On Wed, Aug 9, 2023 at 2:51 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Wed, Aug 09, 2023 at 02:45:17PM +0800, Jason Wang wrote:
> > On Wed, Aug 9, 2023 at 2:23 PM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
> > >
> > > On Tue, 2023-08-08 at 23:13 -0400, Jason Wang wrote:
> > > > Commit 25266128fe16 ("virtio-net: fix race between set queues and
> > > > probe") tries to fix the race between set queues and probe by calling
> > > > _virtnet_set_queues() before DRIVER_OK is set. This violates virtio
> > > > spec. Fixing this by setting queues after virtio_device_ready().
> > > >
> > > > Fixes: 25266128fe16 ("virtio-net: fix race between set queues and probe")
> > > > Reported-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> > > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > > ---
> > > > The patch is needed for -stable.
> > > > ---
> > > > drivers/net/virtio_net.c | 4 ++--
> > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index 1270c8d23463..ff03921e46df 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -4219,8 +4219,6 @@ static int virtnet_probe(struct virtio_device *vdev)
> > > > if (vi->has_rss || vi->has_rss_hash_report)
> > > > virtnet_init_default_rss(vi);
> > > >
> > > > - _virtnet_set_queues(vi, vi->curr_queue_pairs);
> > > > -
> > > > /* serialize netdev register + virtio_device_ready() with ndo_open()
> > > > */
> > > > rtnl_lock();
> > > >
> > > > @@ -4233,6 +4231,8 @@ static int virtnet_probe(struct virtio_device *vdev)
> > > >
> > > > virtio_device_ready(vdev);
> > > >
> > > > + _virtnet_set_queues(vi, vi->curr_queue_pairs);
> > > > +
> > > > /* a random MAC address has been assigned, notify the device.
> > > > * We don't fail probe if VIRTIO_NET_F_CTRL_MAC_ADDR is not there
> > > > * because many devices work fine without getting MAC explicitly
> > >
> > > Thanks for the quick fix. Doesn't this fix though bring back the original race
> > > that was fixed in commit 25266128fe16 ("virtio-net: fix race between set queues
> > > and probe")? Or is being under the same rntl_lock session as register_netdev
> > > enough to avoid the race?
> >
> > Yes, rtnl needs to be held for userspace requests to change the number
> > of queues. So we are serialized in this way.
> >
> > Thanks
>
> maybe post v2 adding this in the commit log.
Ok, v2 will be posted soon.
Thanks
>
>
> > >
> > > Thanks,
> > > Dragos
>
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
