Re: [PATCH net] virtio-net: enable big mode correctly
From: Eli Cohen <hidden>
Date: 2021-11-25 07:11:54
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On Thu, Nov 25, 2021 at 02:05:47PM +0800, Jason Wang wrote:
quoted hunk ↗ jump to hunk
When VIRTIO_NET_F_MTU feature is not negotiated, we assume a very large max_mtu. In this case, using small packet mode is not correct since it may breaks the networking when MTU is grater than ETH_DATA_LEN. To have a quick fix, simply enable the big packet mode when VIRTIO_NET_F_MTU is not negotiated. We can do optimization on top. Reported-by: Eli Cohen <redacted> Cc: Eli Cohen <redacted> Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/net/virtio_net.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 7c43bfc1ce44..83ae3ef5eb11 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c@@ -3200,11 +3200,12 @@ static int virtnet_probe(struct virtio_device *vdev) dev->mtu = mtu; dev->max_mtu = mtu; - /* TODO: size buffers correctly in this case. */ - if (dev->mtu > ETH_DATA_LEN) - vi->big_packets = true; } + /* TODO: size buffers correctly in this case. */ + if (dev->max_mtu > ETH_DATA_LEN) + vi->big_packets = true; +
If VIRTIO_NET_F_MTU is provided, then dev->max_mtu is going to equal ETH_DATA_LEN (will be set in ether_setup()) so I don't think it will set big_packets to true.
if (vi->any_header_sg) dev->needed_headroom = vi->hdr_len; -- 2.25.1