netdev - Re: [PATCH net-next v6 09/10] virtio_net: xsk: rx: support recv merge mode

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Date: Fri, 28 Jun 2024 10:19:44 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>, 
	Eugenio Pérez <eperezma@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, virtualization@...ts.linux.dev, 
	bpf@...r.kernel.org
Subject: Re: [PATCH net-next v6 09/10] virtio_net: xsk: rx: support recv merge mode

On Tue, Jun 18, 2024 at 3:57 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> Support AF-XDP for merge mode.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 139 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 139 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 06608d696e2e..cfa106aa8039 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -504,6 +504,10 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
>                                struct net_device *dev,
>                                unsigned int *xdp_xmit,
>                                struct virtnet_rq_stats *stats);
> +static struct sk_buff *virtnet_skb_append_frag(struct sk_buff *head_skb,
> +                                              struct sk_buff *curr_skb,
> +                                              struct page *page, void *buf,
> +                                              int len, int truesize);
>
>  static bool is_xdp_frame(void *ptr)
>  {
> @@ -1128,6 +1132,139 @@ static struct sk_buff *virtnet_receive_xsk_small(struct net_device *dev, struct
>         }
>  }
>
> +static void xsk_drop_follow_bufs(struct net_device *dev,
> +                                struct receive_queue *rq,
> +                                u32 num_buf,
> +                                struct virtnet_rq_stats *stats)
> +{
> +       struct xdp_buff *xdp;
> +       u32 len;
> +
> +       while (num_buf-- > 1) {
> +               xdp = virtqueue_get_buf(rq->vq, &len);
> +               if (unlikely(!xdp)) {
> +                       pr_debug("%s: rx error: %d buffers missing\n",
> +                                dev->name, num_buf);
> +                       DEV_STATS_INC(dev, rx_length_errors);
> +                       break;
> +               }
> +               u64_stats_add(&stats->bytes, len);
> +               xsk_buff_free(xdp);
> +       }
> +}
> +
> +static int xsk_append_merge_buffer(struct virtnet_info *vi,
> +                                  struct receive_queue *rq,
> +                                  struct sk_buff *head_skb,
> +                                  u32 num_buf,
> +                                  struct virtio_net_hdr_mrg_rxbuf *hdr,
> +                                  struct virtnet_rq_stats *stats)
> +{
> +       struct sk_buff *curr_skb;
> +       struct xdp_buff *xdp;
> +       u32 len, truesize;
> +       struct page *page;
> +       void *buf;
> +
> +       curr_skb = head_skb;
> +
> +       while (--num_buf) {
> +               buf = virtqueue_get_buf(rq->vq, &len);
> +               if (unlikely(!buf)) {
> +                       pr_debug("%s: rx error: %d buffers out of %d missing\n",
> +                                vi->dev->name, num_buf,
> +                                virtio16_to_cpu(vi->vdev,
> +                                                hdr->num_buffers));
> +                       DEV_STATS_INC(vi->dev, rx_length_errors);
> +                       return -EINVAL;
> +               }
> +
> +               u64_stats_add(&stats->bytes, len);
> +
> +               xdp = buf_to_xdp(vi, rq, buf, len);
> +               if (!xdp)
> +                       goto err;
> +
> +               buf = napi_alloc_frag(len);

So we don't do this for non xsk paths. Any reason we can't reuse the
existing codes?

Thanks