2008-03-02 22:38:23

by Anthony Liguori

Subject: [PATCH] Use spin_lock_irqsave/restore for virtio-pci

virtio-pci acquires its spin lock in an interrupt context so it's necessary
to use spin_lock_irqsave/restore variants. This patch fixes guest SMP when
using virtio devices in KVM.

Signed-off-by: Anthony Liguori <[email protected]>

diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 26f787d..59a8f73 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -177,6 +177,7 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
struct virtio_pci_device *vp_dev = opaque;
struct virtio_pci_vq_info *info;
irqreturn_t ret = IRQ_NONE;
+ unsigned long flags;
u8 isr;

/* reading the ISR has the effect of also clearing it so it's very
@@ -197,12 +198,12 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
drv->config_changed(&vp_dev->vdev);
}

- spin_lock(&vp_dev->lock);
+ spin_lock_irqsave(&vp_dev->lock, flags);
list_for_each_entry(info, &vp_dev->virtqueues, node) {
if (vring_interrupt(irq, info->vq) == IRQ_HANDLED)
ret = IRQ_HANDLED;
}
- spin_unlock(&vp_dev->lock);
+ spin_unlock_irqrestore(&vp_dev->lock, flags);

return ret;
}
@@ -214,6 +215,7 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
struct virtio_pci_vq_info *info;
struct virtqueue *vq;
+ unsigned long flags;
u16 num;
int err;

@@ -255,9 +257,9 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
vq->priv = info;
info->vq = vq;

- spin_lock(&vp_dev->lock);
+ spin_lock_irqsave(&vp_dev->lock, flags);
list_add(&info->node, &vp_dev->virtqueues);
- spin_unlock(&vp_dev->lock);
+ spin_unlock_irqrestore(&vp_dev->lock, flags);

return vq;

@@ -274,10 +276,11 @@ static void vp_del_vq(struct virtqueue *vq)
{
struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
struct virtio_pci_vq_info *info = vq->priv;
+ unsigned long flags;

- spin_lock(&vp_dev->lock);
+ spin_lock_irqsave(&vp_dev->lock, flags);
list_del(&info->node);
- spin_unlock(&vp_dev->lock);
+ spin_unlock_irqrestore(&vp_dev->lock, flags);

vring_del_virtqueue(vq);

2008-03-04 00:22:22

by Rusty Russell

Subject: Re: [PATCH] Use spin_lock_irqsave/restore for virtio-pci

On Monday 03 March 2008 09:37:48 Anthony Liguori wrote:
> virtio-pci acquires its spin lock in an interrupt context so it's necessary
> to use spin_lock_irqsave/restore variants. This patch fixes guest SMP when
> using virtio devices in KVM.
>
> Signed-off-by: Anthony Liguori <[email protected]>

Thanks, applied.

Rusty.