netdev - Re: [PATCH net] virtio-net: drop the multi-buffer XDP packet in zerocopy

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Message-ID: <1749779468.7241242-3-xuanzhuo@linux.alibaba.com>
Date: Fri, 13 Jun 2025 09:51:08 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Bui Quang Minh <minhquangbui99@...il.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
 Jason Wang <jasowang@...hat.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 Andrew Lunn <andrew+netdev@...n.ch>,
 "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,
 linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org,
 Bui Quang Minh <minhquangbui99@...il.com>,
 stable@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net] virtio-net: drop the multi-buffer XDP packet in zerocopy

On Tue,  3 Jun 2025 22:06:13 +0700, Bui Quang Minh <minhquangbui99@...il.com> wrote:
> In virtio-net, we have not yet supported multi-buffer XDP packet in
> zerocopy mode when there is a binding XDP program. However, in that
> case, when receiving multi-buffer XDP packet, we skip the XDP program
> and return XDP_PASS. As a result, the packet is passed to normal network
> stack which is an incorrect behavior. This commit instead returns
> XDP_DROP in that case.
>
> Fixes: 99c861b44eb1 ("virtio_net: xsk: rx: support recv merge mode")
> Cc: stable@...r.kernel.org
> Signed-off-by: Bui Quang Minh <minhquangbui99@...il.com>

Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>

> ---
>  drivers/net/virtio_net.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e53ba600605a..4c35324d6e5b 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1309,9 +1309,14 @@ static struct sk_buff *virtnet_receive_xsk_merge(struct net_device *dev, struct
>  	ret = XDP_PASS;
>  	rcu_read_lock();
>  	prog = rcu_dereference(rq->xdp_prog);
> -	/* TODO: support multi buffer. */
> -	if (prog && num_buf == 1)
> -		ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit, stats);
> +	if (prog) {
> +		/* TODO: support multi buffer. */
> +		if (num_buf == 1)
> +			ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit,
> +						  stats);
> +		else
> +			ret = XDP_DROP;
> +	}
>  	rcu_read_unlock();
>
>  	switch (ret) {
> --
> 2.43.0
>