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authorTom Lendacky <thomas.lendacky@amd.com>2018-02-21 13:39:51 -0600
committerRadim Krčmář <rkrcmar@redhat.com>2018-03-01 19:00:28 +0100
commit801e459a6f3a63af9d447e6249088c76ae16efc4 (patch)
treeb23a56566b4ace273ae07cd150acec275e3cd669 /Documentation/virtual
parentd4858aaf6bd8a90e2dacc0dfec2077e334dcedbf (diff)
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KVM: x86: Add a framework for supporting MSR-based features
Provide a new KVM capability that allows bits within MSRs to be recognized as features. Two new ioctls are added to the /dev/kvm ioctl routine to retrieve the list of these MSRs and then retrieve their values. A kvm_x86_ops callback is used to determine support for the listed MSR-based features. Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> [Tweaked documentation. - Radim] Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt40
1 files changed, 28 insertions, 12 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 792fa8717d13..d6b3ff51a14f 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -123,14 +123,15 @@ memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the
flag KVM_VM_MIPS_VZ.
-4.3 KVM_GET_MSR_INDEX_LIST
+4.3 KVM_GET_MSR_INDEX_LIST, KVM_GET_MSR_FEATURE_INDEX_LIST
-Capability: basic
+Capability: basic, KVM_CAP_GET_MSR_FEATURES for KVM_GET_MSR_FEATURE_INDEX_LIST
Architectures: x86
-Type: system
+Type: system ioctl
Parameters: struct kvm_msr_list (in/out)
Returns: 0 on success; -1 on error
Errors:
+ EFAULT: the msr index list cannot be read from or written to
E2BIG: the msr index list is to be to fit in the array specified by
the user.
@@ -139,16 +140,23 @@ struct kvm_msr_list {
__u32 indices[0];
};
-This ioctl returns the guest msrs that are supported. The list varies
-by kvm version and host processor, but does not change otherwise. The
-user fills in the size of the indices array in nmsrs, and in return
-kvm adjusts nmsrs to reflect the actual number of msrs and fills in
-the indices array with their numbers.
+The user fills in the size of the indices array in nmsrs, and in return
+kvm adjusts nmsrs to reflect the actual number of msrs and fills in the
+indices array with their numbers.
+
+KVM_GET_MSR_INDEX_LIST returns the guest msrs that are supported. The list
+varies by kvm version and host processor, but does not change otherwise.
Note: if kvm indicates supports MCE (KVM_CAP_MCE), then the MCE bank MSRs are
not returned in the MSR list, as different vcpus can have a different number
of banks, as set via the KVM_X86_SETUP_MCE ioctl.
+KVM_GET_MSR_FEATURE_INDEX_LIST returns the list of MSRs that can be passed
+to the KVM_GET_MSRS system ioctl. This lets userspace probe host capabilities
+and processor features that are exposed via MSRs (e.g., VMX capabilities).
+This list also varies by kvm version and host processor, but does not change
+otherwise.
+
4.4 KVM_CHECK_EXTENSION
@@ -475,14 +483,22 @@ Support for this has been removed. Use KVM_SET_GUEST_DEBUG instead.
4.18 KVM_GET_MSRS
-Capability: basic
+Capability: basic (vcpu), KVM_CAP_GET_MSR_FEATURES (system)
Architectures: x86
-Type: vcpu ioctl
+Type: system ioctl, vcpu ioctl
Parameters: struct kvm_msrs (in/out)
-Returns: 0 on success, -1 on error
+Returns: number of msrs successfully returned;
+ -1 on error
+
+When used as a system ioctl:
+Reads the values of MSR-based features that are available for the VM. This
+is similar to KVM_GET_SUPPORTED_CPUID, but it returns MSR indices and values.
+The list of msr-based features can be obtained using KVM_GET_MSR_FEATURE_INDEX_LIST
+in a system ioctl.
+When used as a vcpu ioctl:
Reads model-specific registers from the vcpu. Supported msr indices can
-be obtained using KVM_GET_MSR_INDEX_LIST.
+be obtained using KVM_GET_MSR_INDEX_LIST in a system ioctl.
struct kvm_msrs {
__u32 nmsrs; /* number of msrs in entries */