RE: [PATCH v2 1/2] vhost: fix descs count in async vhost packed ring

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

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Friday, October 21, 2022 4:16 PM
> To: Jiang, Cheng1 <cheng1.jiang@intel.com>; Xia, Chenbo
> <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Ding, Xuan
> <xuan.ding@intel.com>; Ma, WenwuX <wenwux.ma@intel.com>; Wang,
> YuanX <yuanx.wang@intel.com>; Yang, YvonneX
> <yvonnex.yang@intel.com>; He, Xingguang <xingguang.he@intel.com>;
> stable@dpdk.org
> Subject: Re: [PATCH v2 1/2] vhost: fix descs count in async vhost packed ring
> 
> 
> 
> On 10/11/22 05:08, Cheng Jiang wrote:
> > When vhost receive packets from the front-end using packed virtqueue,
> > it
> 
> receives
> 
> > might use multiple descriptors for one packet, so we need calculate
> > and
> 
> to calculate
> 
> > record the descriptor number for each packet to update available
> > descriptor counter and used descriptor counter, and rollback when DMA
> > ring is full.
> >
> > Fixes: fe8477ebbd94 ("vhost: support async packed ring dequeue")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Cheng Jiang <cheng1.jiang@intel.com>
> > ---
> >   lib/vhost/virtio_net.c | 24 +++++++++++++++---------
> >   1 file changed, 15 insertions(+), 9 deletions(-)
> >
> > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
> > 8f4d0f0502..457ac2e92a 100644
> > --- a/lib/vhost/virtio_net.c
> > +++ b/lib/vhost/virtio_net.c
> > @@ -3548,14 +3548,15 @@ virtio_dev_tx_async_split_compliant(struct
> virtio_net *dev,
> >   }
> >
> >   static __rte_always_inline void
> > -vhost_async_shadow_dequeue_single_packed(struct vhost_virtqueue
> *vq,
> > uint16_t buf_id)
> > +vhost_async_shadow_dequeue_single_packed(struct vhost_virtqueue
> *vq,
> > +				uint16_t buf_id, uint16_t count)
> >   {
> >   	struct vhost_async *async = vq->async;
> >   	uint16_t idx = async->buffer_idx_packed;
> >
> >   	async->buffers_packed[idx].id = buf_id;
> >   	async->buffers_packed[idx].len = 0;
> > -	async->buffers_packed[idx].count = 1;
> > +	async->buffers_packed[idx].count = count;
> >
> >   	async->buffer_idx_packed++;
> >   	if (async->buffer_idx_packed >= vq->size) @@ -3576,6 +3577,8 @@
> > virtio_dev_tx_async_single_packed(struct virtio_net *dev,
> >   	uint16_t nr_vec = 0;
> >   	uint32_t buf_len;
> >   	struct buf_vector buf_vec[BUF_VECTOR_MAX];
> > +	struct vhost_async *async = vq->async;
> > +	struct async_inflight_info *pkts_info = async->pkts_info;
> >   	static bool allocerr_warned;
> >
> >   	if (unlikely(fill_vec_buf_packed(dev, vq, vq->last_avail_idx,
> > &desc_count, @@ -3604,8 +3607,12 @@
> virtio_dev_tx_async_single_packed(struct virtio_net *dev,
> >   		return -1;
> >   	}
> >
> > +	pkts_info[slot_idx].descs = desc_count;
> > +
> >   	/* update async shadow packed ring */
> > -	vhost_async_shadow_dequeue_single_packed(vq, buf_id);
> > +	vhost_async_shadow_dequeue_single_packed(vq, buf_id,
> desc_count);
> > +
> > +	vq_inc_last_avail_packed(vq, desc_count);
> >
> >   	return err;
> >   }
> > @@ -3644,9 +3651,6 @@ virtio_dev_tx_async_packed(struct virtio_net
> *dev, struct vhost_virtqueue *vq,
> >   		}
> >
> >   		pkts_info[slot_idx].mbuf = pkt;
> > -
> > -		vq_inc_last_avail_packed(vq, 1);
> > -
> >   	}
> >
> >   	n_xfer = vhost_async_dma_transfer(dev, vq, dma_id, vchan_id,
> > async->pkts_idx, @@ -3657,6 +3661,8 @@
> virtio_dev_tx_async_packed(struct virtio_net *dev, struct vhost_virtqueue
> *vq,
> >   	pkt_err = pkt_idx - n_xfer;
> >
> >   	if (unlikely(pkt_err)) {
> > +		uint16_t descs_err = 0;
> > +
> >   		pkt_idx -= pkt_err;
> >
> >   		/**
> > @@ -3673,10 +3679,10 @@ virtio_dev_tx_async_packed(struct virtio_net
> *dev, struct vhost_virtqueue *vq,
> >   		}
> >
> >   		/* recover available ring */
> > -		if (vq->last_avail_idx >= pkt_err) {
> > -			vq->last_avail_idx -= pkt_err;
> > +		if (vq->last_avail_idx >= descs_err) {
> > +			vq->last_avail_idx -= descs_err;
> >   		} else {
> > -			vq->last_avail_idx += vq->size - pkt_err;
> > +			vq->last_avail_idx += vq->size - descs_err;
> >   			vq->avail_wrap_counter ^= 1;
> >   		}
> >   	}
> 
> If only the commit message typos need to be fixed, maybe no need to send
> a new version.

Sure, thanks a lot!
Cheng

> 
> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> 
> Thanks,
> Maxime