virtio: net: Add freeze, restore handlers to support S4

Remove all the vqs, disable napi and detach from the netdev on
hibernation.

Re-create vqs after restoring from a hibernated image, re-enable napi
and re-attach the netdev.  This keeps networking working across
hibernation.
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/net/virtio_net.c

@@ -1178,6 +1178,48 @@ 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;
+
+	virtqueue_disable_cb(vi->rvq);
+	virtqueue_disable_cb(vi->svq);
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ))
+		virtqueue_disable_cb(vi->cvq);
+
+	netif_device_detach(vi->dev);
+	cancel_delayed_work_sync(&vi->refill);
+
+	if (netif_running(vi->dev))
+		napi_disable(&vi->napi);
+
+	remove_vq_common(vi);
+
+	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;
+
+	if (netif_running(vi->dev))
+		virtnet_napi_enable(vi);
+
+	netif_device_attach(vi->dev);
+
+	if (!try_fill_recv(vi, GFP_KERNEL))
+		queue_delayed_work(system_nrt_wq, &vi->refill, 0);
+
+	return 0;
+}
+#endif
+
 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
 	{ 0 },
@@ -1202,6 +1244,10 @@ 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)