Re: [PATCH net-next v1 16/19] virtio_net: xsk: rx: introduce receive_xsk() to recv xsk buffer

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On Mon, Oct 16, 2023 at 8:01 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
>
> Implementing the logic of xsk rx. If this packet is not for XSK
> determined in XDP, then we need to copy once to generate a SKB.
> If it is for XSK, it is a zerocopy receive packet process.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> ---
>  drivers/net/virtio/main.c       |  14 ++--
>  drivers/net/virtio/virtio_net.h |   4 ++
>  drivers/net/virtio/xsk.c        | 120 ++++++++++++++++++++++++++++++++
>  drivers/net/virtio/xsk.h        |   4 ++
>  4 files changed, 137 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
> index 0e740447b142..003dd67ab707 100644
> --- a/drivers/net/virtio/main.c
> +++ b/drivers/net/virtio/main.c
> @@ -822,10 +822,10 @@ static void put_xdp_frags(struct xdp_buff *xdp)
>         }
>  }
>
> -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)
> +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)
>  {
>         struct xdp_frame *xdpf;
>         int err;
> @@ -1589,13 +1589,17 @@ static void receive_buf(struct virtnet_info *vi, struct virtnet_rq *rq,
>                 return;
>         }
>
> -       if (vi->mergeable_rx_bufs)
> +       rcu_read_lock();
> +       if (rcu_dereference(rq->xsk.pool))
> +               skb = virtnet_receive_xsk(dev, vi, rq, buf, len, xdp_xmit, stats);
> +       else if (vi->mergeable_rx_bufs)
>                 skb = receive_mergeable(dev, vi, rq, buf, ctx, len, xdp_xmit,
>                                         stats);
>         else if (vi->big_packets)
>                 skb = receive_big(dev, vi, rq, buf, len, stats);
>         else
>                 skb = receive_small(dev, vi, rq, buf, ctx, len, xdp_xmit, stats);
> +       rcu_read_unlock();
>
>         if (unlikely(!skb))
>                 return;
> diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
> index 6e71622fca45..fd7f34703c9b 100644
> --- a/drivers/net/virtio/virtio_net.h
> +++ b/drivers/net/virtio/virtio_net.h
> @@ -346,6 +346,10 @@ static inline bool virtnet_is_xdp_raw_buffer_queue(struct virtnet_info *vi, int
>                 return false;
>  }
>
> +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);
>  void virtnet_rx_pause(struct virtnet_info *vi, struct virtnet_rq *rq);
>  void virtnet_rx_resume(struct virtnet_info *vi, struct virtnet_rq *rq);
>  void virtnet_tx_pause(struct virtnet_info *vi, struct virtnet_sq *sq);
> diff --git a/drivers/net/virtio/xsk.c b/drivers/net/virtio/xsk.c
> index 841fb078882a..f1c64414fac9 100644
> --- a/drivers/net/virtio/xsk.c
> +++ b/drivers/net/virtio/xsk.c
> @@ -13,6 +13,18 @@ static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
>         sg->length = len;
>  }
>
> +static unsigned int virtnet_receive_buf_num(struct virtnet_info *vi, char *buf)
> +{
> +       struct virtio_net_hdr_mrg_rxbuf *hdr;
> +
> +       if (vi->mergeable_rx_bufs) {
> +               hdr = (struct virtio_net_hdr_mrg_rxbuf *)buf;
> +               return virtio16_to_cpu(vi->vdev, hdr->num_buffers);
> +       }
> +
> +       return 1;
> +}
> +
>  static void virtnet_xsk_check_queue(struct virtnet_sq *sq)
>  {
>         struct virtnet_info *vi = sq->vq->vdev->priv;
> @@ -37,6 +49,114 @@ static void virtnet_xsk_check_queue(struct virtnet_sq *sq)
>                 netif_stop_subqueue(dev, qnum);
>  }
>
> +static void merge_drop_follow_xdp(struct net_device *dev,
> +                                 struct virtnet_rq *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.rx_length_errors++;
> +                       break;
> +               }
> +               stats->bytes += len;
> +               xsk_buff_free(xdp);
> +       }
> +}
> +
> +static struct sk_buff *construct_skb(struct virtnet_rq *rq,
> +                                    struct xdp_buff *xdp)
> +{
> +       unsigned int metasize = xdp->data - xdp->data_meta;
> +       struct sk_buff *skb;
> +       unsigned int size;
> +
> +       size = xdp->data_end - xdp->data_hard_start;
> +       skb = napi_alloc_skb(&rq->napi, size);
> +       if (unlikely(!skb))
> +               return NULL;
> +
> +       skb_reserve(skb, xdp->data_meta - xdp->data_hard_start);
> +
> +       size = xdp->data_end - xdp->data_meta;
> +       memcpy(__skb_put(skb, size), xdp->data_meta, size);
> +
> +       if (metasize) {
> +               __skb_pull(skb, metasize);
> +               skb_metadata_set(skb, metasize);
> +       }
> +
> +       return skb;
> +}
> +
> +struct sk_buff *virtnet_receive_xsk(struct net_device *dev, struct virtnet_info *vi,
> +                                   struct virtnet_rq *rq, void *buf,
> +                                   unsigned int len, unsigned int *xdp_xmit,
> +                                   struct virtnet_rq_stats *stats)
> +{

I wonder if anything blocks us from reusing the existing XDP logic?
Are there some subtle differences?

Thanks

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