[PATCH v2] KVM: SVM: emulate MSR_IA32_PERF_CAPABILITIES

[Vitaly Kuznetsov]

state_test/smm_test selftests are failing on AMD with:
"Unexpected result from KVM_GET_MSRS, r: 51 (failed MSR was 0x345)"

MSR_IA32_PERF_CAPABILITIES is an emulated MSR on Intel but it is not
known to AMD code, emulate it there too (by returning 0 and allowing
userspace to write 0). This way the code is better prepared to the
eventual appearance of the feature in AMD hardware.

Fixes: 27461da31089 ("KVM: x86/pmu: Support full width counting")
Suggested-by: Jim Mattson <jmatt...@google.com>
Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
 arch/x86/kvm/svm/pmu.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 035da07500e8..f13ee3cd6d0f 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -200,7 +200,13 @@ static struct kvm_pmc *amd_rdpmc_ecx_to_pmc(struct 
kvm_vcpu *vcpu,
 
 static bool amd_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
 {
-       /* All MSRs refer to exactly one PMC, so msr_idx_to_pmc is enough.  */
+       switch (msr) {
+       case MSR_IA32_PERF_CAPABILITIES:
+               return true;
+       default:
+               break;
+       }
+
        return false;
 }
 
@@ -221,6 +227,14 @@ static int amd_pmu_get_msr(struct kvm_vcpu *vcpu, struct 
msr_data *msr_info)
        struct kvm_pmc *pmc;
        u32 msr = msr_info->index;
 
+       if (msr == MSR_IA32_PERF_CAPABILITIES) {
+               if (!msr_info->host_initiated &&
+                   !guest_cpuid_has(vcpu, X86_FEATURE_PDCM))
+                       return 1;
+               msr_info->data = vcpu->arch.perf_capabilities;
+               return 0;
+       }
+
        /* MSR_PERFCTRn */
        pmc = get_gp_pmc_amd(pmu, msr, PMU_TYPE_COUNTER);
        if (pmc) {
@@ -244,6 +258,18 @@ static int amd_pmu_set_msr(struct kvm_vcpu *vcpu, struct 
msr_data *msr_info)
        u32 msr = msr_info->index;
        u64 data = msr_info->data;
 
+       if (msr == MSR_IA32_PERF_CAPABILITIES) {
+               if (!msr_info->host_initiated)
+                       return 1;
+
+               /* No feature bits are currently supported */
+               if (data)
+                       return 1;
+
+               vcpu->arch.perf_capabilities = data;
+               return 0;
+       }
+
        /* MSR_PERFCTRn */
        pmc = get_gp_pmc_amd(pmu, msr, PMU_TYPE_COUNTER);
        if (pmc) {
@@ -281,6 +307,7 @@ static void amd_pmu_refresh(struct kvm_vcpu *vcpu)
        pmu->nr_arch_fixed_counters = 0;
        pmu->global_status = 0;
        bitmap_set(pmu->all_valid_pmc_idx, 0, pmu->nr_arch_gp_counters);
+       vcpu->arch.perf_capabilities = 0;
 }
 
 static void amd_pmu_init(struct kvm_vcpu *vcpu)
-- 
2.25.4