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>

3 files changed, 14 insertions, 6 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b5a64621d5af..3dd84c996d56 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/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);
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index cfc258a6bf97..c53e797e7369 100644
--- a/arch/x86/kvm/pmu.c
+++ b/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))) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2aaba814f1c8..78c6f90a60cc 100644
--- a/arch/x86/kvm/x86.c
+++ b/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);