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Commit 14de9d11 authored by Aaron Conole's avatar Aaron Conole Committed by David S. Miller
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virtio-net: Add initial MTU advice feature 



This commit adds the feature bit and associated mtu device entry for the
virtio network device.  When a virtio device comes up, it checks the
feature bit for the VIRTIO_NET_F_MTU feature.  If such feature bit is
enabled, the driver will read the advised MTU and use it as the initial
value.

Signed-off-by: default avatarAaron Conole <aconole@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3d9dc408

drivers/net/virtio_net.c

+10 −0
Original line number Diff line number Diff line
@@ -1780,6 +1780,7 @@ static int virtnet_probe(struct virtio_device *vdev) 
	struct net_device *dev;

	struct virtnet_info *vi;

	u16 max_queue_pairs;

	int mtu;



	if (!vdev->config->get) {

		dev_err(&vdev->dev, "%s failure: config access disabled\n",
@@ -1896,6 +1897,14 @@ 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)) {

		mtu = virtio_cread16(vdev,

				     offsetof(struct virtio_net_config,

					      mtu));

		if (virtnet_change_mtu(dev, mtu))

			__virtio_clear_bit(vdev, VIRTIO_NET_F_MTU);

	}



	if (vi->any_header_sg)

		dev->needed_headroom = vi->hdr_len;
@@ -2067,6 +2076,7 @@ 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 = {

include/uapi/linux/virtio_net.h

+3 −0
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ 
#define VIRTIO_NET_F_MQ	22	/* Device supports Receive Flow

					 * Steering */

#define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */

#define VIRTIO_NET_F_MTU 25	/* Initial MTU advice */



#ifndef VIRTIO_NET_NO_LEGACY

#define VIRTIO_NET_F_GSO	6	/* Host handles pkts w/ any GSO type */
@@ -73,6 +74,8 @@ struct virtio_net_config { 
	 * Legal values are between 1 and 0x8000

	 */

	__u16 max_virtqueue_pairs;

	/* Default maximum transmit unit advice */

	__u16 mtu;

} __attribute__((packed));



/*