Re: [PATCH v4 13/25] virtio_console: enable VQs early

Thomas Graf
2014-10-20T13:10:52Z

On 10/20/14 at 02:42pm, Cornelia Huck wrote:
> On Mon, 20 Oct 2014 13:07:50 +0100
> Thomas Graf <tgraf@suug.ch> wrote:
>
> > On 10/13/14 at 10:50am, Michael S. Tsirkin wrote:
> > > virtio spec requires drivers to set DRIVER_OK before using VQs.
> > > This is set automatically after probe returns, virtio console violated this
> > > rule by adding inbufs, which causes the VQ to be used directly within
> > > probe.
> > >
> > > To fix, call virtio_device_ready before using VQs.
> > >
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > ---
> > > drivers/char/virtio_console.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> > > index b585b47..6ebe8f6 100644
> > > --- a/drivers/char/virtio_console.c
> > > +++ b/drivers/char/virtio_console.c
> > > @@ -1449,6 +1449,8 @@ static int add_port(struct ports_device *portdev, u32 id)
> > > spin_lock_init(&port->outvq_lock);
> > > init_waitqueue_head(&port->waitqueue);
> > >
> > > + virtio_device_ready(portdev->vdev);
> > > +
> > > /* Fill the in_vq with buffers so the host can send us data. */
> > > nr_added_bufs = fill_queue(port->in_vq, &port->inbuf_lock);
> > > if (!nr_added_bufs) {
> >
> > Seems like probe and add_port() now both set VIRTIO_CONFIG_S_DRIVER_OK
>
> I think we need to set this in the probe function instead, otherwise we
> fail for multiqueue (which also wants to use the control queue early).
>
> Completely untested patch below; I can send this with proper s-o-b if
> it helps.

virtio_dev_probe() already sets DRIVER_OK if ->probe() returned
without an error. I assume Michael added it to add_port() because
probing doesn't always occur first. Can we just remove the BUG_ON()?