[PATCH] KVM: do not #GP on perf MSR writes when vPMU is disabled

[Gleb Natapov <gleb@redhat.com>]

Return to behaviour perf MSR had before introducing vPMU in case vPMU
is disabled. Some guests access those registers unconditionally and do
not expect it to fail.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c95ca2d..9c912f0b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1495,6 +1495,8 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 
 int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 {
+	bool pr = false;
+
 	switch (msr) {
 	case MSR_EFER:
 		return set_efer(vcpu, data);
@@ -1635,6 +1637,18 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		pr_unimpl(vcpu, "unimplemented perfctr wrmsr: "
 			"0x%x data 0x%llx\n", msr, data);
 		break;
+	case MSR_P6_PERFCTR0:
+	case MSR_P6_PERFCTR1:
+		pr = true;
+	case MSR_P6_EVNTSEL0:
+	case MSR_P6_EVNTSEL1:
+		if (kvm_pmu_msr(vcpu, msr))
+			return kvm_pmu_set_msr(vcpu, msr, data);
+
+		if (pr || data != 0)
+			pr_unimpl(vcpu, "disabled perfctr wrmsr: "
+				"0x%x data 0x%llx\n", msr, data);
+		break;
 	case MSR_K7_CLK_CTL:
 		/*
 		 * Ignore all writes to this no longer documented MSR.
@@ -1845,6 +1859,14 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	case MSR_FAM10H_MMIO_CONF_BASE:
 		data = 0;
 		break;
+	case MSR_P6_PERFCTR0:
+	case MSR_P6_PERFCTR1:
+	case MSR_P6_EVNTSEL0:
+	case MSR_P6_EVNTSEL1:
+		if (kvm_pmu_msr(vcpu, msr))
+			return kvm_pmu_get_msr(vcpu, msr, pdata);
+		data = 0;
+		break;
 	case MSR_IA32_UCODE_REV:
 		data = 0x100000000ULL;
 		break;
--
			Gleb.