// SPDX-License-Identifier: GPL-2.0-only

  /*
   * virtio transport for vsock
   *
   * Copyright (C) 2013-2015 Red Hat, Inc.
   * Author: Asias He <asias@redhat.com>
   *         Stefan Hajnoczi <stefanha@redhat.com>
   *
   * Some of the code is take from Gerd Hoffmann <kraxel@redhat.com>'s
   * early virtio-vsock proof-of-concept bits.

   */
  #include <linux/spinlock.h>
  #include <linux/module.h>
  #include <linux/list.h>
  #include <linux/atomic.h>
  #include <linux/virtio.h>
  #include <linux/virtio_ids.h>
  #include <linux/virtio_config.h>
  #include <linux/virtio_vsock.h>
  #include <net/sock.h>
  #include <linux/mutex.h>
  #include <net/af_vsock.h>
  
  static struct workqueue_struct *virtio_vsock_workqueue;

  static struct virtio_vsock __rcu *the_virtio_vsock;

  static DEFINE_MUTEX(the_virtio_vsock_mutex); /* protects the_virtio_vsock */
  
  struct virtio_vsock {
  	struct virtio_device *vdev;
  	struct virtqueue *vqs[VSOCK_VQ_MAX];
  
  	/* Virtqueue processing is deferred to a workqueue */
  	struct work_struct tx_work;
  	struct work_struct rx_work;
  	struct work_struct event_work;
  
  	/* The following fields are protected by tx_lock.  vqs[VSOCK_VQ_TX]
  	 * must be accessed with tx_lock held.
  	 */
  	struct mutex tx_lock;

  	bool tx_run;

  
  	struct work_struct send_pkt_work;
  	spinlock_t send_pkt_list_lock;
  	struct list_head send_pkt_list;
  
  	atomic_t queued_replies;
  
  	/* The following fields are protected by rx_lock.  vqs[VSOCK_VQ_RX]
  	 * must be accessed with rx_lock held.
  	 */
  	struct mutex rx_lock;

  	bool rx_run;

  	int rx_buf_nr;
  	int rx_buf_max_nr;
  
  	/* The following fields are protected by event_lock.
  	 * vqs[VSOCK_VQ_EVENT] must be accessed with event_lock held.
  	 */
  	struct mutex event_lock;

  	bool event_run;

  	struct virtio_vsock_event event_list[8];
  
  	u32 guest_cid;
  };

  static u32 virtio_transport_get_local_cid(void)
  {

  	struct virtio_vsock *vsock;
  	u32 ret;

  	rcu_read_lock();
  	vsock = rcu_dereference(the_virtio_vsock);
  	if (!vsock) {
  		ret = VMADDR_CID_ANY;
  		goto out_rcu;
  	}

  	ret = vsock->guest_cid;
  out_rcu:
  	rcu_read_unlock();
  	return ret;

  }
  
  static void
  virtio_transport_send_pkt_work(struct work_struct *work)
  {
  	struct virtio_vsock *vsock =
  		container_of(work, struct virtio_vsock, send_pkt_work);
  	struct virtqueue *vq;
  	bool added = false;
  	bool restart_rx = false;
  
  	mutex_lock(&vsock->tx_lock);

  	if (!vsock->tx_run)
  		goto out;

  	vq = vsock->vqs[VSOCK_VQ_TX];

  	for (;;) {
  		struct virtio_vsock_pkt *pkt;
  		struct scatterlist hdr, buf, *sgs[2];
  		int ret, in_sg = 0, out_sg = 0;
  		bool reply;
  
  		spin_lock_bh(&vsock->send_pkt_list_lock);
  		if (list_empty(&vsock->send_pkt_list)) {
  			spin_unlock_bh(&vsock->send_pkt_list_lock);

  			break;
  		}
  
  		pkt = list_first_entry(&vsock->send_pkt_list,
  				       struct virtio_vsock_pkt, list);
  		list_del_init(&pkt->list);
  		spin_unlock_bh(&vsock->send_pkt_list_lock);

  		virtio_transport_deliver_tap_pkt(pkt);

  		reply = pkt->reply;
  
  		sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
  		sgs[out_sg++] = &hdr;
  		if (pkt->buf) {
  			sg_init_one(&buf, pkt->buf, pkt->len);
  			sgs[out_sg++] = &buf;
  		}
  
  		ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, pkt, GFP_KERNEL);

  		/* Usually this means that there is no more space available in
  		 * the vq
  		 */

  		if (ret < 0) {
  			spin_lock_bh(&vsock->send_pkt_list_lock);
  			list_add(&pkt->list, &vsock->send_pkt_list);
  			spin_unlock_bh(&vsock->send_pkt_list_lock);

  			break;
  		}
  
  		if (reply) {
  			struct virtqueue *rx_vq = vsock->vqs[VSOCK_VQ_RX];
  			int val;
  
  			val = atomic_dec_return(&vsock->queued_replies);
  
  			/* Do we now have resources to resume rx processing? */
  			if (val + 1 == virtqueue_get_vring_size(rx_vq))
  				restart_rx = true;
  		}
  
  		added = true;
  	}
  
  	if (added)
  		virtqueue_kick(vq);

  out:

  	mutex_unlock(&vsock->tx_lock);
  
  	if (restart_rx)
  		queue_work(virtio_vsock_workqueue, &vsock->rx_work);
  }
  
  static int
  virtio_transport_send_pkt(struct virtio_vsock_pkt *pkt)
  {
  	struct virtio_vsock *vsock;
  	int len = pkt->len;

  	rcu_read_lock();
  	vsock = rcu_dereference(the_virtio_vsock);

  	if (!vsock) {
  		virtio_transport_free_pkt(pkt);

  		len = -ENODEV;
  		goto out_rcu;

  	}

  	if (le64_to_cpu(pkt->hdr.dst_cid) == vsock->guest_cid) {

  		virtio_transport_free_pkt(pkt);
  		len = -ENODEV;

  		goto out_rcu;
  	}

  	if (pkt->reply)
  		atomic_inc(&vsock->queued_replies);
  
  	spin_lock_bh(&vsock->send_pkt_list_lock);
  	list_add_tail(&pkt->list, &vsock->send_pkt_list);
  	spin_unlock_bh(&vsock->send_pkt_list_lock);
  
  	queue_work(virtio_vsock_workqueue, &vsock->send_pkt_work);

  
  out_rcu:
  	rcu_read_unlock();

  	return len;
  }

  static int
  virtio_transport_cancel_pkt(struct vsock_sock *vsk)
  {
  	struct virtio_vsock *vsock;
  	struct virtio_vsock_pkt *pkt, *n;

  	int cnt = 0, ret;

  	LIST_HEAD(freeme);

  	rcu_read_lock();
  	vsock = rcu_dereference(the_virtio_vsock);

  	if (!vsock) {

  		ret = -ENODEV;
  		goto out_rcu;

  	}
  
  	spin_lock_bh(&vsock->send_pkt_list_lock);
  	list_for_each_entry_safe(pkt, n, &vsock->send_pkt_list, list) {
  		if (pkt->vsk != vsk)
  			continue;
  		list_move(&pkt->list, &freeme);
  	}
  	spin_unlock_bh(&vsock->send_pkt_list_lock);
  
  	list_for_each_entry_safe(pkt, n, &freeme, list) {
  		if (pkt->reply)
  			cnt++;
  		list_del(&pkt->list);
  		virtio_transport_free_pkt(pkt);
  	}
  
  	if (cnt) {
  		struct virtqueue *rx_vq = vsock->vqs[VSOCK_VQ_RX];
  		int new_cnt;
  
  		new_cnt = atomic_sub_return(cnt, &vsock->queued_replies);
  		if (new_cnt + cnt >= virtqueue_get_vring_size(rx_vq) &&
  		    new_cnt < virtqueue_get_vring_size(rx_vq))
  			queue_work(virtio_vsock_workqueue, &vsock->rx_work);
  	}

  	ret = 0;
  
  out_rcu:
  	rcu_read_unlock();
  	return ret;

  }

  static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
  {
  	int buf_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
  	struct virtio_vsock_pkt *pkt;
  	struct scatterlist hdr, buf, *sgs[2];
  	struct virtqueue *vq;
  	int ret;
  
  	vq = vsock->vqs[VSOCK_VQ_RX];
  
  	do {
  		pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
  		if (!pkt)
  			break;
  
  		pkt->buf = kmalloc(buf_len, GFP_KERNEL);
  		if (!pkt->buf) {
  			virtio_transport_free_pkt(pkt);
  			break;
  		}

  		pkt->buf_len = buf_len;

  		pkt->len = buf_len;
  
  		sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
  		sgs[0] = &hdr;
  
  		sg_init_one(&buf, pkt->buf, buf_len);
  		sgs[1] = &buf;
  		ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
  		if (ret) {
  			virtio_transport_free_pkt(pkt);
  			break;
  		}
  		vsock->rx_buf_nr++;
  	} while (vq->num_free);
  	if (vsock->rx_buf_nr > vsock->rx_buf_max_nr)
  		vsock->rx_buf_max_nr = vsock->rx_buf_nr;
  	virtqueue_kick(vq);
  }
  
  static void virtio_transport_tx_work(struct work_struct *work)
  {
  	struct virtio_vsock *vsock =
  		container_of(work, struct virtio_vsock, tx_work);
  	struct virtqueue *vq;
  	bool added = false;
  
  	vq = vsock->vqs[VSOCK_VQ_TX];
  	mutex_lock(&vsock->tx_lock);

  
  	if (!vsock->tx_run)
  		goto out;

  	do {
  		struct virtio_vsock_pkt *pkt;
  		unsigned int len;
  
  		virtqueue_disable_cb(vq);
  		while ((pkt = virtqueue_get_buf(vq, &len)) != NULL) {
  			virtio_transport_free_pkt(pkt);
  			added = true;
  		}
  	} while (!virtqueue_enable_cb(vq));

  
  out:

  	mutex_unlock(&vsock->tx_lock);
  
  	if (added)
  		queue_work(virtio_vsock_workqueue, &vsock->send_pkt_work);
  }
  
  /* Is there space left for replies to rx packets? */
  static bool virtio_transport_more_replies(struct virtio_vsock *vsock)
  {
  	struct virtqueue *vq = vsock->vqs[VSOCK_VQ_RX];
  	int val;
  
  	smp_rmb(); /* paired with atomic_inc() and atomic_dec_return() */
  	val = atomic_read(&vsock->queued_replies);
  
  	return val < virtqueue_get_vring_size(vq);
  }

  /* event_lock must be held */
  static int virtio_vsock_event_fill_one(struct virtio_vsock *vsock,
  				       struct virtio_vsock_event *event)
  {
  	struct scatterlist sg;
  	struct virtqueue *vq;
  
  	vq = vsock->vqs[VSOCK_VQ_EVENT];
  
  	sg_init_one(&sg, event, sizeof(*event));
  
  	return virtqueue_add_inbuf(vq, &sg, 1, event, GFP_KERNEL);
  }
  
  /* event_lock must be held */
  static void virtio_vsock_event_fill(struct virtio_vsock *vsock)
  {
  	size_t i;
  
  	for (i = 0; i < ARRAY_SIZE(vsock->event_list); i++) {
  		struct virtio_vsock_event *event = &vsock->event_list[i];
  
  		virtio_vsock_event_fill_one(vsock, event);
  	}
  
  	virtqueue_kick(vsock->vqs[VSOCK_VQ_EVENT]);
  }
  
  static void virtio_vsock_reset_sock(struct sock *sk)
  {
  	lock_sock(sk);

  	sk->sk_state = TCP_CLOSE;

  	sk->sk_err = ECONNRESET;
  	sk->sk_error_report(sk);
  	release_sock(sk);
  }
  
  static void virtio_vsock_update_guest_cid(struct virtio_vsock *vsock)
  {
  	struct virtio_device *vdev = vsock->vdev;

  	__le64 guest_cid;

  
  	vdev->config->get(vdev, offsetof(struct virtio_vsock_config, guest_cid),
  			  &guest_cid, sizeof(guest_cid));
  	vsock->guest_cid = le64_to_cpu(guest_cid);
  }
  
  /* event_lock must be held */
  static void virtio_vsock_event_handle(struct virtio_vsock *vsock,
  				      struct virtio_vsock_event *event)
  {
  	switch (le32_to_cpu(event->id)) {
  	case VIRTIO_VSOCK_EVENT_TRANSPORT_RESET:
  		virtio_vsock_update_guest_cid(vsock);
  		vsock_for_each_connected_socket(virtio_vsock_reset_sock);
  		break;
  	}
  }
  
  static void virtio_transport_event_work(struct work_struct *work)
  {
  	struct virtio_vsock *vsock =
  		container_of(work, struct virtio_vsock, event_work);
  	struct virtqueue *vq;
  
  	vq = vsock->vqs[VSOCK_VQ_EVENT];
  
  	mutex_lock(&vsock->event_lock);

  	if (!vsock->event_run)
  		goto out;

  	do {
  		struct virtio_vsock_event *event;
  		unsigned int len;
  
  		virtqueue_disable_cb(vq);
  		while ((event = virtqueue_get_buf(vq, &len)) != NULL) {
  			if (len == sizeof(*event))
  				virtio_vsock_event_handle(vsock, event);
  
  			virtio_vsock_event_fill_one(vsock, event);
  		}
  	} while (!virtqueue_enable_cb(vq));
  
  	virtqueue_kick(vsock->vqs[VSOCK_VQ_EVENT]);

  out:

  	mutex_unlock(&vsock->event_lock);
  }
  
  static void virtio_vsock_event_done(struct virtqueue *vq)
  {
  	struct virtio_vsock *vsock = vq->vdev->priv;
  
  	if (!vsock)
  		return;
  	queue_work(virtio_vsock_workqueue, &vsock->event_work);
  }
  
  static void virtio_vsock_tx_done(struct virtqueue *vq)
  {
  	struct virtio_vsock *vsock = vq->vdev->priv;
  
  	if (!vsock)
  		return;
  	queue_work(virtio_vsock_workqueue, &vsock->tx_work);
  }
  
  static void virtio_vsock_rx_done(struct virtqueue *vq)
  {
  	struct virtio_vsock *vsock = vq->vdev->priv;
  
  	if (!vsock)
  		return;
  	queue_work(virtio_vsock_workqueue, &vsock->rx_work);
  }
  
  static struct virtio_transport virtio_transport = {
  	.transport = {

  		.module                   = THIS_MODULE,

  		.get_local_cid            = virtio_transport_get_local_cid,
  
  		.init                     = virtio_transport_do_socket_init,
  		.destruct                 = virtio_transport_destruct,
  		.release                  = virtio_transport_release,
  		.connect                  = virtio_transport_connect,
  		.shutdown                 = virtio_transport_shutdown,

  		.cancel_pkt               = virtio_transport_cancel_pkt,

  
  		.dgram_bind               = virtio_transport_dgram_bind,
  		.dgram_dequeue            = virtio_transport_dgram_dequeue,
  		.dgram_enqueue            = virtio_transport_dgram_enqueue,
  		.dgram_allow              = virtio_transport_dgram_allow,
  
  		.stream_dequeue           = virtio_transport_stream_dequeue,
  		.stream_enqueue           = virtio_transport_stream_enqueue,
  		.stream_has_data          = virtio_transport_stream_has_data,
  		.stream_has_space         = virtio_transport_stream_has_space,
  		.stream_rcvhiwat          = virtio_transport_stream_rcvhiwat,
  		.stream_is_active         = virtio_transport_stream_is_active,
  		.stream_allow             = virtio_transport_stream_allow,
  
  		.notify_poll_in           = virtio_transport_notify_poll_in,
  		.notify_poll_out          = virtio_transport_notify_poll_out,
  		.notify_recv_init         = virtio_transport_notify_recv_init,
  		.notify_recv_pre_block    = virtio_transport_notify_recv_pre_block,
  		.notify_recv_pre_dequeue  = virtio_transport_notify_recv_pre_dequeue,
  		.notify_recv_post_dequeue = virtio_transport_notify_recv_post_dequeue,
  		.notify_send_init         = virtio_transport_notify_send_init,
  		.notify_send_pre_block    = virtio_transport_notify_send_pre_block,
  		.notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
  		.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,

  		.notify_buffer_size       = virtio_transport_notify_buffer_size,

  	},
  
  	.send_pkt = virtio_transport_send_pkt,
  };

  static void virtio_transport_rx_work(struct work_struct *work)
  {
  	struct virtio_vsock *vsock =
  		container_of(work, struct virtio_vsock, rx_work);
  	struct virtqueue *vq;
  
  	vq = vsock->vqs[VSOCK_VQ_RX];
  
  	mutex_lock(&vsock->rx_lock);
  
  	if (!vsock->rx_run)
  		goto out;
  
  	do {
  		virtqueue_disable_cb(vq);
  		for (;;) {
  			struct virtio_vsock_pkt *pkt;
  			unsigned int len;
  
  			if (!virtio_transport_more_replies(vsock)) {
  				/* Stop rx until the device processes already
  				 * pending replies.  Leave rx virtqueue
  				 * callbacks disabled.
  				 */
  				goto out;
  			}
  
  			pkt = virtqueue_get_buf(vq, &len);
  			if (!pkt) {
  				break;
  			}
  
  			vsock->rx_buf_nr--;
  
  			/* Drop short/long packets */
  			if (unlikely(len < sizeof(pkt->hdr) ||
  				     len > sizeof(pkt->hdr) + pkt->len)) {
  				virtio_transport_free_pkt(pkt);
  				continue;
  			}
  
  			pkt->len = len - sizeof(pkt->hdr);
  			virtio_transport_deliver_tap_pkt(pkt);
  			virtio_transport_recv_pkt(&virtio_transport, pkt);
  		}
  	} while (!virtqueue_enable_cb(vq));
  
  out:
  	if (vsock->rx_buf_nr < vsock->rx_buf_max_nr / 2)
  		virtio_vsock_rx_fill(vsock);
  	mutex_unlock(&vsock->rx_lock);
  }

  static int virtio_vsock_probe(struct virtio_device *vdev)
  {
  	vq_callback_t *callbacks[] = {
  		virtio_vsock_rx_done,
  		virtio_vsock_tx_done,
  		virtio_vsock_event_done,
  	};
  	static const char * const names[] = {
  		"rx",
  		"tx",
  		"event",
  	};
  	struct virtio_vsock *vsock = NULL;
  	int ret;
  
  	ret = mutex_lock_interruptible(&the_virtio_vsock_mutex);
  	if (ret)
  		return ret;
  
  	/* 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;
  	}
  
  	vsock = kzalloc(sizeof(*vsock), GFP_KERNEL);
  	if (!vsock) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	vsock->vdev = vdev;

  	ret = virtio_find_vqs(vsock->vdev, VSOCK_VQ_MAX,
  			      vsock->vqs, callbacks, names,
  			      NULL);

  	if (ret < 0)
  		goto out;
  
  	virtio_vsock_update_guest_cid(vsock);

  	vsock->rx_buf_nr = 0;
  	vsock->rx_buf_max_nr = 0;
  	atomic_set(&vsock->queued_replies, 0);

  	mutex_init(&vsock->tx_lock);
  	mutex_init(&vsock->rx_lock);
  	mutex_init(&vsock->event_lock);
  	spin_lock_init(&vsock->send_pkt_list_lock);
  	INIT_LIST_HEAD(&vsock->send_pkt_list);
  	INIT_WORK(&vsock->rx_work, virtio_transport_rx_work);
  	INIT_WORK(&vsock->tx_work, virtio_transport_tx_work);
  	INIT_WORK(&vsock->event_work, virtio_transport_event_work);
  	INIT_WORK(&vsock->send_pkt_work, virtio_transport_send_pkt_work);

  	mutex_lock(&vsock->tx_lock);
  	vsock->tx_run = true;
  	mutex_unlock(&vsock->tx_lock);

  	mutex_lock(&vsock->rx_lock);
  	virtio_vsock_rx_fill(vsock);

  	vsock->rx_run = true;

  	mutex_unlock(&vsock->rx_lock);
  
  	mutex_lock(&vsock->event_lock);
  	virtio_vsock_event_fill(vsock);

  	vsock->event_run = true;

  	mutex_unlock(&vsock->event_lock);

  	vdev->priv = vsock;
  	rcu_assign_pointer(the_virtio_vsock, vsock);

  	mutex_unlock(&the_virtio_vsock_mutex);
  	return 0;

  out:
  	kfree(vsock);
  	mutex_unlock(&the_virtio_vsock_mutex);
  	return ret;
  }
  
  static void virtio_vsock_remove(struct virtio_device *vdev)
  {
  	struct virtio_vsock *vsock = vdev->priv;
  	struct virtio_vsock_pkt *pkt;

  	mutex_lock(&the_virtio_vsock_mutex);
  
  	vdev->priv = NULL;
  	rcu_assign_pointer(the_virtio_vsock, NULL);
  	synchronize_rcu();

  	/* Reset all connected sockets when the device disappear */
  	vsock_for_each_connected_socket(virtio_vsock_reset_sock);

  	/* Stop all work handlers to make sure no one is accessing the device,
  	 * so we can safely call vdev->config->reset().
  	 */
  	mutex_lock(&vsock->rx_lock);
  	vsock->rx_run = false;
  	mutex_unlock(&vsock->rx_lock);
  
  	mutex_lock(&vsock->tx_lock);
  	vsock->tx_run = false;
  	mutex_unlock(&vsock->tx_lock);
  
  	mutex_lock(&vsock->event_lock);
  	vsock->event_run = false;
  	mutex_unlock(&vsock->event_lock);
  
  	/* Flush all device writes and interrupts, device will not use any
  	 * more buffers.
  	 */

  	vdev->config->reset(vdev);
  
  	mutex_lock(&vsock->rx_lock);
  	while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_RX])))
  		virtio_transport_free_pkt(pkt);
  	mutex_unlock(&vsock->rx_lock);
  
  	mutex_lock(&vsock->tx_lock);
  	while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_TX])))
  		virtio_transport_free_pkt(pkt);
  	mutex_unlock(&vsock->tx_lock);
  
  	spin_lock_bh(&vsock->send_pkt_list_lock);
  	while (!list_empty(&vsock->send_pkt_list)) {
  		pkt = list_first_entry(&vsock->send_pkt_list,
  				       struct virtio_vsock_pkt, list);
  		list_del(&pkt->list);
  		virtio_transport_free_pkt(pkt);
  	}
  	spin_unlock_bh(&vsock->send_pkt_list_lock);

  	/* Delete virtqueues and flush outstanding callbacks if any */

  	vdev->config->del_vqs(vdev);

  	/* Other works can be queued before 'config->del_vqs()', so we flush
  	 * all works before to free the vsock object to avoid use after free.
  	 */

  	flush_work(&vsock->rx_work);
  	flush_work(&vsock->tx_work);
  	flush_work(&vsock->event_work);
  	flush_work(&vsock->send_pkt_work);

  	mutex_unlock(&the_virtio_vsock_mutex);

  	kfree(vsock);
  }
  
  static struct virtio_device_id id_table[] = {
  	{ VIRTIO_ID_VSOCK, VIRTIO_DEV_ANY_ID },
  	{ 0 },
  };
  
  static unsigned int features[] = {
  };
  
  static struct virtio_driver virtio_vsock_driver = {
  	.feature_table = features,
  	.feature_table_size = ARRAY_SIZE(features),
  	.driver.name = KBUILD_MODNAME,
  	.driver.owner = THIS_MODULE,
  	.id_table = id_table,
  	.probe = virtio_vsock_probe,
  	.remove = virtio_vsock_remove,
  };
  
  static int __init virtio_vsock_init(void)
  {
  	int ret;
  
  	virtio_vsock_workqueue = alloc_workqueue("virtio_vsock", 0, 0);
  	if (!virtio_vsock_workqueue)
  		return -ENOMEM;

  	ret = vsock_core_register(&virtio_transport.transport,
  				  VSOCK_TRANSPORT_F_G2H);

  	if (ret)

  		goto out_wq;

  	ret = register_virtio_driver(&virtio_vsock_driver);

  	if (ret)

  		goto out_vci;

  
  	return 0;

  out_vci:

  	vsock_core_unregister(&virtio_transport.transport);

  out_wq:
  	destroy_workqueue(virtio_vsock_workqueue);

  	return ret;
  }
  
  static void __exit virtio_vsock_exit(void)
  {
  	unregister_virtio_driver(&virtio_vsock_driver);

  	vsock_core_unregister(&virtio_transport.transport);

  	destroy_workqueue(virtio_vsock_workqueue);
  }
  
  module_init(virtio_vsock_init);
  module_exit(virtio_vsock_exit);
  MODULE_LICENSE("GPL v2");
  MODULE_AUTHOR("Asias He");
  MODULE_DESCRIPTION("virtio transport for vsock");
  MODULE_DEVICE_TABLE(virtio, id_table);