[PATCH v6 7/8] KVM: x86/pmu: Emulate RDPMC on performance metrics

[Zide Chen]

If the host has the PERF_METRICS capability but it's not present on
the guest, RDPMC interception must be enabled and KVM should inject
an #GP when the guest attempts a PERF_METRICS RDPMC.

If the guest has PERF_METRICS but RDPMC interception is enabled for
other reasons, KVM needs to emulate RDPMC with type 2000H.

For simplicity, Metrics Clear Mode is not supported.

Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
---
v6:
- Merge kvm_pmu_rdpmc_metrics() into intel_emulate_rdpmc().
- Reject non-zero index.
v5:
- new patch.
---
 arch/x86/kvm/pmu.c           |  7 +++++++
 arch/x86/kvm/vmx/pmu_intel.c | 14 ++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 8ef2d4761790..04b9c840f218 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -806,6 +806,12 @@ bool kvm_need_perf_global_ctrl_intercept(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_need_perf_global_ctrl_intercept);
 
+static bool kvm_need_perf_metrics_intercept(struct kvm_vcpu *vcpu)
+{
+	return (kvm_host.perf_capabilities & PERF_CAP_PERF_METRICS) &&
+		!kvm_vcpu_has_perf_metrics(vcpu);
+}
+
 bool kvm_need_rdpmc_intercept(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -818,6 +824,7 @@ bool kvm_need_rdpmc_intercept(struct kvm_vcpu *vcpu)
 		return true;
 
 	return kvm_need_any_pmc_intercept(vcpu) ||
+	       kvm_need_perf_metrics_intercept(vcpu) ||
 	       pmu->counter_bitmask[KVM_PMC_GP] != (BIT_ULL(kvm_host_pmu.bit_width_gp) - 1) ||
 	       pmu->counter_bitmask[KVM_PMC_FIXED] != (BIT_ULL(kvm_host_pmu.bit_width_fixed) - 1);
 }
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 080677372c9b..93b5a8360377 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -30,6 +30,7 @@
  */
 #define INTEL_RDPMC_GP		0
 #define INTEL_RDPMC_FIXED	INTEL_PMC_FIXED_RDPMC_BASE
+#define INTEL_RDPMC_METRICS	INTEL_PMC_FIXED_RDPMC_METRICS
 
 #define INTEL_RDPMC_TYPE_MASK	GENMASK(31, 16)
 #define INTEL_RDPMC_INDEX_MASK	GENMASK(15, 0)
@@ -124,6 +125,19 @@ static int intel_emulate_rdpmc(struct kvm_vcpu *vcpu, unsigned int idx,
 		counters = pmu->gp_counters;
 		num_counters = pmu->nr_arch_gp_counters;
 		break;
+	case INTEL_RDPMC_METRICS:
+		if (!kvm_vcpu_has_perf_metrics(vcpu))
+			return 1;
+
+		/*
+		 * The index in ECX[15:0] is implementation specific, but no
+		 * platform currently supports a non-zero index.
+		 */
+		if (idx)
+			return 1;
+
+		*data = pmu->perf_metrics;
+		return 0;
 	default:
 		return 1;
 	}
-- 
2.54.0