Patchwork virtio_net: add link status handling

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Submitter Mark McLoughlin
Date Dec. 9, 2008, 10:19 a.m.
Message ID <1228817973.26198.1.camel@blaa>
Download mbox | patch
Permalink /patch/12907/
State Changes Requested
Delegated to: David Miller
Headers show

Comments

Mark McLoughlin - Dec. 9, 2008, 10:19 a.m.
Allow the host to inform us that the link is down by adding
a VIRTIO_NET_F_STATUS which indicates that device status is
available in virtio_net config.

This is currently useful for simulating link down conditions
(e.g. using proposed qemu 'set_link' monitor command) but
would also be needed if we were to support device assignment
via virtio.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
---
 drivers/net/virtio_net.c   |   40 +++++++++++++++++++++++++++++++++++++++-
 include/linux/virtio_net.h |    5 +++++
 2 files changed, 44 insertions(+), 1 deletions(-)
Anthony Liguori - Dec. 9, 2008, 9:32 p.m.
Mark McLoughlin wrote:
> Allow the host to inform us that the link is down by adding
> a VIRTIO_NET_F_STATUS which indicates that device status is
> available in virtio_net config.
> 
> This is currently useful for simulating link down conditions
> (e.g. using proposed qemu 'set_link' monitor command) but
> would also be needed if we were to support device assignment
> via virtio.

It would be nice if the virtio-net card wrote some acknowledgement that 
it has received the link status down/up events.

I'm thinking along the lines of doing live migration between two end 
points that are not on the same subnet.  It would be nice to be able to 
signal link status down, have the guest acknowledge that it received it, 
do the live migration, then do link status up so the guest reconnects 
it's networking.

Regards,

Anthony Liguori
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Rusty Russell - Dec. 9, 2008, 11:53 p.m.
On Wednesday 10 December 2008 08:02:14 Anthony Liguori wrote:
> Mark McLoughlin wrote:
> > Allow the host to inform us that the link is down by adding
> > a VIRTIO_NET_F_STATUS which indicates that device status is
> > available in virtio_net config.
> > 
> > This is currently useful for simulating link down conditions
> > (e.g. using proposed qemu 'set_link' monitor command) but
> > would also be needed if we were to support device assignment
> > via virtio.
> 
> It would be nice if the virtio-net card wrote some acknowledgement that 
> it has received the link status down/up events.

How about of every status change event? ie. a generic virtio_pci solution?

Rusty.
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Rusty Russell - Dec. 9, 2008, 11:56 p.m.
On Tuesday 09 December 2008 20:49:33 Mark McLoughlin wrote:
> Allow the host to inform us that the link is down by adding
> a VIRTIO_NET_F_STATUS which indicates that device status is
> available in virtio_net config.

This has been a TODO for a while, thanks!

> +	if (vi->status == v)
> +		return;
> +
> +	vi->status = v;
> +
> +	if (vi->status & VIRTIO_NET_S_LINK_UP) {
> +		netif_carrier_on(vi->dev);
> +		netif_wake_queue(vi->dev);
> +	} else {
> +		netif_carrier_off(vi->dev);
> +		netif_stop_queue(vi->dev);
> +	}

New status bits will screw this logic unless we count
on the host not to set them.  I suggest:

	/* Ignore unknown (future) status bits */
	v &= VIRTIO_NET_S_LINK_UP;

Cheers,
Rusty.
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Anthony Liguori - Dec. 10, 2008, 3:11 a.m.
Rusty Russell wrote:
> On Wednesday 10 December 2008 08:02:14 Anthony Liguori wrote:
>   
>> Mark McLoughlin wrote:
>>     
>>> Allow the host to inform us that the link is down by adding
>>> a VIRTIO_NET_F_STATUS which indicates that device status is
>>> available in virtio_net config.
>>>
>>> This is currently useful for simulating link down conditions
>>> (e.g. using proposed qemu 'set_link' monitor command) but
>>> would also be needed if we were to support device assignment
>>> via virtio.
>>>       
>> It would be nice if the virtio-net card wrote some acknowledgement that 
>> it has received the link status down/up events.
>>     
>
> How about of every status change event? ie. a generic virtio_pci solution?
>   

A really simple way to do it would just be to have another status field 
that was the guest's status (verses the host requested status which the 
current field is).  All config reads/writes result in exits so it's easy 
to track.

Adding YA virtio event may be a little overkill.

Regards,

Anthony Liguori

> Rusty.
>   

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Patch

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 71ca29c..128c38d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -42,6 +42,7 @@  struct virtnet_info
 	struct virtqueue *rvq, *svq;
 	struct net_device *dev;
 	struct napi_struct napi;
+	unsigned int status;
 
 	/* The skb we couldn't send because buffers were full. */
 	struct sk_buff *last_xmit_skb;
@@ -611,6 +612,7 @@  static struct ethtool_ops virtnet_ethtool_ops = {
 	.set_tx_csum = virtnet_set_tx_csum,
 	.set_sg = ethtool_op_set_sg,
 	.set_tso = ethtool_op_set_tso,
+	.get_link = ethtool_op_get_link,
 };
 
 #define MIN_MTU 68
@@ -624,6 +626,38 @@  static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
 	return 0;
 }
 
+static void virtnet_update_status(struct virtnet_info *vi)
+{
+	u16 v;
+
+	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS))
+		return;
+
+        vi->vdev->config->get(vi->vdev,
+                              offsetof(struct virtio_net_config, status),
+                              &v, sizeof(v));
+
+	if (vi->status == v)
+		return;
+
+	vi->status = v;
+
+	if (vi->status & VIRTIO_NET_S_LINK_UP) {
+		netif_carrier_on(vi->dev);
+		netif_wake_queue(vi->dev);
+	} else {
+		netif_carrier_off(vi->dev);
+		netif_stop_queue(vi->dev);
+	}
+}
+
+static void virtnet_config_changed(struct virtio_device *vdev)
+{
+	struct virtnet_info *vi = vdev->priv;
+
+	virtnet_update_status(vi);
+}
+
 static int virtnet_probe(struct virtio_device *vdev)
 {
 	int err;
@@ -732,6 +766,9 @@  static int virtnet_probe(struct virtio_device *vdev)
 		goto unregister;
 	}
 
+	vi->status = VIRTIO_NET_S_LINK_UP;
+	virtnet_update_status(vi);
+
 	pr_debug("virtnet: registered device %s\n", dev->name);
 	return 0;
 
@@ -787,7 +824,7 @@  static unsigned int features[] = {
 	VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
 	VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
 	VIRTIO_NET_F_GUEST_ECN, /* We don't yet handle UFO input. */
-	VIRTIO_NET_F_MRG_RXBUF,
+	VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS,
 	VIRTIO_F_NOTIFY_ON_EMPTY,
 };
 
@@ -799,6 +836,7 @@  static struct virtio_driver virtio_net = {
 	.id_table =	id_table,
 	.probe =	virtnet_probe,
 	.remove =	__devexit_p(virtnet_remove),
+	.config_changed = virtnet_config_changed,
 };
 
 static int __init init(void)
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 5cdd0aa..f76bd4a 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -21,11 +21,16 @@ 
 #define VIRTIO_NET_F_HOST_ECN	13	/* Host can handle TSO[6] w/ ECN in. */
 #define VIRTIO_NET_F_HOST_UFO	14	/* Host can handle UFO in. */
 #define VIRTIO_NET_F_MRG_RXBUF	15	/* Host can merge receive buffers. */
+#define VIRTIO_NET_F_STATUS	16	/* virtio_net_config.status available */
+
+#define VIRTIO_NET_S_LINK_UP	1	/* Link is up */
 
 struct virtio_net_config
 {
 	/* The config defining mac address (if VIRTIO_NET_F_MAC) */
 	__u8 mac[6];
+	/* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
+	__u16 status;
 } __attribute__((packed));
 
 /* This is the first element of the scatter-gather list.  If you don't