[PATCH 20/23] KVM: x86/pmu: Request guest PMI for guest-induced PMIs

[Zide Chen]

When PMU partitioning is enabled, guest-induced PMIs that occur in
guest mode may be delivered to the host perf PMI handler, resulting
in a VM-Exit.

intel_mediated_pmu_put() reads the hardware GLOBAL_STATUS MSR into
pmu->global_status and masks it to the subset owned by the guest.
Request a guest PMI when the saved status indicates a pending guest
PMI, i.e. when

- an overflow status bit (47:0) is set for a counter whose PMI-enable
  bit is enabled; or
- a miscellaneous status bit without a corresponding PMI-enable control
  is set.

Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
---
 arch/x86/kvm/pmu.c           |  3 ++-
 arch/x86/kvm/pmu.h           |  1 +
 arch/x86/kvm/vmx/pmu_intel.c | 42 ++++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 23177c38f286..f99ddd6549f7 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -1112,7 +1112,7 @@ void kvm_pmu_destroy(struct kvm_vcpu *vcpu)
 	kvm_pmu_reset(vcpu);
 }
 
-static bool pmc_is_pmi_enabled(struct kvm_pmc *pmc)
+bool pmc_is_pmi_enabled(struct kvm_pmc *pmc)
 {
 	u8 fixed_ctr_ctrl;
 
@@ -1123,6 +1123,7 @@ static bool pmc_is_pmi_enabled(struct kvm_pmc *pmc)
 					  pmc->idx - KVM_FIXED_PMC_BASE_IDX);
 	return fixed_ctr_ctrl & INTEL_FIXED_0_ENABLE_PMI;
 }
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(pmc_is_pmi_enabled);
 
 static void kvm_pmu_incr_counter(struct kvm_pmc *pmc)
 {
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 30e456302c65..4228eb49c6bf 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -336,6 +336,7 @@ static inline bool kvm_vcpu_has_perf_metrics(struct kvm_vcpu *vcpu)
 	return kvm_vcpu_get_perf_caps(vcpu) & PERF_CAP_PERF_METRICS;
 }
 
+bool pmc_is_pmi_enabled(struct kvm_pmc *pmc);
 void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu);
 int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
 int kvm_pmu_check_rdpmc_early(struct kvm_vcpu *vcpu, unsigned int idx);
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index e43380f79c72..7fab735252d7 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -985,6 +985,46 @@ static void intel_mediated_pmu_load(struct kvm_vcpu *vcpu, u64 host_global_ctrl)
 	       pmu->fixed_ctr_ctrl_hw | intel_fixed_ctrl_host_bits(pmu));
 }
 
+static void intel_perfmon_mask_request_pmi(struct kvm_vcpu *vcpu)
+{
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+	struct kvm_pmc *pmc;
+	int i;
+
+	if (!kvm_vcpu_has_perfmon_mask(vcpu) || !pmu->global_status)
+		return;
+
+	/*
+	 * pmu->global_status should never carry a bit that isn't
+	 * guest-owned per pmu->perfmon_mask; such a bit would mean a
+	 * host-owned resource is being (mis)reported to the guest.
+	 */
+	WARN_ON_ONCE(pmu->global_status & ~pmu->perfmon_mask);
+
+	/*
+	 * Bit 48 is currently the only miscellaneous status bit (63:48) that
+	 * can be guest-owned; it indicates that a PMI is triggered, regardless
+	 * of fixed counter 3's PMI-enable state.
+	 */
+	if (pmu->global_status & GLOBAL_STATUS_PERF_METRICS_OVF) {
+		kvm_make_request(KVM_REQ_PMI, vcpu);
+		return;
+	}
+
+	/*
+	 * Match bare-metal behavior for counter bits (47:0): request a guest
+	 * PMI if any overflowed counter actually has its PMI-enable bit set.
+	 */
+	for_each_set_bit(i, (unsigned long *)&pmu->global_status,
+			 GLOBAL_STATUS_PERF_METRICS_OVF_BIT) {
+		pmc = kvm_pmc_idx_to_pmc(pmu, i);
+		if (pmc && pmc_is_pmi_enabled(pmc)) {
+			kvm_make_request(KVM_REQ_PMI, vcpu);
+			break;
+		}
+	}
+}
+
 static void intel_mediated_pmu_put(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -1029,6 +1069,8 @@ static void intel_mediated_pmu_put(struct kvm_vcpu *vcpu)
 		if (pmu->perf_metrics)
 			wrmsrq(MSR_PERF_METRICS, 0);
 	}
+
+	intel_perfmon_mask_request_pmi(vcpu);
 }
 
 static bool intel_pmu_validate_perfmon_mask(void)
-- 
2.55.0