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

Michael S. Tsirkin
2011-11-17T12:17:44Z

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@redhat.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