drivers/xen/evtchn.c

   1 /******************************************************************************
   2  * evtchn.c
   3  *
   4  * Driver for receiving and demuxing event-channel signals.
   5  *
   6  * Copyright (c) 2004-2005, K A Fraser
   7  * Multi-process extensions Copyright (c) 2004, Steven Smith
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License version 2
  11  * as published by the Free Software Foundation; or, when distributed
  12  * separately from the Linux kernel or incorporated into other
  13  * software packages, subject to the following license:
  14  *
  15  * Permission is hereby granted, free of charge, to any person obtaining a copy
  16  * of this source file (the "Software"), to deal in the Software without
  17  * restriction, including without limitation the rights to use, copy, modify,
  18  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  19  * and to permit persons to whom the Software is furnished to do so, subject to
  20  * the following conditions:
  21  *
  22  * The above copyright notice and this permission notice shall be included in
  23  * all copies or substantial portions of the Software.
  24  *
  25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  26  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  27  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  28  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  29  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  30  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  31  * IN THE SOFTWARE.
  32  */
  33
  34 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
  35
  36 #include <linux/module.h>
  37 #include <linux/kernel.h>
  38 #include <linux/sched.h>
  39 #include <linux/slab.h>
  40 #include <linux/string.h>
  41 #include <linux/errno.h>
  42 #include <linux/fs.h>
  43 #include <linux/miscdevice.h>
  44 #include <linux/major.h>
  45 #include <linux/proc_fs.h>
  46 #include <linux/stat.h>
  47 #include <linux/poll.h>
  48 #include <linux/irq.h>
  49 #include <linux/init.h>
  50 #include <linux/mutex.h>
  51 #include <linux/cpu.h>
  52 #include <linux/mm.h>
  53 #include <linux/vmalloc.h>
  54
  55 #include <xen/xen.h>
  56 #include <xen/events.h>
  57 #include <xen/evtchn.h>
  58 #include <xen/xen-ops.h>
  59 #include <asm/xen/hypervisor.h>
  60
  61 struct per_user_data {
  62         struct mutex bind_mutex; /* serialize bind/unbind operations */
  63         struct rb_root evtchns;
  64         unsigned int nr_evtchns;
  65
  66         /* Notification ring, accessed via /dev/xen/evtchn. */
  67         unsigned int ring_size;
  68         evtchn_port_t *ring;
  69         unsigned int ring_cons, ring_prod, ring_overflow;
  70         struct mutex ring_cons_mutex; /* protect against concurrent readers */
  71         spinlock_t ring_prod_lock; /* product against concurrent interrupts */
  72
  73         /* Processes wait on this queue when ring is empty. */
  74         wait_queue_head_t evtchn_wait;
  75         struct fasync_struct *evtchn_async_queue;
  76         const char *name;
  77
  78         domid_t restrict_domid;
  79 };
  80
  81 #define UNRESTRICTED_DOMID ((domid_t)-1)
  82
  83 struct user_evtchn {
  84         struct rb_node node;
  85         struct per_user_data *user;
  86         unsigned port;
  87         bool enabled;
  88 };
  89
  90 static void evtchn_free_ring(evtchn_port_t *ring)
  91 {
  92         kvfree(ring);
  93 }
  94
  95 static unsigned int evtchn_ring_offset(struct per_user_data *u,
  96                                        unsigned int idx)
  97 {
  98         return idx & (u->ring_size - 1);
  99 }
 100
 101 static evtchn_port_t *evtchn_ring_entry(struct per_user_data *u,
 102                                         unsigned int idx)
 103 {
 104         return u->ring + evtchn_ring_offset(u, idx);
 105 }
 106
 107 static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
 108 {
 109         struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;
 110
 111         u->nr_evtchns++;
 112
 113         while (*new) {
 114                 struct user_evtchn *this;
 115
 116                 this = rb_entry(*new, struct user_evtchn, node);
 117
 118                 parent = *new;
 119                 if (this->port < evtchn->port)
 120                         new = &((*new)->rb_left);
 121                 else if (this->port > evtchn->port)
 122                         new = &((*new)->rb_right);
 123                 else
 124                         return -EEXIST;
 125         }
 126
 127         /* Add new node and rebalance tree. */
 128         rb_link_node(&evtchn->node, parent, new);
 129         rb_insert_color(&evtchn->node, &u->evtchns);
 130
 131         return 0;
 132 }
 133
 134 static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
 135 {
 136         u->nr_evtchns--;
 137         rb_erase(&evtchn->node, &u->evtchns);
 138         kfree(evtchn);
 139 }
 140
 141 static struct user_evtchn *find_evtchn(struct per_user_data *u, unsigned port)
 142 {
 143         struct rb_node *node = u->evtchns.rb_node;
 144
 145         while (node) {
 146                 struct user_evtchn *evtchn;
 147
 148                 evtchn = rb_entry(node, struct user_evtchn, node);
 149
 150                 if (evtchn->port < port)
 151                         node = node->rb_left;
 152                 else if (evtchn->port > port)
 153                         node = node->rb_right;
 154                 else
 155                         return evtchn;
 156         }
 157         return NULL;
 158 }
 159
 160 static irqreturn_t evtchn_interrupt(int irq, void *data)
 161 {
 162         struct user_evtchn *evtchn = data;
 163         struct per_user_data *u = evtchn->user;
 164
 165         WARN(!evtchn->enabled,
 166              "Interrupt for port %d, but apparently not enabled; per-user %p\n",
 167              evtchn->port, u);
 168
 169         disable_irq_nosync(irq);
 170         evtchn->enabled = false;
 171
 172         spin_lock(&u->ring_prod_lock);
 173
 174         if ((u->ring_prod - u->ring_cons) < u->ring_size) {
 175                 *evtchn_ring_entry(u, u->ring_prod) = evtchn->port;
 176                 wmb(); /* Ensure ring contents visible */
 177                 if (u->ring_cons == u->ring_prod++) {
 178                         wake_up_interruptible(&u->evtchn_wait);
 179                         kill_fasync(&u->evtchn_async_queue,
 180                                     SIGIO, POLL_IN);
 181                 }
 182         } else
 183                 u->ring_overflow = 1;
 184
 185         spin_unlock(&u->ring_prod_lock);
 186
 187         return IRQ_HANDLED;
 188 }
 189
 190 static ssize_t evtchn_read(struct file *file, char __user *buf,
 191                            size_t count, loff_t *ppos)
 192 {
 193         int rc;
 194         unsigned int c, p, bytes1 = 0, bytes2 = 0;
 195         struct per_user_data *u = file->private_data;
 196
 197         /* Whole number of ports. */
 198         count &= ~(sizeof(evtchn_port_t)-1);
 199
 200         if (count == 0)
 201                 return 0;
 202
 203         if (count > PAGE_SIZE)
 204                 count = PAGE_SIZE;
 205
 206         for (;;) {
 207                 mutex_lock(&u->ring_cons_mutex);
 208
 209                 rc = -EFBIG;
 210                 if (u->ring_overflow)
 211                         goto unlock_out;
 212
 213                 c = u->ring_cons;
 214                 p = u->ring_prod;
 215                 if (c != p)
 216                         break;
 217
 218                 mutex_unlock(&u->ring_cons_mutex);
 219
 220                 if (file->f_flags & O_NONBLOCK)
 221                         return -EAGAIN;
 222
 223                 rc = wait_event_interruptible(u->evtchn_wait,
 224                                               u->ring_cons != u->ring_prod);
 225                 if (rc)
 226                         return rc;
 227         }
 228
 229         /* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
 230         if (((c ^ p) & u->ring_size) != 0) {
 231                 bytes1 = (u->ring_size - evtchn_ring_offset(u, c)) *
 232                         sizeof(evtchn_port_t);
 233                 bytes2 = evtchn_ring_offset(u, p) * sizeof(evtchn_port_t);
 234         } else {
 235                 bytes1 = (p - c) * sizeof(evtchn_port_t);
 236                 bytes2 = 0;
 237         }
 238
 239         /* Truncate chunks according to caller's maximum byte count. */
 240         if (bytes1 > count) {
 241                 bytes1 = count;
 242                 bytes2 = 0;
 243         } else if ((bytes1 + bytes2) > count) {
 244                 bytes2 = count - bytes1;
 245         }
 246
 247         rc = -EFAULT;
 248         rmb(); /* Ensure that we see the port before we copy it. */
 249         if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) ||
 250             ((bytes2 != 0) &&
 251              copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
 252                 goto unlock_out;
 253
 254         u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
 255         rc = bytes1 + bytes2;
 256
 257  unlock_out:
 258         mutex_unlock(&u->ring_cons_mutex);
 259         return rc;
 260 }
 261
 262 static ssize_t evtchn_write(struct file *file, const char __user *buf,
 263                             size_t count, loff_t *ppos)
 264 {
 265         int rc, i;
 266         evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
 267         struct per_user_data *u = file->private_data;
 268
 269         if (kbuf == NULL)
 270                 return -ENOMEM;
 271
 272         /* Whole number of ports. */
 273         count &= ~(sizeof(evtchn_port_t)-1);
 274
 275         rc = 0;
 276         if (count == 0)
 277                 goto out;
 278
 279         if (count > PAGE_SIZE)
 280                 count = PAGE_SIZE;
 281
 282         rc = -EFAULT;
 283         if (copy_from_user(kbuf, buf, count) != 0)
 284                 goto out;
 285
 286         mutex_lock(&u->bind_mutex);
 287
 288         for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
 289                 unsigned port = kbuf[i];
 290                 struct user_evtchn *evtchn;
 291
 292                 evtchn = find_evtchn(u, port);
 293                 if (evtchn && !evtchn->enabled) {
 294                         evtchn->enabled = true;
 295                         enable_irq(irq_from_evtchn(port));
 296                 }
 297         }
 298
 299         mutex_unlock(&u->bind_mutex);
 300
 301         rc = count;
 302
 303  out:
 304         free_page((unsigned long)kbuf);
 305         return rc;
 306 }
 307
 308 static int evtchn_resize_ring(struct per_user_data *u)
 309 {
 310         unsigned int new_size;
 311         evtchn_port_t *new_ring, *old_ring;
 312
 313         /*
 314          * Ensure the ring is large enough to capture all possible
 315          * events. i.e., one free slot for each bound event.
 316          */
 317         if (u->nr_evtchns <= u->ring_size)
 318                 return 0;
 319
 320         if (u->ring_size == 0)
 321                 new_size = 64;
 322         else
 323                 new_size = 2 * u->ring_size;
 324
 325         new_ring = kvmalloc(new_size * sizeof(*new_ring), GFP_KERNEL);
 326         if (!new_ring)
 327                 return -ENOMEM;
 328
 329         old_ring = u->ring;
 330
 331         /*
 332          * Access to the ring contents is serialized by either the
 333          * prod /or/ cons lock so take both when resizing.
 334          */
 335         mutex_lock(&u->ring_cons_mutex);
 336         spin_lock_irq(&u->ring_prod_lock);
 337
 338         /*
 339          * Copy the old ring contents to the new ring.
 340          *
 341          * To take care of wrapping, a full ring, and the new index
 342          * pointing into the second half, simply copy the old contents
 343          * twice.
 344          *
 345          * +---------+    +------------------+
 346          * |34567  12| -> |34567  1234567  12|
 347          * +-----p-c-+    +-------c------p---+
 348          */
 349         memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
 350         memcpy(new_ring + u->ring_size, old_ring,
 351                u->ring_size * sizeof(*u->ring));
 352
 353         u->ring = new_ring;
 354         u->ring_size = new_size;
 355
 356         spin_unlock_irq(&u->ring_prod_lock);
 357         mutex_unlock(&u->ring_cons_mutex);
 358
 359         evtchn_free_ring(old_ring);
 360
 361         return 0;
 362 }
 363
 364 static int evtchn_bind_to_user(struct per_user_data *u, int port)
 365 {
 366         struct user_evtchn *evtchn;
 367         struct evtchn_close close;
 368         int rc = 0;
 369
 370         /*
 371          * Ports are never reused, so every caller should pass in a
 372          * unique port.
 373          *
 374          * (Locking not necessary because we haven't registered the
 375          * interrupt handler yet, and our caller has already
 376          * serialized bind operations.)
 377          */
 378
 379         evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL);
 380         if (!evtchn)
 381                 return -ENOMEM;
 382
 383         evtchn->user = u;
 384         evtchn->port = port;
 385         evtchn->enabled = true; /* start enabled */
 386
 387         rc = add_evtchn(u, evtchn);
 388         if (rc < 0)
 389                 goto err;
 390
 391         rc = evtchn_resize_ring(u);
 392         if (rc < 0)
 393                 goto err;
 394
 395         rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, 0,
 396                                        u->name, evtchn);
 397         if (rc < 0)
 398                 goto err;
 399
 400         rc = evtchn_make_refcounted(port);
 401         return rc;
 402
 403 err:
 404         /* bind failed, should close the port now */
 405         close.port = port;
 406         if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
 407                 BUG();
 408         del_evtchn(u, evtchn);
 409         return rc;
 410 }
 411
 412 static void evtchn_unbind_from_user(struct per_user_data *u,
 413                                     struct user_evtchn *evtchn)
 414 {
 415         int irq = irq_from_evtchn(evtchn->port);
 416
 417         BUG_ON(irq < 0);
 418
 419         unbind_from_irqhandler(irq, evtchn);
 420
 421         del_evtchn(u, evtchn);
 422 }
 423
 424 static DEFINE_PER_CPU(int, bind_last_selected_cpu);
 425
 426 static void evtchn_bind_interdom_next_vcpu(int evtchn)
 427 {
 428         unsigned int selected_cpu, irq;
 429         struct irq_desc *desc;
 430         unsigned long flags;
 431
 432         irq = irq_from_evtchn(evtchn);
 433         desc = irq_to_desc(irq);
 434
 435         if (!desc)
 436                 return;
 437
 438         raw_spin_lock_irqsave(&desc->lock, flags);
 439         selected_cpu = this_cpu_read(bind_last_selected_cpu);
 440         selected_cpu = cpumask_next_and(selected_cpu,
 441                         desc->irq_common_data.affinity, cpu_online_mask);
 442
 443         if (unlikely(selected_cpu >= nr_cpu_ids))
 444                 selected_cpu = cpumask_first_and(desc->irq_common_data.affinity,
 445                                 cpu_online_mask);
 446
 447         this_cpu_write(bind_last_selected_cpu, selected_cpu);
 448
 449         /* unmask expects irqs to be disabled */
 450         xen_rebind_evtchn_to_cpu(evtchn, selected_cpu);
 451         raw_spin_unlock_irqrestore(&desc->lock, flags);
 452 }
 453
 454 static long evtchn_ioctl(struct file *file,
 455                          unsigned int cmd, unsigned long arg)
 456 {
 457         int rc;
 458         struct per_user_data *u = file->private_data;
 459         void __user *uarg = (void __user *) arg;
 460
 461         /* Prevent bind from racing with unbind */
 462         mutex_lock(&u->bind_mutex);
 463
 464         switch (cmd) {
 465         case IOCTL_EVTCHN_BIND_VIRQ: {
 466                 struct ioctl_evtchn_bind_virq bind;
 467                 struct evtchn_bind_virq bind_virq;
 468
 469                 rc = -EACCES;
 470                 if (u->restrict_domid != UNRESTRICTED_DOMID)
 471                         break;
 472
 473                 rc = -EFAULT;
 474                 if (copy_from_user(&bind, uarg, sizeof(bind)))
 475                         break;
 476
 477                 bind_virq.virq = bind.virq;
 478                 bind_virq.vcpu = xen_vcpu_nr(0);
 479                 rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
 480                                                  &bind_virq);
 481                 if (rc != 0)
 482                         break;
 483
 484                 rc = evtchn_bind_to_user(u, bind_virq.port);
 485                 if (rc == 0)
 486                         rc = bind_virq.port;
 487                 break;
 488         }
 489
 490         case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
 491                 struct ioctl_evtchn_bind_interdomain bind;
 492                 struct evtchn_bind_interdomain bind_interdomain;
 493
 494                 rc = -EFAULT;
 495                 if (copy_from_user(&bind, uarg, sizeof(bind)))
 496                         break;
 497
 498                 rc = -EACCES;
 499                 if (u->restrict_domid != UNRESTRICTED_DOMID &&
 500                     u->restrict_domid != bind.remote_domain)
 501                         break;
 502
 503                 bind_interdomain.remote_dom  = bind.remote_domain;
 504                 bind_interdomain.remote_port = bind.remote_port;
 505                 rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
 506                                                  &bind_interdomain);
 507                 if (rc != 0)
 508                         break;
 509
 510                 rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
 511                 if (rc == 0) {
 512                         rc = bind_interdomain.local_port;
 513                         evtchn_bind_interdom_next_vcpu(rc);
 514                 }
 515                 break;
 516         }
 517
 518         case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
 519                 struct ioctl_evtchn_bind_unbound_port bind;
 520                 struct evtchn_alloc_unbound alloc_unbound;
 521
 522                 rc = -EACCES;
 523                 if (u->restrict_domid != UNRESTRICTED_DOMID)
 524                         break;
 525
 526                 rc = -EFAULT;
 527                 if (copy_from_user(&bind, uarg, sizeof(bind)))
 528                         break;
 529
 530                 alloc_unbound.dom        = DOMID_SELF;
 531                 alloc_unbound.remote_dom = bind.remote_domain;
 532                 rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
 533                                                  &alloc_unbound);
 534                 if (rc != 0)
 535                         break;
 536
 537                 rc = evtchn_bind_to_user(u, alloc_unbound.port);
 538                 if (rc == 0)
 539                         rc = alloc_unbound.port;
 540                 break;
 541         }
 542
 543         case IOCTL_EVTCHN_UNBIND: {
 544                 struct ioctl_evtchn_unbind unbind;
 545                 struct user_evtchn *evtchn;
 546
 547                 rc = -EFAULT;
 548                 if (copy_from_user(&unbind, uarg, sizeof(unbind)))
 549                         break;
 550
 551                 rc = -EINVAL;
 552                 if (unbind.port >= xen_evtchn_nr_channels())
 553                         break;
 554
 555                 rc = -ENOTCONN;
 556                 evtchn = find_evtchn(u, unbind.port);
 557                 if (!evtchn)
 558                         break;
 559
 560                 disable_irq(irq_from_evtchn(unbind.port));
 561                 evtchn_unbind_from_user(u, evtchn);
 562                 rc = 0;
 563                 break;
 564         }
 565
 566         case IOCTL_EVTCHN_NOTIFY: {
 567                 struct ioctl_evtchn_notify notify;
 568                 struct user_evtchn *evtchn;
 569
 570                 rc = -EFAULT;
 571                 if (copy_from_user(&notify, uarg, sizeof(notify)))
 572                         break;
 573
 574                 rc = -ENOTCONN;
 575                 evtchn = find_evtchn(u, notify.port);
 576                 if (evtchn) {
 577                         notify_remote_via_evtchn(notify.port);
 578                         rc = 0;
 579                 }
 580                 break;
 581         }
 582
 583         case IOCTL_EVTCHN_RESET: {
 584                 /* Initialise the ring to empty. Clear errors. */
 585                 mutex_lock(&u->ring_cons_mutex);
 586                 spin_lock_irq(&u->ring_prod_lock);
 587                 u->ring_cons = u->ring_prod = u->ring_overflow = 0;
 588                 spin_unlock_irq(&u->ring_prod_lock);
 589                 mutex_unlock(&u->ring_cons_mutex);
 590                 rc = 0;
 591                 break;
 592         }
 593
 594         case IOCTL_EVTCHN_RESTRICT_DOMID: {
 595                 struct ioctl_evtchn_restrict_domid ierd;
 596
 597                 rc = -EACCES;
 598                 if (u->restrict_domid != UNRESTRICTED_DOMID)
 599                         break;
 600
 601                 rc = -EFAULT;
 602                 if (copy_from_user(&ierd, uarg, sizeof(ierd)))
 603                     break;
 604
 605                 rc = -EINVAL;
 606                 if (ierd.domid == 0 || ierd.domid >= DOMID_FIRST_RESERVED)
 607                         break;
 608
 609                 u->restrict_domid = ierd.domid;
 610                 rc = 0;
 611
 612                 break;
 613         }
 614
 615         default:
 616                 rc = -ENOSYS;
 617                 break;
 618         }
 619         mutex_unlock(&u->bind_mutex);
 620
 621         return rc;
 622 }
 623
 624 static unsigned int evtchn_poll(struct file *file, poll_table *wait)
 625 {
 626         unsigned int mask = POLLOUT | POLLWRNORM;
 627         struct per_user_data *u = file->private_data;
 628
 629         poll_wait(file, &u->evtchn_wait, wait);
 630         if (u->ring_cons != u->ring_prod)
 631                 mask |= POLLIN | POLLRDNORM;
 632         if (u->ring_overflow)
 633                 mask = POLLERR;
 634         return mask;
 635 }
 636
 637 static int evtchn_fasync(int fd, struct file *filp, int on)
 638 {
 639         struct per_user_data *u = filp->private_data;
 640         return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
 641 }
 642
 643 static int evtchn_open(struct inode *inode, struct file *filp)
 644 {
 645         struct per_user_data *u;
 646
 647         u = kzalloc(sizeof(*u), GFP_KERNEL);
 648         if (u == NULL)
 649                 return -ENOMEM;
 650
 651         u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
 652         if (u->name == NULL) {
 653                 kfree(u);
 654                 return -ENOMEM;
 655         }
 656
 657         init_waitqueue_head(&u->evtchn_wait);
 658
 659         mutex_init(&u->bind_mutex);
 660         mutex_init(&u->ring_cons_mutex);
 661         spin_lock_init(&u->ring_prod_lock);
 662
 663         u->restrict_domid = UNRESTRICTED_DOMID;
 664
 665         filp->private_data = u;
 666
 667         return nonseekable_open(inode, filp);
 668 }
 669
 670 static int evtchn_release(struct inode *inode, struct file *filp)
 671 {
 672         struct per_user_data *u = filp->private_data;
 673         struct rb_node *node;
 674
 675         while ((node = u->evtchns.rb_node)) {
 676                 struct user_evtchn *evtchn;
 677
 678                 evtchn = rb_entry(node, struct user_evtchn, node);
 679                 disable_irq(irq_from_evtchn(evtchn->port));
 680                 evtchn_unbind_from_user(u, evtchn);
 681         }
 682
 683         evtchn_free_ring(u->ring);
 684         kfree(u->name);
 685         kfree(u);
 686
 687         return 0;
 688 }
 689
 690 static const struct file_operations evtchn_fops = {
 691         .owner   = THIS_MODULE,
 692         .read    = evtchn_read,
 693         .write   = evtchn_write,
 694         .unlocked_ioctl = evtchn_ioctl,
 695         .poll    = evtchn_poll,
 696         .fasync  = evtchn_fasync,
 697         .open    = evtchn_open,
 698         .release = evtchn_release,
 699         .llseek  = no_llseek,
 700 };
 701
 702 static struct miscdevice evtchn_miscdev = {
 703         .minor        = MISC_DYNAMIC_MINOR,
 704         .name         = "xen/evtchn",
 705         .fops         = &evtchn_fops,
 706 };
 707 static int __init evtchn_init(void)
 708 {
 709         int err;
 710
 711         if (!xen_domain())
 712                 return -ENODEV;
 713
 714         /* Create '/dev/xen/evtchn'. */
 715         err = misc_register(&evtchn_miscdev);
 716         if (err != 0) {
 717                 pr_err("Could not register /dev/xen/evtchn\n");
 718                 return err;
 719         }
 720
 721         pr_info("Event-channel device installed\n");
 722
 723         return 0;
 724 }
 725
 726 static void __exit evtchn_cleanup(void)
 727 {
 728         misc_deregister(&evtchn_miscdev);
 729 }
 730
 731 module_init(evtchn_init);
 732 module_exit(evtchn_cleanup);
 733
 734 MODULE_LICENSE("GPL");