[PATH,1/2] vhost: fix descs count in async vhost packed ring

  When vhost receive packets from the front-end using packed virtqueue, it
might use multiple descriptors for one packet, so we need calculate and
record the descriptor number for each packet to update available
descriptor counter and used descriptor counter, and rollback when DMA
ring is full.

Signed-off-by: Cheng Jiang <cheng1.jiang@intel.com>
---
 lib/vhost/virtio_net.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)
  

On 8/22/22 06:31, 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

so we need to*

> record the descriptor number for each packet to update available
> descriptor counter and used descriptor counter, and rollback when DMA
> ring is full.

This is a fix, so the Fixes tag should be present, and stable@dpdk.org
cc'ed.

> 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 35fa4670fd..bfc6d65b7c 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -3553,14 +3553,15 @@ 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)
> @@ -3581,6 +3582,8 @@ 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,
> @@ -3609,8 +3612,12 @@ 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;
>   }
> @@ -3649,9 +3656,6 @@ 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,
> @@ -3662,6 +3666,8 @@ 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;
>   
>   		/**
> @@ -3678,10 +3684,10 @@ 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;
>   		}
>   	}

I'm not sure to understand, isn't descs_err always 0 here?

Maxime