pmu: prepare for migration support

In order to migrate the PMU state correctly, we need to restore the
values of MSR_CORE_PERF_GLOBAL_STATUS (a read-only register) and
MSR_CORE_PERF_GLOBAL_OVF_CTRL (which has side effects when written).
We also need to write the full 40-bit value of the performance counter,
which would only be possible with a v3 architectural PMU's full-width
counter MSRs.

To distinguish host-initiated writes from the guest's, pass the
full struct msr_data to kvm_pmu_set_msr.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1030,7 +1030,7 @@ void kvm_pmu_reset(struct kvm_vcpu *vcpu);
 void kvm_pmu_cpuid_update(struct kvm_vcpu *vcpu);
 bool kvm_pmu_msr(struct kvm_vcpu *vcpu, u32 msr);
 int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *data);
-int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data);
+int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
 int kvm_pmu_read_pmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
 void kvm_handle_pmu_event(struct kvm_vcpu *vcpu);
 void kvm_deliver_pmi(struct kvm_vcpu *vcpu);

arch/x86/kvm/pmu.c

@@ -360,10 +360,12 @@ int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data)
 	return 1;
 }
 
-int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
+int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
 	struct kvm_pmu *pmu = &vcpu->arch.pmu;
 	struct kvm_pmc *pmc;
+	u32 index = msr_info->index;
+	u64 data = msr_info->data;
 
 	switch (index) {
 	case MSR_CORE_PERF_FIXED_CTR_CTRL:
@@ -375,6 +377,10 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
 		}
 		break;
 	case MSR_CORE_PERF_GLOBAL_STATUS:
+		if (msr_info->host_initiated) {
+			pmu->global_status = data;
+			return 0;
+		}
 		break; /* RO MSR */
 	case MSR_CORE_PERF_GLOBAL_CTRL:
 		if (pmu->global_ctrl == data)
@@ -386,7 +392,8 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
 		break;
 	case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
 		if (!(data & (pmu->global_ctrl_mask & ~(3ull<<62)))) {
-			pmu->global_status &= ~data;
+			if (!msr_info->host_initiated)
+				pmu->global_status &= ~data;
 			pmu->global_ovf_ctrl = data;
 			return 0;
 		}
@@ -394,7 +401,8 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
 	default:
 		if ((pmc = get_gp_pmc(pmu, index, MSR_IA32_PERFCTR0)) ||
 				(pmc = get_fixed_pmc(pmu, index))) {
-			data = (s64)(s32)data;
+			if (!msr_info->host_initiated)
+				data = (s64)(s32)data;
 			pmc->counter += data - read_pmc(pmc);
 			return 0;
 		} else if ((pmc = get_gp_pmc(pmu, index, MSR_P6_EVNTSEL0))) {

arch/x86/kvm/x86.c

@@ -2040,7 +2040,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_P6_EVNTSEL0:
 	case MSR_P6_EVNTSEL1:
 		if (kvm_pmu_msr(vcpu, msr))
-			return kvm_pmu_set_msr(vcpu, msr, data);
+			return kvm_pmu_set_msr(vcpu, msr_info);
 
 		if (pr || data != 0)
 			vcpu_unimpl(vcpu, "disabled perfctr wrmsr: "
@@ -2086,7 +2086,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (msr && (msr == vcpu->kvm->arch.xen_hvm_config.msr))
 			return xen_hvm_config(vcpu, data);
 		if (kvm_pmu_msr(vcpu, msr))
-			return kvm_pmu_set_msr(vcpu, msr, data);
+			return kvm_pmu_set_msr(vcpu, msr_info);
 		if (!ignore_msrs) {
 			vcpu_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n",
 				    msr, data);