linux-kernel - [PATCH v5 39/44] KVM: x86/pmu: Handle emulated instruction for mediated vPMU

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Message-ID: <20250806195706.1650976-40-seanjc@google.com>
Date: Wed,  6 Aug 2025 12:57:01 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Xin Li <xin@...or.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Andy Lutomirski <luto@...nel.org>, 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: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, loongarch@...ts.linux.dev, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, Kan Liang <kan.liang@...ux.intel.com>, 
	Yongwei Ma <yongwei.ma@...el.com>, Mingwei Zhang <mizhang@...gle.com>, 
	Xiong Zhang <xiong.y.zhang@...ux.intel.com>, Sandipan Das <sandipan.das@....com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [PATCH v5 39/44] 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>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/pmu.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 77042cad3155..ddab1630a978 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -1018,10 +1018,45 @@ void kvm_pmu_destroy(struct kvm_vcpu *vcpu)
 	kvm_pmu_reset(vcpu);
 }
 
+static bool pmc_is_pmi_enabled(struct kvm_pmc *pmc)
+{
+	u8 fixed_ctr_ctrl;
+
+	if (pmc_is_gp(pmc))
+		return pmc->eventsel & ARCH_PERFMON_EVENTSEL_INT;
+
+	fixed_ctr_ctrl = fixed_ctrl_field(pmc_to_pmu(pmc)->fixed_ctr_ctrl,
+					  pmc->idx - KVM_FIXED_PMC_BASE_IDX);
+	return fixed_ctr_ctrl & INTEL_FIXED_0_ENABLE_PMI;
+}
+
 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_vcpu_has_mediated_pmu(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_is_pmi_enabled(pmc))
+			kvm_make_request(KVM_REQ_PMI, vcpu);
+	}
 }
 
 static inline bool cpl_is_matched(struct kvm_pmc *pmc)
-- 
2.50.1.565.gc32cd1483b-goog