Re: [PATCH bpf-next] virtio_net: add XDP meta data support in receive_small()

[Yuya Kusakabe <yuya.kusakabe@gmail.com>]

>> This adds XDP meta data support to the code path receive_small().
>>
>> mrg_rxbuf=off is required on qemu, because receive_mergeable() still
>> doesn't support XDP meta data.
>
>
>What's the reason for this?

I didn't have enough time to add support XDP meta data to
receive_mergeable(). But I'll try it a little more. Please wait for the
next patch.

>>
>> Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")
>> Signed-off-by: Yuya Kusakabe <yuya.kusakabe@gmail.com>
>
>
>Could you please cc virtio maintainer through get_maintainer.pl?
>
>Thanks

Sorry. I added them.

Thanks.

> ---
>   drivers/net/virtio_net.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4f3de0ac8b0b..14165c5edb7d 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -644,6 +644,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
>   	unsigned int delta = 0;
>   	struct page *xdp_page;
>   	int err;
> +	unsigned int metasize = 0;
>   
>   	len -= vi->hdr_len;
>   	stats->bytes += len;
> @@ -683,8 +684,8 @@ static struct sk_buff *receive_small(struct net_device *dev,
>   
>   		xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len;
>   		xdp.data = xdp.data_hard_start + xdp_headroom;
> -		xdp_set_data_meta_invalid(&xdp);
>   		xdp.data_end = xdp.data + len;
> +		xdp.data_meta = xdp.data;
>   		xdp.rxq = &rq->xdp_rxq;
>   		orig_data = xdp.data;
>   		act = bpf_prog_run_xdp(xdp_prog, &xdp);
> @@ -695,9 +696,11 @@ static struct sk_buff *receive_small(struct net_device *dev,
>   			/* Recalculate length in case bpf program changed it */
>   			delta = orig_data - xdp.data;
>   			len = xdp.data_end - xdp.data;
> +			metasize = xdp.data - xdp.data_meta;
>   			break;
>   		case XDP_TX:
>   			stats->xdp_tx++;
> +			xdp.data_meta = xdp.data;
>   			xdpf = convert_to_xdp_frame(&xdp);
>   			if (unlikely(!xdpf))
>   				goto err_xdp;
> @@ -735,11 +738,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
>   	}
>   	skb_reserve(skb, headroom - delta);
>   	skb_put(skb, len);
> -	if (!delta) {
> +	if (!delta && !metasize) {
>   		buf += header_offset;
>   		memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
>   	} /* keep zeroed vnet hdr since packet was changed by bpf */
>   
> +	if (metasize)
> +		skb_metadata_set(skb, metasize);
> +
>   err:
>   	return skb;
>