linux-kernel - Re: [PATCH net 1/9] virtio-net: remove the warning before XDP linearizing

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Message-ID: <585D7BA9.50509@iogearbox.net>
Date:   Fri, 23 Dec 2016 20:31:53 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jason Wang <jasowang@...hat.com>, mst@...hat.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
CC:     john.r.fastabend@...el.com
Subject: Re: [PATCH net 1/9] virtio-net: remove the warning before XDP linearizing

Hi Jason,

On 12/23/2016 03:37 PM, Jason Wang wrote:
> Since we use EWMA to estimate the size of rx buffer. When rx buffer
> size is underestimated, it's usual to have a packet with more than one
> buffers. Consider this is not a bug, remove the warning and correct
> the comment before XDP linearizing.
>
> Cc: John Fastabend <john.r.fastabend@...el.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>   drivers/net/virtio_net.c | 8 +-------
>   1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 08327e0..1067253 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -552,14 +552,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>   		struct page *xdp_page;
>   		u32 act;
>
> -		/* No known backend devices should send packets with
> -		 * more than a single buffer when XDP conditions are
> -		 * met. However it is not strictly illegal so the case
> -		 * is handled as an exception and a warning is thrown.
> -		 */
> +		/* This happens when rx buffer size is underestimated */
>   		if (unlikely(num_buf > 1)) {
> -			bpf_warn_invalid_xdp_buffer();

Could you also remove the bpf_warn_invalid_xdp_buffer(), which got added
just for this?

Thanks.

>   			/* linearize data for XDP */
>   			xdp_page = xdp_linearize_page(rq, num_buf,
>   						      page, offset, &len);
>