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

Cornelia Huck
2014-10-20T12:42:23Z

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.

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index bfa6400..cf7a561 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1449,8 +1449,6 @@ 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) {
@@ -2026,6 +2024,8 @@ static int virtcons_probe(struct virtio_device *vdev)
spin_lock_init(&portdev->ports_lock);
INIT_LIST_HEAD(&portdev->ports);

+ virtio_device_ready(portdev->vdev);
+
if (multiport) {
unsigned int nr_added_bufs;