linux-kernel - Re: [PATCH v3 09/11] virtio: net: Add freeze, restore handlers to support S4

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Date:	Thu, 17 Nov 2011 14:19:09 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Amit Shah <amit.shah@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Virtualization List <virtualization@...ts.linux-foundation.org>,
	levinsasha928@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 09/11] virtio: net: Add freeze, restore handlers to
 support S4

On Thu, Nov 17, 2011 at 05:27:40PM +0530, Amit Shah wrote:
> Remove all the vqs and detach from the netdev on hibernation.
> 
> Re-create vqs after restoring from a hibernated image and re-attach the
> netdev.  This keeps networking working across hibernation.
> 
> Signed-off-by: Amit Shah <amit.shah@...hat.com>
> ---
>  drivers/net/virtio_net.c |   37 ++++++++++++++++++++++++++++++++++---
>  1 files changed, 34 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index fbff37a..167b555 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1127,6 +1127,9 @@ static void remove_vq_common(struct virtnet_info *vi)
>  {
>  	cancel_delayed_work_sync(&vi->refill);
>  
> +	/* Stop all the virtqueues. */
> +	vi->vdev->config->reset(vi->vdev);
> +
>  	/* Free unused buffers in both send and recv, if any. */
>  	free_unused_bufs(vi);
>  
> @@ -1140,9 +1143,6 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
>  {
>  	struct virtnet_info *vi = vdev->priv;
>  
> -	/* Stop all the virtqueues. */
> -	vdev->config->reset(vdev);
> -
>  	unregister_netdev(vi->dev);
>  
>  	remove_vq_common(vi);
> @@ -1151,6 +1151,33 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
>  	free_netdev(vi->dev);
>  }
>  
> +#ifdef CONFIG_PM
> +static int virtnet_freeze(struct virtio_device *vdev)
> +{
> +	struct virtnet_info *vi = vdev->priv;
> +
> +	netif_device_detach(vi->dev);
> +	remove_vq_common(vi);

This stops TX in progress, if any, but not RX
which might use the RX VQ. Then remove_vq_common
might delete this VQ while it's still in use.

So I think we need to call something like napi_disable.
However, the subtle twist is that we need to call that
*after interrupts have been disabled*.
Otherwise we might schedule another napi callback.

> +
> +	return 0;
> +}
> +
> +static int virtnet_restore(struct virtio_device *vdev)
> +{
> +	struct virtnet_info *vi = vdev->priv;
> +	int err;
> +
> +	err = init_vqs(vi);
> +	if (err)
> +		return err;
> +
> +	try_fill_recv(vi, GFP_KERNEL);
> +
> +	netif_device_attach(vi->dev);
> +	return 0;
> +}
> +#endif
> +
>  static struct virtio_device_id id_table[] = {
>  	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
>  	{ 0 },
> @@ -1175,6 +1202,10 @@ static struct virtio_driver virtio_net_driver = {
>  	.probe =	virtnet_probe,
>  	.remove =	__devexit_p(virtnet_remove),
>  	.config_changed = virtnet_config_changed,
> +#ifdef CONFIG_PM
> +	.freeze =	virtnet_freeze,
> +	.restore =	virtnet_restore,
> +#endif
>  };
>  
>  static int __init init(void)
> -- 
> 1.7.7.1
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