For userspace that wants to disable KVM_X86_QUIRK_STUFF_FEATURE_MSRS, it
is useful to know what bits can be set to 1 in MSR_PLATFORM_INFO (apart
from the TSC ratio). The right way to do that is via /dev/kvm's
feature MSR mechanism.
In fact, MSR_PLATFORM_INFO is already a feature MSR for the purpose of
blocking updates after the vCPU is run, but KVM_GET_MSRS did not return
a valid value for it.
Just like in a VM that leaves KVM_X86_QUIRK_STUFF_FEATURE_MSRS enabled,
the TSC ratio field is left to 0. Only bit 31 is set.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/x86.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8637bc001096..03b409deb7d7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1675,6 +1675,9 @@ static int kvm_get_feature_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
case MSR_IA32_PERF_CAPABILITIES:
*data = kvm_caps.supported_perf_cap;
break;
+ case MSR_PLATFORM_INFO:
+ msr->data = MSR_PLATFORM_INFO_CPUID_FAULT;
+ break;
case MSR_IA32_UCODE_REV:
rdmsrl_safe(index, data);
break;
--
2.43.5