SAFE public projects git trees. - safe/jmp/linux-2.6/blob - drivers/vhost/net.c

   1 /* Copyright (C) 2009 Red Hat, Inc.
   2  * Author: Michael S. Tsirkin <mst@redhat.com>
   3  *
   4  * This work is licensed under the terms of the GNU GPL, version 2.
   5  *
   6  * virtio-net server in host kernel.
   7  */
   8
   9 #include <linux/compat.h>
  10 #include <linux/eventfd.h>
  11 #include <linux/vhost.h>
  12 #include <linux/virtio_net.h>
  13 #include <linux/mmu_context.h>
  14 #include <linux/miscdevice.h>
  15 #include <linux/module.h>
  16 #include <linux/mutex.h>
  17 #include <linux/workqueue.h>
  18 #include <linux/rcupdate.h>
  19 #include <linux/file.h>
  20
  21 #include <linux/net.h>
  22 #include <linux/if_packet.h>
  23 #include <linux/if_arp.h>
  24 #include <linux/if_tun.h>
  25
  26 #include <net/sock.h>
  27
  28 #include "vhost.h"
  29
  30 /* Max number of bytes transferred before requeueing the job.
  31  * Using this limit prevents one virtqueue from starving others. */
  32 #define VHOST_NET_WEIGHT 0x80000
  33
  34 enum {
  35         VHOST_NET_VQ_RX = 0,
  36         VHOST_NET_VQ_TX = 1,
  37         VHOST_NET_VQ_MAX = 2,
  38 };
  39
  40 enum vhost_net_poll_state {
  41         VHOST_NET_POLL_DISABLED = 0,
  42         VHOST_NET_POLL_STARTED = 1,
  43         VHOST_NET_POLL_STOPPED = 2,
  44 };
  45
  46 struct vhost_net {
  47         struct vhost_dev dev;
  48         struct vhost_virtqueue vqs[VHOST_NET_VQ_MAX];
  49         struct vhost_poll poll[VHOST_NET_VQ_MAX];
  50         /* Tells us whether we are polling a socket for TX.
  51          * We only do this when socket buffer fills up.
  52          * Protected by tx vq lock. */
  53         enum vhost_net_poll_state tx_poll_state;
  54 };
  55
  56 /* Pop first len bytes from iovec. Return number of segments used. */
  57 static int move_iovec_hdr(struct iovec *from, struct iovec *to,
  58                           size_t len, int iov_count)
  59 {
  60         int seg = 0;
  61         size_t size;
  62         while (len && seg < iov_count) {
  63                 size = min(from->iov_len, len);
  64                 to->iov_base = from->iov_base;
  65                 to->iov_len = size;
  66                 from->iov_len -= size;
  67                 from->iov_base += size;
  68                 len -= size;
  69                 ++from;
  70                 ++to;
  71                 ++seg;
  72         }
  73         return seg;
  74 }
  75
  76 /* Caller must have TX VQ lock */
  77 static void tx_poll_stop(struct vhost_net *net)
  78 {
  79         if (likely(net->tx_poll_state != VHOST_NET_POLL_STARTED))
  80                 return;
  81         vhost_poll_stop(net->poll + VHOST_NET_VQ_TX);
  82         net->tx_poll_state = VHOST_NET_POLL_STOPPED;
  83 }
  84
  85 /* Caller must have TX VQ lock */
  86 static void tx_poll_start(struct vhost_net *net, struct socket *sock)
  87 {
  88         if (unlikely(net->tx_poll_state != VHOST_NET_POLL_STOPPED))
  89                 return;
  90         vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);
  91         net->tx_poll_state = VHOST_NET_POLL_STARTED;
  92 }
  93
  94 /* Expects to be always run from workqueue - which acts as
  95  * read-size critical section for our kind of RCU. */
  96 static void handle_tx(struct vhost_net *net)
  97 {
  98         struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX];
  99         unsigned head, out, in, s;
 100         struct msghdr msg = {
 101                 .msg_name = NULL,
 102                 .msg_namelen = 0,
 103                 .msg_control = NULL,
 104                 .msg_controllen = 0,
 105                 .msg_iov = vq->iov,
 106                 .msg_flags = MSG_DONTWAIT,
 107         };
 108         size_t len, total_len = 0;
 109         int err, wmem;
 110         size_t hdr_size;
 111         struct socket *sock = rcu_dereference(vq->private_data);
 112         if (!sock)
 113                 return;
 114
 115         wmem = atomic_read(&sock->sk->sk_wmem_alloc);
 116         if (wmem >= sock->sk->sk_sndbuf)
 117                 return;
 118
 119         use_mm(net->dev.mm);
 120         mutex_lock(&vq->mutex);
 121         vhost_disable_notify(vq);
 122
 123         if (wmem < sock->sk->sk_sndbuf * 2)
 124                 tx_poll_stop(net);
 125         hdr_size = vq->hdr_size;
 126
 127         for (;;) {
 128                 head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
 129                                          ARRAY_SIZE(vq->iov),
 130                                          &out, &in,
 131                                          NULL, NULL);
 132                 /* Nothing new?  Wait for eventfd to tell us they refilled. */
 133                 if (head == vq->num) {
 134                         wmem = atomic_read(&sock->sk->sk_wmem_alloc);
 135                         if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {
 136                                 tx_poll_start(net, sock);
 137                                 set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
 138                                 break;
 139                         }
 140                         if (unlikely(vhost_enable_notify(vq))) {
 141                                 vhost_disable_notify(vq);
 142                                 continue;
 143                         }
 144                         break;
 145                 }
 146                 if (in) {
 147                         vq_err(vq, "Unexpected descriptor format for TX: "
 148                                "out %d, int %d\n", out, in);
 149                         break;
 150                 }
 151                 /* Skip header. TODO: support TSO. */
 152                 s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
 153                 msg.msg_iovlen = out;
 154                 len = iov_length(vq->iov, out);
 155                 /* Sanity check */
 156                 if (!len) {
 157                         vq_err(vq, "Unexpected header len for TX: "
 158                                "%zd expected %zd\n",
 159                                iov_length(vq->hdr, s), hdr_size);
 160                         break;
 161                 }
 162                 /* TODO: Check specific error and bomb out unless ENOBUFS? */
 163                 err = sock->ops->sendmsg(NULL, sock, &msg, len);
 164                 if (unlikely(err < 0)) {
 165                         vhost_discard_vq_desc(vq);
 166                         tx_poll_start(net, sock);
 167                         break;
 168                 }
 169                 if (err != len)
 170                         pr_err("Truncated TX packet: "
 171                                " len %d != %zd\n", err, len);
 172                 vhost_add_used_and_signal(&net->dev, vq, head, 0);
 173                 total_len += len;
 174                 if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
 175                         vhost_poll_queue(&vq->poll);
 176                         break;
 177                 }
 178         }
 179
 180         mutex_unlock(&vq->mutex);
 181         unuse_mm(net->dev.mm);
 182 }
 183
 184 /* Expects to be always run from workqueue - which acts as
 185  * read-size critical section for our kind of RCU. */
 186 static void handle_rx(struct vhost_net *net)
 187 {
 188         struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
 189         unsigned head, out, in, log, s;
 190         struct vhost_log *vq_log;
 191         struct msghdr msg = {
 192                 .msg_name = NULL,
 193                 .msg_namelen = 0,
 194                 .msg_control = NULL, /* FIXME: get and handle RX aux data. */
 195                 .msg_controllen = 0,
 196                 .msg_iov = vq->iov,
 197                 .msg_flags = MSG_DONTWAIT,
 198         };
 199
 200         struct virtio_net_hdr hdr = {
 201                 .flags = 0,
 202                 .gso_type = VIRTIO_NET_HDR_GSO_NONE
 203         };
 204
 205         size_t len, total_len = 0;
 206         int err;
 207         size_t hdr_size;
 208         struct socket *sock = rcu_dereference(vq->private_data);
 209         if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
 210                 return;
 211
 212         use_mm(net->dev.mm);
 213         mutex_lock(&vq->mutex);
 214         vhost_disable_notify(vq);
 215         hdr_size = vq->hdr_size;
 216
 217         vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
 218                 vq->log : NULL;
 219
 220         for (;;) {
 221                 head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
 222                                          ARRAY_SIZE(vq->iov),
 223                                          &out, &in,
 224                                          vq_log, &log);
 225                 /* OK, now we need to know about added descriptors. */
 226                 if (head == vq->num) {
 227                         if (unlikely(vhost_enable_notify(vq))) {
 228                                 /* They have slipped one in as we were
 229                                  * doing that: check again. */
 230                                 vhost_disable_notify(vq);
 231                                 continue;
 232                         }
 233                         /* Nothing new?  Wait for eventfd to tell us
 234                          * they refilled. */
 235                         break;
 236                 }
 237                 /* We don't need to be notified again. */
 238                 if (out) {
 239                         vq_err(vq, "Unexpected descriptor format for RX: "
 240                                "out %d, int %d\n",
 241                                out, in);
 242                         break;
 243                 }
 244                 /* Skip header. TODO: support TSO/mergeable rx buffers. */
 245                 s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, in);
 246                 msg.msg_iovlen = in;
 247                 len = iov_length(vq->iov, in);
 248                 /* Sanity check */
 249                 if (!len) {
 250                         vq_err(vq, "Unexpected header len for RX: "
 251                                "%zd expected %zd\n",
 252                                iov_length(vq->hdr, s), hdr_size);
 253                         break;
 254                 }
 255                 err = sock->ops->recvmsg(NULL, sock, &msg,
 256                                          len, MSG_DONTWAIT | MSG_TRUNC);
 257                 /* TODO: Check specific error and bomb out unless EAGAIN? */
 258                 if (err < 0) {
 259                         vhost_discard_vq_desc(vq);
 260                         break;
 261                 }
 262                 /* TODO: Should check and handle checksum. */
 263                 if (err > len) {
 264                         pr_err("Discarded truncated rx packet: "
 265                                " len %d > %zd\n", err, len);
 266                         vhost_discard_vq_desc(vq);
 267                         continue;
 268                 }
 269                 len = err;
 270                 err = memcpy_toiovec(vq->hdr, (unsigned char *)&hdr, hdr_size);
 271                 if (err) {
 272                         vq_err(vq, "Unable to write vnet_hdr at addr %p: %d\n",
 273                                vq->iov->iov_base, err);
 274                         break;
 275                 }
 276                 len += hdr_size;
 277                 vhost_add_used_and_signal(&net->dev, vq, head, len);
 278                 if (unlikely(vq_log))
 279                         vhost_log_write(vq, vq_log, log, len);
 280                 total_len += len;
 281                 if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
 282                         vhost_poll_queue(&vq->poll);
 283                         break;
 284                 }
 285         }
 286
 287         mutex_unlock(&vq->mutex);
 288         unuse_mm(net->dev.mm);
 289 }
 290
 291 static void handle_tx_kick(struct work_struct *work)
 292 {
 293         struct vhost_virtqueue *vq;
 294         struct vhost_net *net;
 295         vq = container_of(work, struct vhost_virtqueue, poll.work);
 296         net = container_of(vq->dev, struct vhost_net, dev);
 297         handle_tx(net);
 298 }
 299
 300 static void handle_rx_kick(struct work_struct *work)
 301 {
 302         struct vhost_virtqueue *vq;
 303         struct vhost_net *net;
 304         vq = container_of(work, struct vhost_virtqueue, poll.work);
 305         net = container_of(vq->dev, struct vhost_net, dev);
 306         handle_rx(net);
 307 }
 308
 309 static void handle_tx_net(struct work_struct *work)
 310 {
 311         struct vhost_net *net;
 312         net = container_of(work, struct vhost_net, poll[VHOST_NET_VQ_TX].work);
 313         handle_tx(net);
 314 }
 315
 316 static void handle_rx_net(struct work_struct *work)
 317 {
 318         struct vhost_net *net;
 319         net = container_of(work, struct vhost_net, poll[VHOST_NET_VQ_RX].work);
 320         handle_rx(net);
 321 }
 322
 323 static int vhost_net_open(struct inode *inode, struct file *f)
 324 {
 325         struct vhost_net *n = kmalloc(sizeof *n, GFP_KERNEL);
 326         int r;
 327         if (!n)
 328                 return -ENOMEM;
 329         n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick;
 330         n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick;
 331         r = vhost_dev_init(&n->dev, n->vqs, VHOST_NET_VQ_MAX);
 332         if (r < 0) {
 333                 kfree(n);
 334                 return r;
 335         }
 336
 337         vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT);
 338         vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN);
 339         n->tx_poll_state = VHOST_NET_POLL_DISABLED;
 340
 341         f->private_data = n;
 342
 343         return 0;
 344 }
 345
 346 static void vhost_net_disable_vq(struct vhost_net *n,
 347                                  struct vhost_virtqueue *vq)
 348 {
 349         if (!vq->private_data)
 350                 return;
 351         if (vq == n->vqs + VHOST_NET_VQ_TX) {
 352                 tx_poll_stop(n);
 353                 n->tx_poll_state = VHOST_NET_POLL_DISABLED;
 354         } else
 355                 vhost_poll_stop(n->poll + VHOST_NET_VQ_RX);
 356 }
 357
 358 static void vhost_net_enable_vq(struct vhost_net *n,
 359                                 struct vhost_virtqueue *vq)
 360 {
 361         struct socket *sock = vq->private_data;
 362         if (!sock)
 363                 return;
 364         if (vq == n->vqs + VHOST_NET_VQ_TX) {
 365                 n->tx_poll_state = VHOST_NET_POLL_STOPPED;
 366                 tx_poll_start(n, sock);
 367         } else
 368                 vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);
 369 }
 370
 371 static struct socket *vhost_net_stop_vq(struct vhost_net *n,
 372                                         struct vhost_virtqueue *vq)
 373 {
 374         struct socket *sock;
 375
 376         mutex_lock(&vq->mutex);
 377         sock = vq->private_data;
 378         vhost_net_disable_vq(n, vq);
 379         rcu_assign_pointer(vq->private_data, NULL);
 380         mutex_unlock(&vq->mutex);
 381         return sock;
 382 }
 383
 384 static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
 385                            struct socket **rx_sock)
 386 {
 387         *tx_sock = vhost_net_stop_vq(n, n->vqs + VHOST_NET_VQ_TX);
 388         *rx_sock = vhost_net_stop_vq(n, n->vqs + VHOST_NET_VQ_RX);
 389 }
 390
 391 static void vhost_net_flush_vq(struct vhost_net *n, int index)
 392 {
 393         vhost_poll_flush(n->poll + index);
 394         vhost_poll_flush(&n->dev.vqs[index].poll);
 395 }
 396
 397 static void vhost_net_flush(struct vhost_net *n)
 398 {
 399         vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
 400         vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
 401 }
 402
 403 static int vhost_net_release(struct inode *inode, struct file *f)
 404 {
 405         struct vhost_net *n = f->private_data;
 406         struct socket *tx_sock;
 407         struct socket *rx_sock;
 408
 409         vhost_net_stop(n, &tx_sock, &rx_sock);
 410         vhost_net_flush(n);
 411         vhost_dev_cleanup(&n->dev);
 412         if (tx_sock)
 413                 fput(tx_sock->file);
 414         if (rx_sock)
 415                 fput(rx_sock->file);
 416         /* We do an extra flush before freeing memory,
 417          * since jobs can re-queue themselves. */
 418         vhost_net_flush(n);
 419         kfree(n);
 420         return 0;
 421 }
 422
 423 static struct socket *get_raw_socket(int fd)
 424 {
 425         struct {
 426                 struct sockaddr_ll sa;
 427                 char  buf[MAX_ADDR_LEN];
 428         } uaddr;
 429         int uaddr_len = sizeof uaddr, r;
 430         struct socket *sock = sockfd_lookup(fd, &r);
 431         if (!sock)
 432                 return ERR_PTR(-ENOTSOCK);
 433
 434         /* Parameter checking */
 435         if (sock->sk->sk_type != SOCK_RAW) {
 436                 r = -ESOCKTNOSUPPORT;
 437                 goto err;
 438         }
 439
 440         r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa,
 441                                &uaddr_len, 0);
 442         if (r)
 443                 goto err;
 444
 445         if (uaddr.sa.sll_family != AF_PACKET) {
 446                 r = -EPFNOSUPPORT;
 447                 goto err;
 448         }
 449         return sock;
 450 err:
 451         fput(sock->file);
 452         return ERR_PTR(r);
 453 }
 454
 455 static struct socket *get_tun_socket(int fd)
 456 {
 457         struct file *file = fget(fd);
 458         struct socket *sock;
 459         if (!file)
 460                 return ERR_PTR(-EBADF);
 461         sock = tun_get_socket(file);
 462         if (IS_ERR(sock))
 463                 fput(file);
 464         return sock;
 465 }
 466
 467 static struct socket *get_socket(int fd)
 468 {
 469         struct socket *sock;
 470         /* special case to disable backend */
 471         if (fd == -1)
 472                 return NULL;
 473         sock = get_raw_socket(fd);
 474         if (!IS_ERR(sock))
 475                 return sock;
 476         sock = get_tun_socket(fd);
 477         if (!IS_ERR(sock))
 478                 return sock;
 479         return ERR_PTR(-ENOTSOCK);
 480 }
 481
 482 static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 483 {
 484         struct socket *sock, *oldsock;
 485         struct vhost_virtqueue *vq;
 486         int r;
 487
 488         mutex_lock(&n->dev.mutex);
 489         r = vhost_dev_check_owner(&n->dev);
 490         if (r)
 491                 goto err;
 492
 493         if (index >= VHOST_NET_VQ_MAX) {
 494                 r = -ENOBUFS;
 495                 goto err;
 496         }
 497         vq = n->vqs + index;
 498         mutex_lock(&vq->mutex);
 499
 500         /* Verify that ring has been setup correctly. */
 501         if (!vhost_vq_access_ok(vq)) {
 502                 r = -EFAULT;
 503                 goto err;
 504         }
 505         sock = get_socket(fd);
 506         if (IS_ERR(sock)) {
 507                 r = PTR_ERR(sock);
 508                 goto err;
 509         }
 510
 511         /* start polling new socket */
 512         oldsock = vq->private_data;
 513         if (sock == oldsock)
 514                 goto done;
 515
 516         vhost_net_disable_vq(n, vq);
 517         rcu_assign_pointer(vq->private_data, sock);
 518         vhost_net_enable_vq(n, vq);
 519         mutex_unlock(&vq->mutex);
 520 done:
 521         if (oldsock) {
 522                 vhost_net_flush_vq(n, index);
 523                 fput(oldsock->file);
 524         }
 525 err:
 526         mutex_unlock(&n->dev.mutex);
 527         return r;
 528 }
 529
 530 static long vhost_net_reset_owner(struct vhost_net *n)
 531 {
 532         struct socket *tx_sock = NULL;
 533         struct socket *rx_sock = NULL;
 534         long err;
 535         mutex_lock(&n->dev.mutex);
 536         err = vhost_dev_check_owner(&n->dev);
 537         if (err)
 538                 goto done;
 539         vhost_net_stop(n, &tx_sock, &rx_sock);
 540         vhost_net_flush(n);
 541         err = vhost_dev_reset_owner(&n->dev);
 542 done:
 543         mutex_unlock(&n->dev.mutex);
 544         if (tx_sock)
 545                 fput(tx_sock->file);
 546         if (rx_sock)
 547                 fput(rx_sock->file);
 548         return err;
 549 }
 550
 551 static int vhost_net_set_features(struct vhost_net *n, u64 features)
 552 {
 553         size_t hdr_size = features & (1 << VHOST_NET_F_VIRTIO_NET_HDR) ?
 554                 sizeof(struct virtio_net_hdr) : 0;
 555         int i;
 556         mutex_lock(&n->dev.mutex);
 557         if ((features & (1 << VHOST_F_LOG_ALL)) &&
 558             !vhost_log_access_ok(&n->dev)) {
 559                 mutex_unlock(&n->dev.mutex);
 560                 return -EFAULT;
 561         }
 562         n->dev.acked_features = features;
 563         smp_wmb();
 564         for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
 565                 mutex_lock(&n->vqs[i].mutex);
 566                 n->vqs[i].hdr_size = hdr_size;
 567                 mutex_unlock(&n->vqs[i].mutex);
 568         }
 569         vhost_net_flush(n);
 570         mutex_unlock(&n->dev.mutex);
 571         return 0;
 572 }
 573
 574 static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 575                             unsigned long arg)
 576 {
 577         struct vhost_net *n = f->private_data;
 578         void __user *argp = (void __user *)arg;
 579         u64 __user *featurep = argp;
 580         struct vhost_vring_file backend;
 581         u64 features;
 582         int r;
 583         switch (ioctl) {
 584         case VHOST_NET_SET_BACKEND:
 585                 r = copy_from_user(&backend, argp, sizeof backend);
 586                 if (r < 0)
 587                         return r;
 588                 return vhost_net_set_backend(n, backend.index, backend.fd);
 589         case VHOST_GET_FEATURES:
 590                 features = VHOST_FEATURES;
 591                 return copy_to_user(featurep, &features, sizeof features);
 592         case VHOST_SET_FEATURES:
 593                 r = copy_from_user(&features, featurep, sizeof features);
 594                 if (r < 0)
 595                         return r;
 596                 if (features & ~VHOST_FEATURES)
 597                         return -EOPNOTSUPP;
 598                 return vhost_net_set_features(n, features);
 599         case VHOST_RESET_OWNER:
 600                 return vhost_net_reset_owner(n);
 601         default:
 602                 mutex_lock(&n->dev.mutex);
 603                 r = vhost_dev_ioctl(&n->dev, ioctl, arg);
 604                 vhost_net_flush(n);
 605                 mutex_unlock(&n->dev.mutex);
 606                 return r;
 607         }
 608 }
 609
 610 #ifdef CONFIG_COMPAT
 611 static long vhost_net_compat_ioctl(struct file *f, unsigned int ioctl,
 612                                    unsigned long arg)
 613 {
 614         return vhost_net_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
 615 }
 616 #endif
 617
 618 const static struct file_operations vhost_net_fops = {
 619         .owner          = THIS_MODULE,
 620         .release        = vhost_net_release,
 621         .unlocked_ioctl = vhost_net_ioctl,
 622 #ifdef CONFIG_COMPAT
 623         .compat_ioctl   = vhost_net_compat_ioctl,
 624 #endif
 625         .open           = vhost_net_open,
 626 };
 627
 628 static struct miscdevice vhost_net_misc = {
 629         VHOST_NET_MINOR,
 630         "vhost-net",
 631         &vhost_net_fops,
 632 };
 633
 634 int vhost_net_init(void)
 635 {
 636         int r = vhost_init();
 637         if (r)
 638                 goto err_init;
 639         r = misc_register(&vhost_net_misc);
 640         if (r)
 641                 goto err_reg;
 642         return 0;
 643 err_reg:
 644         vhost_cleanup();
 645 err_init:
 646         return r;
 647
 648 }
 649 module_init(vhost_net_init);
 650
 651 void vhost_net_exit(void)
 652 {
 653         misc_deregister(&vhost_net_misc);
 654         vhost_cleanup();
 655 }
 656 module_exit(vhost_net_exit);
 657
 658 MODULE_VERSION("0.0.1");
 659 MODULE_LICENSE("GPL v2");
 660 MODULE_AUTHOR("Michael S. Tsirkin");
 661 MODULE_DESCRIPTION("Host kernel accelerator for virtio net");