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: Aaron Conole <aconole@xxxxxxxxxx>
---
v2->v3:
* Added a check for the MTU, and a bit clear for it being out of range.
drivers/net/virtio_net.c | 10 ++++++++++
include/uapi/linux/virtio_net.h | 3 +++
2 files changed, 13 insertions(+)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e0638e5..192f321 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -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 = {
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index ec32293..1ab4ea6 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -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));
/*
--
2.5.5
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