Merge tag 'kvm-s390-next-5.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into HEAD

KVM: s390: pvdump and selftest improvements

- add an interface to provide a hypervisor dump for secure guests
- improve selftests to show tests

3 files changed, 225 insertions, 2 deletions

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 11e00a46c610f..94d73ec52abad 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5127,7 +5127,15 @@ into ESA mode. This reset is a superset of the initial reset.
 	__u32 reserved[3];
   };
 
-cmd values:
+**Ultravisor return codes**
+The Ultravisor return (reason) codes are provided by the kernel if a
+Ultravisor call has been executed to achieve the results expected by
+the command. Therefore they are independent of the IOCTL return
+code. If KVM changes `rc`, its value will always be greater than 0
+hence setting it to 0 before issuing a PV command is advised to be
+able to detect a change of `rc`.
+
+**cmd values:**
 
 KVM_PV_ENABLE
   Allocate memory and register the VM with the Ultravisor, thereby
@@ -5143,7 +5151,6 @@ KVM_PV_ENABLE
   =====      =============================
 
 KVM_PV_DISABLE
-
   Deregister the VM from the Ultravisor and reclaim the memory that
   had been donated to the Ultravisor, making it usable by the kernel
   again.  All registered VCPUs are converted back to non-protected
@@ -5160,6 +5167,117 @@ KVM_PV_VM_VERIFY
   Verify the integrity of the unpacked image. Only if this succeeds,
   KVM is allowed to start protected VCPUs.
 
+KVM_PV_INFO
+  :Capability: KVM_CAP_S390_PROTECTED_DUMP
+
+  Presents an API that provides Ultravisor related data to userspace
+  via subcommands. len_max is the size of the user space buffer,
+  len_written is KVM's indication of how much bytes of that buffer
+  were actually written to. len_written can be used to determine the
+  valid fields if more response fields are added in the future.
+
+  ::
+
+     enum pv_cmd_info_id {
+	KVM_PV_INFO_VM,
+	KVM_PV_INFO_DUMP,
+     };
+
+     struct kvm_s390_pv_info_header {
+	__u32 id;
+	__u32 len_max;
+	__u32 len_written;
+	__u32 reserved;
+     };
+
+     struct kvm_s390_pv_info {
+	struct kvm_s390_pv_info_header header;
+	struct kvm_s390_pv_info_dump dump;
+	struct kvm_s390_pv_info_vm vm;
+     };
+
+**subcommands:**
+
+  KVM_PV_INFO_VM
+    This subcommand provides basic Ultravisor information for PV
+    hosts. These values are likely also exported as files in the sysfs
+    firmware UV query interface but they are more easily available to
+    programs in this API.
+
+    The installed calls and feature_indication members provide the
+    installed UV calls and the UV's other feature indications.
+
+    The max_* members provide information about the maximum number of PV
+    vcpus, PV guests and PV guest memory size.
+
+    ::
+
+      struct kvm_s390_pv_info_vm {
+	__u64 inst_calls_list[4];
+	__u64 max_cpus;
+	__u64 max_guests;
+	__u64 max_guest_addr;
+	__u64 feature_indication;
+      };
+
+
+  KVM_PV_INFO_DUMP
+    This subcommand provides information related to dumping PV guests.
+
+    ::
+
+      struct kvm_s390_pv_info_dump {
+	__u64 dump_cpu_buffer_len;
+	__u64 dump_config_mem_buffer_per_1m;
+	__u64 dump_config_finalize_len;
+      };
+
+KVM_PV_DUMP
+  :Capability: KVM_CAP_S390_PROTECTED_DUMP
+
+  Presents an API that provides calls which facilitate dumping a
+  protected VM.
+
+  ::
+
+    struct kvm_s390_pv_dmp {
+      __u64 subcmd;
+      __u64 buff_addr;
+      __u64 buff_len;
+      __u64 gaddr;		/* For dump storage state */
+    };
+
+  **subcommands:**
+
+  KVM_PV_DUMP_INIT
+    Initializes the dump process of a protected VM. If this call does
+    not succeed all other subcommands will fail with -EINVAL. This
+    subcommand will return -EINVAL if a dump process has not yet been
+    completed.
+
+    Not all PV vms can be dumped, the owner needs to set `dump
+    allowed` PCF bit 34 in the SE header to allow dumping.
+
+  KVM_PV_DUMP_CONFIG_STOR_STATE
+     Stores `buff_len` bytes of tweak component values starting with
+     the 1MB block specified by the absolute guest address
+     (`gaddr`). `buff_len` needs to be `conf_dump_storage_state_len`
+     aligned and at least >= the `conf_dump_storage_state_len` value
+     provided by the dump uv_info data. buff_user might be written to
+     even if an error rc is returned. For instance if we encounter a
+     fault after writing the first page of data.
+
+  KVM_PV_DUMP_COMPLETE
+    If the subcommand succeeds it completes the dump process and lets
+    KVM_PV_DUMP_INIT be called again.
+
+    On success `conf_dump_finalize_len` bytes of completion data will be
+    stored to the `buff_addr`. The completion data contains a key
+    derivation seed, IV, tweak nonce and encryption keys as well as an
+    authentication tag all of which are needed to decrypt the dump at a
+    later time.
+
+
 4.126 KVM_X86_SET_MSR_FILTER
 ----------------------------
 
@@ -5802,6 +5920,32 @@ of CPUID leaf 0xD on the host.
 
 This ioctl injects an event channel interrupt directly to the guest vCPU.
 
+4.136 KVM_S390_PV_CPU_COMMAND
+-----------------------------
+
+:Capability: KVM_CAP_S390_PROTECTED_DUMP
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: 0 on success, < 0 on error
+
+This ioctl closely mirrors `KVM_S390_PV_COMMAND` but handles requests
+for vcpus. It re-uses the kvm_s390_pv_dmp struct and hence also shares
+the command ids.
+
+**command:**
+
+KVM_PV_DUMP
+  Presents an API that provides calls which facilitate dumping a vcpu
+  of a protected VM.
+
+**subcommand:**
+
+KVM_PV_DUMP_CPU
+  Provides encrypted dump data like register values.
+  The length of the returned data is provided by uv_info.guest_cpu_stor_len.
+
+
 5. The kvm_run structure
 ========================
 
@@ -7956,6 +8100,20 @@ should adjust CPUID leaf 0xA to reflect that the PMU is disabled.
 When enabled, KVM will exit to userspace with KVM_EXIT_SYSTEM_EVENT of
 type KVM_SYSTEM_EVENT_SUSPEND to process the guest suspend request.
 
+8.37 KVM_CAP_S390_PROTECTED_DUMP
+--------------------------------
+
+:Capability: KVM_CAP_S390_PROTECTED_DUMP
+:Architectures: s390
+:Type: vm
+
+This capability indicates that KVM and the Ultravisor support dumping
+PV guests. The `KVM_PV_DUMP` command is available for the
+`KVM_S390_PV_COMMAND` ioctl and the `KVM_PV_INFO` command provides
+dump related UV data. Also the vcpu ioctl `KVM_S390_PV_CPU_COMMAND` is
+available and supports the `KVM_PV_DUMP_CPU` subcommand.
+
+
 9. Known KVM API problems
 =========================
 
diff --git a/Documentation/virt/kvm/s390/index.rst b/Documentation/virt/kvm/s390/index.rst
index 605f488f0cc55..44ec9ab14b59c 100644
--- a/Documentation/virt/kvm/s390/index.rst
+++ b/Documentation/virt/kvm/s390/index.rst
@@ -10,3 +10,4 @@ KVM for s390 systems
    s390-diag
    s390-pv
    s390-pv-boot
+   s390-pv-dump
diff --git a/Documentation/virt/kvm/s390/s390-pv-dump.rst b/Documentation/virt/kvm/s390/s390-pv-dump.rst
new file mode 100644
index 0000000000000..e542f06048f34
--- /dev/null
+++ b/Documentation/virt/kvm/s390/s390-pv-dump.rst
@@ -0,0 +1,64 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================================
+s390 (IBM Z) Protected Virtualization dumps
+===========================================
+
+Summary
+-------
+
+Dumping a VM is an essential tool for debugging problems inside
+it. This is especially true when a protected VM runs into trouble as
+there's no way to access its memory and registers from the outside
+while it's running.
+
+However when dumping a protected VM we need to maintain its
+confidentiality until the dump is in the hands of the VM owner who
+should be the only one capable of analysing it.
+
+The confidentiality of the VM dump is ensured by the Ultravisor who
+provides an interface to KVM over which encrypted CPU and memory data
+can be requested. The encryption is based on the Customer
+Communication Key which is the key that's used to encrypt VM data in a
+way that the customer is able to decrypt.
+
+
+Dump process
+------------
+
+A dump is done in 3 steps:
+
+**Initiation**
+
+This step initializes the dump process, generates cryptographic seeds
+and extracts dump keys with which the VM dump data will be encrypted.
+
+**Data gathering**
+
+Currently there are two types of data that can be gathered from a VM:
+the memory and the vcpu state.
+
+The vcpu state contains all the important registers, general, floating
+point, vector, control and tod/timers of a vcpu. The vcpu dump can
+contain incomplete data if a vcpu is dumped while an instruction is
+emulated with help of the hypervisor. This is indicated by a flag bit
+in the dump data. For the same reason it is very important to not only
+write out the encrypted vcpu state, but also the unencrypted state
+from the hypervisor.
+
+The memory state is further divided into the encrypted memory and its
+metadata comprised of the encryption tweaks and status flags. The
+encrypted memory can simply be read once it has been exported. The
+time of the export does not matter as no re-encryption is
+needed. Memory that has been swapped out and hence was exported can be
+read from the swap and written to the dump target without need for any
+special actions.
+
+The tweaks / status flags for the exported pages need to be requested
+from the Ultravisor.
+
+**Finalization**
+
+The finalization step will provide the data needed to be able to
+decrypt the vcpu and memory data and end the dump process. When this
+step completes successfully a new dump initiation can be started.