linux-kernel - [PATCH] KVM: x86/vPMU: Forbid reading from MSR_F15H_PERF MSRs when guest doesn't have X86_FEATURE_PERFCTR

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Date:   Mon, 29 Mar 2021 14:48:04 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Wei Huang <wei.huang2@....com>, Joerg Roedel <joro@...tes.org>,
        Haiwei Li <lihaiwei.kernel@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86/vPMU: Forbid reading from MSR_F15H_PERF MSRs when guest doesn't have X86_FEATURE_PERFCTR_CORE

MSR_F15H_PERF_CTL0-5, MSR_F15H_PERF_CTR0-5 MSRs have a CPUID bit assigned
to them (X86_FEATURE_PERFCTR_CORE) and when it wasn't exposed to the guest
the correct behavior is to inject #GP an not just return zero.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/x86.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fe806e894212..125453155ede 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3381,6 +3381,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = 0;
 		break;
 	case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
+		if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
+			return kvm_pmu_get_msr(vcpu, msr_info);
+		if (!msr_info->host_initiated)
+			return 1;
+		msr_info->data = 0;
+		break;
 	case MSR_K7_EVNTSEL0 ... MSR_K7_EVNTSEL3:
 	case MSR_K7_PERFCTR0 ... MSR_K7_PERFCTR3:
 	case MSR_P6_PERFCTR0 ... MSR_P6_PERFCTR1:
-- 
2.30.2