linux-kernel - [PATCH v2] KVM: SVM: emulate MSR_IA32_PERF

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Date:   Thu, 18 Jun 2020 13:13:28 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Like Xu <like.xu@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2] KVM: SVM: emulate MSR_IA32_PERF_CAPABILITIES

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 <jmattson@...gle.com>
Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.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