_keys=        [KEYS] This parameter identifies a specific key(s) on
                        the system trusted keyring to be used for certificate
                        trust validation.
                        format: { id:<keyid> | builtin }

        cca=            [MIPS] Override the kernel pages' cache coherency
                        algorithm.  Accepted values range from 0 to 7
                        inclusive. See arch/mips/include/asm/pgtable-bits.h
                        for platform specific values (SB1, Loongson3 and

        ccw_timeout_log [S390]
                        See Documentation/arch/s390/common_io.rst for details.

        cgroup_disable= [KNL] Disable a particular controller or optional feature
                        Format: {name of the controller(s) or feature(s) to disable}
                        The effects of cgroup_disable=foo are:
                        - foo isn't auto-mounted if you mount all cgroups in
                          a single hierarchy
                        - foo isn't visible as an individually mountable
                        - if foo is an optional feature then the feature is
                          disabled and corresponding cgroup files are not
                        {Currently only "memory" controller deal with this and
                        cut the overhead, others just disable the usage. So
                        only cgroup_disable=memory is actually worthy}
                        Specifying "pressure" disables per-cgroup pressure
                        stall information accounting feature

        cgroup_no_v1=   [KNL] Disable cgroup controllers and named hierarchies in v1
                        Format: { { controller | "all" | "named" }
                                  [,{ controller | "all" | "named" }...] }
                        Like cgroup_disable, but only applies to cgroup v1;
                        the blacklisted controllers remain available in cgroup2.
                        "all" blacklists all controllers and "named" disables
                        named mounts. Specifying both "all" and "named" disables
                        all v1 hierarchies.

        cgroup.memory=  [KNL] Pass options to the cgroup memory controller.
                        Format: <string>
                        nosocket -- Disable socket memory accounting.
                        nokmem -- Disable kernel memory accounting.
                        nobpf -- Disable BPF memory accounting.

        checkreqprot=   [SELINUX] Set initial checkreqprot flag value.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- check protection applied by kernel (includes
                                any implied execute protection).
                        1 -- check protection requested by application.
                        Default value is set via a kernel config option.
                        Value can be changed at runtime via
                        Setting checkreqprot to 1 is deprecated.

        cio_ignore=     [S390]
                        See Documentation/arch/s390/common_io.rst for details.

        clearcpuid=X[,X...] [X86]
                        Disable CPUID feature X for the kernel. See
                        arch/x86/include/asm/cpufeatures.h for the valid bit
                        numbers X. Note the Linux-specific bits are not necessarily
                        stable over kernel options, but the vendor-specific
                        ones should be.
                        X can also be a string as appearing in the flags: line
                        in /proc/cpuinfo which does not have the above
                        instability issue. However, not all features have names
                        in /proc/cpuinfo.
                        Note that using this option will taint your kernel.
                        Also note that user programs calling CPUID directly
                        or using the feature without checking anything
                        will still see it. This just prevents it from
                        being used by the kernel or shown in /proc/cpuinfo.
                        Also note the kernel might malfunction if you disable
                        some critical bits.

                        Prevents the clock framework from automatically gating
                        clocks that have not been explicitly enabled by a Linux
                        device driver but are enabled in hardware at reset or
                        by the bootloader/firmware. Note that this does not
                        force such clocks to be always-on nor does it reserve
                        those clocks in any way. This parameter is useful for
                        debug and development, but should not be needed on a
                        platform with proper driver support.  For more
                        information, see Documentation/driver-api/clk.rst.

        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
                        Forces specified clocksource (if available) to be used
                        when calculating gettimeofday(). If specified
                        clocksource is not available, it defaults to PIT.
                        Format: { pit | tsc | cyclone | pmtmr }

        clocksource=    Override the default clocksource
                        Format: <string>
                        Override the default clocksource and use the clocksource
                        with the name specified.
                        Some clocksource names to choose from, depending on
                        the platform:
                        [all] jiffies (this is the base, fallback clocksource)
                        [ACPI] acpi_pm
                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
                        [X86-32] pit,hpet,tsc;
                                scx200_hrt on Geode; cyclone on IBM x440
                        [MIPS] MIPS
                        [PARISC] cr16
                        [S390] tod
                        [SH] SuperH
                        [SPARC64] tick
                        [X86-64] hpet,tsc

                        Format: <bool>
                        Enable/disable the eventstream feature of the ARM
                        architected timer so that code using WFE-based polling
                        loops can be debugged more effectively on production

        clocksource.max_cswd_read_retries= [KNL]
                        Number of clocksource_watchdog() retries due to
                        external delays before the clock will be marked
                        unstable.  Defaults to two retries, that is,
                        three attempts to read the clock under test.

        clocksource.verify_n_cpus= [KNL]
                        Limit the number of CPUs checked for clocksources
                        marked with CLOCK_SOURCE_VERIFY_PERCPU that
                        are marked unstable due to excessive skew.
                        A negative value says to check all CPUs, while
                        zero says not to check any.  Values larger than
                        nr_cpu_ids are silently truncated to nr_cpu_ids.
                        The actual CPUs are chosen randomly, with
                        no replacement if the same CPU is chosen twice.

        clocksource-wdtest.holdoff= [KNL]
                        Set the time in seconds that the clocksource
                        watchdog test waits before commencing its tests.
                        Defaults to zero when built as a module and to
                        10 seconds when built into the kernel.

                        Sets the size of kernel global memory area for
                        contiguous memory allocations and optionally the
                        placement constraint by the physical address range of
                        memory allocations. A value of 0 disables CMA
                        altogether. For more information, see

                        Sets the size of kernel per-numa memory area for
                        contiguous memory allocations. A value of 0 disables
                        per-numa CMA altogether. And If this option is not
                        specified, the default value is 0.
                        With per-numa CMA enabled, DMA users on node nid will
                        first try to allocate buffer from the pernuma area
                        which is located in node nid, if the allocation fails,
                        they will fallback to the global default memory area.

                        Sets the size of kernel numa memory area for
                        contiguous memory allocations. It will reserve CMA
                        area for the specified node.

                        With numa CMA enabled, DMA users on node nid will
                        first try to allocate buffer from the numa area
                        which is located in node nid, if the allocation fails,
                        they will fallback to the global default memory area.

        cmo_free_hint=  [PPC] Format: { yes | no }
                        Specify whether pages are marked as being inactive
                        when they are freed.  This is used in CMO environments
                        to determine OS memory pressure for page stealing by
                        a hypervisor.
                        Default: yes

        coherent_pool=nn[KMG]   [ARM,KNL]
                        Sets the size of memory pool for coherent, atomic dma
                        allocations, by default set to 256K.

        com20020=       [HW,NET] ARCnet - COM20020 chipset

        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
                        Format: <io>[,<irq>]

        com90xx=        [HW,NET]
                        ARCnet - COM90xx chipset (memory-mapped buffers)
                        Format: <io>[,<irq>[,<memstart>]]

        condev=         [HW,S390] console device

        con3215_drop=   [S390] 3215 console drop mode.
                        Format: y|n|Y|N|1|0
                        When set to true, drop data on the 3215 console when
                        the console buffer is full. In this case the
                        operator using a 3270 terminal emulator (for example
                        x3270) does not have to enter the clear key for the
                        console output to advance and the kernel to continue.
                        This leads to a much faster boot time when a 3270
                        terminal emulator is active. If no 3270 terminal
                        emulator is used, this parameter has no effect.

        console=        [KNL] Output console device and options.

                tty<n>  Use the virtual console device <n>.

                        Use the specified serial port.  The options are of
                        the form "bbbbpnf", where "bbbb" is the baud rate,
                        "p" is parity ("n", "o", or "e"), "n" is number of
                        bits, and "f" is flow control ("r" for RTS or
                        omit it).  Default is "9600n8".

                        See Documentation/admin-guide/serial-console.rst for more
                        information.  See
                        Documentation/networking/netconsole.rst for an

                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address,
                        switching to the matching ttyS device later.
                        MMIO inter-register address stride is either 8-bit
                        (mmio), 16-bit (mmio16), or 32-bit (mmio32).
                        If none of [io|mmio|mmio16|mmio32], <addr> is assumed
                        to be equivalent to 'mmio'. 'options' are specified in
                        the same format described for ttyS above; if unspecified,
                        the h/w is not re-initialized.

                hvc<n>  Use the hypervisor console device <n>. This is for
                        both Xen and PowerPC hypervisors.

                { null | "" }
                        Use to disable console output, i.e., to have kernel
                        console messages discarded.
                        This must be the only console= parameter used on the
                        kernel command line.

                If the device connected to the port is not a TTY but a braille
                device, prepend "brl," before the device type, for instance
                For now, only VisioBraille is supported.

                        [KNL] Change console messages format
                        By default we print messages on consoles in
                        "[time stamp] text\n" format (time stamp may not be
                        printed, depending on CONFIG_PRINTK_TIME or
                        `printk_time' param).
                        Switch to syslog format: "<%u>[time stamp] text\n"
                        IOW, each message will have a facility and loglevel
                        prefix. The format is similar to one used by syslog()
                        syscall, or to executing "dmesg -S --raw" or to reading
                        from /proc/kmsg.

        consoleblank=   [KNL] The console blank (screen saver) timeout in
                        seconds. A value of 0 disables the blank timer.
                        Defaults to 0.

                        [KNL] Change the default value for
                        See also Documentation/filesystems/proc.rst.

                        Format: <bool>
                        Enable/disable the CPU sampling based debugging.
                        0: default value, disable debugging
                        1: enable debugging at boot time

        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]   [CPU_IDLE]
                        disable the cpuidle sub-system

                        [CPU_IDLE] Name of the cpuidle governor to use.   [CPU_FREQ]
                        disable the cpufreq sub-system

                        [CPU_FREQ] Name of the default cpufreq governor or
                        policy to use. This governor must be registered in the
                        kernel before the cpufreq driver probes.

                        [X86] Delay for N microsec between assert and de-assert
                        of APIC INIT to start processors.  This delay occurs
                        on every CPU online, such as boot, and resume from suspend.
                        Default: 10000

                        [SMP] Enable/disable parallel bringup of secondary CPUs
                        Format: <bool>
                        Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
                        the parameter has no effect.

                        Run kdump after running panic-notifiers and dumping
                        kmsg. This only for the users who doubt kdump always
                        succeeds in any situation.
                        Note that this also increases risks of kdump failure,
                        because some panic notifiers can make the crashed
                        kernel more unstable.

                        [KNL] Using kexec, Linux can switch to a 'crash kernel'
                        upon panic. This parameter reserves the physical
                        memory region [offset, offset + size] for that kernel
                        image. If '@offset' is omitted, then a suitable offset
                        is selected automatically.
                        [KNL, X86-64, ARM64, RISCV] Select a region under 4G first, and
                        fall back to reserve region above 4G when '@offset'
                        hasn't been specified.
                        See Documentation/admin-guide/kdump/kdump.rst for further details.

                        [KNL] Same as above, but depends on the memory
                        in the running system. The syntax of range is
                        start-[end] where start and end are both
                        a memory unit (amount[KMG]). See also
                        Documentation/admin-guide/kdump/kdump.rst for an example.

                        [KNL, X86-64, ARM64, RISCV] range could be above 4G.
                        Allow kernel to allocate physical memory region from top,
                        so could be above 4G if system have more than 4G ram
                        installed. Otherwise memory region will be allocated
                        below 4G, if available.
                        It will be ignored if crashkernel=X is specified.
                        [KNL, X86-64, ARM64, RISCV] range under 4G. When crashkernel=X,high
                        is passed, kernel could allocate physical memory region
                        above 4G, that cause second kernel crash on system
                        that require some amount of low memory, e.g. swiotlb
                        requires at least 64M+32K low memory, also enough extra
                        low memory is needed to make sure DMA buffers for 32-bit
                        devices won't run out. Kernel would try to allocate
                        default size of memory below 4G automatically. The default
                        size is platform dependent.
                          --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
                          --> arm64: 128MiB
                          --> riscv: 128MiB
                        This one lets the user specify own low range under 4G
                        for second kernel instead.
                        0: to disable low allocation.
                        It will be ignored when crashkernel=X,high is not used
                        or memory reserved is below 4G.

                        [KNL] Disable crypto self-tests

        cs89x0_dma=     [HW,NET]
                        Format: <dma>

        cs89x0_media=   [HW,NET]
                        Format: { rj45 | aui | bnc }

        csdlock_debug=  [KNL] Enable or disable debug add-ons of cross-CPU
                        function call handling. When switched on,
                        additional debug data is printed to the console
                        in case a hanging CPU is detected, and that
                        CPU is pinged again in order to try to resolve
                        the hang situation.  The default value of this
                        option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
                        Kconfig option.

        dasd=           [HW,NET]
                        See header of drivers/s390/block/dasd_devmap.c.[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
                        (one device per port)
                        Format: <port#>,<type>
                        See also Documentation/input/devices/joystick-parport.rst

        debug           [KNL] Enable kernel debugging (events log level).

                        [KNL] Enable printing [hashed] pointers early in the
                        boot sequence.  If enabled, we use a weak hash instead
                        of siphash to hash pointers.  Use this option if you are
                        seeing instances of '(___ptrval___)') and need to see a
                        value (hashed pointer) instead. Cryptographically
                        insecure, please do not use on production kernels.

                        [KNL] verbose locking self-tests
                        Format: <int>
                        Print debugging info while doing the locking API
                        Bitmask for the various LOCKTYPE_ tests. Defaults to 0
                        (no extra messages), setting it to -1 (all bits set)
                        will print _a_lot_ more information - normally only
                        useful to lockdep developers.

        debug_objects   [KNL] Enable object debugging

                        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
                        parameter allows control of the order of pages that will
                        be intentionally kept free (and hence protected) by the
                        buddy allocator. Bigger value increase the probability
                        of catching random memory corruption, but reduce the
                        amount of memory for normal system use. The maximum
                        possible value is MAX_ORDER/2.  Setting this parameter
                        to 1 or 2 should be enough to identify most random
                        memory corruption problems caused by bugs in kernel or
                        driver code when a CPU writes to (or reads from) a
                        random memory location. Note that there exists a class
                        of memory corruptions problems caused by buggy H/W or
                        F/W or by drivers badly programming DMA (basically when
                        memory is written at bus level and the CPU MMU is
                        bypassed) which are not detectable by
                        CONFIG_DEBUG_PAGEALLOC, hence this option will not help
                        tracking down these problems.

                        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
                        enables the feature at boot time. By default, it is
                        disabled and the system will work mostly the same as a
                        kernel built without CONFIG_DEBUG_PAGEALLOC.
                        Note: to get most of debug_pagealloc error reports, it's
                        useful to also enable the page_owner functionality.
                        on: enable the feature

        debugfs=        [KNL] This parameter enables what is exposed to userspace
                        and debugfs internal clients.
                        Format: { on, no-mount, off }
                        on:     All functions are enabled.
                                Filesystem is not registered but kernel clients can
                                access APIs and a crashkernel can be used to read
                                its content. There is nothing to mount.
                        off:    Filesystem is not registered and clients
                                get a -EPERM as result when trying to register files
                                or directories within debugfs.
                                This is equivalent of the runtime functionality if
                                debugfs was not enabled in the kernel at all.
                        Default value is set in build-time with a kernel configuration.

        debugpat        [X86] Enable PAT debugging

                        [HW] The size of the default HugeTLB page. This is
                        the size represented by the legacy /proc/ hugepages
                        APIs.  In addition, this is the default hugetlb size
                        used for shmget(), mmap() and mounting hugetlbfs
                        filesystems.  If not specified, defaults to the
                        architecture's default huge page size.  Huge page
                        sizes are architecture dependent.  See also
                        Format: size[KMG]

                        [KNL] Debugging option to set a timeout in seconds for
                        deferred probe to give up waiting on dependencies to
                        probe. Only specific dependencies (subsystems or
                        drivers) that have opted in will be ignored. A timeout
                        of 0 will timeout at the end of initcalls. If the time
                        out hasn't expired, it'll be restarted by each
                        successful driver registration. This option will also
                        dump out devices still on the deferred probe list after

        delayacct       [KNL] Enable per-task delay accounting

                        [HW] Continue probing hardware even if DMI data
                        indicates that the driver is running on unsupported

                        [HW] Activate driver even if SMM BIOS signature does
                        not match list of supported models and enable otherwise
                        blacklisted features.

                        [HW] Report power status in /proc/i8k
                        (disabled by default).

                        [HW] Allow controlling fans only if SYS_ADMIN
                        capability is set.

                        [HW] Factor to multiply fan speed with.

                        [HW] Maximum configurable fan speed.

        dfltcc=         [HW,S390]
                        Format: { on | off | def_only | inf_only | always }
                        on:       s390 zlib hardware support for compression on
                                  level 1 and decompression (default)
                        off:      No s390 zlib hardware support
                        def_only: s390 zlib hardware support for deflate
                                  only (compression on level 1)
                        inf_only: s390 zlib hardware support for inflate
                                  only (decompression)
                        always:   Same as 'on' but ignores the selected compression
                                  level always using hardware support (used for debugging)

        dhash_entries=  [KNL]
                        Set number of hash buckets for dentry cache.

        disable_1tb_segments [PPC]
                        Disables the use of 1TB hash page table segments. This
                        causes the kernel to fall back to 256MB segments which
                        can be useful when debugging issues that require an SLB
                        miss to occur.

        disable=        [IPV6]
                        See Documentation/networking/ipv6.rst.

        disable_radix   [PPC]
                        Disable RADIX MMU mode on POWER9

        disable_tlbie   [PPC]
                        Disable TLBIE instruction. Currently does not work
                        with KVM, with HASH MMU, or with coherent accelerators.

        disable_cpu_apicid= [X86,APIC,SMP]
                        Format: <int>
                        The number of initial APIC ID for the
                        corresponding CPU to be disabled at boot,
                        mostly used for the kdump 2nd kernel to
                        disable BSP to wake up multiple CPUs without
                        causing system reset or hang due to sending
                        INIT from AP to BSP.

        disable_ddw     [PPC/PSERIES]
                        Disable Dynamic DMA Window support. Use this
                        to workaround buggy firmware.

        disable_ipv6=   [IPV6]
                        See Documentation/networking/ipv6.rst.

        disable_mtrr_cleanup [X86]
                        The kernel tries to adjust MTRR layout from continuous
                        to discrete, to make X server driver able to add WB
                        entry later. This parameter disables that.

        disable_mtrr_trim [X86, Intel and AMD only]
                        By default the kernel will trim any uncacheable
                        memory out of your available memory pool based on
                        MTRR settings.  This parameter disables that behavior,
                        possibly causing your machine to run very slowly.

        disable_timer_pin_1 [X86]
                        Disable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs.

        dis_ucode_ldr   [X86] Disable the microcode loader.

        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
                        this option disables the debugging code at boot.

                        This option allows to tune the number of preallocated
                        entries for DMA-API debugging code. One entry is
                        required per DMA-API allocation. Use this if the
                        DMA-API debugging code disables itself because the
                        architectural default is too low.

                        With this option the DMA-API debugging driver
                        filter feature can be enabled at boot time. Just
                        pass the driver to filter for as the parameter.
                        The filter can be disabled or changed to another
                        driver later using sysfs.

        driver_async_probe=  [KNL]
                        List of driver names to be probed asynchronously. *
                        matches with all driver names. If * is specified, the
                        rest of the listed driver names are those that will NOT
                        match the *.
                        Format: <driver_name1>,<driver_name2>...

                        Broken monitors, graphic adapters, KVMs and EDIDless
                        panels may send no or incorrect EDID data sets.
                        This parameter allows to specify an EDID data sets
                        in the /lib/firmware directory that are used instead.
                        Generic built-in EDID data sets are used, if one of
                        edid/1024x768.bin, edid/1280x1024.bin,
                        edid/1680x1050.bin, or edid/1920x1080.bin is given
                        and no file with the same name exists. Details and
                        instructions how to build your own EDID data are
                        available in Documentation/admin-guide/edid.rst. An EDID
                        data set will only be used for a particular connector,
                        if its name and a colon are prepended to the EDID
                        name. Each connector may use a unique EDID data
                        set by separating the files with a comma.  An EDID
                        data set with no connector name will be used for
                        any connectors not explicitly specified.

        dscc4.setup=    [NET]

        dt_cpu_ftrs=    [PPC]
                        Format: {"off" | "known"}
                        Control how the dt_cpu_ftrs device-tree binding is
                        used for CPU feature discovery and setup (if it
                        off: Do not use it, fall back to legacy cpu table.
                        known: Do not pass through unknown features to guests
                        or userspace, only those that the kernel is aware of.

        dump_apple_properties   [X86]
                        Dump name and content of EFI device properties on
                        x86 Macs.  Useful for driver authors to determine
                        what data is available or for reverse-engineering.

        dyndbg[="val"]          [KNL,DYNAMIC_DEBUG]
                        Enable debug messages at boot time.  See
                        for details.

        early_ioremap_debug [KNL]
                        Enable debug messages in early_ioremap support. This
                        is useful for tracking down temporary early mappings
                        which are not unmapped.

        earlycon=       [KNL] Output early console device and options.

                        When used with no options, the early console is
                        determined by stdout-path property in device tree's
                        chosen node or the ACPI SPCR table if supported by
                        the platform.

                        Start an early, polled-mode console on a Cadence
                        (xuartps) serial port at the specified address. Only
                        supported option is baud rate. If baud rate is not
                        specified, the serial port must already be setup and

                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address.
                        MMIO inter-register address stride is either 8-bit
                        (mmio) or 32-bit (mmio32 or mmio32be).
                        If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
                        to be equivalent to 'mmio'. 'options' are specified
                        in the same format described for "console=ttyS<n>"; if
                        unspecified, the h/w is not initialized. 'uartclk' is
                        the uart clock frequency; if unspecified, it is set
                        to 'BASE_BAUD' * 16.

                        Start an early, polled-mode console on a pl011 serial
                        port at the specified address. The pl011 serial port
                        must already be setup and configured. Options are not
                        yet supported.  If 'mmio32' is specified, then only
                        the driver will use only 32-bit accessors to read/write
                        the device registers.

                        Start an early console on a litex serial port at the
                        specified address. The serial port must already be
                        setup and configured. Options are not yet supported.

                        Start an early, polled-mode console on a meson serial
                        port at the specified address. The serial port must
                        already be setup and configured. Options are not yet

                        Start an early, polled-mode console on an msm serial
                        port at the specified address. The serial port
                        must already be setup and configured. Options are not
                        yet supported.

                        Start an early, polled-mode console on an msm serial
                        dm port at the specified address. The serial port
                        must already be setup and configured. Options are not
                        yet supported.

                        Start an early, polled-mode console on a serial port
                        of an Actions Semi SoC, such as S500 or S900, at the
                        specified address. The serial port must already be
                        setup and configured. Options are not yet supported.

                        Start an early, polled-mode console on a serial port
                        of an RDA Micro SoC, such as RDA8810PL, at the
                        specified address. The serial port must already be
                        setup and configured. Options are not yet supported.

                        Use RISC-V SBI (Supervisor Binary Interface) for early

                smh     Use ARM semihosting calls for early console.

                        Use early console provided by serial driver available
                        on Samsung SoCs, requires selecting proper type and
                        a correct base address of the selected UART port. The
                        serial port must already be setup and configured.
                        Options are not yet supported.

                        Start an early, polled-mode console on a lantiq serial
                        (lqasc) port at the specified address. The serial port
                        must already be setup and configured. Options are not
                        yet supported.

                        Use early console provided by Freescale LP UART driver
                        found on Freescale Vybrid and QorIQ LS1021A processors.
                        A valid base address must be provided, and the serial
                        port must already be setup and configured.

                        Start an early, polled-mode, output-only console on the
                        Freescale i.MX UART at the specified address. The UART
                        must already be setup and configured.

                        Start an early, polled-mode console on the
                        Armada 3700 serial port at the specified
                        address. The serial port must already be setup
                        and configured. Options are not yet supported.

                        Start an early, polled-mode console on a Qualcomm
                        Generic Interface (GENI) based serial port at the
                        specified address. The serial port must already be
                        setup and configured. Options are not yet supported.

                        Start an early, unaccelerated console on the EFI
                        memory mapped framebuffer (if available). On cache
                        coherent non-x86 systems that use system memory for
                        the framebuffer, pass the 'ram' option so that it is
                        mapped with the correct attributes.

                        Use early console provided by Freescale LINFlexD UART
                        serial driver for NXP S32V234 SoCs. A valid base
                        address must be provided, and the serial port must
                        already be setup and configured.

        earlyprintk=    [X86,SH,ARM,M68k,S390]

                        earlyprintk is useful when the kernel crashes before
                        the normal console is initialized. It is not enabled by
                        default because it has some cosmetic problems.

                        Append ",keep" to not disable it when the real console
                        takes over.

                        Only one of vga, serial, or usb debug port can
                        be used at a time.

                        Currently only ttyS0 and ttyS1 may be specified by
                        name.  Other I/O ports may be explicitly specified
                        on some architectures (x86 and arm at least) by
                        replacing ttySn with an I/O port address, like this:
                        You can find the port for a given device in
                                2: uart:ST16650V2 port:00001008 irq:18 ...

                        Interaction with the standard serial driver is not
                        very good.

                        The VGA output is eventually overwritten by
                        the real console.

                        The xen option can only be used in Xen domains.

                        The sclp output can only be used on s390.

                        The optional "force" to "pciserial" enables use of a
                        PCI device even when its classcode is not of the
                        UART class.

        edac_report=    [HW,EDAC] Control how to report EDAC event
                        Format: {"on" | "off" | "force"}
                        on: enable EDAC to report H/W event. May be overridden
                        by other higher priority error reporting module.
                        off: disable H/W event reporting through EDAC.
                        force: enforce the use of EDAC to report H/W event.
                        default: on.

        edd=            [EDD]
                        Format: {"off" | "on" | "skip[mbr]"}

        efi=            [EFI]
                        Format: { "debug", "disable_early_pci_dma",
                                  "nochunk", "noruntime", "nosoftreserve",
                                  "novamap", "no_disable_early_pci_dma" }
                        debug: enable misc debug output.
                        disable_early_pci_dma: disable the busmaster bit on all
                        PCI bridges while in the EFI boot stub.
                        nochunk: disable reading files in "chunks" in the EFI
                        boot stub, as chunking can cause problems with some
                        firmware implementations.
                        noruntime : disable EFI runtime services support
                        nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
                        attribute may cause the kernel to reserve the
                        memory range for a memory mapping driver to
                        claim. Specify efi=nosoftreserve to disable this
                        reservation and treat the memory by its base type
                        (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
                        novamap: do not call SetVirtualAddressMap().
                        no_disable_early_pci_dma: Leave the busmaster bit set
                        on all PCI bridges while in the EFI boot stub

        efi_no_storage_paranoia [EFI; X86]
                        Using this parameter you can use more than 50% of
                        your efi variable storage. Use this parameter only if
                        you are really sure that your UEFI does sane gc and
                        fulfills the spec otherwise your board may brick.

        efi_fake_mem=   nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
                        Add arbitrary attribute to specific memory range by
                        updating original EFI memory map.
                        Region of memory which aa attribute is added to is
                        from ss to ss+nn.

                        If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
                        is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
                        attribute is added to range 0x100000000-0x180000000 and

                        If efi_fake_mem=8G@9G:0x40000 is specified, the
                        EFI_MEMORY_SP(0x40000) attribute is added to
                        range 0x240000000-0x43fffffff.

                        Using this parameter you can do debugging of EFI memmap
                        related features. For example, you can do debugging of
                        Address Range Mirroring feature even if your box
                        doesn't support it, or mark specific memory as
                        "soft reserved".

        efivar_ssdt=    [EFI; X86] Name of an EFI variable that contains an SSDT
                        that is to be dynamically loaded by Linux. If there are
                        multiple variables with the same name but with different
                        vendor GUIDs, all of them will be loaded. See
                        Documentation/admin-guide/acpi/ssdt-overlays.rst for details.

        eisa_irq_edge=  [PARISC,HW]
                        See header of drivers/parisc/eisa.c.

        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
                        Format: ekgdboc=kbd

                        This is designed to be used in conjunction with
                        the boot argument: earlyprintk=vga

                        This parameter works in place of the kgdboc parameter
                        but can only be used if the backing tty is available
                        very early in the boot process. For early debugging
                        via a serial port see kgdboc_earlycon instead.

        elanfreq=       [X86-32]
                        See comment before function elanfreq_setup() in

        elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
                        Specifies physical address of start of kernel core
                        image elf header and optionally the size. Generally
                        kexec loader will pass this option to capture kernel.
                        See Documentation/admin-guide/kdump/kdump.rst for details.

        enable_mtrr_cleanup [X86]
                        The kernel tries to adjust MTRR layout from continuous
                        to discrete, to make X server driver able to add WB
                        entry later. This parameter enables that.

        enable_timer_pin_1 [X86]
                        Enable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs
                        (in particular on some ATI chipsets).
                        The kernel tries to set a reasonable default.

        enforcing=      [SELINUX] Set initial enforcing status.
                        Format: {"0" | "1"}
                        See security/selinux/Kconfig help text.
                        0 -- permissive (log only, no denials).
                        1 -- enforcing (deny and log).
                        Default value is 0.
                        Value can be changed at runtime via

        erst_disable    [ACPI]
                        Disable Error Record Serialization Table (ERST)

        ether=          [HW,NET] Ethernet cards parameters
                        This option is obsoleted by the "netdev=" option, which
                        has equivalent usage. See its documentation for details.

        evm=            [EVM]
                        Format: { "fix" }
                        Permit 'security.evm' to be updated regardless of
                        current integrity status.

        early_page_ext [KNL] Enforces page_ext initialization to earlier
                        stages so cover more early boot allocations.
                        Please note that as side effect some optimizations
                        might be disabled to achieve that (e.g. parallelized
                        memory initialization is disabled) so the boot process
                        might take longer, especially on systems with a lot of
                        memory. Available with CONFIG_PAGE_EXTENSION=y.

                        General fault injection mechanism.
                        Format: <interval>,<probability>,<space>,<times>
                        See also Documentation/fault-injection/.

        fb_tunnels=     [NET]
                        Format: { initns | none }
                        See Documentation/admin-guide/sysctl/net.rst for

        floppy=         [HW]
                        See Documentation/admin-guide/blockdev/floppy.rst.

                        [IA-64] Avoid check_sal_cache_flush which may hang on
                        buggy SAL_CACHE_FLUSH implementations. Using this
                        parameter will force ia64_sal_cache_flush to call
                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

        forcepae        [X86-32]
                        Forcefully enable Physical Address Extension (PAE).
                        Many Pentium M systems disable PAE but may have a
                        functionally usable PAE implementation.
                        Warning: use of this parameter will taint the kernel
                        and may cause unknown problems.

                        [FTRACE] will set and start the specified tracer
                        as early as possible in order to facilitate early
                        boot debugging.

                        [FTRACE] On boot up, a snapshot will be taken of the
                        ftrace ring buffer that can be read at:
                        This is useful if you need tracing information from kernel
                        boot up that is likely to be overridden by user space
                        start up functionality.

                        Optionally, the snapshot can also be defined for a tracing
                        instance that was created by the trace_instance= command
                        line parameter.

                        trace_instance=foo,sched_switch ftrace_boot_snapshot=foo

                        The above will cause the "foo" tracing instance to trigger
                        a snapshot at the end of boot up.

                        [FTRACE] will dump the trace buffers on oops.
                        If no parameter is passed, ftrace will dump
                        buffers of all CPUs, but if you pass orig_cpu, it will
                        dump only the buffer of the CPU that triggered the

                        [FTRACE] Limit the functions traced by the function
                        tracer at boot up. function-list is a comma-separated
                        list of functions. This list can be changed at run
                        time by the set_ftrace_filter file in the debugfs
                        tracing directory.

                        [FTRACE] Do not trace the functions specified in
                        function-list. This list can be changed at run time
                        by the set_ftrace_notrace file in the debugfs
                        tracing directory.

                        [FTRACE] Limit the top level callers functions traced
                        by the function graph tracer at boot up.
                        function-list is a comma-separated list of functions
                        that can be changed at run time by the
                        set_graph_function file in the debugfs tracing directory.

                        [FTRACE] Do not trace from the functions specified in
                        function-list.  This list is a comma-separated list of
                        functions that can be changed at run time by the
                        set_graph_notrace file in the debugfs tracing directory.

                        [FTRACE] Used with the function graph tracer. This is
                        the max depth it will trace into a function. This value
                        can be changed at run time by the max_graph_depth file
                        in the tracefs tracing directory. default: 0 (no limit)

        fw_devlink=     [KNL] Create device links between consumer and supplier
                        devices by scanning the firmware to infer the
                        consumer/supplier relationships. This feature is
                        especially useful when drivers are loaded as modules as
                        it ensures proper ordering of tasks like device probing
                        (suppliers first, then consumers), supplier boot state
                        clean up (only after all consumers have probed),
                        suspend/resume & runtime PM (consumers first, then
                        Format: { off | permissive | on | rpm }
                        off --  Don't create device links from firmware info.
                        permissive -- Create device links from firmware info
                                but use it only for ordering boot state clean
                                up (sync_state() calls).
                        on --   Create device links from firmware info and use it
                                to enforce probe and suspend/resume ordering.
                        rpm --  Like "on", but also use to order runtime PM.

                        [KNL] Treat all inferred dependencies as mandatory
                        dependencies. This only applies for fw_devlink=on|rpm.
                        Format: <bool>

        fw_devlink.sync_state =
                        [KNL] When all devices that could probe have finished
                        probing, this parameter controls what to do with
                        devices that haven't yet received their sync_state()
                        Format: { strict | timeout }
                        strict -- Default. Continue waiting on consumers to
                                probe successfully.
                        timeout -- Give up waiting on consumers and call
                                sync_state() on any devices that haven't yet
                                received their sync_state() calls after
                                deferred_probe_timeout has expired or by
                                late_initcall() if !CONFIG_MODULES.[2|3]=
                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
                        support via parallel port (up to 5 devices per port)
                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
                        See also Documentation/input/devices/joystick-parport.rst

        gamma=          [HW,DRM]

        gart_fix_e820=  [X86-64] disable the fix e820 for K8 GART
                        Format: off | on
                        default: on

                        [X86,INTEL] Control the Gather Data Sampling (GDS)

                        Gather Data Sampling is a hardware vulnerability which
                        allows unprivileged speculative access to data which was
                        previously stored in vector registers.

                        This issue is mitigated by default in updated microcode.
                        The mitigation may have a performance impact but can be
                        disabled. On systems without the microcode mitigation
                        disabling AVX serves as a mitigation.

                        force:  Disable AVX to mitigate systems without
                                microcode mitigation. No effect if the microcode
                                mitigation is present. Known to cause crashes in
                                userspace with buggy AVX enumeration.

                        off:    Disable GDS mitigation.

        gcov_persist=   [GCOV] When non-zero (default), profiling data for
                        kernel modules is saved and remains accessible via
                        debugfs, even when the module is unloaded/reloaded.
                        When zero, profiling data is discarded and associated
                        debugfs files are removed at module unload time.

        goldfish        [X86] Enable the goldfish android emulator platform.
                        Don't use this when you are not running on the
                        android emulator

                        [HW] Sets the ranges of gpiochip of for this device.
                        Format: <start1>,<end1>,<start2>,<end2>...
                        [HW] Let the driver know GPIO lines should be named.

        gpt             [EFI] Forces disk with valid GPT signature but
                        invalid Protective MBR to be treated as GPT. If the
                        primary GPT is corrupted, it enables the backup/alternate
                        GPT to be used instead.

        grcan.enable0=  [HW] Configuration of physical interface 0. Determines
                        the "Enable 0" bit of the configuration register.
                        Format: 0 | 1
                        Default: 0
        grcan.enable1=  [HW] Configuration of physical interface 1. Determines
                        the "Enable 0" bit of the configuration register.
                        Format: 0 | 1
                        Default: 0   [HW] Select which physical interface to use.
                        Format: 0 | 1
                        Default: 0
        grcan.txsize=   [HW] Sets the size of the tx buffer.
                        Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
                        Default: 1024
        grcan.rxsize=   [HW] Sets the size of the rx buffer.
                        Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
                        Default: 1024

                        [KNL] Under CONFIG_HARDENED_USERCOPY, whether
                        hardening is enabled for this boot. Hardened
                        usercopy checking is used to protect the kernel
                        from reading or writing beyond known memory
                        allocation boundaries as a proactive defense
                        against bounds-checking flaws in the kernel's
                        copy_to_user()/copy_from_user() interface.
                on      Perform hardened usercopy checks (default).
                off     Disable hardened usercopy checks.

                        [KNL] Should the hard-lockup detector generate
                        backtraces on all cpus.
                        Format: 0 | 1

        hashdist=       [KNL,NUMA] Large hashes allocated during boot
                        are distributed across NUMA nodes.  Defaults on
                        for 64-bit NUMA, off otherwise.
                        Format: 0 | 1 (for off | on)

        hcl=            [IA-64] SGI's Hardware Graph compatibility layer

        hd=             [EIDE] (E)IDE hard drive subsystem geometry
                        Format: <cyl>,<head>,<sect>

        hest_disable    [ACPI]
                        Disable Hardware Error Source Table (HEST) support;
                        corresponding firmware-first mode error processing
                        logic will be disabled.

        hibernate=      [HIBERNATION]
                noresume        Don't check if there's a hibernation image
                                present during boot.
                nocompress      Don't compress/decompress hibernation images.
                no              Disable hibernation and resume.
                protect_image   Turn on image protection during restoration
                                (that will set all pages holding image data
                                during restoration read-only).

        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
                        size of <nn>. This works even on boxes that have no
                        highmem otherwise. This also works to reduce highmem
                        size on bigger boxes.

        highres=        [KNL] Enable/disable high resolution timer mode.
                        Valid parameters: "on", "off"
                        Default: "on"

        hlt             [BUGS=ARM,SH]

        hostname=       [KNL] Set the hostname (aka UTS nodename).
                        Format: <string>
                        This allows setting the system's hostname during early
                        startup. This sets the name returned by gethostname.
                        Using this parameter to set the hostname makes it
                        possible to ensure the hostname is correctly set before
                        any userspace processes run, avoiding the possibility
                        that a process may call gethostname before the hostname
                        has been explicitly set, resulting in the calling
                        process getting an incorrect result. The string must
                        not exceed the maximum allowed hostname length (usually
                        64 characters) and will be truncated otherwise.

        hpet=           [X86-32,HPET] option to control HPET usage
                        Format: { enable (default) | disable | force |
                                verbose }
                        disable: disable HPET and use PIT instead
                        force: allow force enabled of undocumented chips (ICH4,
                                VIA, nVidia)
                        verbose: show contents of HPET registers during setup

        hpet_mmap=      [X86, HPET_MMAP] Allow userspace to mmap HPET
                        registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.

        hugepages=      [HW] Number of HugeTLB pages to allocate at boot.
                        If this follows hugepagesz (below), it specifies
                        the number of pages of hugepagesz to be allocated.
                        If this is the first HugeTLB parameter on the command
                        line, it specifies the number of pages to allocate for
                        the default huge page size. If using node format, the
                        number of pages to allocate per-node can be specified.
                        See also Documentation/admin-guide/mm/hugetlbpage.rst.
                        Format: <integer> or (node format)

                        [HW] The size of the HugeTLB pages.  This is used in
                        conjunction with hugepages (above) to allocate huge
                        pages of a specific size at boot.  The pair
                        hugepagesz=X hugepages=Y can be specified once for
                        each supported huge page size. Huge page sizes are
                        architecture dependent.  See also
                        Format: size[KMG]

        hugetlb_cma=    [HW,CMA] The size of a CMA area used for allocation
                        of gigantic hugepages. Or using node format, the size
                        of a CMA area per node can be specified.
                        Format: nn[KMGTPE] or (node format)

                        Reserve a CMA area of given size and allocate gigantic
                        hugepages using the CMA allocator. If enabled, the
                        boot-time allocation of gigantic hugepages is skipped.

                        [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
                        Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
                        Allows heavy hugetlb users to free up some more
                        memory (7 * PAGE_SIZE for each 2MB hugetlb page).
                        Format: { on | off (default) }

                        on: enable HVO
                        off: disable HVO

                        Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
                        the default is on.

                        Note that the vmemmap pages may be allocated from the added
                        memory block itself when memory_hotplug.memmap_on_memory is
                        enabled, those vmemmap pages cannot be optimized even if this
                        feature is enabled.  Other vmemmap pages not allocated from
                        the added memory block itself do not be affected.

                        [KNL] Should the hung task detector generate panics.
                        Format: 0 | 1

                        A value of 1 instructs the kernel to panic when a
                        hung task is detected. The default value is controlled
                        by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
                        option. The value selected by this boot parameter can
                        be changed later by the kernel.hung_task_panic sysctl.

        hvc_iucv=       [S390]  Number of z/VM IUCV hypervisor console (HVC)
                                terminal devices. Valid values: 0..8
        hvc_iucv_allow= [S390]  Comma-separated list of z/VM user IDs.
                                If specified, z/VM IUCV HVC accepts connections
                                from listed z/VM user IDs only.

        hv_nopvspin     [X86,HYPER_V] Disables the paravirt spinlock optimizations
                                      which allow the hypervisor to 'idle' the
                                      guest on lock contention.

        i2c_bus=        [HW]    Override the default board specific I2C bus speed
                                or register an additional I2C bus that is not
                                registered from board initialization code.

        i8042.debug     [HW] Toggle i8042 debug mode
                        [HW] Enable printing of interrupt data from the KBD port
                             (disabled by default, and as a pre-condition
                             requires that i8042.debug=1 be enabled)    [HW] Put keyboard port into non-translated mode
        i8042.dumbkbd   [HW] Pretend that controller can only read data from
                             keyboard and cannot control its state
                             (Don't attempt to blink the leds)
        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
        i8042.nokbd     [HW] Don't check/create keyboard port
        i8042.noloop    [HW] Disable the AUX Loopback command while probing
                             for the AUX port
        i8042.nomux     [HW] Don't check presence of an active multiplexing
        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
        i8042.notimeout [HW] Ignore timeout condition signalled by controller
        i8042.reset     [HW] Reset the controller during init, cleanup and
                             suspend-to-ram transitions, only during s2r
                             transitions, or never reset
                        Format: { 1 | Y | y | 0 | N | n }
                        1, Y, y: always reset controller
                        0, N, n: don't ever reset controller
                        Default: only on s2r transitions on x86; most other
                        architectures force reset to be always executed
        i8042.unlock    [HW] Unlock (ignore) the keylock
        i8042.kbdreset  [HW] Reset device connected to KBD port
                        [HW] Allow deferred probing upon i8042 probe errors

        i810=           [HW,DRM]

                        [DRM] Invert the sense of the variable that is used to
                        set the brightness of the panel backlight. Normally a
                        brightness value of 0 indicates backlight switched off,
                        and the maximum of the brightness value sets the backlight
                        to maximum brightness. If this parameter is set to 0
                        (default) and the machine requires it, or this parameter
                        is set to 1, a brightness value of 0 sets the backlight
                        to maximum brightness, and the maximum of the brightness
                        value switches the backlight off.
                        -1 -- never invert brightness
                         0 -- machine default
                         1 -- force brightness inversion

        icn=            [HW,ISDN]
                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]

        idle=           [X86]
                        Format: idle=poll, idle=halt, idle=nomwait
                        Poll forces a polling idle loop that can slightly
                        improve the performance of waking up a idle CPU, but
                        will use a lot of power and make the system run hot.
                        Not recommended.
                        idle=halt: Halt is forced to be used for CPU idle.
                        In such case C2/C3 won't be used again.
                        idle=nomwait: Disable mwait for CPU C-states

        idxd.sva=       [HW]
                        Format: <bool>
                        Allow force disabling of Shared Virtual Memory (SVA)
                        support for the idxd driver. By default it is set to
                        true (1).

        idxd.tc_override= [HW]
                        Format: <bool>
                        Allow override of default traffic class configuration
                        for the device. By default it is set to false (0).

        ieee754=        [MIPS] Select IEEE Std 754 conformance mode
                        Format: { strict | legacy | 2008 | relaxed }
                        Default: strict

                        Choose which programs will be accepted for execution
                        based on the IEEE 754 NaN encoding(s) supported by
                        the FPU and the NaN encoding requested with the value
                        of an ELF file header flag individually set by each
                        binary.  Hardware implementations are permitted to
                        support either or both of the legacy and the 2008 NaN
                        encoding mode.

                        Available settings are as follows:
                        strict  accept binaries that request a NaN encoding
                                supported by the FPU
                        legacy  only accept legacy-NaN binaries, if supported
                                by the FPU
                        2008    only accept 2008-NaN binaries, if supported
                                by the FPU
                        relaxed accept any binaries regardless of whether
                                supported by the FPU

                        The FPU emulator is always able to support both NaN
                        encodings, so if no FPU hardware is present or it has
                        been disabled with 'nofpu', then the settings of
                        'legacy' and '2008' strap the emulator accordingly,
                        'relaxed' straps the emulator for both legacy-NaN and
                        2008-NaN, whereas 'strict' enables legacy-NaN only on
                        legacy processors and both NaN encodings on MIPS32 or
                        MIPS64 CPUs.

                        The setting for ABS.fmt/NEG.fmt instruction execution
                        mode generally follows that for the NaN encoding,
                        except where unsupported by hardware.

        ignore_loglevel [KNL]
                        Ignore loglevel setting - this will print /all/
                        kernel messages to the console. Useful for debugging.
                        We also add it as printk module parameter, so users
                        could change it dynamically, usually by

                        Ignore RLIMIT_DATA setting for data mappings,
                        print warning at first misuse.  Can be changed via

        ihash_entries=  [KNL]
                        Set number of hash buckets for inode cache.

        ima_appraise=   [IMA] appraise integrity measurements
                        Format: { "off" | "enforce" | "fix" | "log" }
                        default: "enforce"

        ima_appraise_tcb [IMA] Deprecated.  Use ima_policy= instead.
                        The builtin appraise policy appraises all files
                        owned by uid=0.

        ima_canonical_fmt [IMA]
                        Use the canonical format for the binary runtime
                        measurements, instead of host native format.

        ima_hash=       [IMA]
                        Format: { md5 | sha1 | rmd160 | sha256 | sha384
                                   | sha512 | ... }
                        default: "sha1"

                        The list of supported hash algorithms is defined
                        in crypto/hash_info.h.

        ima_policy=     [IMA]
                        The builtin policies to load during IMA setup.
                        Format: "tcb | appraise_tcb | secure_boot |
                                 fail_securely | critical_data"

                        The "tcb" policy measures all programs exec'd, files
                        mmap'd for exec, and all files opened with the read
                        mode bit set by either the effective uid (euid=0) or

                        The "appraise_tcb" policy appraises the integrity of
                        all files owned by root.

                        The "secure_boot" policy appraises the integrity
                        of files (eg. kexec kernel image, kernel modules,
                        firmware, policy, etc) based on file signatures.

                        The "fail_securely" policy forces file signature
                        verification failure also on privileged mounted
                        filesystems with the SB_I_UNVERIFIABLE_SIGNATURE

                        The "critical_data" policy measures kernel integrity
                        critical data.

        ima_tcb         [IMA] Deprecated.  Use ima_policy= instead.
                        Load a policy which meets the needs of the Trusted
                        Computing Base.  This means IMA will measure all
                        programs exec'd, files mmap'd for exec, and all files
                        opened for read by uid=0.

        ima_template=   [IMA]
                        Select one of defined IMA measurements template formats.
                        Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
                                   "ima-sigv2" }
                        Default: "ima-ng"

                        [IMA] Define a custom template format.
                        Format: { "field1|...|fieldN" }

        ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
                        Format: <min_file_size>
                        Set the minimal file size for using asynchronous hash.
                        If left unspecified, ahash usage is disabled.

                        ahash performance varies for different data sizes on
                        different crypto accelerators. This option can be used
                        to achieve the best performance for a particular HW.

        ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
                        Format: <bufsize>
                        Set hashing buffer size. Default: 4k.

                        ahash performance varies for different chunk sizes on
                        different crypto accelerators. This option can be used
                        to achieve best performance for particular HW.

        init=           [KNL]
                        Format: <full_path>
                        Run specified binary instead of /sbin/init as init

        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
                        for working out where the kernel is dying during

        initcall_blacklist=  [KNL] Do not execute a comma-separated list of
                        initcall functions.  Useful for debugging built-in
                        modules and initcalls.

        initramfs_async= [KNL]
                        Format: <bool>
                        Default: 1
                        This parameter controls whether the initramfs
                        image is unpacked asynchronously, concurrently
                        with devices being probed and
                        initialized. This should normally just work,
                        but as a debugging aid, one can get the
                        historical behaviour of the initramfs
                        unpacking being completed before device_ and
                        late_ initcalls.

        initrd=         [BOOT] Specify the location of the initial ramdisk

        initrdmem=      [KNL] Specify a physical address and size from which to
                        load the initrd. If an initrd is compiled in or
                        specified in the bootparams, it takes priority over this
                        Format: ss[KMG],nn[KMG]
                        Default is 0, 0

        init_on_alloc=  [MM] Fill newly allocated pages and heap objects with
                        Format: 0 | 1
                        Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.

        init_on_free=   [MM] Fill freed pages and heap objects with zeroes.
                        Format: 0 | 1
                        Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.

        init_pkru=      [X86] Specify the default memory protection keys rights
                        register contents for all processes.  0x55555554 by
                        default (disallow access to all but pkey 0).  Can
                        override in debugfs after boot.

        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
                        Format: <irq>

        int_pln_enable  [X86] Enable power limit notification interrupt

                        Format: { "0" | "1" }
                        0 -- basic integrity auditing messages. (Default)
                        1 -- additional integrity auditing messages.

        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
                        Enable intel iommu driver.
                        Disable intel iommu driver.
                igfx_off [Default Off]
                        By default, gfx is mapped as normal device. If a gfx
                        device has a dedicated DMAR unit, the DMAR unit is
                        bypassed by not enabling DMAR with this option. In
                        this case, gfx device will use physical address for
                strict [Default Off]
                        Deprecated, equivalent to iommu.strict=1.
                sp_off [Default Off]
                        By default, super page will be supported if Intel IOMMU
                        has the capability. With this option, super page will
                        not be supported.
                        Enable the Intel IOMMU scalable mode if the hardware
                        advertises that it has support for the scalable mode
                        Disallow use of the Intel IOMMU scalable mode.
                tboot_noforce [Default Off]
                        Do not force the Intel IOMMU enabled under tboot.
                        By default, tboot will force Intel IOMMU on, which
                        could harm performance of some high-throughput
                        devices like 40GBit network cards, even if identity
                        mapping is enabled.
                        Note that using this option lowers the security
                        provided by tboot because it makes the system
                        vulnerable to DMA attacks.

        intel_idle.max_cstate=  [KNL,HW,ACPI,X86]
                        0       disables intel_idle and fall back on acpi_idle.
                        1 to 9  specify maximum depth of C-state.

        intel_pstate=   [X86]
                          Do not enable intel_pstate as the default
                          scaling driver for the supported processors
                          Use intel_pstate driver to bypass the scaling
                          governors layer of cpufreq and provides it own
                          algorithms for p-state selection. There are two
                          P-state selection algorithms provided by
                          intel_pstate in the active mode: powersave and
                          performance.  The way they both operate depends
                          on whether or not the hardware managed P-states
                          (HWP) feature has been enabled in the processor
                          and possibly on the processor model.
                          Use intel_pstate as a scaling driver, but configure it
                          to work with generic cpufreq governors (instead of
                          enabling its internal governor).  This mode cannot be
                          used along with the hardware-managed P-states (HWP)
                          Enable intel_pstate on systems that prohibit it by default
                          in favor of acpi-cpufreq. Forcing the intel_pstate driver
                          instead of acpi-cpufreq may disable platform features, such
                          as thermal controls and power capping, that rely on ACPI
                          P-States information being indicated to OSPM and therefore
                          should be used with caution. This option does not work with
                          processors that aren't supported by the intel_pstate driver
                          or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
                          Do not enable hardware P state control (HWP)
                          if available.
                          Only load intel_pstate on systems which support
                          hardware P state control (HWP) if available.
                          Enforce ACPI _PPC performance limits. If the Fixed ACPI
                          Description Table, specifies preferred power management
                          profile as "Enterprise Server" or "Performance Server",
                          then this feature is turned on by default.
                          Allow per-logical-CPU P-State performance control limits using
                          cpufreq sysfs interface

        intremap=       [X86-64, Intel-IOMMU]
                        on      enable Interrupt Remapping (default)
                        off     disable Interrupt Remapping
                        nosid   disable Source ID checking
                                BIOS x2APIC opt-out request will be ignored
                        nopost  disable Interrupt Posting

        iomem=          Disable strict checking of access to MMIO memory
                strict  regions from userspace.

        iommu=          [X86]
                pt              [X86]
                nopt            [X86]
                nobypass        [PPC/POWERNV]
                        Disable IOMMU bypass, using IOMMU for PCI devices.

        iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
                        Format: { "0" | "1" }
                        0 - Try to allocate a 32-bit DMA address first, before
                          falling back to the full range if needed.
                        1 - Allocate directly from the full usable range,
                          forcing Dual Address Cycle for PCI cards supporting
                          greater than 32-bit addressing.

        iommu.strict=   [ARM64, X86] Configure TLB invalidation behaviour
                        Format: { "0" | "1" }
                        0 - Lazy mode.
                          Request that DMA unmap operations use deferred
                          invalidation of hardware TLBs, for increased
                          throughput at the cost of reduced device isolation.
                          Will fall back to strict mode if not supported by
                          the relevant IOMMU driver.
                        1 - Strict mode.
                          DMA unmap operations invalidate IOMMU hardware TLBs
                        unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
                        Note: on x86, strict mode specified via one of the
                        legacy driver-specific options takes precedence.

                        [ARM64, X86] Configure DMA to bypass the IOMMU by default.
                        Format: { "0" | "1" }
                        0 - Use IOMMU translation for DMA.
                        1 - Bypass the IOMMU for DMA.
                        unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.

        io7=            [HW] IO7 for Marvel-based Alpha systems
                        See comment before marvel_specify_io7 in

        io_delay=       [X86] I/O delay method
                        Standard port 0x80 based delay
                        Alternate port 0xed based delay (needed on some systems)
                        Simple two microseconds delay
                        No delay

        ip=             [IP_PNP]
                        See Documentation/admin-guide/nfs/nfsroot.rst.

        ipcmni_extend   [KNL] Extend the maximum number of unique System V
                        IPC identifiers from 32,768 to 16,777,216.

        irqaffinity=    [SMP] Set the default irq affinity mask
                        The argument is a cpu list, as described above.

                        [ARM, ARM64]
                        Format: <bool>
                        Force the kernel to look for the second 4kB page
                        of a GICv2 controller even if the memory range
                        exposed by the device tree is too small.

                        [ARM, ARM64]
                        Force the kernel to ignore the availability of
                        LPIs (and by consequence ITSs). Intended for system
                        that use the kernel as a bootloader, and thus want
                        to let secondary kernels in charge of setting up

        irqchip.gicv3_pseudo_nmi= [ARM64]
                        Enables support for pseudo-NMIs in the kernel. This
                        requires the kernel to be built with

        irqfixup        [HW]
                        When an interrupt is not handled search all handlers
                        for it. Intended to get systems with badly broken
                        firmware running.

        irqpoll         [HW]
                        When an interrupt is not handled search all handlers
                        for it. Also check all handlers each timer
                        interrupt. Intended to get systems with badly broken
                        firmware running.

        isapnp=         [ISAPNP]
                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>

        isolcpus=       [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
                        [Deprecated - use cpusets instead]
                        Format: [flag-list,]<cpu-list>

                        Specify one or more CPUs to isolate from disturbances
                        specified in the flag list (default: domain):

                          Disable the tick when a single task runs.

                          A residual 1Hz tick is offloaded to workqueues, which you
                          need to affine to housekeeping through the global
                          workqueue's affinity configured via the
                          /sys/devices/virtual/workqueue/cpumask sysfs file, or
                          by using the 'domain' flag described below.

                          NOTE: by default the global workqueue runs on all CPUs,
                          so to protect individual CPUs the 'cpumask' file has to
                          be configured manually after bootup.

                          Isolate from the general SMP balancing and scheduling
                          algorithms. Note that performing domain isolation this way
                          is irreversible: it's not possible to bring back a CPU to
                          the domains once isolated through isolcpus. It's strongly
                          advised to use cpusets instead to disable scheduler load
                          balancing through the "cpuset.sched_load_balance" file.
                          It offers a much more flexible interface where CPUs can
                          move in and out of an isolated set anytime.

                          You can move a process onto or off an "isolated" CPU via
                          the CPU affinity syscalls or cpuset.
                          <cpu number> begins at 0 and the maximum value is
                          "number of CPUs in system - 1".


                          Isolate from being targeted by managed interrupts
                          which have an interrupt mask containing isolated
                          CPUs. The affinity of managed interrupts is
                          handled by the kernel and cannot be changed via
                          the /proc/irq/* interfaces.

                          This isolation is best effort and only effective
                          if the automatically assigned interrupt mask of a
                          device queue contains isolated and housekeeping
                          CPUs. If housekeeping CPUs are online then such
                          interrupts are directed to the housekeeping CPU
                          so that IO submitted on the housekeeping CPU
                          cannot disturb the isolated CPU.

                          If a queue's affinity mask contains only isolated
                          CPUs then this parameter has no effect on the
                          interrupt routing decision, though interrupts are
                          only delivered when tasks running on those
                          isolated CPUs submit IO. IO submitted on
                          housekeeping CPUs has no influence on those

                        The format of <cpu-list> is described above.

        iucv=           [HW,NET]

        ivrs_ioapic     [HW,X86-64]
                        Provide an override to the IOAPIC-ID<->DEVICE-ID
                        mapping provided in the IVRS ACPI table.
                        By default, PCI segment is 0, and can be omitted.

                        For example, to map IOAPIC-ID decimal 10 to
                        PCI segment 0x1 and PCI device 00:14.0,
                        write the parameter as:

                        Deprecated formats:
                        * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
                          write the parameter as:
                        * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
                          PCI device 00:14.0 write the parameter as:

        ivrs_hpet       [HW,X86-64]
                        Provide an override to the HPET-ID<->DEVICE-ID
                        mapping provided in the IVRS ACPI table.
                        By default, PCI segment is 0, and can be omitted.

                        For example, to map HPET-ID decimal 10 to
                        PCI segment 0x1 and PCI device 00:14.0,
                        write the parameter as:

                        Deprecated formats:
                        * To map HPET-ID decimal 0 to PCI device 00:14.0
                          write the parameter as:
                        * To map HPET-ID decimal 10 to PCI segment 0x1 and
                          PCI device 00:14.0 write the parameter as:

        ivrs_acpihid    [HW,X86-64]
                        Provide an override to the ACPI-HID:UID<->DEVICE-ID
                        mapping provided in the IVRS ACPI table.
                        By default, PCI segment is 0, and can be omitted.

                        For example, to map UART-HID:UID AMD0020:0 to
                        PCI segment 0x1 and PCI device ID 00:14.5,
                        write the parameter as:

                        Deprecated formats:
                        * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
                          PCI device ID 00:14.5, write the parameter as:
                        * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
                          PCI device ID 00:14.5, write the parameter as:

        js=             [HW,JOY] Analog joystick
                        See Documentation/input/joydev/joystick.rst.

                        [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
                        report on every invalid memory access. Without this
                        parameter KASAN will print report only for the first
                        invalid access.

        keep_bootcon    [KNL]
                        Do not unregister boot console at start. This is only
                        useful for debugging when something happens in the window
                        between unregistering the boot console and initializing
                        the real console.

        keepinitrd      [HW,ARM]

        kernelcore=     [KNL,X86,IA-64,PPC]
                        Format: nn[KMGTPE] | nn% | "mirror"
                        This parameter specifies the amount of memory usable by
                        the kernel for non-movable allocations.  The requested
                        amount is spread evenly throughout all nodes in the
                        system as ZONE_NORMAL.  The remaining memory is used for
                        movable memory in its own zone, ZONE_MOVABLE.  In the
                        event, a node is too small to have both ZONE_NORMAL and
                        ZONE_MOVABLE, kernelcore memory will take priority and
                        other nodes will have a larger ZONE_MOVABLE.

                        ZONE_MOVABLE is used for the allocation of pages that
                        may be reclaimed or moved by the page migration
                        subsystem.  Note that allocations like PTEs-from-HighMem
                        still use the HighMem zone if it exists, and the Normal
                        zone if it does not.

                        It is possible to specify the exact amount of memory in
                        the form of "nn[KMGTPE]", a percentage of total system
                        memory in the form of "nn%", or "mirror".  If "mirror"
                        option is specified, mirrored (reliable) memory is used
                        for non-movable allocations and remaining memory is used
                        for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
                        are exclusive, so you cannot specify multiple forms.

        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
                        Format: <Controller#>[,poll interval]
                        The controller # is the number of the ehci usb debug
                        port as it is probed via PCI.  The poll interval is
                        optional and is the number seconds in between
                        each poll cycle to the debug port in case you need
                        the functionality for interrupting the kernel with
                        gdb or control-c on the dbgp connection.  When
                        not using this parameter you use sysrq-g to break into
                        the kernel debugger.

        kgdboc=         [KGDB,HW] kgdb over consoles.
                        Requires a tty driver that supports console polling,
                        or a supported polling keyboard driver (non-usb).
                         Serial only format: <serial_device>[,baud]
                         keyboard only format: kbd
                         keyboard and serial format: kbd,<serial_device>[,baud]
                        Optional Kernel mode setting:
                         kms, kbd format: kms,kbd
                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]

        kgdboc_earlycon=        [KGDB,HW]
                        If the boot console provides the ability to read
                        characters and can work in polling mode, you can use
                        this parameter to tell kgdb to use it as a backend
                        until the normal console is registered. Intended to
                        be used together with the kgdboc parameter which
                        specifies the normal console to transition to.

                        The name of the early console should be specified
                        as the value of this parameter. Note that the name of
                        the early console might be different than the tty
                        name passed to kgdboc. It's OK to leave the value
                        blank and the first boot console that implements
                        read() will be picked.

        kgdbwait        [KGDB] Stop kernel execution and enter the
                        kernel debugger at the earliest opportunity.

        kmac=           [MIPS] Korina ethernet MAC address.
                        Configure the RouterBoard 532 series on-chip
                        Ethernet adapter MAC address.

        kmemleak=       [KNL] Boot-time kmemleak enable/disable
                        Valid arguments: on, off
                        Default: on
                        Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
                        the default is off.

                        [FTRACE] Add kprobe events and enable at boot time.
                        The probe-list is a semicolon delimited list of probe
                        definitions. Each definition is same as kprobe_events
                        interface, but the parameters are comma delimited.
                        For example, to add a kprobe event on vfs_read with
                        arg1 and arg2, add to the command line;


                        See also Documentation/trace/kprobetrace.rst "Kernel
                        Boot Parameter" section.

        kpti=           [ARM64] Control page table isolation of user
                        and kernel address spaces.
                        Default: enabled on cores which need mitigation.
                        0: force disabled
                        1: force enabled

        kunit.enable=   [KUNIT] Enable executing KUnit tests. Requires
                        CONFIG_KUNIT to be set to be fully enabled. The
                        default value can be overridden via
                        Default is 1 (enabled)

        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
                        Default is 0 (don't ignore, but inject #GP)

                        [KVM,X86] Controls whether or not KVM will try to
                        proactively split all huge pages during dirty logging.
                        Eager page splitting reduces interruptions to vCPU
                        execution by eliminating the write-protection faults
                        and MMU lock contention that would otherwise be
                        required to split huge pages lazily.

                        VM workloads that rarely perform writes or that write
                        only to a small region of VM memory may benefit from
                        disabling eager page splitting to allow huge pages to
                        still be used for reads.

                        The behavior of eager page splitting depends on whether
                        KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
                        disabled, all huge pages in a memslot will be eagerly
                        split when dirty logging is enabled on that memslot. If
                        enabled, eager page splitting will be performed during
                        the KVM_CLEAR_DIRTY ioctl, and only for the pages being

                        Eager page splitting is only supported when kvm.tdp_mmu=Y.

                        Default is Y (on).

        kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
                                   Default is false (don't support).

                        [KVM] Controls the software workaround for the
                        X86_BUG_ITLB_MULTIHIT bug.
                        force   : Always deploy workaround.
                        off     : Never deploy workaround.
                        auto    : Deploy workaround based on the presence of

                        Default is 'auto'.

                        If the software workaround is enabled for the host,
                        guests do need not to enable it for nested guests.

                        [KVM] Controls how many 4KiB pages are periodically zapped
                        back to huge pages.  0 disables the recovery, otherwise if
                        the value is N KVM will zap 1/Nth of the 4KiB pages every
                        period (see below).  The default is 60.

                        [KVM] Controls the time period at which KVM zaps 4KiB pages
                        back to huge pages. If the value is a non-zero N, KVM will
                        zap a portion (see ratio above) of the pages every N msecs.
                        If the value is 0 (the default), KVM will pick a period based
                        on the ratio, such that a page is zapped after 1 hour on average.

        kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
                        KVM/SVM. Default is 1 (enabled).

        kvm-amd.npt=    [KVM,AMD] Control KVM's use of Nested Page Tables,
                        a.k.a. Two-Dimensional Page Tables. Default is 1
                        (enabled). Disable by KVM if hardware lacks support
                        for NPT.

                        [KVM,ARM] Select one of KVM/arm64's modes of operation.

                        none: Forcefully disable KVM.

                        nvhe: Standard nVHE-based mode, without support for
                              protected guests.

                        protected: nVHE-based mode with support for guests whose
                                   state is kept private from the host.

                        nested: VHE-based mode with support for nested
                                virtualization. Requires at least ARMv8.3

                        Defaults to VHE/nVHE based on hardware support. Setting
                        mode to "protected" will disable kexec and hibernation
                        for the host. "nested" is experimental and should be
                        used with extreme caution.

                        [KVM,ARM] Trap guest accesses to GICv3 group-0
                        system registers

                        [KVM,ARM] Trap guest accesses to GICv3 group-1
                        system registers

                        [KVM,ARM] Trap guest accesses to GICv3 common
                        system registers

                        [KVM,ARM] Allow use of GICv4 for direct injection of

        kvm_cma_resv_ratio=n [PPC]
                        Reserves given percentage from system memory area for
                        contiguous memory allocation for KVM hash pagetable
                        By default it reserves 5% of total system memory.
                        Format: <integer>
                        Default: 5

        kvm-intel.ept=  [KVM,Intel] Control KVM's use of Extended Page Tables,
                        a.k.a. Two-Dimensional Page Tables.  Default is 1
                        (enabled). Disable by KVM if hardware lacks support
                        for EPT.

                        [KVM,Intel] Control whether to emulate invalid guest
                        state. Ignored if kvm-intel.enable_unrestricted_guest=1,
                        as guest state is never invalid for unrestricted
                        guests. This param doesn't apply to nested guests (L2),
                        as KVM never emulates invalid L2 guest state.
                        Default is 1 (enabled).

                        [KVM,Intel] Control KVM's use of FlexPriority feature
                        (TPR shadow). Default is 1 (enabled). Disable by KVM if
                        hardware lacks support for it.

                        [KVM,Intel] Control nested virtualization feature in
                        KVM/VMX. Default is 1 (enabled).

                        [KVM,Intel] Control KVM's use of unrestricted guest
                        feature (virtualized real and unpaged mode). Default
                        is 1 (enabled). Disable by KVM if EPT is disabled or
                        hardware lacks support for it.

        kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault

                        Valid arguments: never, cond, always

                        always: L1D cache flush on every VMENTER.
                        cond:   Flush L1D on VMENTER only when the code between
                                VMEXIT and VMENTER can leak host memory.
                        never:  Disables the mitigation

                        Default is cond (do L1 cache flush in specific instances)

        kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
                        Identification feature (tagged TLBs). Default is 1
                        (enabled). Disable by KVM if hardware lacks support
                        for it.

        l1d_flush=      [X86,INTEL]
                        Control mitigation for L1D based snooping vulnerability.

                        Certain CPUs are vulnerable to an exploit against CPU
                        internal buffers which can forward information to a
                        disclosure gadget under certain conditions.

                        In vulnerable processors, the speculatively
                        forwarded data can be used in a cache side channel
                        attack, to access data to which the attacker does
                        not have direct access.

                        This parameter controls the mitigation. The
                        options are:

                        on         - enable the interface for the mitigation

        l1tf=           [X86] Control mitigation of the L1TF vulnerability on
                              affected CPUs

                        The kernel PTE inversion protection is unconditionally
                        enabled and cannot be disabled.

                                Provides all available mitigations for the
                                L1TF vulnerability. Disables SMT and
                                enables all mitigations in the
                                hypervisors, i.e. unconditional L1D flush.

                                SMT control and L1D flush control via the
                                sysfs interface is still possible after
                                boot.  Hypervisors will issue a warning
                                when the first VM is started in a
                                potentially insecure configuration,
                                i.e. SMT enabled or L1D flush disabled.

                                Same as 'full', but disables SMT and L1D
                                flush runtime control. Implies the
                                'nosmt=force' command line option.
                                (i.e. sysfs control of SMT is disabled.)

                                Leaves SMT enabled and enables the default
                                hypervisor mitigation, i.e. conditional
                                L1D flush.

                                SMT control and L1D flush control via the
                                sysfs interface is still possible after
                                boot.  Hypervisors will issue a warning
                                when the first VM is started in a
                                potentially insecure configuration,
                                i.e. SMT enabled or L1D flush disabled.


                                Disables SMT and enables the default
                                hypervisor mitigation.

                                SMT control and L1D flush control via the
                                sysfs interface is still possible after
                                boot.  Hypervisors will issue a warning
                                when the first VM is started in a
                                potentially insecure configuration,
                                i.e. SMT enabled or L1D flush disabled.

                                Same as 'flush', but hypervisors will not
                                warn when a VM is started in a potentially
                                insecure configuration.

                                Disables hypervisor mitigations and doesn't
                                emit any warnings.
                                It also drops the swap size and available
                                RAM limit restriction on both hypervisor and
                                bare metal.

                        Default is 'flush'.

                        For details see: Documentation/admin-guide/hw-vuln/l1tf.rst

        l2cr=           [PPC]

        l3cr=           [PPC]

        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
                        disabled it.

        lapic=          [X86,APIC] Do not use TSC deadline
                        value for LAPIC timer one-shot implementation. Default
                        back to the programmable timer unit in the LAPIC.
                        Format: notscdeadline

        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
                        in C2 power state.

        libata.dma=     [LIBATA] DMA control
                        libata.dma=0      Disable all PATA and SATA DMA
                        libata.dma=1      PATA and SATA Disk DMA only
                        libata.dma=2      ATAPI (CDROM) DMA only
                        libata.dma=4      Compact Flash DMA only
                        Combinations also work, so libata.dma=3 enables DMA
                        for disks and CDROMs, but not CFs.

        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
                        libata.ignore_hpa=0       keep BIOS limits (default)
                        libata.ignore_hpa=1       ignore limits, using full disk

        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
                        when set.
                        Format: <int>

        libata.force=   [LIBATA] Force configurations.  The format is a comma-
                        separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
                        PORT and DEVICE are decimal numbers matching port, link
                        or device.  Basically, it matches the ATA ID string
                        printed on console by libata.  If the whole ID part is
                        omitted, the last PORT and DEVICE values are used.  If
                        ID hasn't been specified yet, the configuration applies
                        to all ports, links and devices.

                        If only DEVICE is omitted, the parameter applies to
                        the port and all links and devices behind it.  DEVICE
                        number of 0 either selects the first device or the
                        first fan-out link behind PMP device.  It does not
                        select the host link.  DEVICE number of 15 selects the
                        host link and device attached to it.

                        The VAL specifies the configuration to force.  As long
                        as there is no ambiguity, shortcut notation is allowed.
                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
                        The following configurations can be forced.

                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
                          Any ID with matching PORT is used.

                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.

                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
                          udma[/][16,25,33,44,66,100,133] notation is also

                        * nohrst, nosrst, norst: suppress hard, soft and both

                        * rstonce: only attempt one reset during hot-unplug
                          link recovery.

                        * [no]dbdelay: Enable or disable the extra 200ms delay
                          before debouncing a link PHY and device presence

                        * [no]ncq: Turn on or off NCQ.

                        * [no]ncqtrim: Enable or disable queued DSM TRIM.

                        * [no]ncqati: Enable or disable NCQ trim on ATI chipset.

                        * [no]trim: Enable or disable (unqueued) TRIM.

                        * trim_zero: Indicate that TRIM command zeroes data.

                        * max_trim_128m: Set 128M maximum trim size limit.

                        * [no]dma: Turn on or off DMA transfers.

                        * atapi_dmadir: Enable ATAPI DMADIR bridge support.

                        * atapi_mod16_dma: Enable the use of ATAPI DMA for
                          commands that are not a multiple of 16 bytes.

                        * [no]dmalog: Enable or disable the use of the
                          READ LOG DMA EXT command to access logs.

                        * [no]iddevlog: Enable or disable access to the
                          identify device data log.

                        * [no]logdir: Enable or disable access to the general
                          purpose log directory.

                        * max_sec_128: Set transfer size limit to 128 sectors.

                        * max_sec_1024: Set or clear transfer size limit to
                          1024 sectors.

                        * max_sec_lba48: Set or clear transfer size limit to
                          65535 sectors.

                        * [no]lpm: Enable or disable link power management.

                        * [no]setxfer: Indicate if transfer speed mode setting
                          should be skipped.

                        * [no]fua: Disable or enable FUA (Force Unit Access)
                          support for devices supporting this feature.

                        * dump_id: Dump IDENTIFY data.

                        * disable: Disable this device.

                        If there are multiple matching configurations changing
                        the same attribute, the last one is used.

        load_ramdisk=   [RAM] [Deprecated]

        lockd.nlm_grace_period=P  [NFS] Assign grace period.
                        Format: <integer>

        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
                        Format: <integer>

        lockd.nlm_timeout=T     [NFS] Assign timeout value.
                        Format: <integer>

        lockd.nlm_udpport=M     [NFS] Assign UDP port.
                        Format: <integer>

        lockdown=       [SECURITY]
                        { integrity | confidentiality }
                        Enable the kernel lockdown feature. If set to
                        integrity, kernel features that allow userland to
                        modify the running kernel are disabled. If set to
                        confidentiality, kernel features that allow userland
                        to extract confidential information from the kernel
                        are also disabled.

        locktorture.nreaders_stress= [KNL]
                        Set the number of locking read-acquisition kthreads.
                        Defaults to being automatically set based on the
                        number of online CPUs.

        locktorture.nwriters_stress= [KNL]
                        Set the number of locking write-acquisition kthreads.

        locktorture.onoff_holdoff= [KNL]
                        Set time (s) after boot for CPU-hotplug testing.

        locktorture.onoff_interval= [KNL]
                        Set time (s) between CPU-hotplug operations, or
                        zero to disable CPU-hotplug testing.

        locktorture.shuffle_interval= [KNL]
                        Set task-shuffle interval (jiffies).  Shuffling
                        tasks allows some CPUs to go into dyntick-idle
                        mode during the locktorture test.

        locktorture.shutdown_secs= [KNL]
                        Set time (s) after boot system shutdown.  This
                        is useful for hands-off automated testing.

        locktorture.stat_interval= [KNL]
                        Time (s) between statistics printk()s.

        locktorture.stutter= [KNL]
                        Time (s) to stutter testing, for example,
                        specifying five seconds causes the test to run for
                        five seconds, wait for five seconds, and so on.
                        This tests the locking primitive's ability to
                        transition abruptly to and from idle.

        locktorture.torture_type= [KNL]
                        Specify the locking implementation to test.

        locktorture.writer_fifo= [KNL]
                        Run the write-side locktorture kthreads at
                        sched_set_fifo() real-time priority.

        locktorture.verbose= [KNL]
                        Enable additional printk() statements.

        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
                        Format: <irq>

        loglevel=       All Kernel Messages with a loglevel smaller than the
                        console loglevel will be printed to the console. It can
                        also be changed with klogd or other programs. The
                        loglevels are defined as follows:

                        0 (KERN_EMERG)          system is unusable
                        1 (KERN_ALERT)          action must be taken immediately
                        2 (KERN_CRIT)           critical conditions
                        3 (KERN_ERR)            error conditions
                        4 (KERN_WARNING)        warning conditions
                        5 (KERN_NOTICE)         normal but significant condition
                        6 (KERN_INFO)           informational
                        7 (KERN_DEBUG)          debug-level messages

        log_buf_len=n[KMG]      Sets the size of the printk ring buffer,
                        in bytes.  n must be a power of two and greater
                        than the minimal size. The minimal size is defined
                        by LOG_BUF_SHIFT kernel config parameter. There is
                        also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
                        that allows to increase the default size depending on
                        the number of CPUs. See init/Kconfig for more details.

        logo.nologo     [FB] Disables display of the built-in Linux logo.
                        This may be used to provide more screen space for
                        kernel log messages and is useful when debugging
                        kernel boot problems.

        lp=0            [LP]    Specify parallel ports to use, e.g,
        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
        lp=reset                first parallel port). 'lp=0' disables the
        lp=auto                 printer driver. 'lp=reset' (which can be
                                specified in addition to the ports) causes
                                attached printers to be reset. Using
                                lp=port1,port2,... specifies the parallel ports
                                to associate lp devices with, starting with
                                lp0. A port specification may be 'none' to skip
                                that lp device, or a parport name such as
                                'parport0'. Specifying 'lp=auto' instead of a
                                port specification list means that device IDs
                                from each port should be examined, to see if
                                an IEEE 1284-compliant printer is attached; if
                                so, the driver will manage that printer.
                                See also header of drivers/char/lp.c.

        lpj=n           [KNL]
                        Sets loops_per_jiffy to given constant, thus avoiding
                        time-consuming boot-time autodetection (up to 250 ms per
                        CPU). 0 enables autodetection (default). To determine
                        the correct value for your kernel, boot with normal
                        autodetection and see what value is printed. Note that
                        on SMP systems the preset will be applied to all CPUs,
                        which is likely to cause problems if your CPUs need
                        significantly divergent settings. An incorrect value
                        will cause delays in the kernel to be wrong, leading to
                        unpredictable I/O errors and other breakage. Although
                        unlikely, in the extreme case this might damage your

        ltpc=           [NET]
                        Format: <io>,<irq>,<dma>

        lsm.debug       [SECURITY] Enable LSM initialization debugging output.

                        [SECURITY] Choose order of LSM initialization. This
                        overrides CONFIG_LSM, and the "security=" parameter.

        machvec=        [IA-64] Force the use of a particular machine-vector
                        (machvec) in a generic kernel.
                        Example: machvec=hpzx1

        machtype=       [Loongson] Share the same kernel image file between
                        different yeeloong laptops.
                        Example: machtype=lemote-yeeloong-2f-7inch

        max_addr=nn[KMG]        [KNL,BOOT,IA-64] All physical memory greater
                        than or equal to this physical address is ignored.

        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
                        will bring up during bootup.  maxcpus=n : n >= 0 limits
                        the kernel to bring up 'n' processors. Surely after
                        bootup you can bring up the other plugged cpu by executing
                        "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
                        only takes effect during system bootup.
                        While n=0 is a special case, it is equivalent to "nosmp",
                        which also disables the IO APIC.

        max_loop=       [LOOP] The number of loop block devices that get
        (loop.max_loop) unconditionally pre-created at init time. The default
                        number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
                        of statically allocating a predefined number, loop
                        devices can be requested on-demand with the
                        /dev/loop-control interface.

        mce             [X86-32] Machine Check Exception

        mce=option      [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst

        md=             [HW] RAID subsystems devices and level
                        See Documentation/admin-guide/md.rst.

        mdacon=         [MDA]
                        Format: <first>,<last>
                        Specifies range of consoles to be captured by the MDA.

        mds=            [X86,INTEL]
                        Control mitigation for the Micro-architectural Data
                        Sampling (MDS) vulnerability.

                        Certain CPUs are vulnerable to an exploit against CPU
                        internal buffers which can forward information to a
                        disclosure gadget under certain conditions.

                        In vulnerable processors, the speculatively
                        forwarded data can be used in a cache side channel
                        attack, to access data to which the attacker does
                        not have direct access.

                        This parameter controls the MDS mitigation. The
                        options are:

                        full       - Enable MDS mitigation on vulnerable CPUs
                        full,nosmt - Enable MDS mitigation and disable
                                     SMT on vulnerable CPUs
                        off        - Unconditionally disable MDS mitigation

                        On TAA-affected machines, mds=off can be prevented by
                        an active TAA mitigation as both vulnerabilities are
                        mitigated with the same mechanism so in order to disable
                        this mitigation, you need to specify tsx_async_abort=off

                        Not specifying this option is equivalent to

                        For details see: Documentation/admin-guide/hw-vuln/mds.rst

        mem=nn[KMG]     [HEXAGON] Set the memory size.
                        Must be specified, otherwise memory size will be 0.

        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
                        Amount of memory to be used in cases as follows:

                        1 for test;
                        2 when the kernel is not able to see the whole system memory;
                        3 memory that lies after 'mem=' boundary is excluded from
                         the hypervisor, then assigned to KVM guests.
                        4 to limit the memory available for kdump kernel.

                        [ARC,MICROBLAZE] - the limit applies only to low memory,
                        high memory is not affected.

                        [ARM64] - only limits memory covered by the linear
                        mapping. The NOMAP regions are not affected.

                        [X86] Work as limiting max address. Use together
                        with memmap= to avoid physical address space collisions.
                        Without memmap= PCI devices could be placed at addresses
                        belonging to unused RAM.

                        Note that this only takes effects during boot time since
                        in above case 3, memory may need be hot added after boot
                        if system memory of hypervisor is not sufficient.

                        [ARM,MIPS] - override the memory layout reported by
                        Define a memory region of size nn[KMG] starting at
                        Multiple different regions can be specified with
                        multiple mem= parameters on the command line.

        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel

        memblock=debug  [KNL] Enable memblock debug messages.

                        [KNL,SH] Allow user to override the default size for
                        per-device physically contiguous DMA buffers.

                        [KNL] Set the initial state for the memory hotplug
                        onlining policy. If not specified, the default value is
                        set according to the
                        CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
                        See Documentation/admin-guide/mm/memory-hotplug.rst.

        memmap=exactmap [KNL,X86] Enable setting of an exact
                        E820 memory map, as specified by the user.
                        Such memmap=exactmap lines can be constructed based on
                        BIOS output or other requirements. See the memmap=nn@ss
                        option description.

                        [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
                        Region of memory to be used is from ss to ss+nn.
                        If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
                        which limits max address to nn[KMG].
                        Multiple different regions can be specified,
                        comma delimited.

                        [KNL,ACPI] Mark specific memory as ACPI data.
                        Region of memory to be marked is from ss to ss+nn.

                        [KNL,ACPI] Mark specific memory as reserved.
                        Region of memory to be reserved is from ss to ss+nn.
                        Example: Exclude memory from 0x18690000-0x1869ffff
                        Some bootloaders may need an escape character before '$',
                        like Grub2, otherwise '$' and the following number
                        will be eaten.

                        [KNL,X86] Mark specific memory as protected.
                        Region of memory to be used, from ss to ss+nn.
                        The memory region may be marked as e820 type 12 (0xc)
                        and is NVDIMM or ADR memory.

                        [KNL,ACPI] Convert memory within the specified region
                        from <oldtype> to <newtype>. If "-<oldtype>" is left
                        out, the whole region will be marked as <newtype>,
                        even if previously unavailable. If "+<newtype>" is left
                        out, matching memory will be removed. Types are
                        specified as e820 types, e.g., 1 = RAM, 2 = reserved,
                        3 = ACPI, 12 = PRAM.

        memory_corruption_check=0/1 [X86]
                        Some BIOSes seem to corrupt the first 64k of
                        memory when doing things like suspend/resume.
                        Setting this option will scan the memory
                        looking for corruption.  Enabling this will
                        both detect corruption and prevent the kernel
                        from using the memory being corrupted.
                        However, its intended as a diagnostic tool; if
                        repeatable BIOS-originated corruption always
                        affects the same memory, you can use memmap=
                        to prevent the kernel from using that memory.

        memory_corruption_check_size=size [X86]
                        By default it checks for corruption in the low
                        64k, making this memory unavailable for normal
                        use.  Use this parameter to scan for
                        corruption in more or less memory.

        memory_corruption_check_period=seconds [X86]
                        By default it checks for corruption every 60
                        seconds.  Use this parameter to check at some
                        other rate.  0 disables periodic checking.

                        [KNL,X86,ARM] Boolean flag to enable this feature.
                        Format: {on | off (default)}
                        When enabled, runtime hotplugged memory will
                        allocate its internal metadata (struct pages,
                        those vmemmap pages cannot be optimized even
                        if hugetlb_free_vmemmap is enabled) from the
                        hotadded memory which will allow to hotadd a
                        lot of memory without requiring additional
                        memory to do so.
                        This feature is disabled by default because it
                        has some implication on large (e.g. GB)
                        allocations in some configurations (e.g. small
                        memory blocks).
                        The state of the flag can be read in
                        Note that even when enabled, there are a few cases where
                        the feature is not effective.

        memtest=        [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
                        Format: <integer>
                        default : 0 <disable>
                        Specifies the number of memtest passes to be
                        performed. Each pass selects another test
                        pattern from a given set of patterns. Memtest
                        fills the memory with this pattern, validates
                        memory contents and reserves bad memory
                        regions that are detected.

        mem_encrypt=    [X86-64] AMD Secure Memory Encryption (SME) control
                        Valid arguments: on, off
                        Default (depends on kernel configuration option):
                          on  (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
                          off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
                        mem_encrypt=on:         Activate SME
                        mem_encrypt=off:        Do not activate SME

                        Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
                        for details on when memory encryption can be activated.

        mem_sleep_default=      [SUSPEND] Default system suspend mode:
                        s2idle  - Suspend-To-Idle
                        shallow - Power-On Suspend or equivalent (if supported)
                        deep    - Suspend-To-RAM or equivalent (if supported)
                        See Documentation/admin-guide/pm/sleep-states.rst.

        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
                        Multi-Function General Purpose Timers on AMD Geode

        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
                        the BIOS has incorrectly applied a workaround. TinyBIOS
                        version 0.98 is known to be affected, 0.99 fixes the
                        problem by letting the user disable the workaround.

        mga=            [HW,DRM]

        min_addr=nn[KMG]        [KNL,BOOT,IA-64] All physical memory below this
                        physical address is ignored.

        mini2440=       [ARM,HW,KNL]
                        Default: "0tb"
                        MINI2440 configuration specification:
                        0 - The attached screen is the 3.5" TFT
                        1 - The attached screen is the 7" TFT
                        2 - The VGA Shield is attached (1024x768)
                        Leaving out the screen size parameter will not load
                        the TFT driver, and the framebuffer will be left
                        b - Enable backlight. The TFT backlight pin will be
                        linked to the kernel VESA blanking code and a GPIO
                        LED. This parameter is not necessary when using the
                        VGA shield.
                        c - Enable the s3c camera interface.
                        t - Reserved for enabling touchscreen support. The
                        touchscreen support is not enabled in the mainstream
                        kernel as of 2.6.30, a preliminary port can be found
                        in the "bleeding edge" mini2440 support kernel at

                        [X86,PPC,S390,ARM64] Control optional mitigations for
                        CPU vulnerabilities.  This is a set of curated,
                        arch-independent options, each of which is an
                        aggregation of existing arch-specific options.

                                Disable all optional CPU mitigations.  This
                                improves system performance, but it may also
                                expose users to several CPU vulnerabilities.
                                Equivalent to: if nokaslr then kpti=0 [ARM64]
                                               gather_data_sampling=off [X86]
                                               kvm.nx_huge_pages=off [X86]
                                               l1tf=off [X86]
                                               mds=off [X86]
                                               mmio_stale_data=off [X86]
                                               no_entry_flush [PPC]
                                               no_uaccess_flush [PPC]
                                               nobp=0 [S390]
                                               nopti [X86,PPC]
                                               nospectre_bhb [ARM64]
                                               nospectre_v1 [X86,PPC]
                                               nospectre_v2 [X86,PPC,S390,ARM64]
                                               retbleed=off [X86]
                                               spec_store_bypass_disable=off [X86,PPC]
                                               spectre_v2_user=off [X86]
                                               srbds=off [X86,INTEL]
                                               ssbd=force-off [ARM64]
                                               tsx_async_abort=off [X86]

                                               This does not have any effect on
                                               kvm.nx_huge_pages when

                        auto (default)
                                Mitigate all CPU vulnerabilities, but leave SMT
                                enabled, even if it's vulnerable.  This is for
                                users who don't want to be surprised by SMT
                                getting disabled across kernel upgrades, or who
                                have other ways of avoiding SMT-based attacks.
                                Equivalent to: (default behavior)

                                Mitigate all CPU vulnerabilities, disabling SMT
                                if needed.  This is for users who always want to
                                be fully mitigated, even if it means losing SMT.
                                Equivalent to: l1tf=flush,nosmt [X86]
                                               mds=full,nosmt [X86]
                                               tsx_async_abort=full,nosmt [X86]
                                               mmio_stale_data=full,nosmt [X86]
                                               retbleed=auto,nosmt [X86]

                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
                        parameter allows control of the logging verbosity for
                        the additional memory initialisation checks. A value
                        of 0 disables mminit logging and a level of 4 will
                        log everything. Information is printed at KERN_DEBUG
                        so loglevel=8 may also need to be specified.

                        [X86,INTEL] Control mitigation for the Processor
                        MMIO Stale Data vulnerabilities.

                        Processor MMIO Stale Data is a class of
                        vulnerabilities that may expose data after an MMIO
                        operation. Exposed data could originate or end in
                        the same CPU buffers as affected by MDS and TAA.
                        Therefore, similar to MDS and TAA, the mitigation
                        is to clear the affected CPU buffers.

                        This parameter controls the mitigation. The
                        options are:

                        full       - Enable mitigation on vulnerable CPUs

                        full,nosmt - Enable mitigation and disable SMT on
                                     vulnerable CPUs.

                        off        - Unconditionally disable mitigation

                        On MDS or TAA affected machines,
                        mmio_stale_data=off can be prevented by an active
                        MDS or TAA mitigation as these vulnerabilities are
                        mitigated with the same mechanism so in order to
                        disable this mitigation, you need to specify
                        mds=off and tsx_async_abort=off too.

                        Not specifying this option is equivalent to

                        For details see:

        <module>.async_probe[=<bool>] [KNL]
                        If no <bool> value is specified or if the value
                        specified is not a valid <bool>, enable asynchronous
                        probe on this module.  Otherwise, enable/disable
                        asynchronous probe on this module as indicated by the
                        <bool> value. See also: module.async_probe

                        [KNL] When set to true, modules will use async probing
                        by default. To enable/disable async probing for a
                        specific module, use the module specific control that
                        is documented under <module>.async_probe. When both
                        module.async_probe and <module>.async_probe are
                        specified, <module>.async_probe takes precedence for
                        the specific module.

                        [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
                        this means that duplicate request_module() calls will
                        trigger a WARN_ON() instead of a pr_warn(). Note that
                        if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
                        will always be issued and this option does nothing.
                        [KNL] When CONFIG_MODULE_SIG is set, this means that
                        modules without (valid) signatures will fail to load.
                        Note that if CONFIG_MODULE_SIG_FORCE is set, that
                        is always true, so this option does nothing.

        module_blacklist=  [KNL] Do not load a comma-separated list of
                        modules.  Useful for debugging problem modules.

                        [MOUSE] Maximum time between finger touching and
                        leaving touchpad surface for touch to be considered
                        a tap and be reported as a left button click (for
                        touchpads working in absolute mode only).
                        Format: <msecs>
        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
                        reporting absolute coordinates, such as tablets
        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
                        reporting absolute coordinates, such as tablets

        movablecore=    [KNL,X86,IA-64,PPC]
                        Format: nn[KMGTPE] | nn%
                        This parameter is the complement to kernelcore=, it
                        specifies the amount of memory used for migratable
                        allocations.  If both kernelcore and movablecore is
                        specified, then kernelcore will be at *least* the
                        specified value but may be more.  If movablecore on its
                        own is specified, the administrator must be careful
                        that the amount of memory usable for all allocations
                        is not too small.

        movable_node    [KNL] Boot-time switch to make hotplugable memory
                        NUMA nodes to be movable. This means that the memory
                        of such nodes will be usable only for movable
                        allocations which rules out almost all kernel
                        allocations. Use with caution!

        MTD_Partition=  [MTD]
                        Format: <name>,<region-number>,<size>,<offset>

        MTD_Region=     [MTD] Format:

        mtdparts=       [MTD]
                        See drivers/mtd/parsers/cmdlinepart.c

        mtdset=         [ARM]
                        ARM/S3C2412 JIVE boot control

                        See arch/arm/mach-s3c/mach-jive.c

                        [HW] Make the MicroTouch USB driver use raw coordinates
                        ('y', default) or cooked coordinates ('n')

        mtrr=debug      [X86]
                        Enable printing debug information related to MTRR
                        registers at boot time.

        mtrr_chunk_size=nn[KMG] [X86]
                        used for mtrr cleanup. It is largest continuous chunk
                        that could hold holes aka. UC entries.

        mtrr_gran_size=nn[KMG] [X86]
                        Used for mtrr cleanup. It is granularity of mtrr block.
                        Default is 1.
                        Large value could prevent small alignment from
                        using up MTRRs.

        mtrr_spare_reg_nr=n [X86]
                        Format: <integer>
                        Range: 0,7 : spare reg number
                        Default : 1
                        Used for mtrr cleanup. It is spare mtrr entries number.
                        Set to 2 or more if your graphical card needs more.

        multitce=off    [PPC]  This parameter disables the use of the pSeries
                        firmware feature for updating multiple TCE entries
                        at a time.

        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card

        netdev=         [NET] Network devices parameters
                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
                        Note that mem_start is often overloaded to mean
                        something different and driver-specific.
                        This usage is only documented in each driver source
                        file if at all.

                        [NET] Specifies amount of time (in seconds) that
                        netpoll should wait for a carrier. By default netpoll
                        waits 4 seconds.

                        [NETFILTER] Enable connection tracking flow accounting
                        0 to disable accounting
                        1 to enable accounting
                        Default value is 0.

                        [NFS] sets the pathname to the program which is used
                        to update the NFS client cache entries.

                        [NFS] sets the timeout after which an attempt to
                        update a cache entry is deemed to have failed.

                        [NFSv4] set the total number of threads that the
                        NFS client will assign to service NFSv4 callback

                        [NFS] set the TCP port on which the NFSv4 callback
                        channel should listen.

                        [NFS] enable 64-bit inode numbers.
                        If zero, the NFS client will fake up a 32-bit inode
                        number for the readdir() and stat() syscalls instead
                        of returning the full 64-bit number.
                        The default is to return 64-bit inode numbers.

                        [NFS] set the maximum lifetime for idmapper cache

                        [NFSv4.1] Sets the maximum number of session
                        slots the client will assign to the callback
                        channel. This determines the maximum number of
                        callbacks the client will process in parallel for
                        a particular server.

                        [NFSv4.1] Sets the maximum number of session slots
                        the client will attempt to negotiate with the server.
                        This limits the number of simultaneous RPC requests
                        that the client can send to the NFSv4.1 server.
                        Note that there is little point in setting this
                        value higher than the max_tcp_slot_table_limit.

                        [NFSv4] When set to the default of '1', this option
                        ensures that both the RPC level authentication
                        scheme and the NFS level operations agree to use
                        numeric uids/gids if the mount is using the
                        'sec=sys' security flavour. In effect it is
                        disabling idmapping, which can make migration from
                        legacy NFSv2/v3 systems to NFSv4 easier.
                        Servers that do not support this mode of operation
                        will be autodetected by the client, and it will fall
                        back to using the idmapper.
                        To turn off this behaviour, set the value to '0'.

                        [NFS4] Specify an additional fixed unique ident-
                        ification string that NFSv4 clients can insert into
                        their nfs_client_id4 string.  This is typically a
                        UUID that is generated at system install time.

                        [NFSv4] Attempt to recover locks that were lost due
                        to a lease timeout on the server. Please note that
                        doing this risks data corruption, since there are
                        no guarantees that the file will remain unchanged
                        after the locks are lost.
                        If you want to enable the kernel legacy behaviour of
                        attempting to recover these locks, then set this
                        parameter to '1'.
                        The default parameter value of '0' causes the kernel
                        not to attempt recovery of lost locks.

                        [NFSv4.1] Send client implementation identification
                        information in exchange_id requests.
                        If zero, no implementation identification information
                        will be sent.
                        The default is to send the implementation identification

                        [NFSv4.2] Change the rate at which the kernel sends
                        layoutstats to the pNFS metadata server.

                        Setting this to value to 0 causes the kernel to use
                        whatever value is the default set by the layout
                        driver. A non-zero value sets the minimum interval
                        in seconds between layoutstats transmissions.

                        [NFSv4.2] When set to 1, the server will support
                        server-to-server copies for which this server is
                        the destination of the copy.

                        [NFSv4] When set to the default of '1', the NFSv4
                        server will return only numeric uids and gids to
                        clients using auth_sys, and will accept numeric uids
                        and gids from such clients.  This is intended to ease
                        migration from NFSv2/v3.

                        [NFSv4.2] When used as the destination of a
                        server-to-server copy, knfsd temporarily mounts
                        the source server.  It caches the mount in case
                        it will be needed again, and discards it if not
                        used for the number of milliseconds specified by
                        this parameter.

        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
                        See Documentation/admin-guide/nfs/nfsroot.rst.

        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
                        See Documentation/admin-guide/nfs/nfsroot.rst.

        nfsrootdebug    [NFS] enable nfsroot debugging messages.
                        See Documentation/admin-guide/nfs/nfsroot.rst.

        nmi_backtrace.backtrace_idle [KNL]
                        Dump stacks even of idle CPUs in response to an
                        NMI stack-backtrace request.

        nmi_debug=      [KNL,SH] Specify one or more actions to take
                        when a NMI is triggered.
                        Format: [state][,regs][,debounce][,die]

        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
                        Format: [panic,][nopanic,][num]
                        Valid num: 0 or 1
                        0 - turn hardlockup detector in nmi_watchdog off
                        1 - turn hardlockup detector in nmi_watchdog on
                        When panic is specified, panic when an NMI watchdog
                        timeout occurs (or 'nopanic' to not panic on an NMI
                        watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
                        To disable both hard and soft lockup detectors,
                        please see 'nowatchdog'.
                        This is useful when you use a panic=... timeout and
                        need the box quickly up again.

                        These settings can be accessed at runtime via
                        the nmi_watchdog and hardlockup_panic sysctls.

        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
                        emulation library even if a 387 maths coprocessor
                        is present.

        no4lvl          [RISCV] Disable 4-level and 5-level paging modes. Forces
                        kernel to use 3-level paging instead.

        no5lvl          [X86-64,RISCV] Disable 5-level paging mode. Forces
                        kernel to use 4-level paging instead.

        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
                        caches in the slab allocator.  Saves per-node memory,
                        but will impact performance.

        noalign         [KNL,ARM]

        noaltinstr      [S390] Disables alternative instructions patching
                        (CPU alternatives feature).

        noapic          [SMP,APIC] Tells the kernel to not make use of any
                        IOAPICs that may be present in the system.

        noautogroup     Disable scheduler automatic task group creation.

        nocache         [ARM]

                        [HW] Never suspend the console
                        Disable suspending of consoles during suspend and
                        hibernate operations.  Once disabled, debugging
                        messages can reach various consoles while the rest
                        of the system is being put to sleep (ie, while
                        debugging driver suspend/resume hooks).  This may
                        not work reliably with all consoles, but is known
                        to work with serial and VGA consoles.
                        To facilitate more flexible debugging, we also add
                        console_suspend, a printk module parameter to control
                        it. Users could use console_suspend (usually
                        /sys/module/printk/parameters/console_suspend) to
                        turn on/off it dynamically.

                        [KNL] Disable object debugging

        nodsp           [SH] Disable hardware DSP at boot time.

        noefi           Disable EFI runtime services support.

        no_entry_flush  [PPC] Don't flush the L1-D cache when entering the kernel.

        noexec          [IA-64]

        noexec32        [X86-64]
                        This affects only 32-bit executables.
                        noexec32=on: enable non-executable mappings (default)
                                read doesn't imply executable mappings
                        noexec32=off: disable non-executable mappings
                                read implies executable mappings

        no_file_caps    Tells the kernel not to honor file capabilities.  The
                        only way then for a file to be executed with privilege
                        is to be setuid root or executed by root.

        nofpu           [MIPS,SH] Disable hardware FPU at boot time.

        nofsgsbase      [X86] Disables FSGSBASE instructions.

        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
                        register save and restore. The kernel will only save
                        legacy floating-point registers on task switch.

        nohalt          [IA-64] Tells the kernel not to use the power saving
                        function PAL_HALT_LIGHT when idle. This increases
                        power-consumption. On the positive side, it reduces
                        interrupt wake-up latency, which may improve performance
                        in certain environments such as networked servers or
                        real-time systems.

                        Force pointers printed to the console or buffers to be
                        unhashed.  By default, when a pointer is printed via %p
                        format string, that pointer is "hashed", i.e. obscured
                        by hashing the pointer value.  This is a security feature
                        that hides actual kernel addresses from unprivileged
                        users, but it also makes debugging the kernel more
                        difficult since unequal pointers can no longer be
                        compared.  However, if this command-line option is
                        specified, then all normal pointers will have their true
                        value printed. This option should only be specified when
                        debugging the kernel.  Please do not use on production

        nohibernate     [HIBERNATION] Disable hibernation and resume.

        nohlt           [ARM,ARM64,MICROBLAZE,MIPS,PPC,SH] Forces the kernel to
                        busy wait in do_idle() and not use the arch_cpu_idle()
                        implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
                        to be effective. This is useful on platforms where the
                        sleep(SH) or wfi(ARM,ARM64) instructions do not work
                        correctly or when doing power measurements to evaluate
                        the impact of the sleep instructions. This is also
                        useful when using JTAG debugger.

        nohugeiomap     [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.

        nohugevmalloc   [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.

        nohz=           [KNL] Boottime enable/disable dynamic ticks
                        Valid arguments: on, off
                        Default: on

        nohz_full=      [KNL,BOOT,SMP,ISOL]
                        The argument is a cpu list, as described above.
                        In kernels built with CONFIG_NO_HZ_FULL=y, set
                        the specified list of CPUs whose tick will be stopped
                        whenever possible. The boot CPU will be forced outside
                        the range to maintain the timekeeping.  Any CPUs
                        in this list will have their RCU callbacks offloaded,
                        just as if they had also been called out in the
                        rcu_nocbs= boot parameter.

                        Note that this argument takes precedence over
                        the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.

        noinitrd        [RAM] Tells the kernel not to load any configured
                        initial RAM disk.

        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
                        [Deprecated - use intremap=off]

        nointroute      [IA-64]

        noinvpcid       [X86] Disable the INVPCID cpu feature.

        noiotrap        [SH] Disables trapped I/O port accesses.

        noirqdebug      [X86-32] Disables the code which attempts to detect and
                        disable unhandled interrupt sources.

        noisapnp        [ISAPNP] Disables ISA PnP code.

        nojitter        [IA-64] Disables jitter checking for ITC timers.

        nokaslr         [KNL]
                        When CONFIG_RANDOMIZE_BASE is set, this disables
                        kernel and module base offset ASLR (Address Space
                        Layout Randomization).

        no-kvmapf       [X86,KVM] Disable paravirtualized asynchronous page
                        fault handling.

        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver

        nolapic         [X86-32,APIC] Do not enable or use the local APIC.

        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.

        nomca           [IA-64] Disable machine check abort handling

        nomce           [X86-32] Disable Machine Check Exception

        nomfgpt         [X86-32] Disable Multi-Function General Purpose
                        Timer usage (for AMD Geode machines).

        nomodeset       Disable kernel modesetting. Most systems' firmware
                        sets up a display mode and provides framebuffer memory
                        for output. With nomodeset, DRM and fbdev drivers will
                        not load if they could possibly displace the pre-
                        initialized output. Only the system framebuffer will
                        be available for use. The respective drivers will not
                        perform display-mode changes or accelerated rendering.

                        Useful as error fallback, or for testing and debugging.

        nomodule        Disable module load

        nonmi_ipi       [X86] Disable using NMI IPIs during panic/reboot to
                        shutdown the other cpus.  Instead use the REBOOT_VECTOR

        nopat           [X86] Disable PAT (page attribute table extension of
                        pagetables) support.

        nopcid          [X86-64] Disable the PCID cpu feature.

        nopku           [X86] Disable Memory Protection Keys CPU feature found
                        in some Intel CPUs.

        nopti           [X86-64]
                        Equivalent to pti=off

        nopv=           [X86,XEN,KVM,HYPER_V,VMWARE]
                        Disables the PV optimizations forcing the guest to run
                        as generic guest with no PV drivers. Currently support
                        XEN HVM, KVM, HYPER_V and VMWARE guest.

        nopvspin        [X86,XEN,KVM]
                        Disables the qspinlock slow path using PV optimizations
                        which allow the hypervisor to 'idle' the guest on lock

        norandmaps      Don't use address space randomization.  Equivalent to
                        echo 0 > /proc/sys/kernel/randomize_va_space

        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
                        with UP alternatives

        noresume        [SWSUSP] Disables resume and restores original swap

        nosbagart       [IA-64]

        no-scroll       [VGA] Disables scrollback.
                        This is required for the Braillex ib80-piezo Braille
                        reader made by F.H. Papenmeier (Germany).

        nosgx           [X86-64,SGX] Disables Intel SGX kernel support.

        nosmap          [PPC]
                        Disable SMAP (Supervisor Mode Access Prevention)
                        even if it is supported by processor.

        nosmep          [PPC64s]
                        Disable SMEP (Supervisor Mode Execution Prevention)
                        even if it is supported by processor.

        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
                        and disable the IO APIC.  legacy for "maxcpus=0".

        nosmt           [KNL,MIPS,PPC,S390] Disable symmetric multithreading (SMT).
                        Equivalent to smt=1.

                        [KNL,X86,PPC] Disable symmetric multithreading (SMT).
                        nosmt=force: Force disable SMT, cannot be undone
                                     via the sysfs control file.

        nosoftlockup    [KNL] Disable the soft-lockup detector.

                        [HW] Disable all mitigations for the Speculative Store Bypass vulnerability

        nospectre_bhb   [ARM64] Disable all mitigations for Spectre-BHB (branch
                        history injection) vulnerability. System may allow data leaks
                        with this option.

        nospectre_v1    [X86,PPC] Disable mitigations for Spectre Variant 1
                        (bounds check bypass). With this option data leaks are
                        possible in the system.

        nospectre_v2    [X86,PPC_E500,ARM64] Disable all mitigations for
                        the Spectre variant 2 (indirect branch prediction)
                        vulnerability. System may allow data leaks with this

        no-steal-acc    [X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
                        steal time accounting. steal time is computed, but
                        won't influence scheduler behaviour

        nosync          [HW,M68K] Disables sync negotiation for all devices.

        no_timer_check  [X86,APIC] Disables the code which tests for
                        broken timer IRQ sources.

                        [PPC] Don't flush the L1-D cache after accessing user data.

        novmcoredd      [KNL,KDUMP]
                        Disable device dump. Device dump allows drivers to
                        append dump data to vmcore so you can collect driver
                        specified debug info.  Drivers can append the data
                        without any limit and this data is stored in memory,
                        so this may cause significant memory stress.  Disabling
                        device dump can help save memory but the driver debug
                        data will be no longer available.  This parameter
                        is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
                        is set.

                        [X86,PV_OPS] Disable paravirtualized VMware scheduler
                        clock and use the default one.

        nowatchdog      [KNL] Disable both lockup detectors, i.e.
                        soft-lockup and NMI watchdog (hard-lockup).

        nowb            [ARM]

        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.

                        NOTE: this parameter will be ignored on systems with the
                        LEGACY_XAPIC_DISABLED bit set in the
                        IA32_XAPIC_DISABLE_STATUS MSR.

        noxsave         [BUGS=X86] Disables x86 extended register state save
                        and restore using xsave. The kernel will fallback to
                        enabling legacy floating-point and sse state.

        noxsaveopt      [X86] Disables xsaveopt used in saving x86 extended
                        register states. The kernel will fall back to use
                        xsave to save the states. By using this parameter,
                        performance of saving the states is degraded because
                        xsave doesn't support modified optimization while
                        xsaveopt supports it on xsaveopt enabled systems.

        noxsaves        [X86] Disables xsaves and xrstors used in saving and
                        restoring x86 extended register state in compacted
                        form of xsave area. The kernel will fall back to use
                        xsaveopt and xrstor to save and restore the states
                        in standard form of xsave area. By using this
                        parameter, xsave area per process might occupy more
                        memory on xsaves enabled systems.

        nps_mtm_hs_ctr= [KNL,ARC]
                        This parameter sets the maximum duration, in
                        cycles, each HW thread of the CTOP can run
                        without interruptions, before HW switches it.
                        The actual maximum duration is 16 times this
                        parameter's value.
                        Format: integer between 1 and 255
                        Default: 255

        nptcg=          [IA-64] Override max number of concurrent global TLB
                        purges which is reported from either PAL_VM_SUMMARY or
                        SAL PALO.

        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
                        could support.  nr_cpus=n : n >= 1 limits the kernel to
                        support 'n' processors. It could be larger than the
                        number of already plugged CPU during bootup, later in
                        runtime you can physically add extra cpu until it reaches
                        n. So during boot up some boot time memory for per-cpu
                        variables need be pre-allocated for later physical cpu
                        hot plugging.

        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.

        numa=off        [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
                        set up a single NUMA node spanning all memory.

        numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
                        NUMA balancing.
                        Allowed values are enable and disable

        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
                        'node', 'default' can be specified
                        This can be set from sysctl after boot.
                        See Documentation/admin-guide/sysctl/vm.rst for details.

        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
                        See Documentation/core-api/debugging-via-ohci1394.rst for more

        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
                        Rather than timing out after 20 ms if an EC
                        command is not properly ACKed, override the length
                        of the timeout.  We have interrupts disabled while
                        waiting for the ACK, so if this is set too high
                        interrupts *may* be lost!

        omap_mux=       [OMAP] Override bootloader pin multiplexing.
                        Format: <mux_mode0.mode_name=value>...
                        For example, to override I2C bus2:

        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration

                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]

                        boundary - index of last SLC block on Flex-OneNAND.
                                   The remaining blocks are configured as MLC blocks.
                        lock     - Configure if Flex-OneNAND boundary should be locked.
                                   Once locked, the boundary cannot be changed.
                                   1 indicates lock status, 0 indicates unlock status.

        oops=panic      Always panic on oopses. Default is to just kill the
                        process, but there is a small probability of
                        deadlocking the machine.
                        This will also cause panics on machine check exceptions.
                        Useful together with panic=30 to trigger a reboot.

                        [KNL] Boolean flag to control whether the page allocator
                        should randomize its free lists. The randomization may
                        be automatically enabled if the kernel detects it is
                        running on a platform with a direct-mapped memory-side
                        cache, and this parameter can be used to
                        override/disable that behavior. The state of the flag
                        can be read from sysfs at:

        page_owner=     [KNL] Boot-time page_owner enabling option.
                        Storage of the information about who allocated
                        each page is disabled in default. With this switch,
                        we can turn it on.
                        on: enable the feature

        page_poison=    [KNL] Boot-time parameter changing the state of
                        poisoning on the buddy allocator, available with
                        off: turn off poisoning (default)
                        on: turn on poisoning

                        [KNL] Minimal page reporting order
                        Format: <integer>
                        Adjust the minimal page reporting order. The page
                        reporting is disabled when it exceeds MAX_ORDER.

        panic=          [KNL] Kernel behaviour on panic: delay <timeout>
                        timeout > 0: seconds before rebooting
                        timeout = 0: wait forever
                        timeout < 0: reboot immediately
                        Format: <timeout>

        panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
                        Format: <hex>[,nousertaint]
                        Hexadecimal bitmask representing the set of TAINT flags
                        that will cause the kernel to panic when add_taint() is
                        called with any of the flags in this set.
                        The optional switch "nousertaint" can be utilized to
                        prevent userspace forced crashes by writing to sysctl
                        /proc/sys/kernel/tainted any flagset matching with the
                        bitmask set on panic_on_taint.
                        See Documentation/admin-guide/tainted-kernels.rst for
                        extra details on the taint flags that users can pick
                        to compose the bitmask to assign to panic_on_taint.

        panic_on_warn=1 panic() instead of WARN().  Useful to cause kdump
                        on a WARN().

        panic_print=    Bitmask for printing system info when panic happens.
                        User can chose combination of the following bits:
                        bit 0: print all tasks info
                        bit 1: print system memory info
                        bit 2: print timer info
                        bit 3: print locks info if CONFIG_LOCKDEP is on
                        bit 4: print ftrace buffer
                        bit 5: print all printk messages in buffer
                        bit 6: print all CPUs backtrace (if available in the arch)
                        *Be aware* that this option may print a _lot_ of lines,
                        so there are risks of losing older messages in the log.
                        Use this option carefully, maybe worth to setup a
                        bigger log buffer with "log_buf_len" along with this.

        parkbd.port=    [HW] Parallel port number the keyboard adapter is
                        connected to, default is 0.
                        Format: <parport#>
        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
                        0 for XT, 1 for AT (default is AT).
                        Format: <mode>

        parport=        [HW,PPT] Specify parallel ports. 0 disables.
                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
                        Use 'auto' to force the driver to use any
                        IRQ/DMA settings detected (the default is to
                        ignore detected IRQ/DMA settings because of
                        possible conflicts). You can specify the base
                        address, IRQ, and DMA settings; IRQ and DMA
                        should be numbers, or 'auto' (for using detected
                        settings on that particular port), or 'nofifo'
                        (to avoid using a FIFO even if it is detected).
                        Parallel ports are assigned in the order they
                        are specified on the command line, starting
                        with parport0.

        parport_init_mode=      [HW,PPT]
                        Configure VIA parallel port to operate in
                        a specific mode. This is necessary on Pegasos
                        computer where firmware has no options for setting
                        up parallel port mode and sets it to spp.
                        Currently this function knows 686a and 8231 chips.
                        Format: [spp|ps2|epp|ecp|ecpepp]

        pata_legacy.all=        [HW,LIBATA]
                        Format: <int>
                        Set to non-zero to probe primary and secondary ISA
                        port ranges on PCI systems where no PCI PATA device
                        has been found at either range.  Disabled by default.

        pata_legacy.autospeed=  [HW,LIBATA]
                        Format: <int>
                        Set to non-zero if a chip is present that snoops speed
                        changes.  Disabled by default.

        pata_legacy.ht6560a=    [HW,LIBATA]
                        Format: <int>
                        Set to 1, 2, or 3 for HT 6560A on the primary channel,
                        the secondary channel, or both channels respectively.
                        Disabled by default.

        pata_legacy.ht6560b=    [HW,LIBATA]
                        Format: <int>
                        Set to 1, 2, or 3 for HT 6560B on the primary channel,
                        the secondary channel, or both channels respectively.
                        Disabled by default.

        pata_legacy.iordy_mask= [HW,LIBATA]
                        Format: <int>
                        IORDY enable mask.  Set individual bits to allow IORDY
                        for the respective channel.  Bit 0 is for the first
                        legacy channel handled by this driver, bit 1 is for
                        the second channel, and so on.  The sequence will often
                        correspond to the primary legacy channel, the secondary
                        legacy channel, and so on, but the handling of a PCI
                        bus and the use of other driver options may interfere
                        with the sequence.  By default IORDY is allowed across
                        all channels.

        pata_legacy.opti82c46x= [HW,LIBATA]
                        Format: <int>
                        Set to 1, 2, or 3 for Opti 82c611A on the primary
                        channel, the secondary channel, or both channels
                        respectively.  Disabled by default.

        pata_legacy.opti82c611a=        [HW,LIBATA]
                        Format: <int>
                        Set to 1, 2, or 3 for Opti 82c465MV on the primary
                        channel, the secondary channel, or both channels
                        respectively.  Disabled by default.

        pata_legacy.pio_mask=   [HW,LIBATA]
                        Format: <int>
                        PIO mode mask for autospeed devices.  Set individual
                        bits to allow the use of the respective PIO modes.
                        Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
                        All modes allowed by default.

        pata_legacy.probe_all=  [HW,LIBATA]
                        Format: <int>
                        Set to non-zero to probe tertiary and further ISA
                        port ranges on PCI systems.  Disabled by default.

        pata_legacy.probe_mask= [HW,LIBATA]
                        Format: <int>
                        Probe mask for legacy ISA PATA ports.  Depending on
                        platform configuration and the use of other driver
                        options up to 6 legacy ports are supported: 0x1f0,
                        0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
                        of individual ports can be disabled by setting the
                        corresponding bits in the mask to 1.  Bit 0 is for
                        the first port in the list above (0x1f0), and so on.
                        By default all supported ports are probed.

        pata_legacy.qdi=        [HW,LIBATA]
                        Format: <int>
                        Set to non-zero to probe QDI controllers.  By default
                        set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.

        pata_legacy.winbond=    [HW,LIBATA]
                        Format: <int>
                        Set to non-zero to probe Winbond controllers.  Use
                        the standard I/O port (0x130) if 1, otherwise the
                        value given is the I/O port to use (typically 0x1b0).
                        By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
                        0 otherwise.

        pata_platform.pio_mask= [HW,LIBATA]
                        Format: <int>
                        Supported PIO mode mask.  Set individual bits to allow
                        the use of the respective PIO modes.  Bit 0 is for
                        mode 0, bit 1 is for mode 1, and so on.  Mode 0 only
                        allowed by default.

                        Halt all CPUs after the first oops has been printed for
                        the specified number of seconds.  This is to be used if
                        your oopses keep scrolling off the screen.

        pcbit=          [HW,ISDN]

        pci=option[,option...]  [PCI] various PCI subsystem options.

                                Some options herein operate on a specific device
                                or a set of devices (<pci_dev>). These are
                                specified in one of the following formats:


                                Note: the first format specifies a PCI
                                bus/device/function address which may change
                                if new hardware is inserted, if motherboard
                                firmware changes, or due to changes caused
                                by other kernel parameters. If the
                                domain is left unspecified, it is
                                taken to be zero. Optionally, a path
                                to a device through multiple device/function
                                addresses can be specified after the base
                                address (this is more robust against
                                renumbering issues).  The second format
                                selects devices using IDs from the
                                configuration space which may match multiple
                                devices in the system.

                earlydump       dump PCI config space before the kernel
                                changes anything
                off             [X86] don't probe for the PCI bus
                bios            [X86-32] force use of PCI BIOS, don't access
                                the hardware directly. Use this if your machine
                                has a non-standard PCI host bridge.
                nobios          [X86-32] disallow use of PCI BIOS, only direct
                                hardware access methods are allowed. Use this
                                if you experience crashes upon bootup and you
                                suspect they are caused by the BIOS.
                conf1           [X86] Force use of PCI Configuration Access
                                Mechanism 1 (config address in IO port 0xCF8,
                                data in IO port 0xCFC, both 32-bit).
                conf2           [X86] Force use of PCI Configuration Access
                                Mechanism 2 (IO port 0xCF8 is an 8-bit port for
                                the function, IO port 0xCFA, also 8-bit, sets
                                bus number. The config space is then accessed
                                through ports 0xC000-0xCFFF).
                                See for more info
                                on the configuration access mechanisms.
                noaer           [PCIE] If the PCIEAER kernel config parameter is
                                enabled, this kernel boot option can be used to
                                disable the use of PCIE advanced error reporting.
                nodomains       [PCI] Disable support for multiple PCI
                                root domains (aka PCI segments, in ACPI-speak).
                nommconf        [X86] Disable use of MMCONFIG for PCI
                check_enable_amd_mmconf [X86] check for and enable
                                properly configured MMIO access to PCI
                                config space on AMD family 10h CPU
                nomsi           [MSI] If the PCI_MSI kernel config parameter is
                                enabled, this kernel boot option can be used to
                                disable the use of MSI interrupts system-wide.
                noioapicquirk   [APIC] Disable all boot interrupt quirks.
                                Safety option to keep boot IRQs enabled. This
                                should never be necessary.
                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
                                primary IO-APIC for bridges that cannot disable
                                boot IRQs. This fixes a source of spurious IRQs
                                when the system masks IRQs.
                noioapicreroute [APIC] Disable workaround that uses the
                                boot IRQ equivalent of an IRQ that connects to
                                a chipset where boot IRQs cannot be disabled.
                                The opposite of ioapicreroute.
                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
                                routing table. These calls are known to be buggy
                                on several machines and they hang the machine
                                when used, but on other computers it's the only
                                way to get the interrupt routing table. Try
                                this option if the kernel is unable to allocate
                                IRQs or discover secondary PCI buses on your
                rom             [X86] Assign address space to expansion ROMs.
                                Use with caution as certain devices share
                                address decoders between ROMs and other
                norom           [X86] Do not assign address space to
                                expansion ROMs that do not already have
                                BIOS assigned address ranges.
                nobar           [X86] Do not assign address space to the
                                BARs that weren't assigned by the BIOS.
                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
                                assigned automatically to PCI devices. You can
                                make the kernel exclude IRQs of your ISA cards
                                this way.
                pirqaddr=0xAAAAA        [X86] Specify the physical address
                                of the PIRQ table (normally generated
                                by the BIOS) if it is outside the
                                F0000h-100000h range.
                lastbus=N       [X86] Scan all buses thru bus #N. Can be
                                useful if the kernel is unable to find your
                                secondary buses and you want to tell it
                                explicitly which ones they are.
                assign-busses   [X86] Always assign all PCI bus
                                numbers ourselves, overriding
                                whatever the firmware may have done.
                usepirqmask     [X86] Honor the possible IRQ mask stored
                                in the BIOS $PIR table. This is needed on
                                some systems with broken BIOSes, notably
                                some HP Pavilion N5400 and Omnibook XE3
                                notebooks. This will have no effect if ACPI
                                IRQ routing is enabled.
                noacpi          [X86] Do not use ACPI for IRQ routing
                                or for PCI scanning.
                use_crs         [X86] Use PCI host bridge window information
                                from ACPI.  On BIOSes from 2008 or later, this
                                is enabled by default.  If you need to use this,
                                please report a bug.
                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
                                If you need to use this, please report a bug.
                use_e820        [X86] Use E820 reservations to exclude parts of
                                PCI host bridge windows. This is a workaround
                                for BIOS defects in host bridge _CRS methods.
                                If you need to use this, please report a bug to
                no_e820         [X86] Ignore E820 reservations for PCI host
                                bridge windows. This is the default on modern
                                hardware. If you need to use this, please report
                                a bug to <>.
                routeirq        Do IRQ routing for all PCI devices.
                                This is normally done in pci_enable_device(),
                                so this option is a temporary workaround
                                for broken drivers that don't call it.
                skip_isa_align  [X86] do not align io start addr, so can
                                handle more pci cards
                noearly         [X86] Don't do any early type 1 scanning.
                                This might help on some broken boards which
                                machine check when some devices' config space
                                is read. But various workarounds are disabled
                                and some IOMMU drivers will not work.
                bfsort          Sort PCI devices into breadth-first order.
                                This sorting is done to get a device
                                order compatible with older (<= 2.4) kernels.
                nobfsort        Don't sort PCI devices into breadth-first order.
                pcie_bus_tune_off       Disable PCIe MPS (Max Payload Size)
                                tuning and use the BIOS-configured MPS defaults.
                pcie_bus_safe   Set every device's MPS to the largest value
                                supported by all devices below the root complex.
                pcie_bus_perf   Set device MPS to the largest allowable MPS
                                based on its parent bus. Also set MRRS (Max
                                Read Request Size) to the largest supported
                                value (no larger than the MPS that the device
                                or bus can support) for best performance.
                pcie_bus_peer2peer      Set every device's MPS to 128B, which
                                every device is guaranteed to support. This
                                configuration allows peer-to-peer DMA between
                                any pair of devices, possibly at the cost of
                                reduced performance.  This also guarantees
                                that hot-added devices will work.
                cbiosize=nn[KMG]        The fixed amount of bus space which is
                                reserved for the CardBus bridge's IO window.
                                The default value is 256 bytes.
                cbmemsize=nn[KMG]       The fixed amount of bus space which is
                                reserved for the CardBus bridge's memory
                                window. The default value is 64 megabytes.
                                [<order of align>@]<pci_dev>[; ...]
                                Specifies alignment and device to reassign
                                aligned memory resources. How to
                                specify the device is described above.
                                If <order of align> is not specified,
                                PAGE_SIZE is used as alignment.
                                A PCI-PCI bridge can be specified if resource
                                windows need to be expanded.
                                To specify the alignment for several
                                instances of a device, the PCI vendor,
                                device, subvendor, and subdevice may be
                                specified, e.g., 12@pci:8086:9c22:103c:198f
                                for 4096-byte alignment.
                ecrc=           Enable/disable PCIe ECRC (transaction layer
                                end-to-end CRC checking). Only effective if
                                OS has native AER control (either granted by
                                ACPI _OSC or forced via "pcie_ports=native")
                                bios: Use BIOS/firmware settings. This is the
                                the default.
                                off: Turn ECRC off
                                on: Turn ECRC on.
                hpiosize=nn[KMG]        The fixed amount of bus space which is
                                reserved for hotplug bridge's IO window.
                                Default size is 256 bytes.
                hpmmiosize=nn[KMG]      The fixed amount of bus space which is
                                reserved for hotplug bridge's MMIO window.
                                Default size is 2 megabytes.
                hpmmioprefsize=nn[KMG]  The fixed amount of bus space which is
                                reserved for hotplug bridge's MMIO_PREF window.
                                Default size is 2 megabytes.
                hpmemsize=nn[KMG]       The fixed amount of bus space which is
                                reserved for hotplug bridge's MMIO and
                                MMIO_PREF window.
                                Default size is 2 megabytes.
                hpbussize=nn    The minimum amount of additional bus numbers
                                reserved for buses below a hotplug bridge.
                                Default is 1.
                realloc=        Enable/disable reallocating PCI bridge resources
                                if allocations done by BIOS are too small to
                                accommodate resources required by all child
                                off: Turn realloc off
                                on: Turn realloc on
                realloc         same as realloc=on
                noari           do not use PCIe ARI.
                noats           [PCIE, Intel-IOMMU, AMD-IOMMU]
                                do not use PCIe ATS (and IOMMU device IOTLB).
                pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
                                only look for one device below a PCIe downstream
                big_root_window Try to add a big 64bit memory window to the PCIe
                                root complex on AMD CPUs. Some GFX hardware
                                can resize a BAR to allow access to all VRAM.
                                Adding the window is slightly risky (it may
                                conflict with unreported devices), so this
                                taints the kernel.
                disable_acs_redir=<pci_dev>[; ...]
                                Specify one or more PCI devices (in the format
                                specified above) separated by semicolons.
                                Each device specified will have the PCI ACS
                                redirect capabilities forced off which will
                                allow P2P traffic between devices through
                                bridges without forcing it upstream. Note:
                                this removes isolation between devices and
                                may put more devices in an IOMMU group.
                force_floating  [S390] Force usage of floating interrupts.
                nomio           [S390] Do not use MIO instructions.
                norid           [S390] ignore the RID field and force use of
                                one PCI domain per PCI function

        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
                off     Disable ASPM.
                force   Enable ASPM even on devices that claim not to support it.
                        WARNING: Forcing ASPM on may cause system lockups.

        pcie_ports=     [PCIE] PCIe port services handling:
                native  Use native PCIe services (PME, AER, DPC, PCIe hotplug)
                        even if the platform doesn't give the OS permission to
                        use them.  This may cause conflicts if the platform
                        also tries to use these services.
                dpc-native      Use native PCIe service for DPC only.  May
                                cause conflicts if firmware uses AER or DPC.
                compat  Disable native PCIe services (PME, AER, DPC, PCIe

        pcie_port_pm=   [PCIE] PCIe port power management handling:
                off     Disable power management of all PCIe ports
                force   Forcibly enable power management of all PCIe ports

        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
                nomsi   Do not use MSI for native PCIe PME signaling (this makes
                        all PCIe root ports use INTx for all services).

        pcmv=           [HW,PCMCIA] BadgePAD 4

                        Keep all power-domains already enabled by bootloader on,
                        even if no driver has claimed them. This is useful
                        for debug and development, but should not be
                        needed on a platform with proper driver support.

        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
                        boot time.
                        Format: { 0 | 1 }
                        See arch/parisc/kernel/pdc_chassis.c

        percpu_alloc=   Select which percpu first chunk allocator to use.
                        Currently supported values are "embed" and "page".
                        Archs may support subset or none of the selections.
                        See comments in mm/percpu.c for details on each
                        allocator.  This parameter is primarily for debugging
                        and performance comparison.

        pirq=           [SMP,APIC] Manual mp-table setup
                        See Documentation/arch/x86/i386/IO-APIC.rst.

        plip=           [PPT,NET] Parallel port network link
                        Format: { parport<nr> | timid | 0 }
                        See also Documentation/admin-guide/parport.rst.

        pmtmr=          [X86] Manual setup of pmtmr I/O Port.
                        Override pmtimer IOPort with a hex value.
                        e.g. pmtmr=0x508

        pmu_override=   [PPC] Override the PMU.
                        This option takes over the PMU facility, so it is no
                        longer usable by perf. Setting this option starts the
                        PMU counters by setting MMCR0 to 0 (the FC bit is
                        cleared). If a number is given, then MMCR1 is set to
                        that number, otherwise (e.g., 'pmu_override=on'), MMCR1
                        remains 0.

        pm_debug_messages       [SUSPEND,KNL]
                        Enable suspend/resume debug messages during boot up.

        pnp.debug=1     [PNP]
                        Enable PNP debug messages (depends on the
                        CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
                        via /sys/module/pnp/parameters/debug.  We always show
                        current resource usage; turning this on also shows
                        possible settings and some assignment information.

        pnpacpi=        [ACPI]
                        { off }

        pnpbios=        [ISAPNP]
                        { on | off | curr | res | no-curr | no-res }

                        [ISAPNP] Exclude IRQs for the autoconfiguration

                        [ISAPNP] Exclude DMAs for the autoconfiguration

        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
                        Ranges are in pairs (I/O port base and size).

                        [ISAPNP] Exclude memory regions for the
                        Ranges are in pairs (memory base and size).

        ports=          [IP_VS_FTP] IPVS ftp helper module
                        Default is 21.
                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
                        may be specified.
                        Format: <port>,<port>....

        powersave=off   [PPC] This option disables power saving features.
                        It specifically disables cpuidle and sets the
                        platform machine description specific power_save
                        function to NULL. On Idle the CPU just reduces
                        execution priority.

                        [PPC] This option catches any kernel floating point,
                        Altivec, VSX and SPE outside of regions specifically
                        allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
                        There is some performance impact when enabling this.

        ppc_tm=         [PPC]
                        Format: {"off"}
                        Disable Hardware Transactional Memory

        preempt=        [KNL]
                        Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
                        none - Limited to cond_resched() calls
                        voluntary - Limited to cond_resched() and might_sleep() calls
                        full - Any section that isn't explicitly preempt disabled
                               can be preempted anytime.

                        [KNL] debug: print fatal signals

                        If enabled, warn about various signal handling
                        related application anomalies: too many signals,
                        too many POSIX.1 timers, fatal signals causing a
                        coredump - etc.

                        If you hit the warning due to signal overflow,
                        you might want to try "ulimit -i unlimited".

                        default: off.

                        Trigger kmsg_dump for cases other than kernel oops or
                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
                        default: disabled

                        Disable console loglevel raise on oops, panic
                        or lockdep-detected issues (only if lock debug is on).
                        With an exception to setups with low baudrate on
                        serial console, keeping this 0 is a good choice
                        in order to provide more debug information.
                        Format: <bool>
                        default: 0 (auto_verbose is enabled)

                        Control writing to /dev/kmsg.
                        on - unlimited logging to /dev/kmsg from userspace
                        off - logging to /dev/kmsg disabled
                        ratelimit - ratelimit the logging
                        Default: ratelimit

        printk.time=    Show timing data prefixed to each printk message line
                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

        processor.max_cstate=   [HW,ACPI]
                        Limit processor to maximum C-state
                        max_cstate=9 overrides any DMI blacklist limit.

        processor.nocst [HW,ACPI]
                        Ignore the _CST method to determine C-states,
                        instead using the legacy FADT method

        profile=        [KNL] Enable kernel profiling via /proc/profile
                        Format: [<profiletype>,]<number>
                        Param: <profiletype>: "schedule", "sleep", or "kvm"
                                [defaults to kernel profiling]
                        Param: "schedule" - profile schedule points.
                        Param: "sleep" - profile D-state sleeping (millisecs).
                                Requires CONFIG_SCHEDSTATS
                        Param: "kvm" - profile VM exits.
                        Param: <number> - step/bucket size as a power of 2 for
                                statistical time based profiling.

        prompt_ramdisk= [RAM] [Deprecated]

        prot_virt=      [S390] enable hosting protected virtual machines
                        isolated from the hypervisor (if hardware supports
                        Format: <bool>

        psi=            [KNL] Enable or disable pressure stall information
                        Format: <bool>

        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
                        probe for; one of (bare|imps|exps|lifebook|any).
        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
                        per second.
        psmouse.resetafter=     [HW,MOUSE]
                        Try to reset the device after so many bad packets
                        (0 = never).
                        [HW,MOUSE] Set desired mouse resolution, in dpi.
                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
                        0 = disabled, 1 = enabled (default).

        pstore.backend= Specify the name of the pstore backend to use

        pti=            [X86-64] Control Page Table Isolation of user and
                        kernel address spaces.  Disabling this feature
                        removes hardening, but improves performance of
                        system calls and interrupts.

                        on   - unconditionally enable
                        off  - unconditionally disable
                        auto - kernel detects whether your CPU model is
                               vulnerable to issues that PTI mitigates

                        Not specifying this option is equivalent to pti=auto.

                        [KNL] Number of legacy pty's. Overwrites compiled-in
                        default number.

        quiet           [KNL] Disable most log messages

        r128=           [HW,DRM]

        radix_hcall_invalidate=on  [PPC/PSERIES]
                        Disable RADIX GTSE feature and use hcall for TLB

        raid=           [HW,RAID]
                        See Documentation/admin-guide/md.rst.

        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
                        See Documentation/admin-guide/blockdev/ramdisk.rst.

        ramdisk_start=  [RAM] RAM disk image start address

                        [KNL] Disable trusting the use of the CPU's
                        random number generator (if available) to
                        initialize the kernel's RNG.

                        [KNL] Disable trusting the use of the a seed
                        passed by the bootloader (if available) to
                        initialize the kernel's RNG.

                        [KNL] Enable or disable kernel stack offset
                        randomization, which provides roughly 5 bits of
                        entropy, frustrating memory corruption attacks
                        that depend on stack address determinism or
                        cross-syscall address exposures. This is only
                        available on architectures that have defined
                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
                        Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.

        ras=option[,option,...] [KNL] RAS-specific options

                cec_disable     [X86]
                                Disable the Correctable Errors Collector,
                                see CONFIG_RAS_CEC help text.

                        [KNL] The optional argument is a cpu list,
                        as described above.

                        In kernels built with CONFIG_RCU_NOCB_CPU=y,
                        enable the no-callback CPU mode, which prevents
                        such CPUs' callbacks from being invoked in
                        softirq context.  Invocation of such CPUs' RCU
                        callbacks will instead be offloaded to "rcuox/N"
                        kthreads created for that purpose, where "x" is
                        "p" for RCU-preempt, "s" for RCU-sched, and "g"
                        for the kthreads that mediate grace periods; and
                        "N" is the CPU number. This reduces OS jitter on
                        the offloaded CPUs, which can be useful for HPC
                        and real-time workloads.  It can also improve
                        energy efficiency for asymmetric multiprocessors.

                        If a cpulist is passed as an argument, the specified
                        list of CPUs is set to no-callback mode from boot.

                        Otherwise, if the '=' sign and the cpulist
                        arguments are omitted, no CPU will be set to
                        no-callback mode from boot but the mode may be
                        toggled at runtime via cpusets.

                        Note that this argument takes precedence over
                        the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.

        rcu_nocb_poll   [KNL]
                        Rather than requiring that offloaded CPUs
                        (specified by rcu_nocbs= above) explicitly
                        awaken the corresponding "rcuoN" kthreads,
                        make these kthreads poll for callbacks.
                        This improves the real-time response for the
                        offloaded CPUs by relieving them of the need to
                        wake up the corresponding kthread, but degrades
                        energy efficiency by requiring that the kthreads
                        periodically wake up to do the polling.

        rcutree.blimit= [KNL]
                        Set maximum number of finished RCU callbacks to
                        process in one batch.

        rcutree.dump_tree=      [KNL]
                        Dump the structure of the rcu_node combining tree
                        out at early boot.  This is used for diagnostic
                        purposes, to verify correct tree setup.

        rcutree.gp_cleanup_delay=       [KNL]
                        Set the number of jiffies to delay each step of
                        RCU grace-period cleanup.

        rcutree.gp_init_delay=  [KNL]
                        Set the number of jiffies to delay each step of
                        RCU grace-period initialization.

        rcutree.gp_preinit_delay=       [KNL]
                        Set the number of jiffies to delay each step of
                        RCU grace-period pre-initialization, that is,
                        the propagation of recent CPU-hotplug changes up
                        the rcu_node combining tree.

        rcutree.jiffies_till_first_fqs= [KNL]
                        Set delay from grace-period initialization to
                        first attempt to force quiescent states.
                        Units are jiffies, minimum value is zero,
                        and maximum value is HZ.

        rcutree.jiffies_till_next_fqs= [KNL]
                        Set delay between subsequent attempts to force
                        quiescent states.  Units are jiffies, minimum
                        value is one, and maximum value is HZ.

        rcutree.jiffies_till_sched_qs= [KNL]
                        Set required age in jiffies for a
                        given grace period before RCU starts
                        soliciting quiescent-state help from
                        rcu_note_context_switch() and cond_resched().
                        If not specified, the kernel will calculate
                        a value based on the most recent settings
                        of rcutree.jiffies_till_first_fqs
                        and rcutree.jiffies_till_next_fqs.
                        This calculated value may be viewed in
                        rcutree.jiffies_to_sched_qs.  Any attempt to set
                        rcutree.jiffies_to_sched_qs will be cheerfully

        rcutree.kthread_prio=    [KNL,BOOT]
                        Set the SCHED_FIFO priority of the RCU per-CPU
                        kthreads (rcuc/N). This value is also used for
                        the priority of the RCU boost threads (rcub/N)
                        and for the RCU grace-period kthreads (rcu_bh,
                        rcu_preempt, and rcu_sched). If RCU_BOOST is
                        set, valid values are 1-99 and the default is 1
                        (the least-favored priority).  Otherwise, when
                        RCU_BOOST is not set, valid values are 0-99 and
                        the default is zero (non-realtime operation).
                        When RCU_NOCB_CPU is set, also adjust the
                        priority of NOCB callback kthreads.

        rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
                        On callback-offloaded (rcu_nocbs) CPUs,
                        RCU reduces the lock contention that would
                        otherwise be caused by callback floods through
                        use of the ->nocb_bypass list.  However, in the
                        common non-flooded case, RCU queues directly to
                        the main ->cblist in order to avoid the extra
                        overhead of the ->nocb_bypass list and its lock.
                        But if there are too many callbacks queued during
                        a single jiffy, RCU pre-queues the callbacks into
                        the ->nocb_bypass queue.  The definition of "too
                        many" is supplied by this kernel boot parameter.

        rcutree.qhimark= [KNL]
                        Set threshold of queued RCU callbacks beyond which
                        batch limiting is disabled.

        rcutree.qlowmark= [KNL]
                        Set threshold of queued RCU callbacks below which
                        batch limiting is re-enabled.

        rcutree.qovld= [KNL]
                        Set threshold of queued RCU callbacks beyond which
                        RCU's force-quiescent-state scan will aggressively
                        enlist help from cond_resched() and sched IPIs to
                        help CPUs more quickly reach quiescent states.
                        Set to less than zero to make this be set based
                        on rcutree.qhimark at boot time and to zero to
                        disable more aggressive help enlistment.

        rcutree.rcu_delay_page_cache_fill_msec= [KNL]
                        Set the page-cache refill delay (in milliseconds)
                        in response to low-memory conditions.  The range
                        of permitted values is in the range 0:100000.

        rcutree.rcu_divisor= [KNL]
                        Set the shift-right count to use to compute
                        the callback-invocation batch limit bl from
                        the number of callbacks queued on this CPU.
                        The result will be bounded below by the value of
                        the rcutree.blimit kernel parameter.  Every bl
                        callbacks, the softirq handler will exit in
                        order to allow the CPU to do other work.

                        Please note that this callback-invocation batch
                        limit applies only to non-offloaded callback
                        invocation.  Offloaded callbacks are instead
                        invoked in the context of an rcuoc kthread, which
                        scheduler will preempt as it does any other task.

        rcutree.rcu_fanout_exact= [KNL]
                        Disable autobalancing of the rcu_node combining
                        tree.  This is used by rcutorture, and might
                        possibly be useful for architectures having high
                        cache-to-cache transfer latencies.

        rcutree.rcu_fanout_leaf= [KNL]
                        Change the number of CPUs assigned to each
                        leaf rcu_node structure.  Useful for very
                        large systems, which will choose the value 64,
                        and for NUMA systems with large remote-access
                        latencies, which will choose a value aligned
                        with the appropriate hardware boundaries.

        rcutree.rcu_min_cached_objs= [KNL]
                        Minimum number of objects which are cached and
                        maintained per one CPU. Object size is equal
                        to PAGE_SIZE. The cache allows to reduce the
                        pressure to page allocator, also it makes the
                        whole algorithm to behave better in low memory

        rcutree.rcu_nocb_gp_stride= [KNL]
                        Set the number of NOCB callback kthreads in
                        each group, which defaults to the square root
                        of the number of CPUs.  Larger numbers reduce
                        the wakeup overhead on the global grace-period
                        kthread, but increases that same overhead on
                        each group's NOCB grace-period kthread.

        rcutree.rcu_kick_kthreads= [KNL]
                        Cause the grace-period kthread to get an extra
                        wake_up() if it sleeps three times longer than
                        it should at force-quiescent-state time.
                        This wake_up() will be accompanied by a
                        WARN_ONCE() splat and an ftrace_dump().

        rcutree.rcu_resched_ns= [KNL]
                        Limit the time spend invoking a batch of RCU
                        callbacks to the specified number of nanoseconds.
                        By default, this limit is checked only once
                        every 32 callbacks in order to limit the pain
                        inflicted by local_clock() overhead.

        rcutree.rcu_unlock_delay= [KNL]
                        In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
                        this specifies an rcu_read_unlock()-time delay
                        in microseconds.  This defaults to zero.
                        Larger delays increase the probability of
                        catching RCU pointer leaks, that is, buggy use
                        of RCU-protected pointers after the relevant
                        rcu_read_unlock() has completed.

        rcutree.sysrq_rcu= [KNL]
                        Commandeer a sysrq key to dump out Tree RCU's
                        rcu_node tree with an eye towards determining
                        why a new grace period has not yet started.

        rcutree.use_softirq=    [KNL]
                        If set to zero, move all RCU_SOFTIRQ processing to
                        per-CPU rcuc kthreads.  Defaults to a non-zero
                        value, meaning that RCU_SOFTIRQ is used by default.
                        Specify rcutree.use_softirq=0 to use rcuc kthreads.

                        But note that CONFIG_PREEMPT_RT=y kernels disable
                        this kernel boot parameter, forcibly setting it
                        to zero.

        rcuscale.gp_async= [KNL]
                        Measure performance of asynchronous
                        grace-period primitives such as call_rcu().

        rcuscale.gp_async_max= [KNL]
                        Specify the maximum number of outstanding
                        callbacks per writer thread.  When a writer
                        thread exceeds this limit, it invokes the
                        corresponding flavor of rcu_barrier() to allow
                        previously posted callbacks to drain.

        rcuscale.gp_exp= [KNL]
                        Measure performance of expedited synchronous
                        grace-period primitives.

        rcuscale.holdoff= [KNL]
                        Set test-start holdoff period.  The purpose of
                        this parameter is to delay the start of the
                        test until boot completes in order to avoid

        rcuscale.kfree_by_call_rcu= [KNL]
                        In kernels built with CONFIG_RCU_LAZY=y, test
                        call_rcu() instead of kfree_rcu().

        rcuscale.kfree_mult= [KNL]
                        Instead of allocating an object of size kfree_obj,
                        allocate one of kfree_mult * sizeof(kfree_obj).
                        Defaults to 1.

        rcuscale.kfree_rcu_test= [KNL]
                        Set to measure performance of kfree_rcu() flooding.

        rcuscale.kfree_rcu_test_double= [KNL]
                        Test the double-argument variant of kfree_rcu().
                        If this parameter has the same value as
                        rcuscale.kfree_rcu_test_single, both the single-
                        and double-argument variants are tested.

        rcuscale.kfree_rcu_test_single= [KNL]
                        Test the single-argument variant of kfree_rcu().
                        If this parameter has the same value as
                        rcuscale.kfree_rcu_test_double, both the single-
                        and double-argument variants are tested.

        rcuscale.kfree_nthreads= [KNL]
                        The number of threads running loops of kfree_rcu().

        rcuscale.kfree_alloc_num= [KNL]
                        Number of allocations and frees done in an iteration.

        rcuscale.kfree_loops= [KNL]
                        Number of loops doing rcuscale.kfree_alloc_num number
                        of allocations and frees.

        rcuscale.minruntime= [KNL]
                        Set the minimum test run time in seconds.  This
                        does not affect the data-collection interval,
                        but instead allows better measurement of things
                        like CPU consumption.

        rcuscale.nreaders= [KNL]
                        Set number of RCU readers.  The value -1 selects
                        N, where N is the number of CPUs.  A value
                        "n" less than -1 selects N-n+1, where N is again
                        the number of CPUs.  For example, -2 selects N
                        (the number of CPUs), -3 selects N+1, and so on.
                        A value of "n" less than or equal to -N selects
                        a single reader.

        rcuscale.nwriters= [KNL]
                        Set number of RCU writers.  The values operate
                        the same as for rcuscale.nreaders.
                        N, where N is the number of CPUs

        rcuscale.scale_type= [KNL]
                        Specify the RCU implementation to test.

        rcuscale.shutdown= [KNL]
                        Shut the system down after performance tests
                        complete.  This is useful for hands-off automated

        rcuscale.verbose= [KNL]
                        Enable additional printk() statements.

        rcuscale.writer_holdoff= [KNL]
                        Write-side holdoff between grace periods,
                        in microseconds.  The default of zero says
                        no holdoff.

        rcuscale.writer_holdoff_jiffies= [KNL]
                        Additional write-side holdoff between grace
                        periods, but in jiffies.  The default of zero
                        says no holdoff.

        rcutorture.fqs_duration= [KNL]
                        Set duration of force_quiescent_state bursts
                        in microseconds.

        rcutorture.fqs_holdoff= [KNL]
                        Set holdoff time within force_quiescent_state bursts
                        in microseconds.

        rcutorture.fqs_stutter= [KNL]
                        Set wait time between force_quiescent_state bursts
                        in seconds.

        rcutorture.fwd_progress= [KNL]
                        Specifies the number of kthreads to be used
                        for  RCU grace-period forward-progress testing
                        for the types of RCU supporting this notion.
                        Defaults to 1 kthread, values less than zero or
                        greater than the number of CPUs cause the number
                        of CPUs to be used.

        rcutorture.fwd_progress_div= [KNL]
                        Specify the fraction of a CPU-stall-warning
                        period to do tight-loop forward-progress testing.

        rcutorture.fwd_progress_holdoff= [KNL]
                        Number of seconds to wait between successive
                        forward-progress tests.

        rcutorture.fwd_progress_need_resched= [KNL]
                        Enclose cond_resched() calls within checks for
                        need_resched() during tight-loop forward-progress

        rcutorture.gp_cond= [KNL]
                        Use conditional/asynchronous update-side
                        primitives, if available.

        rcutorture.gp_exp= [KNL]
                        Use expedited update-side primitives, if available.

        rcutorture.gp_normal= [KNL]
                        Use normal (non-expedited) asynchronous
                        update-side primitives, if available.

        rcutorture.gp_sync= [KNL]
                        Use normal (non-expedited) synchronous
                        update-side primitives, if available.  If all
                        of rcutorture.gp_cond=, rcutorture.gp_exp=,
                        rcutorture.gp_normal=, and rcutorture.gp_sync=
                        are zero, rcutorture acts as if is interpreted
                        they are all non-zero.

        rcutorture.irqreader= [KNL]
                        Run RCU readers from irq handlers, or, more
                        accurately, from a timer handler.  Not all RCU
                        flavors take kindly to this sort of thing.

        rcutorture.leakpointer= [KNL]
                        Leak an RCU-protected pointer out of the reader.
                        This can of course result in splats, and is
                        intended to test the ability of things like
                        CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
                        such leaks.

        rcutorture.n_barrier_cbs= [KNL]
                        Set callbacks/threads for rcu_barrier() testing.

        rcutorture.nfakewriters= [KNL]
                        Set number of concurrent RCU writers.  These just
                        stress RCU, they don't participate in the actual
                        test, hence the "fake".

        rcutorture.nocbs_nthreads= [KNL]
                        Set number of RCU callback-offload togglers.
                        Zero (the default) disables toggling.

        rcutorture.nocbs_toggle= [KNL]
                        Set the delay in milliseconds between successive
                        callback-offload toggling attempts.

        rcutorture.nreaders= [KNL]
                        Set number of RCU readers.  The value -1 selects
                        N-1, where N is the number of CPUs.  A value
                        "n" less than -1 selects N-n-2, where N is again
                        the number of CPUs.  For example, -2 selects N
                        (the number of CPUs), -3 selects N+1, and so on.

        rcutorture.object_debug= [KNL]
                        Enable debug-object double-call_rcu() testing.

        rcutorture.onoff_holdoff= [KNL]
                        Set time (s) after boot for CPU-hotplug testing.

        rcutorture.onoff_interval= [KNL]
                        Set time (jiffies) between CPU-hotplug operations,
                        or zero to disable CPU-hotplug testing.

        rcutorture.read_exit= [KNL]
                        Set the number of read-then-exit kthreads used
                        to test the interaction of RCU updaters and
                        task-exit processing.

        rcutorture.read_exit_burst= [KNL]
                        The number of times in a given read-then-exit
                        episode that a set of read-then-exit kthreads
                        is spawned.

        rcutorture.read_exit_delay= [KNL]
                        The delay, in seconds, between successive
                        read-then-exit testing episodes.

        rcutorture.shuffle_interval= [KNL]
                        Set task-shuffle interval (s).  Shuffling tasks
                        allows some CPUs to go into dyntick-idle mode
                        during the rcutorture test.

        rcutorture.shutdown_secs= [KNL]
                        Set time (s) after boot system shutdown.  This
                        is useful for hands-off automated testing.

        rcutorture.stall_cpu= [KNL]
                        Duration of CPU stall (s) to test RCU CPU stall
                        warnings, zero to disable.

        rcutorture.stall_cpu_block= [KNL]
                        Sleep while stalling if set.  This will result
                        in warnings from preemptible RCU in addition to
                        any other stall-related activity.  Note that
                        in kernels built with CONFIG_PREEMPTION=n and
                        CONFIG_PREEMPT_COUNT=y, this parameter will
                        cause the CPU to pass through a quiescent state.
                        Given CONFIG_PREEMPTION=n, this will suppress
                        RCU CPU stall warnings, but will instead result
                        in scheduling-while-atomic splats.

                        Use of this module parameter results in splats.

        rcutorture.stall_cpu_holdoff= [KNL]
                        Time to wait (s) after boot before inducing stall.

        rcutorture.stall_cpu_irqsoff= [KNL]
                        Disable interrupts while stalling if set.

        rcutorture.stall_gp_kthread= [KNL]
                        Duration (s) of forced sleep within RCU
                        grace-period kthread to test RCU CPU stall
                        warnings, zero to disable.  If both stall_cpu
                        and stall_gp_kthread are specified, the
                        kthread is starved first, then the CPU.

        rcutorture.stat_interval= [KNL]
                        Time (s) between statistics printk()s.

        rcutorture.stutter= [KNL]
                        Time (s) to stutter testing, for example, specifying
                        five seconds causes the test to run for five seconds,
                        wait for five seconds, and so on.  This tests RCU's
                        ability to transition abruptly to and from idle.

        rcutorture.test_boost= [KNL]
                        Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
                        "Maybe" means test if the RCU implementation
                        under test support RCU priority boosting.

        rcutorture.test_boost_duration= [KNL]
                        Duration (s) of each individual boost test.

        rcutorture.test_boost_interval= [KNL]
                        Interval (s) between each boost test.

        rcutorture.test_no_idle_hz= [KNL]
                        Test RCU's dyntick-idle handling.  See also the
                        rcutorture.shuffle_interval parameter.

        rcutorture.torture_type= [KNL]
                        Specify the RCU implementation to test.

        rcutorture.verbose= [KNL]
                        Enable additional printk() statements.

        rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
                        Dump ftrace buffer after reporting RCU CPU
                        stall warning.

        rcupdate.rcu_cpu_stall_suppress= [KNL]
                        Suppress RCU CPU stall warning messages.

        rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
                        Suppress RCU CPU stall warning messages and
                        rcutorture writer stall warnings that occur
                        during early boot, that is, during the time
                        before the init task is spawned.

        rcupdate.rcu_cpu_stall_timeout= [KNL]
                        Set timeout for RCU CPU stall warning messages.
                        The value is in seconds and the maximum allowed
                        value is 300 seconds.

        rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
                        Set timeout for expedited RCU CPU stall warning
                        messages.  The value is in milliseconds
                        and the maximum allowed value is 21000
                        milliseconds. Please note that this value is
                        adjusted to an arch timer tick resolution.
                        Setting this to zero causes the value from
                        rcupdate.rcu_cpu_stall_timeout to be used (after
                        conversion from seconds to milliseconds).

        rcupdate.rcu_cpu_stall_cputime= [KNL]
                        Provide statistics on the cputime and count of
                        interrupts and tasks during the sampling period. For
                        multiple continuous RCU stalls, all sampling periods
                        begin at half of the first RCU stall timeout.

        rcupdate.rcu_exp_stall_task_details= [KNL]
                        Print stack dumps of any tasks blocking the
                        current expedited RCU grace period during an
                        expedited RCU CPU stall warning.

        rcupdate.rcu_expedited= [KNL]
                        Use expedited grace-period primitives, for
                        example, synchronize_rcu_expedited() instead
                        of synchronize_rcu().  This reduces latency,
                        but can increase CPU utilization, degrade
                        real-time latency, and degrade energy efficiency.
                        No effect on CONFIG_TINY_RCU kernels.

        rcupdate.rcu_normal= [KNL]
                        Use only normal grace-period primitives,
                        for example, synchronize_rcu() instead of
                        synchronize_rcu_expedited().  This improves
                        real-time latency, CPU utilization, and
                        energy efficiency, but can expose users to
                        increased grace-period latency.  This parameter
                        overrides rcupdate.rcu_expedited.  No effect on
                        CONFIG_TINY_RCU kernels.

        rcupdate.rcu_normal_after_boot= [KNL]
                        Once boot has completed (that is, after
                        rcu_end_inkernel_boot() has been invoked), use
                        only normal grace-period primitives.  No effect
                        on CONFIG_TINY_RCU kernels.

                        But note that CONFIG_PREEMPT_RT=y kernels enables
                        this kernel boot parameter, forcibly setting
                        it to the value one, that is, converting any
                        post-boot attempt at an expedited RCU grace
                        period to instead use normal non-expedited
                        grace-period processing.

        rcupdate.rcu_task_collapse_lim= [KNL]
                        Set the maximum number of callbacks present
                        at the beginning of a grace period that allows
                        the RCU Tasks flavors to collapse back to using
                        a single callback queue.  This switching only
                        occurs when rcupdate.rcu_task_enqueue_lim is
                        set to the default value of -1.

        rcupdate.rcu_task_contend_lim= [KNL]
                        Set the minimum number of callback-queuing-time
                        lock-contention events per jiffy required to
                        cause the RCU Tasks flavors to switch to per-CPU
                        callback queuing.  This switching only occurs
                        when rcupdate.rcu_task_enqueue_lim is set to
                        the default value of -1.

        rcupdate.rcu_task_enqueue_lim= [KNL]
                        Set the number of callback queues to use for the
                        RCU Tasks family of RCU flavors.  The default
                        of -1 allows this to be automatically (and
                        dynamically) adjusted.  This parameter is intended
                        for use in testing.

        rcupdate.rcu_task_ipi_delay= [KNL]
                        Set time in jiffies during which RCU tasks will
                        avoid sending IPIs, starting with the beginning
                        of a given grace period.  Setting a large
                        number avoids disturbing real-time workloads,
                        but lengthens grace periods.

        rcupdate.rcu_task_lazy_lim= [KNL]
                        Number of callbacks on a given CPU that will
                        cancel laziness on that CPU.  Use -1 to disable
                        cancellation of laziness, but be advised that
                        doing so increases the danger of OOM due to
                        callback flooding.

        rcupdate.rcu_task_stall_info= [KNL]
                        Set initial timeout in jiffies for RCU task stall
                        informational messages, which give some indication
                        of the problem for those not patient enough to
                        wait for ten minutes.  Informational messages are
                        only printed prior to the stall-warning message
                        for a given grace period. Disable with a value
                        less than or equal to zero.  Defaults to ten
                        seconds.  A change in value does not take effect
                        until the beginning of the next grace period.

        rcupdate.rcu_task_stall_info_mult= [KNL]
                        Multiplier for time interval between successive
                        RCU task stall informational messages for a given
                        RCU tasks grace period.  This value is clamped
                        to one through ten, inclusive.  It defaults to
                        the value three, so that the first informational
                        message is printed 10 seconds into the grace
                        period, the second at 40 seconds, the third at
                        160 seconds, and then the stall warning at 600
                        seconds would prevent a fourth at 640 seconds.

        rcupdate.rcu_task_stall_timeout= [KNL]
                        Set timeout in jiffies for RCU task stall
                        warning messages.  Disable with a value less
                        than or equal to zero.  Defaults to ten minutes.
                        A change in value does not take effect until
                        the beginning of the next grace period.

        rcupdate.rcu_tasks_lazy_ms= [KNL]
                        Set timeout in milliseconds RCU Tasks asynchronous
                        callback batching for call_rcu_tasks().
                        A negative value will take the default.  A value
                        of zero will disable batching.  Batching is
                        always disabled for synchronize_rcu_tasks().

        rcupdate.rcu_tasks_rude_lazy_ms= [KNL]
                        Set timeout in milliseconds RCU Tasks
                        Rude asynchronous callback batching for
                        call_rcu_tasks_rude().  A negative value
                        will take the default.  A value of zero will
                        disable batching.  Batching is always disabled
                        for synchronize_rcu_tasks_rude().

        rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
                        Set timeout in milliseconds RCU Tasks
                        Trace asynchronous callback batching for
                        call_rcu_tasks_trace().  A negative value
                        will take the default.  A value of zero will
                        disable batching.  Batching is always disabled
                        for synchronize_rcu_tasks_trace().

        rcupdate.rcu_self_test= [KNL]
                        Run the RCU early boot self tests

        rdinit=         [KNL]
                        Format: <full_path>
                        Run specified binary instead of /init from the ramdisk,
                        used for early userspace startup. See initrd.

        rdrand=         [X86]
                        force - Override the decision by the kernel to hide the
                                advertisement of RDRAND support (this affects
                                certain AMD processors because of buggy BIOS
                                support, specifically around the suspend/resume

        rdt=            [HW,X86,RDT]
                        Turn on/off individual RDT features. List is:
                        cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
                        mba, smba, bmec.
                        E.g. to turn on cmt and turn off mba use:

        reboot=         [KNL]
                        Format (x86 or x86_64):
                                [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
                                [[,]s[mp]#### \
                                [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
                        Where reboot_mode is one of warm (soft) or cold (hard) or gpio
                                        (prefix with 'panic_' to set mode for panic
                                        reboot only),
                              reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
                              reboot_force is either force or not specified,
                              reboot_cpu is s[mp]#### with #### being the processor
                                        to be used for rebooting.

        refscale.holdoff= [KNL]
                        Set test-start holdoff period.  The purpose of
                        this parameter is to delay the start of the
                        test until boot completes in order to avoid

        refscale.loops= [KNL]
                        Set the number of loops over the synchronization
                        primitive under test.  Increasing this number
                        reduces noise due to loop start/end overhead,
                        but the default has already reduced the per-pass
                        noise to a handful of picoseconds on ca. 2020
                        x86 laptops.

        refscale.nreaders= [KNL]
                        Set number of readers.  The default value of -1
                        selects N, where N is roughly 75% of the number
                        of CPUs.  A value of zero is an interesting choice.

        refscale.nruns= [KNL]
                        Set number of runs, each of which is dumped onto
                        the console log.

        refscale.readdelay= [KNL]
                        Set the read-side critical-section duration,
                        measured in microseconds.

        refscale.scale_type= [KNL]
                        Specify the read-protection implementation to test.

        refscale.shutdown= [KNL]
                        Shut down the system at the end of the performance
                        test.  This defaults to 1 (shut it down) when
                        refscale is built into the kernel and to 0 (leave
                        it running) when refscale is built as a module.

        refscale.verbose= [KNL]
                        Enable additional printk() statements.

        refscale.verbose_batched= [KNL]
                        Batch the additional printk() statements.  If zero
                        (the default) or negative, print everything.  Otherwise,
                        print every Nth verbose statement, where N is the value

                        [KNL, SMP] Set scheduler's default relax_domain_level.
                        See Documentation/admin-guide/cgroup-v1/cpusets.rst.

        reserve=        [KNL,BUGS] Force kernel to ignore I/O ports or memory
                        Format: <base1>,<size1>[,<base2>,<size2>,...]
                        Reserve I/O ports or memory so the kernel won't use
                        them.  If <base> is less than 0x10000, the region
                        is assumed to be I/O ports; otherwise it is memory.

        reservetop=     [X86-32]
                        Format: nn[KMG]
                        Reserves a hole at the top of the kernel virtual
                        address space.

        reset_devices   [KNL] Force drivers to reset the underlying device
                        during initialization.

        resume=         [SWSUSP]
                        Specify the partition device for software suspend
                        {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}

        resume_offset=  [SWSUSP]
                        Specify the offset from the beginning of the partition
                        given by "resume=" at which the swap header is located,
                        in <PAGE_SIZE> units (needed only for swap files).
                        See  Documentation/power/swsusp-and-swap-files.rst

        resumedelay=    [HIBERNATION] Delay (in seconds) to pause before attempting to
                        read the resume files

        resumewait      [HIBERNATION] Wait (indefinitely) for resume device to show up.
                        Useful for devices that are detected asynchronously
                        (e.g. USB and MMC devices).

        retain_initrd   [RAM] Keep initrd memory after extraction

        retbleed=       [X86] Control mitigation of RETBleed (Arbitrary
                        Speculative Code Execution with Return Instructions)

                        AMD-based UNRET and IBPB mitigations alone do not stop
                        sibling threads from influencing the predictions of other
                        sibling threads. For that reason, STIBP is used on pro-
                        cessors that support it, and mitigate SMT on processors
                        that don't.

                        off          - no mitigation
                        auto         - automatically select a migitation
                        auto,nosmt   - automatically select a mitigation,
                                       disabling SMT if necessary for
                                       the full mitigation (only on Zen1
                                       and older without STIBP).
                        ibpb         - On AMD, mitigate short speculation
                                       windows on basic block boundaries too.
                                       Safe, highest perf impact. It also
                                       enables STIBP if present. Not suitable
                                       on Intel.
                        ibpb,nosmt   - Like "ibpb" above but will disable SMT
                                       when STIBP is not available. This is
                                       the alternative for systems which do not
                                       have STIBP.
                        unret        - Force enable untrained return thunks,
                                       only effective on AMD f15h-f17h based
                        unret,nosmt  - Like unret, but will disable SMT when STIBP
                                       is not available. This is the alternative for
                                       systems which do not have STIBP.

                        Selecting 'auto' will choose a mitigation method at run
                        time according to the CPU.

                        Not specifying this option is equivalent to retbleed=auto.

                0       "airplane mode".  All wifi, bluetooth, wimax, gps, fm,
                        etc. communication is blocked by default.
                1       Unblocked.

                0       The "airplane mode" button does nothing.
                1       The "airplane mode" button toggles between everything
                        blocked and the previous configuration.
                2       The "airplane mode" button toggles between everything
                        blocked and everything unblocked.

        rhash_entries=  [KNL,NET]
                        Set number of hash buckets for route cache

                        [KNL] Disable ring 3 MONITOR/MWAIT feature on supported

        riscv_isa_fallback [RISCV]
                        When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
                        falling back to detecting extension support by parsing
                        "riscv,isa" property on devicetree systems when the
                        replacement properties are not found. See the Kconfig
                        entry for RISCV_ISA_FALLBACK.

        ro              [KNL] Mount root device read-only on boot

        rodata=         [KNL]
                on      Mark read-only kernel memory as read-only (default).
                off     Leave read-only kernel memory writable for debugging.
                full    Mark read-only kernel memory and aliases as read-only

                        Enable the uart passthrough on the designated usb port
                        on Rockchip SoCs. When active, the signals of the
                        debug-uart get routed to the D+ and D- pins of the usb
                        port and the regular usb controller gets disabled.

        root=           [KNL] Root filesystem
                        Usually this a a block device specifier of some kind,
                        see the early_lookup_bdev comment in
                        block/early-lookup.c for details.
                        Alternatively this can be "ram" for the legacy initial
                        ramdisk, "nfs" and "cifs" for root on a network file
                        system, or "mtd" and "ubi" for mounting from raw flash.

        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
                        mount the root filesystem

        rootflags=      [KNL] Set root filesystem mount option string

        rootfstype=     [KNL] Set root filesystem type

        rootwait        [KNL] Wait (indefinitely) for root device to show up.
                        Useful for devices that are detected asynchronously
                        (e.g. USB and MMC devices).

        rootwait=       [KNL] Maximum time (in seconds) to wait for root device
                        to show up before attempting to mount the root

                        [KNL,ARM,CMA] Remoteproc physical memory block.
                        Memory area to be used by remote processor image,
                        managed by CMA.

        rw              [KNL] Mount root device read-write on boot

        S               [KNL] Run init in single mode

        s390_iommu=     [HW,S390]
                        Set s390 IOTLB flushing mode
                        With strict flushing every unmap operation will result in
                        an IOTLB flush. Default is lazy flushing before reuse,
                        which is faster.

        s390_iommu_aperture=    [KNL,S390]
                        Specifies the size of the per device DMA address space
                        accessible through the DMA and IOMMU APIs as a decimal
                        factor of the size of main memory.
                        The default is 1 meaning that one can concurrently use
                        as many DMA addresses as physical memory is installed,
                        if supported by hardware, and thus map all of memory
                        once. With a value of 2 one can map all of memory twice
                        and so on. As a special case a factor of 0 imposes no
                        restrictions other than those given by hardware at the
                        cost of significant additional memory use for tables.

        sa1100ir        [NET]
                        See drivers/net/irda/sa1100_ir.c.

        sched_verbose   [KNL] Enables verbose scheduler debug messages.

        schedstats=     [KNL,X86] Enable or disable scheduled statistics.
                        Allowed values are enable and disable. This feature
                        incurs a small amount of overhead in the scheduler
                        but is useful for debugging and performance tuning.

                        [KNL, SMP] Set a decay shift for scheduler thermal
                        pressure signal. Thermal pressure signal follows the
                        default decay period of other scheduler pelt
                        signals(usually 32 ms but configurable). Setting
                        sched_thermal_decay_shift will left shift the decay
                        period for the thermal pressure signal by the shift
                        i.e. with the default pelt decay period of 32 ms
                        sched_thermal_decay_shift   thermal pressure decay pr
                                1                       64 ms
                                2                       128 ms
                        and so on.
                        Format: integer between 0 and 10
                        Default is 0.

        scftorture.holdoff= [KNL]
                        Number of seconds to hold off before starting
                        test.  Defaults to zero for module insertion and
                        to 10 seconds for built-in smp_call_function()

        scftorture.longwait= [KNL]
                        Request ridiculously long waits randomly selected
                        up to the chosen limit in seconds.  Zero (the
                        default) disables this feature.  Please note
                        that requesting even small non-zero numbers of
                        seconds can result in RCU CPU stall warnings,
                        softlockup complaints, and so on.

        scftorture.nthreads= [KNL]
                        Number of kthreads to spawn to invoke the
                        smp_call_function() family of functions.
                        The default of -1 specifies a number of kthreads
                        equal to the number of CPUs.

        scftorture.onoff_holdoff= [KNL]
                        Number seconds to wait after the start of the
                        test before initiating CPU-hotplug operations.

        scftorture.onoff_interval= [KNL]
                        Number seconds to wait between successive
                        CPU-hotplug operations.  Specifying zero (which
                        is the default) disables CPU-hotplug operations.

        scftorture.shutdown_secs= [KNL]
                        The number of seconds following the start of the
                        test after which to shut down the system.  The
                        default of zero avoids shutting down the system.
                        Non-zero values are useful for automated tests.

        scftorture.stat_interval= [KNL]
                        The number of seconds between outputting the
                        current test statistics to the console.  A value
                        of zero disables statistics output.

        scftorture.stutter_cpus= [KNL]
                        The number of jiffies to wait between each change
                        to the set of CPUs under test.

        scftorture.use_cpus_read_lock= [KNL]
                        Use use_cpus_read_lock() instead of the default
                        preempt_disable() to disable CPU hotplug
                        while invoking one of the smp_call_function*()

        scftorture.verbose= [KNL]
                        Enable additional printk() statements.

        scftorture.weight_single= [KNL]
                        The probability weighting to use for the
                        smp_call_function_single() function with a zero
                        "wait" parameter.  A value of -1 selects the
                        default if all other weights are -1.  However,
                        if at least one weight has some other value, a
                        value of -1 will instead select a weight of zero.

        scftorture.weight_single_wait= [KNL]
                        The probability weighting to use for the
                        smp_call_function_single() function with a
                        non-zero "wait" parameter.  See weight_single.

        scftorture.weight_many= [KNL]
                        The probability weighting to use for the
                        smp_call_function_many() function with a zero
                        "wait" parameter.  See weight_single.
                        Note well that setting a high probability for
                        this weighting can place serious IPI load
                        on the system.

        scftorture.weight_many_wait= [KNL]
                        The probability weighting to use for the
                        smp_call_function_many() function with a
                        non-zero "wait" parameter.  See weight_single
                        and weight_many.

        scftorture.weight_all= [KNL]
                        The probability weighting to use for the
                        smp_call_function_all() function with a zero
                        "wait" parameter.  See weight_single and

        scftorture.weight_all_wait= [KNL]
                        The probability weighting to use for the
                        smp_call_function_all() function with a
                        non-zero "wait" parameter.  See weight_single
                        and weight_many.

        skew_tick=      [KNL] Offset the periodic timer tick per cpu to mitigate
                        xtime_lock contention on larger systems, and/or RCU lock
                        contention on all systems with CONFIG_MAXSMP set.
                        Format: { "0" | "1" }
                        0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
                        1 -- enable.
                        Note: increases power consumption, thus should only be
                        enabled if running jitter sensitive (HPC/RT) workloads.

        security=       [SECURITY] Choose a legacy "major" security module to
                        enable at boot. This has been deprecated by the
                        "lsm=" parameter.

        selinux=        [SELINUX] Disable or enable SELinux at boot time.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- disable.
                        1 -- enable.
                        Default value is 1.

        serialnumber    [BUGS=X86-32]

        sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst

        shapers=        [NET]
                        Maximal number of shapers.

        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
                        Limit apic dumping. The parameter defines the maximal
                        number of local apics being dumped. Also it is possible
                        to set it to "all" by meaning -- no limit here.
                        Format: { 1 (default) | 2 | ... | all }.
                        The parameter valid if only apic=debug or
                        apic=verbose is specified.
                        Example: apic=debug show_lapic=all

        simeth=         [IA-64]

        slram=          [HW,MTD]

        slab_merge      [MM]
                        Enable merging of slabs with similar size when the
                        kernel is built without CONFIG_SLAB_MERGE_DEFAULT.

        slab_nomerge    [MM]
                        Disable merging of slabs with similar size. May be
                        necessary if there is some reason to distinguish
                        allocs to different slabs, especially in hardened
                        environments where the risk of heap overflows and
                        layout control by attackers can usually be
                        frustrated by disabling merging. This will reduce
                        most of the exposure of a heap attack to a single
                        cache (risks via metadata attacks are mostly
                        unchanged). Debug options disable merging on their
                        For more information see Documentation/mm/slub.rst.

        slab_max_order= [MM, SLAB]
                        Determines the maximum allowed order for slabs.
                        A high setting may cause OOMs due to memory
                        fragmentation.  Defaults to 1 for systems with
                        more than 32MB of RAM, 0 otherwise.

        slub_debug[=options[,slabs][;[options[,slabs]]...]      [MM, SLUB]
                        Enabling slub_debug allows one to determine the
                        culprit if slab objects become corrupted. Enabling
                        slub_debug can create guard zones around objects and
                        may poison objects when not in use. Also tracks the
                        last alloc / free. For more information see

        slub_max_order= [MM, SLUB]
                        Determines the maximum allowed order for slabs.
                        A high setting may cause OOMs due to memory
                        fragmentation. For more information see

        slub_min_objects=       [MM, SLUB]
                        The minimum number of objects per slab. SLUB will
                        increase the slab order up to slub_max_order to
                        generate a sufficiently large slab able to contain
                        the number of objects indicated. The higher the number
                        of objects the smaller the overhead of tracking slabs
                        and the less frequently locks need to be acquired.
                        For more information see Documentation/mm/slub.rst.

        slub_min_order= [MM, SLUB]
                        Determines the minimum page order for slabs. Must be
                        lower than slub_max_order.
                        For more information see Documentation/mm/slub.rst.

        slub_merge      [MM, SLUB]
                        Same with slab_merge.

        slub_nomerge    [MM, SLUB]
                        Same with slab_nomerge. This is supported for legacy.
                        See slab_nomerge for more information.

        smart2=         [HW]
                        Format: <io1>[,<io2>[,...,<io8>]]

        smp.csd_lock_timeout= [KNL]
                        Specify the period of time in milliseconds
                        that smp_call_function() and friends will wait
                        for a CPU to release the CSD lock.  This is
                        useful when diagnosing bugs involving CPUs
                        disabling interrupts for extended periods
                        of time.  Defaults to 5,000 milliseconds, and
                        setting a value of zero disables this feature.
                        This feature may be more efficiently disabled
                        using the csdlock_debug- kernel parameter.

        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
        smsc-ircc2.ircc_irq=    [HW] IRQ line
        smsc-ircc2.ircc_dma=    [HW] DMA channel
        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
                                0: Toshiba Satellite 1800 (GP data pin select)
                                1: Fast pin select (default)
                                2: ATC IRMode

        smt=            [KNL,MIPS,S390] Set the maximum number of threads (logical
                        CPUs) to use per physical CPU on systems capable of
                        symmetric multithreading (SMT). Will be capped to the
                        actual hardware limit.
                        Format: <integer>
                        Default: -1 (no limit)

                        [KNL] Should the soft-lockup detector generate panics.
                        Format: 0 | 1

                        A value of 1 instructs the soft-lockup detector
                        to panic the machine when a soft-lockup occurs. It is
                        also controlled by the kernel.softlockup_panic sysctl
                        and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
                        respective build-time switch to that functionality.

                        [KNL] Should the soft-lockup detector generate
                        backtraces on all cpus.
                        Format: 0 | 1

        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
                        See Documentation/admin-guide/laptops/sonypi.rst

        spectre_v2=     [X86] Control mitigation of Spectre variant 2
                        (indirect branch speculation) vulnerability.
                        The default operation protects the kernel from
                        user space attacks.

                        on   - unconditionally enable, implies
                        off  - unconditionally disable, implies
                        auto - kernel detects whether your CPU model is

                        Selecting 'on' will, and 'auto' may, choose a
                        mitigation method at run time according to the
                        CPU, the available microcode, the setting of the
                        CONFIG_RETPOLINE configuration option, and the
                        compiler with which the kernel was built.

                        Selecting 'on' will also enable the mitigation
                        against user space to user space task attacks.

                        Selecting 'off' will disable both the kernel and
                        the user space protections.

                        Specific mitigations can also be selected manually:

                        retpoline         - replace indirect branches
                        retpoline,generic - Retpolines
                        retpoline,lfence  - LFENCE; indirect branch
                        retpoline,amd     - alias for retpoline,lfence
                        eibrs             - Enhanced/Auto IBRS
                        eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
                        eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
                        ibrs              - use IBRS to protect kernel

                        Not specifying this option is equivalent to

                        [X86] Control mitigation of Spectre variant 2
                        (indirect branch speculation) vulnerability between
                        user space tasks

                        on      - Unconditionally enable mitigations. Is
                                  enforced by spectre_v2=on

                        off     - Unconditionally disable mitigations. Is
                                  enforced by spectre_v2=off

                        prctl   - Indirect branch speculation is enabled,
                                  but mitigation can be enabled via prctl
                                  per thread.  The mitigation control state
                                  is inherited on fork.

                                - Like "prctl" above, but only STIBP is
                                  controlled per thread. IBPB is issued
                                  always when switching between different user
                                  space processes.

                                - Same as "prctl" above, but all seccomp
                                  threads will enable the mitigation unless
                                  they explicitly opt out.

                                - Like "seccomp" above, but only STIBP is
                                  controlled per thread. IBPB is issued
                                  always when switching between different
                                  user space processes.

                        auto    - Kernel selects the mitigation depending on
                                  the available CPU features and vulnerability.

                        Default mitigation: "prctl"

                        Not specifying this option is equivalent to

                        [X86] Control RAS overflow mitigation on AMD Zen CPUs

                        off             - Disable mitigation
                        microcode       - Enable microcode mitigation only
                        safe-ret        - Enable sw-only safe RET mitigation (default)
                        ibpb            - Enable mitigation by issuing IBPB on
                                          kernel entry
                        ibpb-vmexit     - Issue IBPB only on VMEXIT
                                          (cloud-specific mitigation)

                        [HW] Control Speculative Store Bypass (SSB) Disable mitigation
                        (Speculative Store Bypass vulnerability)

                        Certain CPUs are vulnerable to an exploit against a
                        a common industry wide performance optimization known
                        as "Speculative Store Bypass" in which recent stores
                        to the same memory location may not be observed by
                        later loads during speculative execution. The idea
                        is that such stores are unlikely and that they can
                        be detected prior to instruction retirement at the
                        end of a particular speculation execution window.

                        In vulnerable processors, the speculatively forwarded
                        store can be used in a cache side channel attack, for
                        example to read memory to which the attacker does not
                        directly have access (e.g. inside sandboxed code).

                        This parameter controls whether the Speculative Store
                        Bypass optimization is used.

                        On x86 the options are:

                        on      - Unconditionally disable Speculative Store Bypass
                        off     - Unconditionally enable Speculative Store Bypass
                        auto    - Kernel detects whether the CPU model contains an
                                  implementation of Speculative Store Bypass and
                                  picks the most appropriate mitigation. If the
                                  CPU is not vulnerable, "off" is selected. If the
                                  CPU is vulnerable the default mitigation is
                                  architecture and Kconfig dependent. See below.
                        prctl   - Control Speculative Store Bypass per thread
                                  via prctl. Speculative Store Bypass is enabled
                                  for a process by default. The state of the control
                                  is inherited on fork.
                        seccomp - Same as "prctl" above, but all seccomp threads
                                  will disable SSB unless they explicitly opt out.

                        Default mitigations:
                        X86:    "prctl"

                        On powerpc the options are:

                        on,auto - On Power8 and Power9 insert a store-forwarding
                                  barrier on kernel entry and exit. On Power7
                                  perform a software flush on kernel entry and
                        off     - No action.

                        Not specifying this option is equivalent to

        spia_io_base=   [HW,MTD]

                        [X86] Enable split lock detection or bus lock detection

                        When enabled (and if hardware support is present), atomic
                        instructions that access data across cache line
                        boundaries will result in an alignment check exception
                        for split lock detection or a debug exception for
                        bus lock detection.

                        off     - not enabled

                        warn    - the kernel will emit rate-limited warnings
                                  about applications triggering the #AC
                                  exception or the #DB exception. This mode is
                                  the default on CPUs that support split lock
                                  detection or bus lock detection. Default
                                  behavior is by #AC if both features are
                                  enabled in hardware.

                        fatal   - the kernel will send SIGBUS to applications
                                  that trigger the #AC exception or the #DB
                                  exception. Default behavior is by #AC if
                                  both features are enabled in hardware.

                        ratelimit:N -
                                  Set system wide rate limit to N bus locks
                                  per second for bus lock detection.
                                  0 < N <= 1000.

                                  N/A for split lock detection.

                        If an #AC exception is hit in the kernel or in
                        firmware (i.e. not while executing in user mode)
                        the kernel will oops in either "warn" or "fatal"

                        #DB exception for bus lock is triggered only when
                        CPL > 0.

        srbds=          [X86,INTEL]
                        Control the Special Register Buffer Data Sampling
                        (SRBDS) mitigation.

                        Certain CPUs are vulnerable to an MDS-like
                        exploit which can leak bits from the random
                        number generator.

                        By default, this issue is mitigated by
                        microcode.  However, the microcode fix can cause
                        the RDRAND and RDSEED instructions to become
                        much slower.  Among other effects, this will
                        result in reduced throughput from /dev/urandom.

                        The microcode mitigation can be disabled with
                        the following option:

                        off:    Disable mitigation and remove
                                performance impact to RDRAND and RDSEED

        srcutree.big_cpu_lim [KNL]
                        Specifies the number of CPUs constituting a
                        large system, such that srcu_struct structures
                        should immediately allocate an srcu_node array.
                        This kernel-boot parameter defaults to 128,
                        but takes effect only when the low-order four
                        bits of srcutree.convert_to_big is equal to 3
                        (decide at boot).

        srcutree.convert_to_big [KNL]
                        Specifies under what conditions an SRCU tree
                        srcu_struct structure will be converted to big
                        form, that is, with an rcu_node tree:

                                   0:  Never.
                                   1:  At init_srcu_struct() time.
                                   2:  When rcutorture decides to.
                                   3:  Decide at boot time (default).
                                0x1X:  Above plus if high contention.

                        Either way, the srcu_node tree will be sized based
                        on the actual runtime number of CPUs (nr_cpu_ids)
                        instead of the compile-time CONFIG_NR_CPUS.

        srcutree.counter_wrap_check [KNL]
                        Specifies how frequently to check for
                        grace-period sequence counter wrap for the
                        srcu_data structure's ->srcu_gp_seq_needed field.
                        The greater the number of bits set in this kernel
                        parameter, the less frequently counter wrap will
                        be checked for.  Note that the bottom two bits
                        are ignored.

        srcutree.exp_holdoff [KNL]
                        Specifies how many nanoseconds must elapse
                        since the end of the last SRCU grace period for
                        a given srcu_struct until the next normal SRCU
                        grace period will be considered for automatic
                        expediting.  Set to zero to disable automatic

        srcutree.srcu_max_nodelay [KNL]
                        Specifies the number of no-delay instances
                        per jiffy for which the SRCU grace period
                        worker thread will be rescheduled with zero
                        delay. Beyond this limit, worker thread will
                        be rescheduled with a sleep delay of one jiffy.

        srcutree.srcu_max_nodelay_phase [KNL]
                        Specifies the per-grace-period phase, number of
                        non-sleeping polls of readers. Beyond this limit,
                        grace period worker thread will be rescheduled
                        with a sleep delay of one jiffy, between each
                        rescan of the readers, for a grace period phase.

        srcutree.srcu_retry_check_delay [KNL]
                        Specifies number of microseconds of non-sleeping
                        delay between each non-sleeping poll of readers.

        srcutree.small_contention_lim [KNL]
                        Specifies the number of update-side contention
                        events per jiffy will be tolerated before
                        initiating a conversion of an srcu_struct
                        structure to big form.  Note that the value of
                        srcutree.convert_to_big must have the 0x10 bit
                        set for contention-based conversions to occur.

        ssbd=           [ARM64,HW]
                        Speculative Store Bypass Disable control

                        On CPUs that are vulnerable to the Speculative
                        Store Bypass vulnerability and offer a
                        firmware based mitigation, this parameter
                        indicates how the mitigation should be used:

                        force-on:  Unconditionally enable mitigation for
                                   for both kernel and userspace
                        force-off: Unconditionally disable mitigation for
                                   for both kernel and userspace
                        kernel:    Always enable mitigation in the
                                   kernel, and offer a prctl interface
                                   to allow userspace to register its
                                   interest in being mitigated too.

        stack_guard_gap=        [MM]
                        override the default stack gap protection. The value
                        is in page units and it defines how many pages prior
                        to (for stacks growing down) resp. after (for stacks
                        growing up) the main stack are reserved for no other
                        mapping. Default value is 256 pages.

        stack_depot_disable= [KNL]
                        Setting this to true through kernel command line will
                        disable the stack depot thereby saving the static memory
                        consumed by the stack hash table. By default this is set
                        to false.

        stacktrace      [FTRACE]
                        Enabled the stack tracer on boot up.

                        [FTRACE] Limit the functions that the stack tracer
                        will trace at boot up. function-list is a comma-separated
                        list of functions. This list can be changed at run
                        time by the stack_trace_filter file in the debugfs
                        tracing directory. Note, this enables stack tracing
                        and the stacktrace above is not needed.

        sti=            [PARISC,HW]
                        Format: <num>
                        Set the STI (builtin display/keyboard on the HP-PARISC
                        machines) console (graphic card) which should be used
                        as the initial boot-console.
                        See also comment in drivers/video/console/sticore.c.

        sti_font=       [HW]
                        See comment in drivers/video/console/sticore.c.

        stifb=          [HW]
                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]

                        Format: <bool>
                        Enable or disable strict sigaltstack size checks
                        against the required signal frame size which
                        depends on the supported FPU features. This can
                        be used to filter out binaries which have
                        not yet been made aware of AT_MINSIGSTKSZ.

        stress_hpt      [PPC]
                        Limits the number of kernel HPT entries in the hash
                        page table to increase the rate of hash page table
                        faults on kernel addresses.

        stress_slb      [PPC]
                        Limits the number of kernel SLB entries, and flushes
                        them frequently to increase the rate of SLB faults
                        on kernel addresses.

                        SunRPC servers often require that client requests
                        originate from a privileged port (i.e. a port in the
                        range 0 < portnr < 1024).
                        An administrator who wishes to reserve some of these
                        ports for other uses may adjust the range that the
                        kernel's sunrpc client considers to be privileged
                        using these two parameters to set the minimum and
                        maximum port values.

                        Limit the number of requests that the server will
                        process in parallel from a single connection.
                        The default value is 0 (no limit).

                        Control how the NFS server code allocates CPUs to
                        service thread pools.  Depending on how many NICs
                        you have and where their interrupts are bound, this
                        option will affect which CPUs will do NFS serving.
                        Note: this parameter cannot be changed while the
                        NFS server is running.

                        auto        the server chooses an appropriate mode
                                    automatically using heuristics
                        global      a single global pool contains all CPUs
                        percpu      one pool for each CPU
                        pernode     one pool for each NUMA node (equivalent
                                    to global on non-NUMA machines)

                        Sets the upper limit on the number of simultaneous
                        RPC calls that can be sent from the client to a
                        server. Increasing these values may allow you to
                        improve throughput, but will also increase the
                        amount of memory reserved for use by the client.

                        Sets the number of seconds to remain in a suspend test
                        mode before resuming the system (see
                        /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
                        is set. Default value is 5.

        svm=            [PPC]
                        Format: { on | off | y | n | 1 | 0 }
                        This parameter controls use of the Protected
                        Execution Facility on pSeries.

        swiotlb=        [ARM,IA-64,PPC,MIPS,X86]
                        Format: { <int> [,<int>] | force | noforce }
                        <int> -- Number of I/O TLB slabs
                        <int> -- Second integer after comma. Number of swiotlb
                                 areas with their own lock. Will be rounded up
                                 to a power of 2.
                        force -- force using of bounce buffers even if they
                                 wouldn't be automatically used by the kernel
                        noforce -- Never use bounce buffers (for debugging)

        switches=       [HW,M68k]

        sysctl.*=       [KNL]
                        Set a sysctl parameter, right before loading the init
                        process, as if the value was written to the respective
                        /proc/sys/... file. Both '.' and '/' are recognized as
                        separators. Unrecognized parameters and invalid values
                        are reported in the kernel log. Sysctls registered
                        later by a loaded module cannot be set this way.
                        Example: sysctl.vm.swappiness=40

                        Ignore sysrq setting - this boot parameter will
                        neutralize any effect of /proc/sys/kernel/sysrq.
                        Useful for debugging.

        tcpmhash_entries= [KNL,NET]
                        Set the number of tcp_metrics_hash slots.
                        Default value is 8192 or 16384 depending on total
                        ram pages. This is used to specify the TCP metrics
                        cache size. See Documentation/networking/ip-sysctl.rst
                        "tcp_no_metrics_save" section for more details.

        tdfx=           [HW,DRM]

        test_suspend=   [SUSPEND]
                        Format: { "mem" | "standby" | "freeze" }[,N]
                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
                        standby suspend) or "freeze" (for suspend type freeze)
                        as the system sleep state during system startup with
                        the optional capability to repeat N number of times.
                        The system is woken from this state using a
                        wakeup-capable RTC alarm.

        thash_entries=  [KNL,NET]
                        Set number of hash buckets for TCP connection

        thermal.act=    [HW,ACPI]
                        -1: disable all active trip points in all thermal zones
                        <degrees C>: override all lowest active trip points

        thermal.crt=    [HW,ACPI]
                        -1: disable all critical trip points in all thermal zones
                        <degrees C>: override all critical trip points    [HW,ACPI]
                        1: disable ACPI thermal control

        thermal.psv=    [HW,ACPI]
                        -1: disable all passive trip points
                        <degrees C>: override all passive trip points to this

        thermal.tzp=    [HW,ACPI]
                        Specify global default ACPI thermal zone polling rate
                        <deci-seconds>: poll all this frequency
                        0: no polling (default)

        threadirqs      [KNL]
                        Force threading of all interrupt handlers except those
                        marked explicitly IRQF_NO_THREAD.

        topology=       [S390]
                        Format: {off | on}
                        Specify if the kernel should make use of the cpu
                        topology information if the hardware supports this.
                        The scheduler will make use of this information and
                        e.g. base its process migration decisions on it.
                        Default is on.

        topology_updates= [KNL, PPC, NUMA]
                        Format: {off}
                        Specify if the kernel should ignore (off)
                        topology updates sent by the hypervisor to this

        torture.disable_onoff_at_boot= [KNL]
                        Prevent the CPU-hotplug component of torturing
                        until after init has spawned.

        torture.ftrace_dump_at_shutdown= [KNL]
                        Dump the ftrace buffer at torture-test shutdown,
                        even if there were no errors.  This can be a
                        very costly operation when many torture tests
                        are running concurrently, especially on systems
                        with rotating-rust storage.

        torture.verbose_sleep_frequency= [KNL]
                        Specifies how many verbose printk()s should be
                        emitted between each sleep.  The default of zero
                        disables verbose-printk() sleeping.

        torture.verbose_sleep_duration= [KNL]
                        Duration of each verbose-printk() sleep in jiffies.

        tp720=          [HW,PS2]

                        Format: integer pcr id
                        Specify that at suspend time, the tpm driver
                        should extend the specified pcr with zeros,
                        as a workaround for some chips which fail to
                        flush the last written pcr on TPM_SaveState.
                        This will guarantee that all the other pcrs
                        are saved.

        tpm_tis.interrupts= [HW,TPM]
                        Enable interrupts for the MMIO based physical layer
                        for the FIFO interface. By default it is set to false
                        (0). For more information about TPM hardware interfaces
                        defined by Trusted Computing Group (TCG) see

        tp_printk       [FTRACE]
                        Have the tracepoints sent to printk as well as the
                        tracing ring buffer. This is useful for early boot up
                        where the system hangs or reboots and does not give the
                        option for reading the tracing buffer or performing a

                        To turn off having tracepoints sent to printk,
                         echo 0 > /proc/sys/kernel/tracepoint_printk
                        Note, echoing 1 into this file without the
                        tracepoint_printk kernel cmdline option has no effect.

                        The tp_printk_stop_on_boot (see below) can also be used
                        to stop the printing of events to console at

                        ** CAUTION **

                        Having tracepoints sent to printk() and activating high
                        frequency tracepoints such as irq or sched, can cause
                        the system to live lock.

        tp_printk_stop_on_boot [FTRACE]
                        When tp_printk (above) is set, it can cause a lot of noise
                        on the console. It may be useful to only include the
                        printing of events during boot up, as user space may
                        make the system inoperable.

                        This command line option will stop the printing of events
                        to console at the late_initcall_sync() time frame.

                        [FTRACE] will set tracing buffer size on each cpu.

        trace_clock=    [FTRACE] Set the clock used for tracing events
                        at boot up.
                        local - Use the per CPU time stamp counter
                                (converted into nanoseconds). Fast, but
                                depending on the architecture, may not be
                                in sync between CPUs.
                        global - Event time stamps are synchronize across
                                CPUs. May be slower than the local clock,
                                but better for some race conditions.
                        counter - Simple counting of events (1, 2, ..)
                                note, some counts may be skipped due to the
                                infrastructure grabbing the clock more than
                                once per event.
                        uptime - Use jiffies as the time stamp.
                        perf - Use the same clock that perf uses.
                        mono - Use ktime_get_mono_fast_ns() for time stamps.
                        mono_raw - Use ktime_get_raw_fast_ns() for time
                        boot - Use ktime_get_boot_fast_ns() for time stamps.
                        Architectures may add more clocks. See
                        Documentation/trace/ftrace.rst for more details.

                        [FTRACE] Set and start specified trace events in order
                        to facilitate early boot debugging. The event-list is a
                        comma-separated list of trace events to enable. See
                        also Documentation/trace/events.rst

                        [FTRACE] Create a ring buffer instance early in boot up.
                        This will be listed in:


                        Events can be enabled at the time the instance is created


                        Note, the "<system*>:" portion is optional if the event is


                        will enable the "sched_switch" event (note, the "sched:" is optional, and
                        the same thing would happen if it was left off). The irq_handler_entry
                        event, and all events under the "initcall" system.

                        [FTRACE] Enable or disable tracer options at boot.
                        The option-list is a comma delimited list of options
                        that can be enabled or disabled just as if you were
                        to echo the option name into


                        For example, to enable stacktrace option (to dump the
                        stack trace of each event), add to the command line:


                        See also Documentation/trace/ftrace.rst "trace options"

                        [FTRACE] Add a event trigger on specific events.
                        Set a trigger on top of a specific event, with an optional

                        The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
                        Where more than one trigger may be specified that are comma deliminated.

                        For example:

                          trace_trigger="sched_switch.stacktrace if prev_state == 2"

                        The above will enable the "stacktrace" trigger on the "sched_switch"
                        event but only trigger it if the "prev_state" of the "sched_switch"
                        event is "2" (TASK_UNINTERUPTIBLE).

                        See also "Event triggers" in Documentation/trace/events.rst

                        [FTRACE] enable this option to disable tracing when a
                        warning is hit. This turns off "tracing_on". Tracing can
                        be enabled again by echoing '1' into the "tracing_on"
                        file located in /sys/kernel/tracing/

                        This option is useful, as it disables the trace before
                        the WARNING dump is called, which prevents the trace to
                        be filled with content caused by the warning output.

                        This option can also be set at run time via the sysctl
                        option:  kernel/traceoff_on_warning

                        Format: [always|madvise|never]
                        Can be used to control the default behavior of the system
                        with respect to transparent hugepages.
                        See Documentation/admin-guide/mm/transhuge.rst
                        for more details.

        trusted.source= [KEYS]
                        Format: <string>
                        This parameter identifies the trust source as a backend
                        for trusted keys implementation. Supported trust
                        - "tpm"
                        - "tee"
                        - "caam"
                        If not specified then it defaults to iterating through
                        the trust source list starting with TPM and assigns the
                        first trust source as a backend which is initialized
                        successfully during iteration.

        trusted.rng=    [KEYS]
                        Format: <string>
                        The RNG used to generate key material for trusted keys.
                        Can be one of:
                        - "kernel"
                        - the same value as trusted.source: "tpm" or "tee"
                        - "default"
                        If not specified, "default" is used. In this case,
                        the RNG's choice is left to each individual trust source.

        tsc=            Disable clocksource stability checks for TSC.
                        Format: <string>
                        [x86] reliable: mark tsc clocksource as reliable, this
                        disables clocksource verification at runtime, as well
                        as the stability checks done at bootup. Used to enable
                        high-resolution timer mode on older hardware, and in
                        virtualized environment.
                        [x86] noirqtime: Do not use TSC to do irq accounting.
                        Used to run time disable IRQ_TIME_ACCOUNTING on any
                        platforms where RDTSC is slow and this accounting
                        can add overhead.
                        [x86] unstable: mark the TSC clocksource as unstable, this
                        marks the TSC unconditionally unstable at bootup and
                        avoids any further wobbles once the TSC watchdog notices.
                        [x86] nowatchdog: disable clocksource watchdog. Used
                        in situations with strict latency requirements (where
                        interruptions from clocksource watchdog are not
                        [x86] recalibrate: force recalibration against a HW timer
                        (HPET or PM timer) on systems whose TSC frequency was
                        obtained from HW or FW using either an MSR or CPUID(0x15).
                        Warn if the difference is more than 500 ppm.
                        [x86] watchdog: Use TSC as the watchdog clocksource with
                        which to check other HW timers (HPET or PM timer), but
                        only on systems where TSC has been deemed trustworthy.
                        This will be suppressed by an earlier tsc=nowatchdog and
                        can be overridden by a later tsc=nowatchdog.  A console
                        message will flag any such suppression or overriding.

        tsc_early_khz=  [X86] Skip early TSC calibration and use the given
                        value instead. Useful when the early TSC frequency discovery
                        procedure is not reliable, such as on overclocked systems
                        with CPUID.16h support and partial CPUID.15h support.
                        Format: <unsigned int>

        tsx=            [X86] Control Transactional Synchronization
                        Extensions (TSX) feature in Intel processors that
                        support TSX control.

                        This parameter controls the TSX feature. The options are:

                        on      - Enable TSX on the system. Although there are
                                mitigations for all known security vulnerabilities,
                                TSX has been known to be an accelerator for
                                several previous speculation-related CVEs, and
                                so there may be unknown security risks associated
                                with leaving it enabled.

                        off     - Disable TSX on the system. (Note that this
                                option takes effect only on newer CPUs which are
                                not vulnerable to MDS, i.e., have
                                MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
                                the new IA32_TSX_CTRL MSR through a microcode
                                update. This new MSR allows for the reliable
                                deactivation of the TSX functionality.)

                        auto    - Disable TSX if X86_BUG_TAA is present,
                                  otherwise enable TSX on the system.

                        Not specifying this option is equivalent to tsx=off.

                        See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
                        for more details.

        tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
                        Abort (TAA) vulnerability.

                        Similar to Micro-architectural Data Sampling (MDS)
                        certain CPUs that support Transactional
                        Synchronization Extensions (TSX) are vulnerable to an
                        exploit against CPU internal buffers which can forward
                        information to a disclosure gadget under certain

                        In vulnerable processors, the speculatively forwarded
                        data can be used in a cache side channel attack, to
                        access data to which the attacker does not have direct

                        This parameter controls the TAA mitigation.  The
                        options are:

                        full       - Enable TAA mitigation on vulnerable CPUs
                                     if TSX is enabled.

                        full,nosmt - Enable TAA mitigation and disable SMT on
                                     vulnerable CPUs. If TSX is disabled, SMT
                                     is not disabled because CPU is not
                                     vulnerable to cross-thread TAA attacks.
                        off        - Unconditionally disable TAA mitigation

                        On MDS-affected machines, tsx_async_abort=off can be
                        prevented by an active MDS mitigation as both vulnerabilities
                        are mitigated with the same mechanism so in order to disable
                        this mitigation, you need to specify mds=off too.

                        Not specifying this option is equivalent to
                        tsx_async_abort=full.  On CPUs which are MDS affected
                        and deploy MDS mitigation, TAA mitigation is not
                        required and doesn't provide any additional

                        For details see:
                        Documentation/admin-guide/hw-vuln/tsx_async_abort.rst[2|3]=    [HW,JOY]
                        TurboGraFX parallel port interface
                        See also Documentation/input/devices/joystick-parport.rst

        udbg-immortal   [PPC] When debugging early kernel crashes that
                        happen after console_init() and before a proper
                        console driver takes over, this boot options might
                        help "seeing" what's going on.

        uhash_entries=  [KNL,NET]
                        Set number of hash buckets for UDP/UDP-Lite connections

                        [USB] Ignore overcurrent events (default N).
                        Some badly-designed motherboards generate lots of
                        bogus events, for ports that aren't wired to
                        anything.  Set this parameter to avoid log spamming.
                        Note that genuine overcurrent events won't be
                        reported either.

                        [X86] Cause panic on unknown NMI.

        unwind_debug    [X86-64]
                        Enable unwinder debug output.  This can be
                        useful for debugging certain unwinder error
                        conditions, including corrupt stacks and
                        bad/missing unwinder metadata.

                        [USB] Default USB device authorization:
                        (default -1 = authorized (same as 1),
                        0 = not authorized, 1 = authorized, 2 = authorized
                        if device connected to internal port)

                        [USB] The autosuspend time delay (in seconds) used
                        for newly-detected USB devices (default 2).  This
                        is the time required before an idle device will be
                        autosuspended.  Devices for which the delay is set
                        to a negative value won't be autosuspended at all.

                        [USB] Set to log all usbfs traffic (default 0 = off).

                        [USB] Maximum number of bytes to snoop in each URB
                        (default = 65536).

                        [USB] Set to cycle leds on hubs (default 0 = off).

                        [USB] Start with the old device initialization
                        scheme (default 0 = off).

                        [USB] Memory limit (in MB) for buffers allocated by
                        usbfs (default = 16, 0 = max = 2047).

                        [USB] Try the other device initialization scheme
                        if the first one fails (default 1 = enabled).

                        [USB] Specifies timeout for the initial 64-byte
                        USB_REQ_GET_DESCRIPTOR request in milliseconds
                        (default 5000 = 5.0 seconds).

        usbcore.nousb   [USB] Disable the USB subsystem

                        [USB] A list of quirk entries to augment the built-in
                        usb core quirk list. List entries are separated by
                        commas. Each entry has the form
                        VendorID:ProductID:Flags. The IDs are 4-digit hex
                        numbers and Flags is a set of letters. Each letter
                        will change the built-in quirk; setting it if it is
                        clear and clearing it if it is set. The letters have
                        the following meanings:
                                a = USB_QUIRK_STRING_FETCH_255 (string
                                        descriptors must not be fetched using
                                        a 255-byte read);
                                b = USB_QUIRK_RESET_RESUME (device can't resume
                                        correctly so reset it instead);
                                c = USB_QUIRK_NO_SET_INTF (device can't handle
                                        Set-Interface requests);
                                d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
                                        handle its Configuration or Interface
                                e = USB_QUIRK_RESET (device can't be reset
                                        (e.g morph devices), don't use reset);
                                f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
                                        more interface descriptions than the
                                        bNumInterfaces count, and can't handle
                                        talking to these interfaces);
                                g = USB_QUIRK_DELAY_INIT (device needs a pause
                                        during initialization, after we read
                                        the device descriptor);
                                h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
                                        high speed and super speed interrupt
                                        endpoints, the USB 2.0 and USB 3.0 spec
                                        require the interval in microframes (1
                                        microframe = 125 microseconds) to be
                                        calculated as interval = 2 ^
                                        Devices with this quirk report their
                                        bInterval as the result of this
                                        calculation instead of the exponent
                                        variable used in the calculation);
                                i = USB_QUIRK_DEVICE_QUALIFIER (device can't
                                        handle device_qualifier descriptor
                                j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
                                        generates spurious wakeup, ignore
                                        remote wakeup capability);
                                k = USB_QUIRK_NO_LPM (device can't handle Link
                                        Power Management);
                                l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
                                        (Device reports its bInterval as linear
                                        frames instead of the USB 2.0
                                m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
                                        to be disconnected before suspend to
                                        prevent spurious wakeup);
                                n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
                                        pause after every control message);
                                o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
                                        delay after resetting its port);
                        Example: quirks=0781:5580:bk,0a5c:5834:gij

                        [USBHID] The interval which mice are to be polled at.

                        [USBHID] The interval which joysticks are to be polled at.

                        [USBHID] The interval which keyboards are to be polled at.

                        [UMS] The delay in seconds before a new device is
                        scanned for Logical Units (default 1).

                        [UMS] A list of quirks entries to supplement or
                        override the built-in unusual_devs list.  List
                        entries are separated by commas.  Each entry has
                        the form VID:PID:Flags where VID and PID are Vendor
                        and Product ID values (4-digit hex numbers) and
                        Flags is a set of characters, each corresponding
                        to a common usb-storage quirk flag as follows:
                                a = SANE_SENSE (collect more than 18 bytes
                                        of sense data, not on uas);
                                b = BAD_SENSE (don't collect more than 18
                                        bytes of sense data, not on uas);
                                c = FIX_CAPACITY (decrease the reported
                                        device capacity by one sector);
                                d = NO_READ_DISC_INFO (don't use
                                        READ_DISC_INFO command, not on uas);
                                e = NO_READ_CAPACITY_16 (don't use
                                        READ_CAPACITY_16 command);
                                f = NO_REPORT_OPCODES (don't use report opcodes
                                        command, uas only);
                                g = MAX_SECTORS_240 (don't transfer more than
                                        240 sectors at a time, uas only);
                                h = CAPACITY_HEURISTICS (decrease the
                                        reported device capacity by one
                                        sector if the number is odd);
                                i = IGNORE_DEVICE (don't bind to this
                                j = NO_REPORT_LUNS (don't use report luns
                                        command, uas only);
                                k = NO_SAME (do not use WRITE_SAME, uas only)
                                l = NOT_LOCKABLE (don't try to lock and
                                        unlock ejectable media, not on uas);
                                m = MAX_SECTORS_64 (don't transfer more
                                        than 64 sectors = 32 KB at a time,
                                        not on uas);
                                n = INITIAL_READ10 (force a retry of the
                                        initial READ(10) command, not on uas);
                                o = CAPACITY_OK (accept the capacity
                                        reported by the device, not on uas);
                                p = WRITE_CACHE (the device cache is ON
                                        by default, not on uas);
                                r = IGNORE_RESIDUE (the device reports
                                        bogus residue values, not on uas);
                                s = SINGLE_LUN (the device has only one
                                        Logical Unit);
                                t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
                                        commands, uas only);
                                u = IGNORE_UAS (don't bind to the uas driver);
                                w = NO_WP_DETECT (don't test whether the
                                        medium is write-protected).
                                y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
                                        even if the device claims no cache,
                                        not on uas)
                        Example: quirks=0419:aaf5:rl,0421:0433:rc

        user_debug=     [KNL,ARM]
                        Format: <int>
                        See arch/arm/Kconfig.debug help text.
                                 1 - undefined instruction events
                                 2 - system calls
                                 4 - invalid data aborts
                                 8 - SIGSEGV faults
                                16 - SIGBUS faults
                        Example: user_debug=31

                        [X86] Flags controlling user PTE allocations.

                                nohigh = do not allocate PTE pages in
                                        HIGHMEM regardless of setting
                                        of CONFIG_HIGHPTE.

        vdso=           [X86,SH,SPARC]
                        On X86_32, this is an alias for vdso32=.  Otherwise:

                        vdso=1: enable VDSO (the default)
                        vdso=0: disable VDSO mapping

        vdso32=         [X86] Control the 32-bit vDSO
                        vdso32=1: enable 32-bit VDSO
                        vdso32=0 or vdso32=2: disable 32-bit VDSO

                        See the help text for CONFIG_COMPAT_VDSO for more
                        details.  If CONFIG_COMPAT_VDSO is set, the default is
                        vdso32=0; otherwise, the default is vdso32=1.

                        For compatibility with older kernels, vdso32=2 is an
                        alias for vdso32=0.

                        Try vdso32=0 if you encounter an error that says:
                        dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!

        vector=         [IA-64,SMP]
                        vector=percpu: enable percpu vector domain

        video=          [FB] Frame buffer configuration
                        See Documentation/fb/modedb.rst.

        video.brightness_switch_enabled= [ACPI]
                        Format: [0|1]
                        If set to 1, on receiving an ACPI notify event
                        generated by hotkey, video driver will adjust brightness
                        level and then send out the event to user space through
                        the allocated input device. If set to 0, video driver
                        will only send out the event without touching backlight
                        brightness level.
                        default: 1

                        [VMMIO] Memory mapped virtio (platform) device.

                                <size>     := size (can use standard suffixes
                                                like K, M and G)
                                <baseaddr> := physical base address
                                <irq>      := interrupt number (as passed to
                                <id>       := (optional) platform device id

                        Can be used multiple times for multiple devices.

        vga=            [BOOT,X86-32] Select a particular video mode
                        See Documentation/arch/x86/boot.rst and
                        Use vga=ask for menu.
                        This is actually a boot loader parameter; the value is
                        passed to the kernel using a special protocol.

        vm_debug[=options]      [KNL] Available with CONFIG_DEBUG_VM=y.
                        May slow down system boot speed, especially when
                        enabled on systems with a large amount of memory.
                        All options are enabled by default, and this
                        interface is meant to allow for selectively
                        enabling or disabling specific virtual memory
                        debugging features.

                        Available options are:
                          P     Enable page structure init time poisoning
                          -     Disable all of the above options

        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
                        size of <nn>. This can be used to increase the
                        minimum size (128MB on x86). It can also be used to
                        decrease the size and leave more room for directly
                        mapped kernel RAM.

        vmcp_cma=nn[MG] [KNL,S390]
                        Sets the memory size reserved for contiguous memory
                        allocations for the vmcp device driver.

        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
                        Format: <command>

        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
                        Format: <command>

        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
                        Format: <command>

        vsyscall=       [X86-64]
                        Controls the behavior of vsyscalls (i.e. calls to
                        fixed addresses of 0xffffffffff600x00 from legacy
                        code).  Most statically-linked binaries and older
                        versions of glibc use these calls.  Because these
                        functions are at fixed addresses, they make nice
                        targets for exploits that can control RIP.

                        emulate     Vsyscalls turn into traps and are emulated
                                    reasonably safely.  The vsyscall page is

                        xonly       [default] Vsyscalls turn into traps and are
                                    emulated reasonably safely.  The vsyscall
                                    page is not readable.

                        none        Vsyscalls don't work at all.  This makes
                                    them quite hard to use for exploits but
                                    might break your system.

        vt.color=       [VT] Default text color.
                        Format: 0xYX, X = foreground, Y = background.
                        Default: 0x07 = light gray on black.

        vt.cur_default= [VT] Default cursor shape.
                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
                        the parameters of the <Esc>[?A;B;Cc escape sequence;
                        see VGA-softcursor.txt. Default: 2 = underline.

        vt.default_blu= [VT]
                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
                        Change the default blue palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_grn= [VT]
                        Format: <green0>,<green1>,<green2>,...,<green15>
                        Change the default green palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_red= [VT]
                        Format: <red0>,<red1>,<red2>,...,<red15>
                        Change the default red palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

                        Set system-wide default UTF-8 mode for all tty's.
                        Default is 1, i.e. UTF-8 mode is enabled for all
                        newly opened terminals.

                        Set system-wide default for whether a cursor
                        is shown on new VTs. Default is -1,
                        i.e. cursors will be created by default unless
                        overridden by individual drivers. 0 will hide
                        cursors, 1 will display them.

        vt.italic=      [VT] Default color for italic text; 0-15.
                        Default: 2 = green.

        vt.underline=   [VT] Default color for underlined text; 0-15.
                        Default: 3 = cyan.

        watchdog timers [HW,WDT] For information on watchdog timers,
                        see Documentation/watchdog/watchdog-parameters.rst
                        or other driver-specific files in the
                        Documentation/watchdog/ directory.

                        Set the hard lockup detector stall duration
                        threshold in seconds. The soft lockup detector
                        threshold is set to twice the value. A value of 0
                        disables both lockup detectors. Default is 10

                        [KNL,SMP] Specify to constrain one or some CPUs
                        to use in unbound workqueues.
                        Format: <cpu-list>
                        By default, all online CPUs are available for
                        unbound workqueues.

                        If CONFIG_WQ_WATCHDOG is configured, workqueue can
                        warn stall conditions and dump internal state to
                        help debugging.  0 disables workqueue stall
                        detection; otherwise, it's the stall threshold
                        duration in seconds.  The default value is 30 and
                        it can be updated at runtime by writing to the
                        corresponding sysfs file.

                        Per-cpu work items which run for longer than this
                        threshold are automatically considered CPU intensive
                        and excluded from concurrency management to prevent
                        them from noticeably delaying other per-cpu work
                        items. Default is 10000 (10ms).

                        If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
                        will report the work functions which violate this
                        threshold repeatedly. They are likely good
                        candidates for using WQ_UNBOUND workqueues instead.

                        Per-cpu workqueues are generally preferred because
                        they show better performance thanks to cache
                        locality; unfortunately, per-cpu workqueues tend to
                        be more power hungry than unbound workqueues.

                        Enabling this makes the per-cpu workqueues which
                        were observed to contribute significantly to power
                        consumption unbound, leading to measurably lower
                        power usage at the cost of small performance

                        The default value of this parameter is determined by
                        the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.

                        Select the default affinity scope to use for unbound
                        workqueues. Can be one of "cpu", "smt", "cache",
                        "numa" and "system". Default is "cache". For more
                        information, see the Affinity Scopes section in

                        This can be changed after boot by writing to the
                        matching /sys/module/workqueue/parameters file. All
                        workqueues with the "default" affinity scope will be
                        updated accordignly.

                        Workqueue used to implicitly guarantee that work
                        items queued without explicit CPU specified are put
                        on the local CPU.  This guarantee is no longer true
                        and while local CPU is still preferred work items
                        may be put on foreign CPUs.  This debug option
                        forces round-robin CPU selection to flush out
                        usages which depend on the now broken guarantee.
                        When enabled, memory and cache locality will be

        writecombine=   [LOONGARCH] Control the MAT (Memory Access Type) of

                        on   - Enable writecombine, use WUC for ioremap_wc()
                        off  - Disable writecombine, use SUC for ioremap_wc()

        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
                        default x2apic cluster mode on platforms
                        supporting x2apic.

        xen_512gb_limit         [KNL,X86-64,XEN]
                        Restricts the kernel running paravirtualized under Xen
                        to use only up to 512 GB of RAM. The reason to do so is
                        crash analysis tools and Xen tools for doing domain
                        save/restore/migration must be enabled to handle larger

        xen_emul_unplug=                [HW,X86,XEN]
                        Unplug Xen emulated devices
                        Format: [unplug0,][unplug1]
                        ide-disks -- unplug primary master IDE devices
                        aux-ide-disks -- unplug non-primary-master IDE devices
                        nics -- unplug network devices
                        all -- unplug all emulated devices (NICs and IDE disks)
                        unnecessary -- unplugging emulated devices is
                                unnecessary even if the host did not respond to
                                the unplug protocol
                        never -- do not unplug even if version check succeeds

        xen_legacy_crash        [X86,XEN]
                        Crash from Xen panic notifier, without executing late
                        panic() code such as dumping handler.

        xen_msr_safe=   [X86,XEN]
                        Format: <bool>
                        Select whether to always use non-faulting (safe) MSR
                        access functions when running as Xen PV guest. The
                        default value is controlled by CONFIG_XEN_PV_MSR_SAFE.

        xen_nopvspin    [X86,XEN]
                        Disables the qspinlock slowpath using Xen PV optimizations.
                        This parameter is obsoleted by "nopvspin" parameter, which
                        has equivalent effect for XEN platform.

        xen_nopv        [X86]
                        Disables the PV optimizations forcing the HVM guest to
                        run as generic HVM guest with no PV drivers.
                        This option is obsoleted by the "nopv" option, which
                        has equivalent effect for XEN platform.

                        [KNL,X86,XEN] Disable the vector callback for Xen
                        event channel interrupts.

        xen_scrub_pages=        [XEN]
                        Boolean option to control scrubbing pages before giving them back
                        to Xen, for use by other domains. Can be also changed at runtime
                        with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
                        Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.

        xen_timer_slop= [X86-64,XEN]
                        Set the timer slop (in nanoseconds) for the virtual Xen
                        timers (default is 100000). This adjusts the minimum
                        delta of virtualized Xen timers, where lower values
                        improve timer resolution at the expense of processing
                        more timer interrupts.

        xen.balloon_boot_timeout= [XEN]
                        The time (in seconds) to wait before giving up to boot
                        in case initial ballooning fails to free enough memory.
                        Applies only when running as HVM or PVH guest and
                        started with less memory configured than allowed at
                        max. Default is 180.

        xen.event_eoi_delay=    [XEN]
                        How long to delay EOI handling in case of event
                        storms (jiffies). Default is 10.

        xen.event_loop_timeout= [XEN]
                        After which time (jiffies) the event handling loop
                        should start to delay EOI handling. Default is 2.

        xen.fifo_events=        [XEN]
                        Boolean parameter to disable using fifo event handling
                        even if available. Normally fifo event handling is
                        preferred over the 2-level event handling, as it is
                        fairer and the number of possible event channels is
                        much higher. Default is on (use fifo events).

        xirc2ps_cs=     [NET,PCMCIA]

        xive=           [PPC]
                        By default on POWER9 and above, the kernel will
                        natively use the XIVE interrupt controller. This option
                        allows the fallback firmware mode to be used:

                        off       Fallback to firmware control of XIVE interrupt
                                  controller on both pseries and powernv
                                  platforms. Only useful on POWER9 and above.      [PPC]
                        By default on POWER10 and above, the kernel will use
                        stores for EOI handling when the XIVE interrupt mode
                        is active. This option allows the XIVE driver to use
                        loads instead, as on POWER9.

        xhci-hcd.quirks         [USB,KNL]
                        A hex value specifying bitmask with supplemental xhci
                        host controller quirks. Meaning of each bit can be
                        consulted in header drivers/usb/host/xhci.h.

        xmon            [PPC]
                        Format: { early | on | rw | ro | off }
                        Controls if xmon debugger is enabled. Default is off.
                        Passing only "xmon" is equivalent to "xmon=early".
                        early   Call xmon as early as possible on boot; xmon
                                debugger is called from setup_arch().
                        on      xmon debugger hooks will be installed so xmon
                                is only called on a kernel crash. Default mode,
                                i.e. either "ro" or "rw" mode, is controlled
                                with CONFIG_XMON_DEFAULT_RO_MODE.
                        rw      xmon debugger hooks will be installed so xmon
                                is called only on a kernel crash, mode is write,
                                meaning SPR registers, memory and, other data
                                can be written using xmon commands.
                        ro      same as "rw" option above but SPR registers,
                                memory, and other data can't be written using
                                xmon commands.
                        off     xmon is disabled.


Add more DRM drivers.