When using an NMI for the PMU interrupt, taking any lock migh cause a
deadlock. The current PMU overflow handler in KVM takes takes locks when
trying to wake up a vcpu.
When overflow handler is called by an NMI, defer the vcpu waking in an
irq_work queue.
Signed-off-by: Julien Thierry <julien.thie...@arm.com>
Cc: Christoffer Dall <christoffer.d...@arm.com>
Cc: Marc Zyngier <marc.zyng...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: James Morse <james.mo...@arm.com>
Cc: Suzuki K Pouloze <suzuki.poul...@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
---
include/kvm/arm_pmu.h | 1 +
virt/kvm/arm/pmu.c | 25 ++++++++++++++++++++++++-
2 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 16c769a..8202ed7 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -27,6 +27,7 @@ struct kvm_pmu {
bool ready;
bool created;
bool irq_level;
+ struct irq_work overflow_work;
};
#define kvm_arm_pmu_v3_ready(v) ((v)->arch.pmu.ready)
diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 3dd8238..63f358e 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -421,6 +421,22 @@ void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu)
}
/**
+ * When perf interrupt is an NMI, we cannot safely notify the vcpu
corresponding
+ * to the even.
+ * 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]);
+
+ kvm_vcpu_kick(vcpu);
+}
+
+/**
* When the perf event overflows, set the overflow status and inform the vcpu.
*/
static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
@@ -435,7 +451,11 @@ static void kvm_pmu_perf_overflow(struct perf_event
*perf_event,
if (kvm_pmu_overflow_status(vcpu)) {
kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
- kvm_vcpu_kick(vcpu);
+
+ if (!in_nmi())
+ kvm_vcpu_kick(vcpu);
+ else
+ irq_work_queue(&vcpu->arch.pmu.overflow_work);
}
}
@@ -706,6 +726,9 @@ static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
return ret;
}
+ init_irq_work(&vcpu->arch.pmu.overflow_work,
+ kvm_pmu_perf_overflow_notify_vcpu);
+
vcpu->arch.pmu.created = true;
return 0;
}
--
1.9.1
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