linux-kernel - [PATCH] KVM: VMX: Always treat MSR_IA32_PERF

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Date:   Wed,  3 Jun 2020 13:33:03 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Like Xu <like.xu@...ux.intel.com>
Subject: [PATCH] KVM: VMX: Always treat MSR_IA32_PERF_CAPABILITIES as a valid PMU MSR

Unconditionally return true when querying the validity of
MSR_IA32_PERF_CAPABILITIES so as to defer the validity check to
intel_pmu_{get,set}_msr(), which can properly give the MSR a pass when
the access is initiated from host userspace.  The MSR is emulated so
there is no underlying hardware dependency to worry about.

Fixes: 27461da31089a ("KVM: x86/pmu: Support full width counting")
Cc: Like Xu <like.xu@...ux.intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---

KVM selftests are completely hosed for me, everything fails on KVM_GET_MSRS.

 arch/x86/kvm/vmx/pmu_intel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index d33d890b605f..bdcce65c7a1d 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -181,7 +181,7 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
 		ret = pmu->version > 1;
 		break;
 	case MSR_IA32_PERF_CAPABILITIES:
-		ret = guest_cpuid_has(vcpu, X86_FEATURE_PDCM);
+		ret = 1;
 		break;
 	default:
 		ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) ||
-- 
2.26.0