linux-kernel - [PATCH v5 34/44] KVM: x86/pmu: Introduce eventsel

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Message-ID: <20250806195706.1650976-35-seanjc@google.com>
Date: Wed,  6 Aug 2025 12:56:56 -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 34/44] KVM: x86/pmu: Introduce eventsel_hw to prepare for
 pmu event filtering

From: Mingwei Zhang <mizhang@...gle.com>

Introduce eventsel_hw and fixed_ctr_ctrl_hw to store the actual HW value in
PMU event selector MSRs. In mediated PMU checks events before allowing the
event values written to the PMU MSRs. However, to match the HW behavior,
when PMU event checks fails, KVM should allow guest to read the value back.

This essentially requires an extra variable to separate the guest requested
value from actual PMU MSR value. Note this only applies to event selectors.

Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
Co-developed-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/kvm_host.h | 2 ++
 arch/x86/kvm/pmu.c              | 7 +++++--
 arch/x86/kvm/svm/pmu.c          | 1 +
 arch/x86/kvm/vmx/pmu_intel.c    | 2 ++
 4 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b891bd92fc83..5512e33db14a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -528,6 +528,7 @@ struct kvm_pmc {
 	 */
 	u64 emulated_counter;
 	u64 eventsel;
+	u64 eventsel_hw;
 	struct perf_event *perf_event;
 	struct kvm_vcpu *vcpu;
 	/*
@@ -556,6 +557,7 @@ struct kvm_pmu {
 	unsigned nr_arch_fixed_counters;
 	unsigned available_event_types;
 	u64 fixed_ctr_ctrl;
+	u64 fixed_ctr_ctrl_hw;
 	u64 fixed_ctr_ctrl_rsvd;
 	u64 global_ctrl;
 	u64 global_status;
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 082d2905882b..e39ae37f0280 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -890,11 +890,14 @@ static void kvm_pmu_reset(struct kvm_vcpu *vcpu)
 		pmc->counter = 0;
 		pmc->emulated_counter = 0;
 
-		if (pmc_is_gp(pmc))
+		if (pmc_is_gp(pmc)) {
 			pmc->eventsel = 0;
+			pmc->eventsel_hw = 0;
+		}
 	}
 
-	pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status = 0;
+	pmu->fixed_ctr_ctrl = pmu->fixed_ctr_ctrl_hw = 0;
+	pmu->global_ctrl = pmu->global_status = 0;
 
 	kvm_pmu_call(reset)(vcpu);
 }
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 9ffd44a5d474..9641ef5d0dd7 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -165,6 +165,7 @@ static int amd_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		data &= ~pmu->reserved_bits;
 		if (data != pmc->eventsel) {
 			pmc->eventsel = data;
+			pmc->eventsel_hw = data;
 			kvm_pmu_request_counter_reprogram(pmc);
 		}
 		return 0;
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 2bdddb95816e..6874c522577e 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -61,6 +61,7 @@ static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
 	int i;
 
 	pmu->fixed_ctr_ctrl = data;
+	pmu->fixed_ctr_ctrl_hw = data;
 	for (i = 0; i < pmu->nr_arch_fixed_counters; i++) {
 		u8 new_ctrl = fixed_ctrl_field(data, i);
 		u8 old_ctrl = fixed_ctrl_field(old_fixed_ctr_ctrl, i);
@@ -430,6 +431,7 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 			if (data != pmc->eventsel) {
 				pmc->eventsel = data;
+				pmc->eventsel_hw = data;
 				kvm_pmu_request_counter_reprogram(pmc);
 			}
 			break;
-- 
2.50.1.565.gc32cd1483b-goog