KVM ARM Archive on lore.kernel.org
 help / color / Atom feed
* [PATCH v4 7/9] arm/arm64: kvm: pmu: Make overflow handler NMI safe
       [not found] <1563351432-55652-1-git-send-email-julien.thierry@arm.com>
@ 2019-07-17  8:17 ` Julien Thierry
  2019-07-30 20:57   ` Marc Zyngier
  0 siblings, 1 reply; 2+ messages in thread
From: Julien Thierry @ 2019-07-17  8:17 UTC (permalink / raw)
  To: linux-arm-kernel
  Cc: peterz, jolsa, will.deacon, acme, alexander.shishkin, mingo,
	Marc Zyngier, namhyung, sthotton, liwei391, kvmarm

When using an NMI for the PMU interrupt, taking any lock might cause a
deadlock. The current PMU overflow handler in KVM 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.thierry@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Pouloze <suzuki.poulose@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..deed8fb 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 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]);
+
+	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
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH v4 7/9] arm/arm64: kvm: pmu: Make overflow handler NMI safe
  2019-07-17  8:17 ` [PATCH v4 7/9] arm/arm64: kvm: pmu: Make overflow handler NMI safe Julien Thierry
@ 2019-07-30 20:57   ` Marc Zyngier
  0 siblings, 0 replies; 2+ messages in thread
From: Marc Zyngier @ 2019-07-30 20:57 UTC (permalink / raw)
  To: Julien Thierry
  Cc: peterz, liwei391, will.deacon, acme, alexander.shishkin, mingo,
	namhyung, sthotton, jolsa, kvmarm, linux-arm-kernel

On Wed, 17 Jul 2019 09:17:10 +0100
Julien Thierry <julien.thierry@arm.com> wrote:

> When using an NMI for the PMU interrupt, taking any lock might cause a
> deadlock. The current PMU overflow handler in KVM 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.thierry@arm.com>
> Cc: Christoffer Dall <christoffer.dall@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: James Morse <james.morse@arm.com>
> Cc: Suzuki K Pouloze <suzuki.poulose@arm.com>
> Cc: kvmarm@lists.cs.columbia.edu

Acked-by: Marc Zyngier <maz@kernel.org>

	M.
-- 
Without deviation from the norm, progress is not possible.
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, back to index

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <1563351432-55652-1-git-send-email-julien.thierry@arm.com>
2019-07-17  8:17 ` [PATCH v4 7/9] arm/arm64: kvm: pmu: Make overflow handler NMI safe Julien Thierry
2019-07-30 20:57   ` Marc Zyngier

KVM ARM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvmarm/0 kvmarm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvmarm kvmarm/ https://lore.kernel.org/kvmarm \
		kvmarm@lists.cs.columbia.edu kvmarm@archiver.kernel.org
	public-inbox-index kvmarm


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/edu.columbia.cs.lists.kvmarm


AGPL code for this site: git clone https://public-inbox.org/ public-inbox