[v3,2/5] vhost: prepare async for descriptor to mbuf refactoring

  From: Xuan Ding <xuan.ding@intel.com>

This patch refactors vhost async enqueue path and dequeue path to use
the same function async_fill_seg() for preparing batch elements,
which simplifies the code without performance degradation.

Signed-off-by: Xuan Ding <xuan.ding@intel.com>
---
 lib/vhost/virtio_net.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)
  

On 4/19/22 05:43, xuan.ding@intel.com wrote:
> From: Xuan Ding <xuan.ding@intel.com>
> 
> This patch refactors vhost async enqueue path and dequeue path to use
> the same function async_fill_seg() for preparing batch elements,
> which simplifies the code without performance degradation.
> 
> Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> ---
>   lib/vhost/virtio_net.c | 23 +++++++++++++++--------
>   1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
> index 6d53016c75..391fb82f0e 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -997,13 +997,14 @@ async_iter_reset(struct vhost_async *async)
>   }
>   
>   static __rte_always_inline int
> -async_mbuf_to_desc_seg(struct virtio_net *dev, struct vhost_virtqueue *vq,
> +async_fill_seg(struct virtio_net *dev, struct vhost_virtqueue *vq,
>   		struct rte_mbuf *m, uint32_t mbuf_offset,
> -		uint64_t buf_iova, uint32_t cpy_len)
> +		uint64_t buf_iova, uint32_t cpy_len, bool to_desc)
>   {
>   	struct vhost_async *async = vq->async;
>   	uint64_t mapped_len;
>   	uint32_t buf_offset = 0;
> +	void *src, *dst;
>   	void *host_iova;
>   
>   	while (cpy_len) {
> @@ -1015,10 +1016,16 @@ async_mbuf_to_desc_seg(struct virtio_net *dev, struct vhost_virtqueue *vq,
>   			return -1;
>   		}
>   
> -		if (unlikely(async_iter_add_iovec(dev, async,
> -						(void *)(uintptr_t)rte_pktmbuf_iova_offset(m,
> -							mbuf_offset),
> -						host_iova, (size_t)mapped_len)))
> +		if (to_desc) {
> +			src = (void *)(uintptr_t)rte_pktmbuf_iova_offset(m, mbuf_offset);
> +			dst = host_iova;
> +		} else {
> +			src = host_iova;
> +			dst = (void *)(uintptr_t)rte_pktmbuf_iova_offset(m, mbuf_offset);
> +		}
> +
> +		if (unlikely(async_iter_add_iovec(dev, async, src, dst,
> +						 (size_t)mapped_len)))

Minor, but it may fit in a single line.

>   			return -1;
>   
>   		cpy_len -= (uint32_t)mapped_len;
> @@ -1167,8 +1174,8 @@ mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
>   		cpy_len = RTE_MIN(buf_avail, mbuf_avail);
>   
>   		if (is_async) {
> -			if (async_mbuf_to_desc_seg(dev, vq, m, mbuf_offset,
> -						buf_iova + buf_offset, cpy_len) < 0)
> +			if (async_fill_seg(dev, vq, m, mbuf_offset,
> +						buf_iova + buf_offset, cpy_len, true) < 0)
>   				goto error;
>   		} else {
>   			sync_fill_seg(dev, vq, m, mbuf_offset,

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

Thanks,
Maxime