vsock/virtio: add support for device suspend/resume

Implement .freeze and .restore callbacks of struct virtio_driver
to support device suspend/resume.

During suspension all connected sockets are reset and VQs deleted.
During resume the VQs are re-initialized.

Reported by: Vilas R K <vilas.r.k@intel.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: stefano-garzarella

net/vmw_vsock/virtio_transport.c

@@ -743,6 +743,49 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
 	kfree(vsock);
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int virtio_vsock_freeze(struct virtio_device *vdev)
+{
+	struct virtio_vsock *vsock = vdev->priv;
+
+	mutex_lock(&the_virtio_vsock_mutex);
+
+	rcu_assign_pointer(the_virtio_vsock, NULL);
+	synchronize_rcu();
+
+	virtio_vsock_vqs_del(vsock);
+
+	mutex_unlock(&the_virtio_vsock_mutex);
+
+	return 0;
+}
+
+static int virtio_vsock_restore(struct virtio_device *vdev)
+{
+	struct virtio_vsock *vsock = vdev->priv;
+	int ret;
+
+	mutex_lock(&the_virtio_vsock_mutex);
+
+	/* Only one virtio-vsock device per guest is supported */
+	if (rcu_dereference_protected(the_virtio_vsock,
+				lockdep_is_held(&the_virtio_vsock_mutex))) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	ret = virtio_vsock_vqs_init(vsock);
+	if (ret < 0)
+		goto out;
+
+	rcu_assign_pointer(the_virtio_vsock, vsock);
+
+out:
+	mutex_unlock(&the_virtio_vsock_mutex);
+	return ret;
+}
+#endif /* CONFIG_PM_SLEEP */
+
 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_VSOCK, VIRTIO_DEV_ANY_ID },
 	{ 0 },
@@ -760,6 +803,10 @@ static struct virtio_driver virtio_vsock_driver = {
 	.id_table = id_table,
 	.probe = virtio_vsock_probe,
 	.remove = virtio_vsock_remove,
+#ifdef CONFIG_PM_SLEEP
+	.freeze = virtio_vsock_freeze,
+	.restore = virtio_vsock_restore,
+#endif
 };
 
 static int __init virtio_vsock_init(void)