Am Donnerstag, 10. Januar 2008 schrieb Christian Borntraeger:
> Am Donnerstag, 10. Januar 2008 schrieb Christian Borntraeger:
> > Am Dienstag, 18. Dezember 2007 schrieb Rusty Russell:
> > > To me this points to doing interrupt suppression a different way. If
we
> > > have a ->disable_cb() virtio function, and call it before we call
> > > netif_rx_schedule, does that fix it?
> >
> > The fix looks good and I agree with it.
> >
> > There is one problem that I try to find for some days, but the following
> > BUG_ON triggers:
> >
> > static void vring_disable_cb(struct virtqueue *_vq)
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> >
> > START_USE(vq);
> > ----> BUG_ON(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);
> > vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
> > END_USE(vq);
> > }
>
> Ok, I found it:
>
> static int virtnet_open(struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> try_fill_recv(vi);
> /* If we didn't even get one input buffer, we're useless. */
> if (vi->num == 0)
> return -ENOMEM;
> ---> int for new packet
> static void skb_recv_done(struct virtqueue *rvq)
> {
> struct virtnet_info *vi = rvq->vdev->priv;
> /* Suppress further interrupts. */
> rvq->vq_ops->disable_cb(rvq);
> netif_rx_schedule(vi->dev, &vi->napi);
> }
> - poll is not yet possible, no softirq
> - return from interrupt
> napi_enable(&vi->napi);
> vi->rvq->vq_ops->disable_cb(vi->rvq);
> ---> BUG: its already disabled
Btw. this problem also happens on single processor guests.
What about the following patch:
---
drivers/net/virtio_net.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
Index: kvm/drivers/net/virtio_net.c
===================================================================
--- kvm.orig/drivers/net/virtio_net.c
+++ kvm/drivers/net/virtio_net.c
@@ -179,9 +179,12 @@ static void try_fill_recv(struct virtnet
static void skb_recv_done(struct virtqueue *rvq)
{
struct virtnet_info *vi = rvq->vdev->priv;
- /* Suppress further interrupts. */
- rvq->vq_ops->disable_cb(rvq);
- netif_rx_schedule(vi->dev, &vi->napi);
+ /* Schedule NAPI, Suppress further interrupts if successful. */
+
+ if (netif_rx_schedule_prep(vi->dev, &vi->napi)) {
+ rvq->vq_ops->disable_cb(rvq);
+ __netif_rx_schedule(vi->dev, &vi->napi);
+ }
}
static int virtnet_poll(struct napi_struct *napi, int budget)
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