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

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Date:	Wed, 3 Nov 2010 10:00:19 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	rusty@...tcorp.com.au, davem@...emloft.net, markmc@...hat.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH] virtio-net: init link state correctly

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@...hat.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;
--
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