On Wed, Jun 29, 2022 at 11:43:18AM -0600, Mathieu Poirier wrote:
> Hi Anup,
>
> On Wed, Jun 08, 2022 at 10:43:34PM +0530, Anup Patel wrote:
> > The rpmsg_probe() is broken at the moment because virtqueue_add_inbuf()
> > fails due to both virtqueues (Rx and Tx) marked as broken by the
> > __vring_new_virtqueue() function. To solve this, virtio_device_ready()
> > (which unbreaks queues) should be called before virtqueue_add_inbuf().
> >
> > Fixes: 8b4ec69d7e09 ("virtio: harden vring IRQ")
> > Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> > ---
> > drivers/rpmsg/virtio_rpmsg_bus.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> > index 905ac7910c98..71a64d2c7644 100644
> > --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> > +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> > @@ -929,6 +929,9 @@ static int rpmsg_probe(struct virtio_device *vdev)
> > /* and half is dedicated for TX */
> > vrp->sbufs = bufs_va + total_buf_space / 2;
> >
> > + /* From this point on, we can notify and get callbacks. */
> > + virtio_device_ready(vdev);
> > +
>
> Calling virtio_device_ready() here means that virtqueue_get_buf_ctx_split() can
> potentially be called (by way of rpmsg_recv_done()), which will race with
> virtqueue_add_inbuf(). If buffers in the virtqueue aren't available then
> rpmsg_recv_done() will fail, potentially breaking remote processors' state
> machines that don't expect their initial name service to fail when the "device"
> has been marked as ready.
When you say available I am guessing you really need used.
With a non broken device you won't get a callback
until some buffers have been used.
Or, if no used buffers are present then you will get another
callback down the road.
>
> What does make me curious though is that nobody on the remoteproc mailing list
> has complained about commit 8b4ec69d7e09 breaking their environment... By now,
> i.e rc4, that should have happened. Anyone from TI, ST and Xilinx care to test this on
> their rig?
>
> Thanks,
> Mathieu
>
> > /* set up the receive buffers */
> > for (i = 0; i < vrp->num_bufs / 2; i++) {
> > struct scatterlist sg;
> > @@ -983,9 +986,6 @@ static int rpmsg_probe(struct virtio_device *vdev)
> > */
> > notify = virtqueue_kick_prepare(vrp->rvq);
> >
> > - /* From this point on, we can notify and get callbacks. */
> > - virtio_device_ready(vdev);
> > -
> > /* tell the remote processor it can start sending messages */
> > /*
> > * this might be concurrent with callbacks, but we are only
> > --
> > 2.34.1
> >
>
