Re: [PATCH] virtio_console: free unused buffers with virtio port

Pankaj Gupta
2019-03-05T07:09:09Z

Hello Michael,

Thanks for your reply.

>
> On Mon, Mar 04, 2019 at 06:35:11PM +0530, Pankaj Gupta wrote:
> > The commit a7a69ec0d8e4 ("virtio_console: free buffers after reset")
> > deffered detaching of unused buffer to virtio device unplug time.
> >
> > This causes unplug/replug of single port in virtio device with an
> > error "Error allocating inbufs\n". As we don't free the unused buffers
> > attached with the port. Re-plug the same port tries to allocate new
> > buffers in virtqueue and results in this error if queue is full.
> >
> > This patch removes the unused buffers in vq's when we unplug the port.
> > This is the best we can do as we cannot call device_reset because virtio
> > device is still active. This was the working behaviour before the change
> > introduced in commit b3258ff1d6.
> >
> > Reported-by: Xiaohui Li <xiaohli@redhat.com>
> > Fixes: b3258ff1d6 ("virtio_console: free buffers after reset")
> > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
>
> I think if you do this you need to add support
> in the packed ring.

o.k. I will look at the implementation details for "support
of packed ring" for virtio_console. This will take some time.

Meanwhile "virtio_console" port hotplug/unplug is broken in upstream.
Can we accept this patch as it fixes the upstream and together
with parent patch(b3258ff1d6) does nice cleanups as well.

Thanks,
Pankaj

>
> > ---
> > drivers/char/virtio_console.c | 14 +++++++++++---
> > 1 file changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> > index fbeb71953526..5fbf2ac73111 100644
> > --- a/drivers/char/virtio_console.c
> > +++ b/drivers/char/virtio_console.c
> > @@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
> > kfree(port);
> > }
> >
> > +static void remove_unused_bufs(struct virtqueue *vq)
> > +{
> > + struct port_buffer *buf;
> > +
> > + while ((buf = virtqueue_detach_unused_buf(vq)))
> > + free_buf(buf, true);
> > +}
> > +
> > static void remove_port_data(struct port *port)
> > {
> > spin_lock_irq(&port->inbuf_lock);
> > /* Remove unused data this port might have received. */
> > discard_port_data(port);
> > + remove_unused_bufs(port->in_vq);
> > spin_unlock_irq(&port->inbuf_lock);
> >
> > spin_lock_irq(&port->outvq_lock);
> > reclaim_consumed_buffers(port);
> > + remove_unused_bufs(port->out_vq);
> > spin_unlock_irq(&port->outvq_lock);
> > }
> >
> > @@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device *portdev)
> > struct virtqueue *vq;
> >
> > virtio_device_for_each_vq(portdev->vdev, vq) {
> > - struct port_buffer *buf;
> >
> > flush_bufs(vq, true);
> > - while ((buf = virtqueue_detach_unused_buf(vq)))
> > - free_buf(buf, true);
> > + remove_unused_bufs(vq);
> > }
> > portdev->vdev->config->del_vqs(portdev->vdev);
> > kfree(portdev->in_vqs);
> > --
> > 2.20.1
>