KVM: x86/pmu: preserve IA32_PERF_CAPABILITIES across CPUID refresh

Once MSR_IA32_PERF_CAPABILITIES is changed via vmx_set_msr(), the
value should not be changed by cpuid(). To ensure that the new value
is kept, the default initialization path is moved to intel_pmu_init().
The effective value of the MSR will be 0 if PDCM is clear, however.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/pmu_intel.c

@@ -152,12 +152,17 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
 	return &counters[array_index_nospec(idx, num_counters)];
 }
 
-static inline bool fw_writes_is_enabled(struct kvm_vcpu *vcpu)
+static inline u64 vcpu_get_perf_capabilities(struct kvm_vcpu *vcpu)
 {
 	if (!guest_cpuid_has(vcpu, X86_FEATURE_PDCM))
-		return false;
+		return 0;
 
-	return vcpu->arch.perf_capabilities & PMU_CAP_FW_WRITES;
+	return vcpu->arch.perf_capabilities;
+}
+
+static inline bool fw_writes_is_enabled(struct kvm_vcpu *vcpu)
+{
+	return (vcpu_get_perf_capabilities(vcpu) & PMU_CAP_FW_WRITES) != 0;
 }
 
 static inline struct kvm_pmc *get_fw_gp_pmc(struct kvm_pmu *pmu, u32 msr)
@@ -327,7 +332,6 @@ 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)
@@ -340,8 +344,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		return;
 
 	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);
@@ -405,6 +407,8 @@ 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 = vmx_get_perf_capabilities();
 }
 
 static void intel_pmu_reset(struct kvm_vcpu *vcpu)