Re: [dpdk-stable] [PATCH 2/3] net/virtio: rationalize queue flushing

[Olivier Matz <olivier.matz@6wind.com>]

On Thu, Jan 18, 2018 at 10:05:49PM +0800, Tiwei Bie wrote:
> On Thu, Jan 18, 2018 at 10:07:32AM +0100, Olivier Matz wrote:
> > Rationalize the function virtio_dev_free_mbufs():
> > 
> > - skip NULL vqs instead of crashing: this is required for the
> >   next commit
> > - use the same kind of loop than in virtio_free_queues()
> > - also flush mbufs from the control queue (this is useless yet)
> > - factorize common code between rxq, txq, cq
> > 
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> > ---
> >  drivers/net/virtio/virtio_ethdev.c | 55 ++++++++++++++++++--------------------
> >  1 file changed, 26 insertions(+), 29 deletions(-)
> > 
> > diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> > index c7426951c..d8b3b8ed7 100644
> > --- a/drivers/net/virtio/virtio_ethdev.c
> > +++ b/drivers/net/virtio/virtio_ethdev.c
> > @@ -1868,47 +1868,44 @@ virtio_dev_start(struct rte_eth_dev *dev)
> >  
> >  static void virtio_dev_free_mbufs(struct rte_eth_dev *dev)
> >  {
> [...]
> >  
> > -		mbuf_num = 0;
> > -		while ((buf = virtqueue_detach_unused(txvq->vq)) != NULL) {
> > +		while ((buf = virtqueue_detach_unused(vq)) != NULL) {
> 
> Thanks for working on this! The virtqueue_detach_unused() can't
> handle the vector Rx case correctly. Because vq->vq_descx[] is
> initialized for vector Rx, but isn't updated by the vector Rx.
> So together with the next commit, it may cause problems during
> dev_stop/dev_configure/dev_start if vector Rx is used.

What would be the appropriate way to fix it?

Either we fix the vector functions to set vq->vq_descx, or we find
another method to flush the mbufs in case of vector rx. Can we use
vq->sw_ring[] to get the mbufs instead?

Thanks