Re: [PATCH net-next v2 06/13] virtio-net: rq submits premapped per-buffer

Jason Wang
2024-11-05T03:24:05Z

On Wed, Oct 30, 2024 at 4:25 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> virtio-net rq submits premapped per-buffer by setting sg page to NULL;
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
> drivers/net/virtio_net.c | 24 +++++++++++++-----------
> 1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 792e9eadbfc3..09757fa408bd 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -542,6 +542,12 @@ static struct sk_buff *ptr_to_skb(void *ptr)
> return (struct sk_buff *)((unsigned long)ptr & ~VIRTIO_ORPHAN_FLAG);
> }
>
> +static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> +{
> + sg->dma_address = addr;
> + sg->length = len;

This may work but I think it's better to reuse existing dma sg helpers like:

sg_dma_address(sg) = addr;
sg_dma_length(sg) = len;

And we probably need to fix the virtio core which only uses
sg_dma_address() but not sg_dma_length().

This helps us to avoid future issues when CONFIG_NEED_SG_DMA_LENGTH is set.

Others look good.

Thanks

> +}
> +
> static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,
> bool in_napi, struct virtnet_sq_free_stats *stats)
> {
> @@ -915,8 +921,7 @@ static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
> addr = dma->addr - sizeof(*dma) + offset;
>
> sg_init_table(rq->sg, 1);
> - rq->sg[0].dma_address = addr;
> - rq->sg[0].length = len;
> + sg_fill_dma(rq->sg, addr, len);
> }
>
> static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
> @@ -1068,12 +1073,6 @@ static void check_sq_full_and_disable(struct virtnet_info *vi,
> }
> }
>
> -static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> -{
> - sg->dma_address = addr;
> - sg->length = len;
> -}
> -
> static struct xdp_buff *buf_to_xdp(struct virtnet_info *vi,
> struct receive_queue *rq, void *buf, u32 len)
> {
> @@ -1354,7 +1353,8 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue
> sg_init_table(rq->sg, 1);
> sg_fill_dma(rq->sg, addr, len);
>
> - err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, xsk_buffs[i], gfp);
> + err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, xsk_buffs[i],
> + NULL, true, gfp);
> if (err)
> goto err;
> }
> @@ -2431,7 +2431,8 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
>
> virtnet_rq_init_one_sg(rq, buf, vi->hdr_len + GOOD_PACKET_LEN);
>
> - err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
> + err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx,
> + rq->do_dma, gfp);
> if (err < 0) {
> if (rq->do_dma)
> virtnet_rq_unmap(rq, buf, 0);
> @@ -2546,7 +2547,8 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
> virtnet_rq_init_one_sg(rq, buf, len);
>
> ctx = mergeable_len_to_ctx(len + room, headroom);
> - err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
> + err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx,
> + rq->do_dma, gfp);
> if (err < 0) {
> if (rq->do_dma)
> virtnet_rq_unmap(rq, buf, 0);
> --
> 2.32.0.3.g01195cf9f
>