On Fri, Sep 19, 2025 at 09:34:50AM +0800, Xuan Zhuo wrote:
> The purpose of commit 703eec1b2422 ("virtio_net: fixing XDP for fully
> checksummed packets handling") is to record the flags in advance, as
> their value may be overwritten in the XDP case. However, the flags
> recorded under big mode are incorrect, because in big mode, the passed
> buf does not point to the rx buffer, but rather to the page of the
> submitted buffer. This commit fixes this issue.
>
> For the small mode, the commit c11a49d58ad2 ("virtio_net: Fix mismatched
> buf address when unmapping for small packets") fixed it.
>
> Fixes: 703eec1b2422 ("virtio_net: fixing XDP for fully checksummed packets
> handling")
> Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
Thanks for the patch! Yet something to improve:
> ---
> drivers/net/virtio_net.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 975bdc5dab84..6e6e74390955 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2630,13 +2630,19 @@ static void receive_buf(struct virtnet_info *vi,
> struct receive_queue *rq,
> */
> flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;
>
> - if (vi->mergeable_rx_bufs)
> + if (vi->mergeable_rx_bufs) {
> skb = receive_mergeable(dev, vi, rq, buf, ctx, len, xdp_xmit,
> stats);
> - else if (vi->big_packets)
> + } else if (vi->big_packets) {
> + void *p;
> +
> + p = page_address((struct page *)buf);
I'd move this assignment to where p is declared:
void *p = page_address((struct page *)buf);
> + flags = ((struct virtio_net_common_hdr *)p)->hdr.flags;
> +
> skb = receive_big(dev, vi, rq, buf, len, stats);
> - else
> + } else {
> skb = receive_small(dev, vi, rq, buf, ctx, len, xdp_xmit,
> stats);
> + }
>
> if (unlikely(!skb))
> return;
Indeed but let's please not do the initial
flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;
for the big mode at all, it's confusing, and only works because struct
page is bigger than struct virtio_net_common_hdr.
pls move it into the clauses for mergeable and small.
> --
> 2.32.0.3.g01195cf9f
