KVM: x86/pmu: Accept 0 for absent PMU MSRs when host-initiated if !enable_pmu

Whenever an MSR is part of KVM_GET_MSR_INDEX_LIST, as is the case for
MSR_K7_EVNTSEL0 or MSR_F15H_PERF_CTL0, it has to be always retrievable
and settable with KVM_GET_MSR and KVM_SET_MSR.

Accept a zero value for these MSRs to obey the contract.
Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20220601031925.59693-1-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/pmu.c

@@ -442,11 +442,19 @@ static void kvm_pmu_mark_pmc_in_use(struct kvm_vcpu *vcpu, u32 msr)
 
 int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
+	if (msr_info->host_initiated && !vcpu->kvm->arch.enable_pmu) {
+		msr_info->data = 0;
+		return 0;
+	}
+
 	return static_call(kvm_x86_pmu_get_msr)(vcpu, msr_info);
 }
 
 int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
+	if (msr_info->host_initiated && !vcpu->kvm->arch.enable_pmu)
+		return !!msr_info->data;
+
 	kvm_pmu_mark_pmc_in_use(vcpu, msr_info->index);
 	return static_call(kvm_x86_pmu_set_msr)(vcpu, msr_info);
 }

arch/x86/kvm/svm/pmu.c

@@ -182,7 +182,16 @@ static struct kvm_pmc *amd_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
 static bool amd_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr, bool host_initiated)
 {
 	/* All MSRs refer to exactly one PMC, so msr_idx_to_pmc is enough.  */
-	return false;
+	if (!host_initiated)
+		return false;
+
+	switch (msr) {
+	case MSR_K7_EVNTSEL0 ... MSR_K7_PERFCTR3:
+	case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
+		return true;
+	default:
+		return false;
+	}
 }
 
 static struct kvm_pmc *amd_msr_idx_to_pmc(struct kvm_vcpu *vcpu, u32 msr)