linux-kernel - Re: [PATCH 06/11] virtio: blk: Add freeze, restore handlers to support S4

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Date:	Sun, 2 Oct 2011 11:37:33 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Amit Shah <amit.shah@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/11] virtio: blk: Add freeze, restore handlers to
 support S4

On Thu, Sep 29, 2011 at 08:56:02PM +0530, Amit Shah wrote:
> Delete the vq on the freeze callback to prepare for hibernation.
> Re-create the vq in the restore callback to resume normal function.
> 
> Signed-off-by: Amit Shah <amit.shah@...hat.com>
> ---
>  drivers/block/virtio_blk.c |   17 +++++++++++++++++
>  1 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 509760b..9844d2c 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -549,6 +549,19 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
>  	kfree(vblk);
>  }
>  
> +#ifdef CONFIG_PM
> +static int virtblk_freeze(struct virtio_device *vdev)
> +{
> +	vdev->config->del_vqs(vdev);

What prevents the guest from trying to use the VQ while
this is in progress? IF it does, what prevents a crash?

> +	return 0;
> +}
> +
> +static int virtblk_restore(struct virtio_device *vdev)
> +{
> +	return init_vq(vdev->priv);;
> +}
> +#endif
> +
>  static const struct virtio_device_id id_table[] = {
>  	{ VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
>  	{ 0 },
> @@ -574,6 +587,10 @@ static struct virtio_driver __refdata virtio_blk = {
>  	.probe			= virtblk_probe,
>  	.remove			= __devexit_p(virtblk_remove),
>  	.config_changed		= virtblk_config_changed,
> +#ifdef CONFIG_PM
> +	.freeze			= virtblk_freeze,
> +	.restore		= virtblk_restore,
> +#endif
>  };
>  
>  static int __init init(void)
> -- 
> 1.7.6.2
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