[PATCH 2/2] KVM: vmx/pmu: Use IA32_PERF_CAPABILITIES to adjust features visibility

[Like Xu]

On Intel platforms, KVM agent could configure MSR_IA32_PERF_CAPABILITIES
(such as unmask some vmx-supported bits in vcpu->arch.perf_capabilities)
to adjust the visibility of guest PMU features for vPMU-enabled guests.

Once MSR_IA32_PERF_CAPABILITIES is changed via vmx_set_msr() validly,
the adjustment in intel_pmu_refresh() will be triggered. To ensure the
sustainability of the new value, the default initialization path is
moved to intel_pmu_init().

Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx/pmu_intel.c | 6 +++---
 arch/x86/kvm/vmx/vmx.c       | 5 +++++
 arch/x86/kvm/x86.c           | 2 +-
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 01c7d84ecf3e..7c18c85328da 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -327,7 +327,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
 	pmu->version = 0;
 	pmu->reserved_bits = 0xffffffff00200000ull;
-	vcpu->arch.perf_capabilities = 0;
 
 	entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);
 	if (!entry)
@@ -342,8 +341,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	vcpu->arch.ia32_misc_enable_msr |= MSR_IA32_MISC_ENABLE_EMON;
 
 	perf_get_x86_pmu_capability(&x86_pmu);
-	if (guest_cpuid_has(vcpu, X86_FEATURE_PDCM))
-		vcpu->arch.perf_capabilities = vmx_get_perf_capabilities();
 
 	pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
 					 x86_pmu.num_counters_gp);
@@ -403,6 +400,9 @@ static void intel_pmu_init(struct kvm_vcpu *vcpu)
 		pmu->fixed_counters[i].idx = i + INTEL_PMC_IDX_FIXED;
 		pmu->fixed_counters[i].current_config = 0;
 	}
+
+	vcpu->arch.perf_capabilities = guest_cpuid_has(vcpu, X86_FEATURE_PDCM) ?
+		vmx_get_perf_capabilities() : 0;
 }
 
 static void intel_pmu_reset(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4551a7e80ebc..a3f3ce222af1 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2182,6 +2182,11 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if ((data >> 32) != 0)
 			return 1;
 		goto find_uret_msr;
+	case MSR_IA32_PERF_CAPABILITIES:
+		if (data && !vcpu_to_pmu(vcpu)->version)
+			return 1;
+		ret = kvm_set_msr_common(vcpu, msr_info);
+		break;
 
 	default:
 	find_uret_msr:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d7b8f98ada93..a525447a92c6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2985,7 +2985,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 
 		vcpu->arch.perf_capabilities = data;
-
+		kvm_pmu_refresh(vcpu);
 		return 0;
 		}
 	case MSR_EFER:
-- 
2.21.3