[PATCH] virtio-net: init link state correctly

[PATCH] virtio-net: init link state correctly

[Jason Wang]

We need call netif_carrier_off() and do not assume VIRTIO_NET_S_LINKUP
before querying device state during probing, otherwise we may get
wrong operstate after driver was loaded because the link watch event
was not fired as expected.

Since the device state changed could be caught through interrupt, the
unconditional call to nerif_carrier_on() is also removed.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/virtio_net.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index bb6b67f..0a0cd35 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -986,9 +986,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 		goto unregister;
 	}
 
-	vi->status = VIRTIO_NET_S_LINK_UP;
+	netif_carrier_off(dev);
 	virtnet_update_status(vi);
-	netif_carrier_on(dev);
 
 	pr_debug("virtnet: registered device %s\n", dev->name);
 	return 0;

Re: [PATCH] virtio-net: init link state correctly

[Michael S. Tsirkin]

On Wed, Nov 03, 2010 at 03:08:17PM +0800, Jason Wang wrote:
> We need call netif_carrier_off() and do not assume VIRTIO_NET_S_LINKUP
> before querying device state during probing, otherwise we may get
> wrong operstate after driver was loaded because the link watch event
> was not fired as expected.
> 
> Since the device state changed could be caught through interrupt, the
> unconditional call to nerif_carrier_on() is also removed.
> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>

OK, but this seems broken for hosts without VIRTIO_NET_F_STATUS.  Right?
Probably

	/* Assume link up if device can't report link status,
	   otherwise get link status from config. */
	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
		vi->status = 0;
		netif_carrier_off(dev);
  		virtnet_update_status(vi);
	} else {
		vi->status = VIRTIO_NET_S_LINK_UP;
		netif_carrier_on(dev);
	}

Makes sense?

> ---
>  drivers/net/virtio_net.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index bb6b67f..0a0cd35 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -986,9 +986,8 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		goto unregister;
>  	}
>  
> -	vi->status = VIRTIO_NET_S_LINK_UP;
> +	netif_carrier_off(dev);
>  	virtnet_update_status(vi);
> -	netif_carrier_on(dev);
>  
>  	pr_debug("virtnet: registered device %s\n", dev->name);
>  	return 0;

[PATCH] virtio-net: init link state correctly

[Rusty Russell]

From: Jason Wang <jasowang@redhat.com>

For device that supports VIRTIO_NET_F_STATUS, there's no need to
assume the link is up and we need to call nerif_carrier_off() before
querying device status, otherwise we may get wrong operstate after
diver was loaded because the link watch event was not fired as
expected.

For device that does not support VIRITO_NET_F_STATUS, we could not get
its status through virtnet_update_status() and what we can only do is
always assuming the link is up.

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 drivers/net/virtio_net.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index bb6b67f..b6d4028 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -986,9 +986,15 @@ static int virtnet_probe(struct virtio_device *vdev)
 		goto unregister;
 	}
 
-	vi->status = VIRTIO_NET_S_LINK_UP;
-	virtnet_update_status(vi);
-	netif_carrier_on(dev);
+	/* Assume link up if device can't report link status,
+	   otherwise get link status from config. */
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
+		netif_carrier_off(dev);
+		virtnet_update_status(vi);
+	} else {
+		vi->status = VIRTIO_NET_S_LINK_UP;
+		netif_carrier_on(dev);
+	}
 
 	pr_debug("virtnet: registered device %s\n", dev->name);
 	return 0;