[PATCH v6 15/19] KVM: arm64: Detect overflows for the Partitioned PMU
From: Colton Lewis <hidden>
Date: 2026-02-09 22:41:01
Also in:
kvm, kvmarm, linux-doc, linux-kselftest, linux-perf-users, lkml
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
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 <redacted> --- 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))
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2.53.0.rc2.204.g2597b5adb4-goog