Re: [PATCH v6 5/7] KVM: arm64: pmu: Make overflow handler NMI safe
flat view
From: Will Deacon <will@kernel.org>
Date: 2020-09-21 13:43:13
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On Wed, Aug 19, 2020 at 02:34:17PM +0100, Alexandru Elisei wrote:
From: Julien Thierry <redacted> kvm_vcpu_kick() is not NMI safe. When the overflow handler is called from NMI context, defer waking the vcpu to an irq_work queue. Cc: Julien Thierry <redacted> Cc: Marc Zyngier <redacted> Cc: Will Deacon <redacted> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Suzuki K Pouloze <suzuki.poulose@arm.com> Cc: kvm@vger.kernel.org Cc: kvmarm@lists.cs.columbia.edu Signed-off-by: Julien Thierry <redacted> Signed-off-by: Alexandru Elisei <redacted> --- arch/arm64/kvm/pmu-emul.c | 25 ++++++++++++++++++++++++- include/kvm/arm_pmu.h | 1 + 2 files changed, 25 insertions(+), 1 deletion(-)
I'd like an Ack from the KVM side on this one, but some minor comments inline.
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c index f0d0312c0a55..30268397ed06 100644 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c@@ -433,6 +433,22 @@ void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu) kvm_pmu_update_state(vcpu); } +/** + * When perf interrupt is an NMI, we cannot safely notify the vcpu corresponding + * to the event. + * This is why we need a callback to do it once outside of the NMI context. + */ +static void kvm_pmu_perf_overflow_notify_vcpu(struct irq_work *work) +{ + struct kvm_vcpu *vcpu; + struct kvm_pmu *pmu; + + pmu = container_of(work, struct kvm_pmu, overflow_work); + vcpu = kvm_pmc_to_vcpu(&pmu->pmc[0]);
Can you spell this kvm_pmc_to_vcpu(pmu->pmc); ?
+ + kvm_vcpu_kick(vcpu);
How do we guarantee that the vCPU is still around by the time this runs? Sorry to ask such a horrible question, but I don't see anything associating the workqueue with the lifetime of the vCPU. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel