Re: [PATCH net] virtio-net: fix incorrect flags recording in big mode
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2025-09-19 08:07:20
Also in:
virtualization
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 <xuanzhuo@linux.alibaba.com>Thanks for the patch! Yet something to improve:
quoted hunk ↗ jump to hunk
--- 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