netdev - Re: [PATCH net-next v6 07/10] virtio_net: xsk: rx: support fill with xsk buffer

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Date: Fri, 28 Jun 2024 10:19:37 +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 07/10] virtio_net: xsk: rx: support fill with
 xsk buffer

On Tue, Jun 18, 2024 at 3:57 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> Implement the logic of filling rq with XSK buffers.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 68 ++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 66 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 2bbc715f22c6..2ac5668a94ce 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -355,6 +355,8 @@ struct receive_queue {
>
>                 /* xdp rxq used by xsk */
>                 struct xdp_rxq_info xdp_rxq;
> +
> +               struct xdp_buff **xsk_buffs;
>         } xsk;
>  };
>
> @@ -1032,6 +1034,53 @@ 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 int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue *rq,
> +                                  struct xsk_buff_pool *pool, gfp_t gfp)
> +{
> +       struct xdp_buff **xsk_buffs;
> +       dma_addr_t addr;
> +       u32 len, i;
> +       int err = 0;
> +       int num;
> +
> +       xsk_buffs = rq->xsk.xsk_buffs;
> +
> +       num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->vq->num_free);
> +       if (!num)
> +               return -ENOMEM;
> +
> +       len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len;
> +
> +       for (i = 0; i < num; ++i) {
> +               /* use the part of XDP_PACKET_HEADROOM as the virtnet hdr space */
> +               addr = xsk_buff_xdp_get_dma(xsk_buffs[i]) - vi->hdr_len;

We had VIRTIO_XDP_HEADROOM, can we reuse it? Or if it's redundant
let's send a patch to switch to XDP_PACKET_HEADROOM.

Btw, the code assumes vi->hdr_len < xsk_pool_get_headroom(). It's
better to fail if it's not true when enabling xsk.

Thanks