KVM: arm/arm64: Fix spinlock acquisition in vgic_set_owner

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>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 786cce7bd2ec620051e144e1287182c499676739..ecb8e25f5fe56d69065757a80c44c2d4a532bbcb 100644 (file)
--- 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;
 }