[dpdk-dev] [PATCH v2 1/4] net/virtio: fix queue flushing with vector Rx enabled

[Tiwei Bie]

On Mon, Jan 22, 2018 at 11:38:58AM +0100, Olivier Matz wrote:
> On Mon, Jan 22, 2018 at 10:56:41AM +0800, Tiwei Bie wrote:
> > On Fri, Jan 19, 2018 at 04:55:53PM +0100, Olivier Matz wrote:
> > > When using vector Rx mode (use_simple_rx = 1), vq->vq_descx[] is not
> > > kept up to date. To properly detach the mbufs in this case, browse
> > > sw_ring[] instead, as it's done in virtqueue_rxvq_flush().
> > > 
> > > Since we need virtio_get_queue_type(), also move this function in
> > > virtqueue.h as a static inline.
> > > 
> > > Fixes: fc3d66212fed ("virtio: add vector Rx")
> > > Cc: stable at dpdk.org
> > > 
> > > Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
> > > ---
> > > 
> > > Tiwei,
> > > 
> > > While it passes my test plan, please carefully check that what I did in
> > > virtqueue_detatch_unused() is correct. I tried to reproduce what is done
> > > in virtqueue_rxvq_flush(), but I may be mistaking due to the different
> > > ring layout assumption and mbuf management between standard and vector.
> > > 
> > > Thanks
> > > Olivier
> > > 
> > > 
> > >  drivers/net/virtio/virtio_ethdev.c | 11 -----------
> > >  drivers/net/virtio/virtqueue.c     | 17 +++++++++++++++--
> > >  drivers/net/virtio/virtqueue.h     | 11 +++++++++++
> > >  3 files changed, 26 insertions(+), 13 deletions(-)
> > > 
> > [...]
> > >  struct rte_mbuf *
> > >  virtqueue_detatch_unused(struct virtqueue *vq)
> > >  {
> > > +	struct virtio_hw *hw = vq->hw;
> > >  	struct rte_mbuf *cookie;
> > >  	int idx;
> > > +	int type = virtio_get_queue_type(hw, vq->vq_queue_index);
> > > +
> > > +	if (vq == NULL)
> > > +		return NULL;
> > >  
> > > -	if (vq != NULL)
> > > -		for (idx = 0; idx < vq->vq_nentries; idx++) {
> > > +	for (idx = 0; idx < vq->vq_nentries; idx++) {
> > > +		if (hw->use_simple_rx && type == VTNET_RQ) {
> > > +			cookie = vq->sw_ring[idx];
> > > +			if (cookie != NULL) {
> > > +				vq->sw_ring[idx] = NULL;
> > 
> > Thanks for working on this!
> > 
> > The vq->sw_ring[idx] isn't zeroed during Rx. So besides the
> > check of (cookie != NULL), some other check is also needed
> > to avoid freeing the mbufs already delivered to application.
> > 
> > The mbufs in below interval belong to application:
> > 
> > start: sw_ring[vq->vq_avail_idx & (vq->vq_nentries - 1)] (included)
> > end: sw_ring[(vq->vq_avail_idx + vq->vq_free_cnt) & (vq->vq_nentries - 1)] (excluded)
> > 
> > PS. (vq->vq_avail_idx & (vq->vq_nentries - 1)) can be greater than
> >     (vq->vq_avail_idx + vq->vq_free_cnt) & (vq->vq_nentries - 1).
> 
> Thank you for the review. What about something like this?
> 
> struct rte_mbuf *
> virtqueue_detach_unused(struct virtqueue *vq)
> {
> 	struct rte_mbuf *cookie;
> 	struct virtio_hw *hw;
> 	uint16_t start, end;
> 	int type, idx;
> 
> 	if (vq == NULL)
> 		return NULL;
> 
> 	hw = vq->hw;
> 	type = virtio_get_queue_type(hw, vq->vq_queue_index);
> 	start = vq->vq_avail_idx & (vq->vq_nentries - 1);
> 	end = (vq->vq_avail_idx + vq->vq_free_cnt) & (vq->vq_nentries - 1);
> 	end = (vq->vq_avail_idx + vq->vq_free_cnt) & (vq->vq_nentries - 1);
> 
> 	for (idx = 0; idx < vq->vq_nentries; idx++) {
> 		if (hw->use_simple_rx && type == VTNET_RQ) {
> 			if (start <= end && idx >= start && idx < end)
> 				continue;
> 			if (start > end && (idx >= start || idx < end))
> 				continue;
> 			cookie = vq->sw_ring[idx];
> 			if (cookie == NULL)
> 				continue;
> 			vq->sw_ring[idx] = NULL;
> 			return cookie;
> 		} else {
> 			cookie = vq->vq_descx[idx].cookie;
> 			if (cookie != NULL) {
> 				vq->vq_descx[idx].cookie = NULL;
> 				return cookie;
> 			}
> 		}
> 	}
> 
> 	return NULL;
> }

Apart from the repeated line, it looks good to me. Thanks!

Thanks,
Tiwei