Re: [dpdk-dev] [PATCH] vhost: fix index overflow issue in async vhost

["Jiang, Cheng1" <cheng1.jiang@intel.com>]

Hi Chenbo,

> -----Original Message-----
> From: Xia, Chenbo <chenbo.xia@intel.com>
> Sent: Thursday, July 15, 2021 4:37 PM
> To: Jiang, Cheng1 <cheng1.jiang@intel.com>; maxime.coquelin@redhat.com
> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Yang, YvonneX
> <yvonnex.yang@intel.com>; stable@dpdk.org
> Subject: RE: [PATCH] vhost: fix index overflow issue in async vhost
> 
> Hi Cheng,
> 
> > -----Original Message-----
> > From: Jiang, Cheng1 <cheng1.jiang@intel.com>
> > Sent: Thursday, July 8, 2021 6:45 PM
> > To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> > Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Yang, YvonneX
> > <yvonnex.yang@intel.com>; Jiang, Cheng1 <cheng1.jiang@intel.com>;
> > stable@dpdk.org
> > Subject: [PATCH] vhost: fix index overflow issue in async vhost
> 
> Since this fix is packed ring only, maybe 'fix index overflow for packed ring in
> async vhost' is better.
> 

Sure, that make sense.
I'll fix it in the next version.

> >
> > We introduced some new indexes in async vhost. If we don't pay
> > attention to the management of these indexes, they will eventually
> > overflow and lead to errors. This patch is to check and keep these
> > indexes within a reasonable range.
> 
> Ditto. Should mention packed ring here.

Sure.


> 
> >
> > Fixes: 873e8dad6f49 ("vhost: support packed ring in async datapath")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Cheng Jiang <cheng1.jiang@intel.com>
> > ---
> >  lib/vhost/virtio_net.c | 22 +++++++++++++++-------
> >  1 file changed, 15 insertions(+), 7 deletions(-)
> >
> > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
> > f4a2c88d8b..61cb5a126c 100644
> > --- a/lib/vhost/virtio_net.c
> > +++ b/lib/vhost/virtio_net.c
> > @@ -1614,6 +1614,7 @@ store_dma_desc_info_packed(struct
> > vring_used_elem_packed *s_ring,
> >
> >  	if (d_idx + count <= ring_size) {
> >  		rte_memcpy(d_ring + d_idx, s_ring + s_idx, count *
> elem_size);
> > +
> 
Maybe it's a typo. I'll fix it.

Thanks,
Cheng

> Do we need a blank line here?
> 
> Thanks,
> Chenbo
> 
> >  	} else {
> >  		uint16_t size = ring_size - d_idx;
> >
> > @@ -2036,7 +2037,7 @@ virtio_dev_rx_async_submit_packed(struct
> > virtio_net *dev,
> >
> >  		slot_idx = (vq->async_pkts_idx + num_async_pkts) % vq-
> >size;
> >  		if (it_pool[it_idx].count) {
> > -			uint16_t from, to;
> > +			uint16_t from;
> >
> >  			async_descs_idx += num_descs;
> >  			async_fill_desc(&tdes[pkt_burst_idx++],
> > @@ -2055,11 +2056,13 @@ virtio_dev_rx_async_submit_packed(struct
> > virtio_net *dev,
> >  			 * descriptors.
> >  			 */
> >  			from = vq->shadow_used_idx - num_buffers;
> > -			to = vq->async_buffer_idx_packed % vq->size;
> >  			store_dma_desc_info_packed(vq-
> >shadow_used_packed,
> > -					vq->async_buffers_packed, vq->size,
> from, to,
> > num_buffers);
> > +					vq->async_buffers_packed, vq->size,
> from,
> > +					vq->async_buffer_idx_packed,
> num_buffers);
> >
> >  			vq->async_buffer_idx_packed += num_buffers;
> > +			if (vq->async_buffer_idx_packed >= vq->size)
> > +				vq->async_buffer_idx_packed -= vq->size;
> >  			vq->shadow_used_idx -= num_buffers;
> >  		} else {
> >  			comp_pkts[num_done_pkts++] = pkts[pkt_idx]; @@
> -2112,6 +2115,8 @@
> > virtio_dev_rx_async_submit_packed(struct virtio_net *dev,
> >  		dma_error_handler_packed(vq, async_descs,
> async_descs_idx,
> > slot_idx, pkt_err,
> >  					&pkt_idx, &num_async_pkts,
> &num_done_pkts);
> >  	vq->async_pkts_idx += num_async_pkts;
> > +	if (vq->async_pkts_idx >= vq->size)
> > +		vq->async_pkts_idx -= vq->size;
> >  	*comp_count = num_done_pkts;
> >
> >  	if (likely(vq->shadow_used_idx)) {
> > @@ -2160,7 +2165,7 @@ write_back_completed_descs_packed(struct
> > vhost_virtqueue *vq,
> >  	uint16_t from, to;
> >
> >  	do {
> > -		from = vq->last_async_buffer_idx_packed % vq->size;
> > +		from = vq->last_async_buffer_idx_packed;
> >  		to = (from + nr_left) % vq->size;
> >  		if (to > from) {
> >  			vhost_update_used_packed(vq, vq-
> >async_buffers_packed + from, to -
> > from); @@ -2169,7 +2174,7 @@
> write_back_completed_descs_packed(struct
> > vhost_virtqueue *vq,
> >  		} else {
> >  			vhost_update_used_packed(vq, vq-
> >async_buffers_packed + from,
> >  				vq->size - from);
> > -			vq->last_async_buffer_idx_packed += vq->size -
> from;
> > +			vq->last_async_buffer_idx_packed = 0;
> >  			nr_left -= vq->size - from;
> >  		}
> >  	} while (nr_left > 0);
> > @@ -2252,10 +2257,13 @@ uint16_t
> rte_vhost_poll_enqueue_completed(int
> > vid, uint16_t queue_id,
> >  			vhost_vring_call_split(dev, vq);
> >  		}
> >  	} else {
> > -		if (vq_is_packed(dev))
> > +		if (vq_is_packed(dev)) {
> >  			vq->last_async_buffer_idx_packed += n_buffers;
> > -		else
> > +			if (vq->last_async_buffer_idx_packed >= vq->size)
> > +				vq->last_async_buffer_idx_packed -= vq-
> >size;
> > +		} else {
> >  			vq->last_async_desc_idx_split += n_descs;
> > +		}
> >  	}
> >
> >  done:
> > --
> > 2.29.2