From b467ab82a9fde4b46c0cd2c299220857afb0e0d4 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 13 Nov 2024 12:39:45 +0100 Subject: [PATCH] KVM: x86: expose MSR_PLATFORM_INFO as a feature MSR 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 --- 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 8637bc0010965..2e713480933a1 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: + *data = MSR_PLATFORM_INFO_CPUID_FAULT; + break; case MSR_IA32_UCODE_REV: rdmsrl_safe(index, data); break; -- 2.47.2