linux-kernel - [PATCH v4 30/38] KVM: x86/pmu: Handle emulated instruction for mediated vPMU

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Message-ID: <20250324173121.1275209-31-mizhang@google.com>
Date: Mon, 24 Mar 2025 17:31:10 +0000
From: Mingwei Zhang <mizhang@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, Liang@...gle.com, 
	Kan <kan.liang@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	Mingwei Zhang <mizhang@...gle.com>, Yongwei Ma <yongwei.ma@...el.com>, 
	Xiong Zhang <xiong.y.zhang@...ux.intel.com>, Dapeng Mi <dapeng1.mi@...ux.intel.com>, 
	Jim Mattson <jmattson@...gle.com>, Sandipan Das <sandipan.das@....com>, 
	Zide Chen <zide.chen@...el.com>, Eranian Stephane <eranian@...gle.com>, 
	Das Sandipan <Sandipan.Das@....com>, Shukla Manali <Manali.Shukla@....com>, 
	Nikunj Dadhania <nikunj.dadhania@....com>
Subject: [PATCH v4 30/38] KVM: x86/pmu: Handle emulated instruction for
 mediated vPMU

From: Dapeng Mi <dapeng1.mi@...ux.intel.com>

Mediated vPMU needs to accumulate the emulated instructions into counter
and load the counter into HW at vm-entry.

Moreover, if the accumulation leads to counter overflow, KVM needs to
update GLOBAL_STATUS and inject PMI into guest as well.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
---
 arch/x86/kvm/pmu.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 68f203454bbc..f71009ec92cf 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -911,10 +911,50 @@ void kvm_pmu_destroy(struct kvm_vcpu *vcpu)
 	kvm_pmu_reset(vcpu);
 }
 
+static bool pmc_pmi_enabled(struct kvm_pmc *pmc)
+{
+	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
+	u8 fixed_ctr_ctrl;
+	bool pmi_enabled;
+
+	if (pmc_is_gp(pmc)) {
+		pmi_enabled = pmc->eventsel & ARCH_PERFMON_EVENTSEL_INT;
+	} else {
+		fixed_ctr_ctrl = fixed_ctrl_field(pmu->fixed_ctr_ctrl,
+						  pmc->idx - KVM_FIXED_PMC_BASE_IDX);
+		pmi_enabled = fixed_ctr_ctrl & INTEL_FIXED_0_ENABLE_PMI;
+	}
+
+	return pmi_enabled;
+}
+
 static void kvm_pmu_incr_counter(struct kvm_pmc *pmc)
 {
-	pmc->emulated_counter++;
-	kvm_pmu_request_counter_reprogram(pmc);
+	struct kvm_vcpu *vcpu = pmc->vcpu;
+
+	/*
+	 * For perf-based PMUs, accumulate software-emulated events separately
+	 * from pmc->counter, as pmc->counter is offset by the count of the
+	 * associated perf event. Request reprogramming, which will consult
+	 * both emulated and hardware-generated events to detect overflow.
+	 */
+	if (!kvm_mediated_pmu_enabled(vcpu)) {
+		pmc->emulated_counter++;
+		kvm_pmu_request_counter_reprogram(pmc);
+		return;
+	}
+
+	/*
+	 * For mediated PMUs, pmc->counter is updated when the vCPU's PMU is
+	 * put, and will be loaded into hardware when the PMU is loaded. Simply
+	 * increment the counter and signal overflow if it wraps to zero.
+	 */
+	pmc->counter = (pmc->counter + 1) & pmc_bitmask(pmc);
+	if (!pmc->counter) {
+		pmc_to_pmu(pmc)->global_status |= BIT_ULL(pmc->idx);
+		if (pmc_pmi_enabled(pmc))
+			kvm_make_request(KVM_REQ_PMI, vcpu);
+	}
 }
 
 static inline bool cpl_is_matched(struct kvm_pmc *pmc)
-- 
2.49.0.395.g12beb8f557-goog