This patch checks the feature bit for the VIRTIO_NET_F_MTU feature. If it
exists, read the advised MTU and use it.
No proper error handling is provided for the case where a user changes the
negotiated MTU. A future commit will add proper error handling. Instead, a
warning is emitted if the guest changes the device MTU after previously
being given advice.
Signed-off-by: Aaron Conole <acon...@bytheb.org>
---
v2:
* Whitespace cleanup in the last hunk
* Code style change around the pr_warn
* Additional test for mtu change before printing warning
drivers/net/virtio_net.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 767ab11..429fe01 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -146,6 +146,7 @@ struct virtnet_info {
virtio_net_ctrl_ack ctrl_status;
u8 ctrl_promisc;
u8 ctrl_allmulti;
+ bool negotiated_mtu;
};
struct padded_vnet_hdr {
@@ -1390,8 +1391,11 @@ static const struct ethtool_ops virtnet_ethtool_ops = {
static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
{
+ struct virtnet_info *vi = netdev_priv(dev);
if (new_mtu < MIN_MTU || new_mtu > MAX_MTU)
return -EINVAL;
+ if ((vi->negotiated_mtu) && (dev->mtu != new_mtu))
+ pr_warn("changing mtu while the advised mtu bit exists.");
dev->mtu = new_mtu;
return 0;
}
@@ -1836,6 +1840,13 @@ static int virtnet_probe(struct virtio_device *vdev)
if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
vi->has_cvq = true;
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) {
+ vi->negotiated_mtu = true;
+ dev->mtu = virtio_cread16(vdev,
+ offsetof(struct virtio_net_config,
+ mtu));
+ }
+
if (vi->any_header_sg)
dev->needed_headroom = vi->hdr_len;
@@ -2019,6 +2030,7 @@ static unsigned int features[] = {
VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ,
VIRTIO_NET_F_CTRL_MAC_ADDR,
VIRTIO_F_ANY_LAYOUT,
+ VIRTIO_NET_F_MTU,
};
static struct virtio_driver virtio_net_driver = {
--
2.5.0
