[RFC PATCH v3 44/58] KVM: x86/pmu: Implement emulated counter increment for passthrough PMU

[Mingwei Zhang <mizhang@xxxxxxxxxx>]

Implement emulated counter increment for passthrough PMU under KVM_REQ_PMU.
Defer the counter increment to KVM_REQ_PMU handler because counter
increment requests come from kvm_pmu_trigger_event() which can be triggered
within the KVM_RUN inner loop or outside of the inner loop. This means the
counter increment could happen before or after PMU context switch.

So process counter increment in one place makes the implementation simple.

Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Co-developed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/pmu.c | 41 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 5cc539bdcc7e..41057d0122bd 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -510,6 +510,18 @@ static int reprogram_counter(struct kvm_pmc *pmc)
 				     eventsel & ARCH_PERFMON_EVENTSEL_INT);
 }
 
+static void kvm_pmu_handle_event_in_passthrough_pmu(struct kvm_vcpu *vcpu)
+{
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
+	static_call_cond(kvm_x86_pmu_set_overflow)(vcpu);
+
+	if (atomic64_read(&pmu->__reprogram_pmi)) {
+		kvm_make_request(KVM_REQ_PMI, vcpu);
+		atomic64_set(&pmu->__reprogram_pmi, 0ull);
+	}
+}
+
 void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
 {
 	DECLARE_BITMAP(bitmap, X86_PMC_IDX_MAX);
@@ -517,6 +529,9 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
 	struct kvm_pmc *pmc;
 	int bit;
 
+	if (is_passthrough_pmu_enabled(vcpu))
+		return kvm_pmu_handle_event_in_passthrough_pmu(vcpu);
+
 	bitmap_copy(bitmap, pmu->reprogram_pmi, X86_PMC_IDX_MAX);
 
 	/*
@@ -848,6 +863,17 @@ void kvm_pmu_destroy(struct kvm_vcpu *vcpu)
 	kvm_pmu_reset(vcpu);
 }
 
+static void kvm_passthrough_pmu_incr_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
+{
+	if (static_call(kvm_x86_pmu_incr_counter)(pmc)) {
+		__set_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->global_status);
+		kvm_make_request(KVM_REQ_PMU, vcpu);
+
+		if (pmc->eventsel & ARCH_PERFMON_EVENTSEL_INT)
+			set_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->reprogram_pmi);
+	}
+}
+
 static void kvm_pmu_incr_counter(struct kvm_pmc *pmc)
 {
 	pmc->emulated_counter++;
@@ -880,7 +906,8 @@ static inline bool cpl_is_matched(struct kvm_pmc *pmc)
 	return (static_call(kvm_x86_get_cpl)(pmc->vcpu) == 0) ? select_os : select_user;
 }
 
-void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 eventsel)
+static void __kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 eventsel,
+				    bool is_passthrough)
 {
 	DECLARE_BITMAP(bitmap, X86_PMC_IDX_MAX);
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -914,9 +941,19 @@ void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 eventsel)
 		    !pmc_event_is_allowed(pmc) || !cpl_is_matched(pmc))
 			continue;
 
-		kvm_pmu_incr_counter(pmc);
+		if (is_passthrough)
+			kvm_passthrough_pmu_incr_counter(vcpu, pmc);
+		else
+			kvm_pmu_incr_counter(pmc);
 	}
 }
+
+void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 eventsel)
+{
+	bool is_passthrough = is_passthrough_pmu_enabled(vcpu);
+
+	__kvm_pmu_trigger_event(vcpu, eventsel, is_passthrough);
+}
 EXPORT_SYMBOL_GPL(kvm_pmu_trigger_event);
 
 static bool is_masked_filter_valid(const struct kvm_x86_pmu_event_filter *filter)
-- 
2.46.0.rc1.232.g9752f9e123-goog