Re: [Qemu-devel] [PATCH for-2.4] virtio-net: Flush incoming queues when DRIVER_OK is being set

[Fam Zheng]

On Tue, 07/14 13:09, Michael S. Tsirkin wrote:
> On Tue, Jul 14, 2015 at 05:41:04PM +0800, Fam Zheng wrote:
> > This patch fixes network hang after "stop" then "cont", while network
> > packets keep arriving.
> > 
> > Tested both manually (tap, host pinging guest) and with Jason's qtest
> > series (plus his "[PATCH 2.4] socket: pass correct size in
> > net_socket_send()" fix).
> > 
> > As virtio_net_set_status is called when guest driver is setting status
> > byte and when vm state is changing, it is a good opportunity to flush
> > queued packets.
> > 
> > This is necessary because during vm stop the backend (e.g. tap) would
> > stop rx processing after .can_receive returns false, until the queue is
> > explicitly flushed or purged.
> > 
> > The other interesting condition in .can_receive, virtio_queue_ready(),
> > is handled by virtio_net_handle_rx() when guest kicks; the 3rd condition
> > is invalid queue index which doesn't need flushing.
> > 
> > Signed-off-by: Fam Zheng <address@hidden>
> > ---
> >  hw/net/virtio-net.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > index d728233..7c178c6 100644
> > --- a/hw/net/virtio-net.c
> > +++ b/hw/net/virtio-net.c
> > @@ -162,8 +162,13 @@ static void virtio_net_set_status(struct VirtIODevice 
> > *vdev, uint8_t status)
> >      virtio_net_vhost_status(n, status);
> >  
> >      for (i = 0; i < n->max_queues; i++) {
> > +        NetClientState *ncs = qemu_get_subqueue(n->nic, i);
> >          q = &n->vqs[i];
> >  
> > +        if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> > +            qemu_flush_queued_packets(ncs);
> > +        }
> > +
> >          if ((!n->multiqueue && i != 0) || i >= n->curr_queues) {
> >              queue_status = 0;
> >          } else {
> 
> I think this should be limited to
>       virtio_net_started(n, queue_status) && !n->vhost_started

Yes, that looks better.

Fam