linux-kernel - [PATCH v6 15/19] KVM: arm64: Detect overflows for the Partitioned PMU

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Message-ID: <20260209221414.2169465-16-coltonlewis@google.com>
Date: Mon,  9 Feb 2026 22:14:10 +0000
From: Colton Lewis <coltonlewis@...gle.com>
To: kvm@...r.kernel.org
Cc: Alexandru Elisei <alexandru.elisei@....com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Jonathan Corbet <corbet@....net>, Russell King <linux@...linux.org.uk>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Mingwei Zhang <mizhang@...gle.com>, 
	Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>, 
	Zenghui Yu <yuzenghui@...wei.com>, Mark Rutland <mark.rutland@....com>, 
	Shuah Khan <shuah@...nel.org>, Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	linux-perf-users@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	Colton Lewis <coltonlewis@...gle.com>
Subject: [PATCH v6 15/19] KVM: arm64: Detect overflows for the Partitioned PMU

When we re-enter the VM after handling a PMU interrupt, calculate
whether it was any of the guest counters that overflowed and inject an
interrupt into the guest if so.

Signed-off-by: Colton Lewis <coltonlewis@...gle.com>
---
 arch/arm64/kvm/pmu-direct.c | 30 ++++++++++++++++++++++++++++++
 arch/arm64/kvm/pmu-emul.c   |  4 ++--
 arch/arm64/kvm/pmu.c        |  6 +++++-
 include/kvm/arm_pmu.h       |  2 ++
 4 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 79d13a0aa2fd6..6ebb59d2aa0e7 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -378,3 +378,33 @@ void kvm_pmu_handle_guest_irq(struct arm_pmu *pmu, u64 pmovsr)
 
 	__vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, govf);
 }
+
+/**
+ * kvm_pmu_part_overflow_status() - Determine if any guest counters have overflowed
+ * @vcpu: Pointer to struct kvm_vcpu
+ *
+ * Determine if any guest counters have overflowed and therefore an
+ * IRQ needs to be injected into the guest. If access is still free,
+ * then the guest hasn't accessed the PMU yet so we know the guest
+ * context is not loaded onto the pCPU and an overflow is impossible.
+ *
+ * Return: True if there was an overflow, false otherwise
+ */
+bool kvm_pmu_part_overflow_status(struct kvm_vcpu *vcpu)
+{
+	struct arm_pmu *pmu;
+	u64 mask, pmovs, pmint, pmcr;
+	bool overflow;
+
+	if (vcpu->arch.pmu.access == VCPU_PMU_ACCESS_FREE)
+		return false;
+
+	pmu = vcpu->kvm->arch.arm_pmu;
+	mask = kvm_pmu_guest_counter_mask(pmu);
+	pmovs = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
+	pmint = read_pmintenset();
+	pmcr = read_pmcr();
+	overflow = (pmcr & ARMV8_PMU_PMCR_E) && (mask & pmovs & pmint);
+
+	return overflow;
+}
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index a40db0d5120ff..c5438de3e5a74 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -268,7 +268,7 @@ void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val)
  * counter where the values of the global enable control, PMOVSSET_EL0[n], and
  * PMINTENSET_EL1[n] are all 1.
  */
-bool kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
+bool kvm_pmu_emul_overflow_status(struct kvm_vcpu *vcpu)
 {
 	u64 reg = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
 
@@ -405,7 +405,7 @@ static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
 		kvm_pmu_counter_increment(vcpu, BIT(idx + 1),
 					  ARMV8_PMUV3_PERFCTR_CHAIN);
 
-	if (kvm_pmu_overflow_status(vcpu)) {
+	if (kvm_pmu_emul_overflow_status(vcpu)) {
 		kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
 
 		if (!in_nmi())
diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index b198356d772ca..72d5b7cb3d93e 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -408,7 +408,11 @@ static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
 	struct kvm_pmu *pmu = &vcpu->arch.pmu;
 	bool overflow;
 
-	overflow = kvm_pmu_overflow_status(vcpu);
+	if (kvm_vcpu_pmu_is_partitioned(vcpu))
+		overflow = kvm_pmu_part_overflow_status(vcpu);
+	else
+		overflow = kvm_pmu_emul_overflow_status(vcpu);
+
 	if (pmu->irq_level == overflow)
 		return;
 
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 3d922bd145d4e..93586691a2790 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -90,6 +90,8 @@ bool kvm_set_pmuserenr(u64 val);
 void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu);
 void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
 void kvm_vcpu_pmu_resync_el0(void);
+bool kvm_pmu_emul_overflow_status(struct kvm_vcpu *vcpu);
+bool kvm_pmu_part_overflow_status(struct kvm_vcpu *vcpu);
 
 #define kvm_vcpu_has_pmu(vcpu)					\
 	(vcpu_has_feature(vcpu, KVM_ARM_VCPU_PMU_V3))
-- 
2.53.0.rc2.204.g2597b5adb4-goog