[PATH 2/2] vhost: fix slot index calculation in async vhost

[Jiang, Cheng1]

Hi,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Monday, October 3, 2022 6:10 PM
> To: Jiang, Cheng1 <cheng1.jiang at intel.com>; Xia, Chenbo
> <chenbo.xia at intel.com>
> Cc: dev at dpdk.org; Hu, Jiayu <jiayu.hu at intel.com>; Ding, Xuan
> <xuan.ding at intel.com>; Ma, WenwuX <wenwux.ma at intel.com>; Wang,
> YuanX <yuanx.wang at intel.com>; Yang, YvonneX
> <yvonnex.yang at intel.com>; He, Xingguang <xingguang.he at intel.com>
> Subject: Re: [PATH 2/2] vhost: fix slot index calculation in async vhost
> 
> 
> 
> On 8/22/22 06:31, Cheng Jiang wrote:
> > When the packet receiving failure and the DMA ring full occur
> > simultaneously in the asynchronous vhost, the slot_idx needs to be
> > reduced by 1. For packed virtqueue, the slot index should be
> 
> s/reduced/decreased/

Sure, thanks.

> 
> > ring_size - 1, if the slot_idx is currently 0, since the ring size is
> > not necessarily the power of 2.
> 
> This is a fix, so fixes tag and stable at dpdk.org is required.

Sorry for the miss. It will be fixed in the next version.

Thanks,
Cheng

> 
> > Signed-off-by: Cheng Jiang <cheng1.jiang at intel.com>
> > ---
> >   lib/vhost/virtio_net.c | 16 ++++++++++++++--
> >   1 file changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
> > bfc6d65b7c..f804bce0bd 100644
> > --- a/lib/vhost/virtio_net.c
> > +++ b/lib/vhost/virtio_net.c
> > @@ -3462,6 +3462,7 @@ virtio_dev_tx_async_split(struct virtio_net *dev,
> struct vhost_virtqueue *vq,
> >   				allocerr_warned = true;
> >   			}
> >   			dropped = true;
> > +			slot_idx--;
> >   			break;
> >   		}
> >
> > @@ -3652,6 +3653,12 @@ virtio_dev_tx_async_packed(struct virtio_net
> *dev, struct vhost_virtqueue *vq,
> >   		if (unlikely(virtio_dev_tx_async_single_packed(dev, vq,
> mbuf_pool, pkt,
> >   				slot_idx, legacy_ol_flags))) {
> >   			rte_pktmbuf_free_bulk(&pkts_prealloc[pkt_idx],
> count - pkt_idx);
> > +
> > +			if (slot_idx == 0)
> > +				slot_idx = vq->size - 1;
> > +			else
> > +				slot_idx--;
> > +
> >   			break;
> >   		}
> >
> > @@ -3679,8 +3686,13 @@ virtio_dev_tx_async_packed(struct virtio_net
> *dev, struct vhost_virtqueue *vq,
> >   			async->buffer_idx_packed += vq->size - pkt_err;
> >
> >   		while (pkt_err-- > 0) {
> > -			rte_pktmbuf_free(pkts_info[slot_idx % vq-
> >size].mbuf);
> > -			slot_idx--;
> > +			rte_pktmbuf_free(pkts_info[slot_idx].mbuf);
> > +			descs_err += pkts_info[slot_idx].descs;
> > +
> > +			if (slot_idx == 0)
> > +				slot_idx = vq->size - 1;
> > +			else
> > +				slot_idx--;
> >   		}
> >
> >   		/* recover available ring */