linux-kernel - [PATCH] virtio-net: Update the mtu code to match virtio spec

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Message-Id: <1477413335-17296-1-git-send-email-aconole@redhat.com>
Date:   Tue, 25 Oct 2016 12:35:35 -0400
From:   Aaron Conole <aconole@...hat.com>
To:     netdev@...r.kernel.org
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jarod Wilson <jarod@...hat.com>
Subject: [PATCH] virtio-net: Update the mtu code to match virtio spec

From: Aaron Conole <aconole@...heb.org>

The virtio committee recently ratified a change, VIRTIO-152, which
defines the mtu field to be 'max' MTU, not simply desired MTU.

This commit brings the virtio-net device in compliance with VIRTIO-152.

Additionally, drop the max_mtu branch - it cannot be taken since the u16
returned by virtio_cread16 will never exceed the initial value of
max_mtu.

Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jarod Wilson <jarod@...hat.com>
Signed-off-by: Aaron Conole <aconole@...hat.com>
---
 drivers/net/virtio_net.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 720809f..2cafd12 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1870,10 +1870,12 @@ static int virtnet_probe(struct virtio_device *vdev)
 		mtu = virtio_cread16(vdev,
 				     offsetof(struct virtio_net_config,
 					      mtu));
-		if (mtu < dev->min_mtu || mtu > dev->max_mtu)
+		if (mtu < dev->min_mtu) {
 			__virtio_clear_bit(vdev, VIRTIO_NET_F_MTU);
-		else
+		} else {
 			dev->mtu = mtu;
+			dev->max_mtu = mtu;
+		}
 	}
 
 	if (vi->any_header_sg)
-- 
2.7.4