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Sun, 09 Nov 2025 13:34:41 -0800 (PST) X-Google-Smtp-Source: AGHT+IGW9iA+CzK/FjpBM/e7D6gQ+zW6aVjSPr8rNlm1S3UdLgIp9ALg50OwxbW/747hMDqIG1CnxA== X-Received: by 2002:a05:600c:4ed2:b0:477:7d94:5d0e with SMTP id 5b1f17b1804b1-4777d945f1dmr1196595e9.27.1762724080621; Sun, 09 Nov 2025 13:34:40 -0800 (PST) Received: from redhat.com ([2a0d:6fc0:1536:2700:9203:49b4:a0d:b580]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42b322d533dsm7761055f8f.0.2025.11.09.13.34.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 09 Nov 2025 13:34:40 -0800 (PST) Date: Sun, 9 Nov 2025 16:34:37 -0500 From: "Michael S. Tsirkin" To: Xuan Zhuo Cc: netdev@vger.kernel.org, Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Heng Qi , Willem de Bruijn , Jiri Pirko , Alvaro Karsz , virtualization@lists.linux.dev Subject: Re: [PATCH net v4 1/4] virtio-net: fix incorrect flags recording in big mode Message-ID: <20251109163431-mutt-send-email-mst@kernel.org> References: <20251029030913.20423-1-xuanzhuo@linux.alibaba.com> <20251029030913.20423-2-xuanzhuo@linux.alibaba.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251029030913.20423-2-xuanzhuo@linux.alibaba.com> On Wed, Oct 29, 2025 at 11:09:10AM +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 > Acked-by: Jason Wang Acked-by: Michael S. Tsirkin > --- > drivers/net/virtio_net.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 8e8a179aaa49..59f116b609f6 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -2625,22 +2625,28 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq, > return; > } > > - /* 1. Save the flags early, as the XDP program might overwrite them. > + /* About the flags below: > + * 1. Save the flags early, as the XDP program might overwrite them. > * These flags ensure packets marked as VIRTIO_NET_HDR_F_DATA_VALID > * stay valid after XDP processing. > * 2. XDP doesn't work with partially checksummed packets (refer to > * virtnet_xdp_set()), so packets marked as > * VIRTIO_NET_HDR_F_NEEDS_CSUM get dropped during XDP processing. > */ > - flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags; > > - if (vi->mergeable_rx_bufs) > + if (vi->mergeable_rx_bufs) { > + flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags; > skb = receive_mergeable(dev, vi, rq, buf, ctx, len, xdp_xmit, > stats); > - else if (vi->big_packets) > + } else if (vi->big_packets) { > + 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 { > + flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags; > skb = receive_small(dev, vi, rq, buf, ctx, len, xdp_xmit, stats); > + } > > if (unlikely(!skb)) > return; > -- > 2.32.0.3.g01195cf9f