We use "pmc->idx" and the "chained" bitmap to determine if the pmc is chained, in kvm_pmu_pmc_is_chained(). But idx might be uninitialized (and random) when we doing this decision, through a KVM_ARM_VCPU_INIT ioctl -> kvm_pmu_vcpu_reset(). And the test_bit() against this random idx will potentially hit a KASAN BUG [1]. In general, idx is the static property of a PMU counter that is not expected to be modified across resets, as suggested by Julien. It looks more reasonable if we can setup the PMU counter idx for a vcpu in its creation time. Introduce a new function - kvm_pmu_vcpu_init() for this basic setup. Oh, and the KASAN BUG will get fixed this way. [1] https://www.spinics.net/lists/kvm-arm/msg36700.html Fixes: 80f393a23be6 ("KVM: arm/arm64: Support chained PMU counters") Suggested-by: Andrew Murray <andrew.murray@xxxxxxx> Suggested-by: Julien Thierry <julien.thierry@xxxxxxx> Cc: Marc Zyngier <maz@xxxxxxxxxx> Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx> --- Changes since v1: - Introduce kvm_pmu_vcpu_init() in vcpu's creation time, move the assignment of pmc->idx into it. - Thus change the subject. The old one is "KVM: arm/arm64: Assign pmc->idx before kvm_pmu_stop_counter()". Julien, I haven't collected your Acked-by into this version. If you're still happy with the change, please Ack again. Thanks! include/kvm/arm_pmu.h | 2 ++ virt/kvm/arm/arm.c | 2 ++ virt/kvm/arm/pmu.c | 18 +++++++++++++++--- 3 files changed, 19 insertions(+), 3 deletions(-) diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h index 16c769a..6db0304 100644 --- a/include/kvm/arm_pmu.h +++ b/include/kvm/arm_pmu.h @@ -34,6 +34,7 @@ struct kvm_pmu { u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx); void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val); u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu); +void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu); void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu); void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu); void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val); @@ -71,6 +72,7 @@ static inline u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu) { return 0; } +static inline void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu) {} static inline void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu) {} static inline void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu) {} static inline void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val) {} diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index f645c0f..c704fa6 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -340,6 +340,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) /* Set up the timer */ kvm_timer_vcpu_init(vcpu); + kvm_pmu_vcpu_init(vcpu); + kvm_arm_reset_debug_ptr(vcpu); return kvm_vgic_vcpu_init(vcpu); diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c index 3dd8238..362a018 100644 --- a/virt/kvm/arm/pmu.c +++ b/virt/kvm/arm/pmu.c @@ -215,6 +215,20 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc) } /** + * kvm_pmu_vcpu_init - assign pmu counter idx for cpu + * @vcpu: The vcpu pointer + * + */ +void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu) +{ + int i; + struct kvm_pmu *pmu = &vcpu->arch.pmu; + + for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) + pmu->pmc[i].idx = i; +} + +/** * kvm_pmu_vcpu_reset - reset pmu state for cpu * @vcpu: The vcpu pointer * @@ -224,10 +238,8 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu) int i; struct kvm_pmu *pmu = &vcpu->arch.pmu; - for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) { + for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]); - pmu->pmc[i].idx = i; - } bitmap_zero(vcpu->arch.pmu.chained, ARMV8_PMU_MAX_COUNTER_PAIRS); } -- 1.8.3.1 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
