Re: [PATCH v2 1/9] virtio_net: disable the hole mechanism for xdp

[Jason Wang <jasowang@redhat.com>]

在 2022/12/20 22:14, Heng Qi 写道:
> XDP core assumes that the frame_size of xdp_buff and the length of
> the frag are PAGE_SIZE. The hole may cause the processing of xdp to
> fail, so we disable the hole mechanism when xdp is set.
>
> Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>   drivers/net/virtio_net.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 9cce7dec7366..443aa7b8f0ad 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1419,8 +1419,11 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>   		/* To avoid internal fragmentation, if there is very likely not
>   		 * enough space for another buffer, add the remaining space to
>   		 * the current buffer.
> +		 * XDP core assumes that frame_size of xdp_buff and the length
> +		 * of the frag are PAGE_SIZE, so we disable the hole mechanism.
>   		 */
> -		len += hole;
> +		if (!headroom)
> +			len += hole;


Is this only a requirement of multi-buffer XDP? If not, it need to be 
backported to stable.

Thanks


>   		alloc_frag->offset += hole;
>   	}
>