From: Christoffer Dall <cdall@linaro.org>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH] KVM: arm/arm64: Fix spinlock acquisition in vgic_set_owner
Date: Fri, 1 Dec 2017 08:55:07 +0100 [thread overview]
Message-ID: <20171201075507.GA4218@cbox> (raw)
In-Reply-To: <20171130170030.29827-1-marc.zyngier@arm.com>
On Thu, Nov 30, 2017 at 05:00:30PM +0000, Marc Zyngier wrote:
> vgic_set_owner acquires the irq lock without disabling interrupts,
> resulting in a lockdep splat (an interrupt could fire and result
> in the same lock being taken if the same virtual irq is to be
> injected).
>
> In practice, it is almost impossible to trigger this bug, but
> better safe than sorry. Convert the lock acquisition to a
> spin_lock_irqsave() and keep lockdep happy.
>
> Reported-by: James Morse <james.morse@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Applied, thanks.
-Christoffer
> ---
> virt/kvm/arm/vgic/vgic.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
> index b168a328a9e0..8d863e6405a5 100644
> --- a/virt/kvm/arm/vgic/vgic.c
> +++ b/virt/kvm/arm/vgic/vgic.c
> @@ -492,6 +492,7 @@ int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int vintid)
> int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner)
> {
> struct vgic_irq *irq;
> + unsigned long flags;
> int ret = 0;
>
> if (!vgic_initialized(vcpu->kvm))
> @@ -502,12 +503,12 @@ int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner)
> return -EINVAL;
>
> irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
> - spin_lock(&irq->irq_lock);
> + spin_lock_irqsave(&irq->irq_lock, flags);
> if (irq->owner && irq->owner != owner)
> ret = -EEXIST;
> else
> irq->owner = owner;
> - spin_unlock(&irq->irq_lock);
> + spin_unlock_irqrestore(&irq->irq_lock, flags);
>
> return ret;
> }
> --
> 2.11.0
>
prev parent reply other threads:[~2017-12-01 7:55 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 17:00 [PATCH] KVM: arm/arm64: Fix spinlock acquisition in vgic_set_owner Marc Zyngier
2017-12-01 7:55 ` Christoffer Dall [this message]
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