[PATCH V5 6/7] 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 to read it.

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>
---
v5: new patch.
---
 arch/x86/kvm/pmu.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 7aafc5db1346..af5b14f44e4b 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -755,6 +755,16 @@ static int kvm_pmu_rdpmc_vmware(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
 	return 0;
 }
 
+static int kvm_pmu_rdpmc_metrics(struct kvm_vcpu *vcpu,
+				 unsigned idx, u64 *data)
+{
+	if (!kvm_vcpu_has_perf_metrics(vcpu))
+		return 1;
+
+	*data = vcpu_to_pmu(vcpu)->perf_metrics;
+	return 0;
+}
+
 int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -767,15 +777,18 @@ int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
 	if (is_vmware_backdoor_pmc(idx))
 		return kvm_pmu_rdpmc_vmware(vcpu, idx, data);
 
-	pmc = kvm_pmu_call(rdpmc_ecx_to_pmc)(vcpu, idx, &mask);
-	if (!pmc)
-		return 1;
-
 	if (!kvm_is_cr4_bit_set(vcpu, X86_CR4_PCE) &&
 	    (kvm_x86_call(get_cpl)(vcpu) != 0) &&
 	    kvm_is_cr0_bit_set(vcpu, X86_CR0_PE))
 		return 1;
 
+	if (idx & INTEL_PMC_FIXED_RDPMC_METRICS)
+		return kvm_pmu_rdpmc_metrics(vcpu, idx, data);
+
+	pmc = kvm_pmu_call(rdpmc_ecx_to_pmc)(vcpu, idx, &mask);
+	if (!pmc)
+		return 1;
+
 	*data = pmc_read_counter(pmc) & mask;
 	return 0;
 }
@@ -803,6 +816,14 @@ 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)
+{
+	if (!(kvm_host.perf_capabilities & PERF_CAP_PERF_METRICS))
+		return false;
+
+	return !kvm_vcpu_has_perf_metrics(vcpu);
+}
+
 bool kvm_need_rdpmc_intercept(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -815,6 +836,7 @@ 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);
 }
-- 
2.54.0