4.19-stable patches

added patches:
	x86-apic-force-native_apic_mem_read-to-use-the-mov-instruction.patch

2 files changed, 71 insertions, 0 deletions

diff --git a/queue-4.19/series b/queue-4.19/series
index 0ca7798704..838c58ec55 100644
--- a/queue-4.19/series
+++ b/queue-4.19/series
@@ -9,3 +9,4 @@ net-mlx5-properly-link-new-fs-rules-into-the-tree.patch
 tracing-hide-unused-ftrace_event_id_fops.patch
 vhost-add-smp_rmb-in-vhost_vq_avail_empty.patch
 selftests-timers-fix-abs-warning-in-posix_timers-test.patch
+x86-apic-force-native_apic_mem_read-to-use-the-mov-instruction.patch
diff --git a/queue-4.19/x86-apic-force-native_apic_mem_read-to-use-the-mov-instruction.patch b/queue-4.19/x86-apic-force-native_apic_mem_read-to-use-the-mov-instruction.patch
new file mode 100644
index 0000000000..ec3cae9e1b
--- /dev/null
+++ b/queue-4.19/x86-apic-force-native_apic_mem_read-to-use-the-mov-instruction.patch
@@ -0,0 +1,70 @@
+From 5ce344beaca688f4cdea07045e0b8f03dc537e74 Mon Sep 17 00:00:00 2001
+From: Adam Dunlap <acdunlap@google.com>
+Date: Mon, 18 Mar 2024 16:09:27 -0700
+Subject: x86/apic: Force native_apic_mem_read() to use the MOV instruction
+
+From: Adam Dunlap <acdunlap@google.com>
+
+commit 5ce344beaca688f4cdea07045e0b8f03dc537e74 upstream.
+
+When done from a virtual machine, instructions that touch APIC memory
+must be emulated. By convention, MMIO accesses are typically performed
+via io.h helpers such as readl() or writeq() to simplify instruction
+emulation/decoding (ex: in KVM hosts and SEV guests) [0].
+
+Currently, native_apic_mem_read() does not follow this convention,
+allowing the compiler to emit instructions other than the MOV
+instruction generated by readl(). In particular, when the kernel is
+compiled with clang and run as a SEV-ES or SEV-SNP guest, the compiler
+would emit a TESTL instruction which is not supported by the SEV-ES
+emulator, causing a boot failure in that environment. It is likely the
+same problem would happen in a TDX guest as that uses the same
+instruction emulator as SEV-ES.
+
+To make sure all emulators can emulate APIC memory reads via MOV, use
+the readl() function in native_apic_mem_read(). It is expected that any
+emulator would support MOV in any addressing mode as it is the most
+generic and is what is usually emitted currently.
+
+The TESTL instruction is emitted when native_apic_mem_read() is inlined
+into apic_mem_wait_icr_idle(). The emulator comes from
+insn_decode_mmio() in arch/x86/lib/insn-eval.c. It's not worth it to
+extend insn_decode_mmio() to support more instructions since, in theory,
+the compiler could choose to output nearly any instruction for such
+reads which would bloat the emulator beyond reason.
+
+  [0] https://lore.kernel.org/all/20220405232939.73860-12-kirill.shutemov@linux.intel.com/
+
+  [ bp: Massage commit message, fix typos. ]
+
+Signed-off-by: Adam Dunlap <acdunlap@google.com>
+Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
+Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
+Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
+Tested-by: Kevin Loughlin <kevinloughlin@google.com>
+Cc: <stable@vger.kernel.org>
+Link: https://lore.kernel.org/r/20240318230927.2191933-1-acdunlap@google.com
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/x86/include/asm/apic.h |    3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+--- a/arch/x86/include/asm/apic.h
++++ b/arch/x86/include/asm/apic.h
+@@ -11,6 +11,7 @@
+ #include <asm/mpspec.h>
+ #include <asm/msr.h>
+ #include <asm/hardirq.h>
++#include <asm/io.h>
+ 
+ #define ARCH_APICTIMER_STOPS_ON_C3	1
+ 
+@@ -110,7 +111,7 @@ static inline void native_apic_mem_write
+ 
+ static inline u32 native_apic_mem_read(u32 reg)
+ {
+-	return *((volatile u32 *)(APIC_BASE + reg));
++	return readl((void __iomem *)(APIC_BASE + reg));
+ }
+ 
+ extern void native_apic_wait_icr_idle(void);