* [RFC v3 -net 1/2] virtio: Start feature MTU support
2016-04-01 19:32 [RFC v3 -next 0/2] virtio-net: Advised MTU feature Aaron Conole
@ 2016-04-01 19:32 ` Aaron Conole
2016-04-01 19:32 ` [RFC v3 -next 2/2] virtio_net: Read the advised MTU Aaron Conole
1 sibling, 0 replies; 3+ messages in thread
From: Aaron Conole @ 2016-04-01 19:32 UTC (permalink / raw)
To: netdev, Michael S. Tsirkin, virtualization, linux-kernel,
Paolo Abeni, Sergei Shtylyov, Pankaj Gupta
This commit adds the feature bit and associated mtu device entry for the
virtio network device. Future commits will make use of these bits to support
negotiated MTU.
Signed-off-by: Aaron Conole <aconole@bytheb.org>
---
v2,v3:
* No change
include/uapi/linux/virtio_net.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index ec32293..41a6a01 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 /* Device supports Default MTU Negotiation */
#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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [RFC v3 -next 2/2] virtio_net: Read the advised MTU
2016-04-01 19:32 [RFC v3 -next 0/2] virtio-net: Advised MTU feature Aaron Conole
2016-04-01 19:32 ` [RFC v3 -net 1/2] virtio: Start feature MTU support Aaron Conole
@ 2016-04-01 19:32 ` Aaron Conole
1 sibling, 0 replies; 3+ messages in thread
From: Aaron Conole @ 2016-04-01 19:32 UTC (permalink / raw)
To: netdev, Michael S. Tsirkin, virtualization, linux-kernel,
Paolo Abeni, Sergei Shtylyov, Pankaj Gupta
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 <aconole@bytheb.org>
---
v2:
* Whitespace cleanup in the last hunk
* Code style change around the pr_warn
* Additional test for mtu change before printing warning
v3:
* removed the mtu change warning
drivers/net/virtio_net.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 49d84e5..2308083 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1450,6 +1450,7 @@ 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;
dev->mtu = new_mtu;
@@ -1896,6 +1897,12 @@ 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)) {
+ dev->mtu = virtio_cread16(vdev,
+ offsetof(struct virtio_net_config,
+ mtu));
+ }
+
if (vi->any_header_sg)
dev->needed_headroom = vi->hdr_len;
@@ -2081,6 +2088,7 @@ 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 = {
--
2.5.5
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