drivers/vhost/vhost.c

   1 /* Copyright (C) 2009 Red Hat, Inc.
   2  * Copyright (C) 2006 Rusty Russell IBM Corporation
   3  *
   4  * Author: Michael S. Tsirkin <mst@redhat.com>
   5  *
   6  * Inspiration, some code, and most witty comments come from
   7  * Documentation/lguest/lguest.c, by Rusty Russell
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.
  10  *
  11  * Generic code for virtio server in host kernel.
  12  */
  13
  14 #include <linux/eventfd.h>
  15 #include <linux/vhost.h>
  16 #include <linux/virtio_net.h>
  17 #include <linux/mm.h>
  18 #include <linux/miscdevice.h>
  19 #include <linux/mutex.h>
  20 #include <linux/rcupdate.h>
  21 #include <linux/poll.h>
  22 #include <linux/file.h>
  23 #include <linux/highmem.h>
  24 #include <linux/slab.h>
  25 #include <linux/kthread.h>
  26 #include <linux/cgroup.h>
  27
  28 #include <linux/net.h>
  29 #include <linux/if_packet.h>
  30 #include <linux/if_arp.h>
  31
  32 #include <net/sock.h>
  33
  34 #include "vhost.h"
  35
  36 enum {
  37         VHOST_MEMORY_MAX_NREGIONS = 64,
  38         VHOST_MEMORY_F_LOG = 0x1,
  39 };
  40
  41 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  42                             poll_table *pt)
  43 {
  44         struct vhost_poll *poll;
  45         poll = container_of(pt, struct vhost_poll, table);
  46
  47         poll->wqh = wqh;
  48         add_wait_queue(wqh, &poll->wait);
  49 }
  50
  51 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
  52                              void *key)
  53 {
  54         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  55
  56         if (!((unsigned long)key & poll->mask))
  57                 return 0;
  58
  59         vhost_poll_queue(poll);
  60         return 0;
  61 }
  62
  63 /* Init poll structure */
  64 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  65                      unsigned long mask, struct vhost_dev *dev)
  66 {
  67         struct vhost_work *work = &poll->work;
  68
  69         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  70         init_poll_funcptr(&poll->table, vhost_poll_func);
  71         poll->mask = mask;
  72         poll->dev = dev;
  73
  74         INIT_LIST_HEAD(&work->node);
  75         work->fn = fn;
  76         init_waitqueue_head(&work->done);
  77         work->flushing = 0;
  78         work->queue_seq = work->done_seq = 0;
  79 }
  80
  81 /* Start polling a file. We add ourselves to file's wait queue. The caller must
  82  * keep a reference to a file until after vhost_poll_stop is called. */
  83 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
  84 {
  85         unsigned long mask;
  86         mask = file->f_op->poll(file, &poll->table);
  87         if (mask)
  88                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  89 }
  90
  91 /* Stop polling a file. After this function returns, it becomes safe to drop the
  92  * file reference. You must also flush afterwards. */
  93 void vhost_poll_stop(struct vhost_poll *poll)
  94 {
  95         remove_wait_queue(poll->wqh, &poll->wait);
  96 }
  97
  98 /* Flush any work that has been scheduled. When calling this, don't hold any
  99  * locks that are also used by the callback. */
 100 void vhost_poll_flush(struct vhost_poll *poll)
 101 {
 102         struct vhost_work *work = &poll->work;
 103         unsigned seq;
 104         int left;
 105         int flushing;
 106
 107         spin_lock_irq(&poll->dev->work_lock);
 108         seq = work->queue_seq;
 109         work->flushing++;
 110         spin_unlock_irq(&poll->dev->work_lock);
 111         wait_event(work->done, ({
 112                    spin_lock_irq(&poll->dev->work_lock);
 113                    left = seq - work->done_seq <= 0;
 114                    spin_unlock_irq(&poll->dev->work_lock);
 115                    left;
 116         }));
 117         spin_lock_irq(&poll->dev->work_lock);
 118         flushing = --work->flushing;
 119         spin_unlock_irq(&poll->dev->work_lock);
 120         BUG_ON(flushing < 0);
 121 }
 122
 123 void vhost_poll_queue(struct vhost_poll *poll)
 124 {
 125         struct vhost_dev *dev = poll->dev;
 126         struct vhost_work *work = &poll->work;
 127         unsigned long flags;
 128
 129         spin_lock_irqsave(&dev->work_lock, flags);
 130         if (list_empty(&work->node)) {
 131                 list_add_tail(&work->node, &dev->work_list);
 132                 work->queue_seq++;
 133                 wake_up_process(dev->worker);
 134         }
 135         spin_unlock_irqrestore(&dev->work_lock, flags);
 136 }
 137
 138 static void vhost_vq_reset(struct vhost_dev *dev,
 139                            struct vhost_virtqueue *vq)
 140 {
 141         vq->num = 1;
 142         vq->desc = NULL;
 143         vq->avail = NULL;
 144         vq->used = NULL;
 145         vq->last_avail_idx = 0;
 146         vq->avail_idx = 0;
 147         vq->last_used_idx = 0;
 148         vq->used_flags = 0;
 149         vq->used_flags = 0;
 150         vq->log_used = false;
 151         vq->log_addr = -1ull;
 152         vq->vhost_hlen = 0;
 153         vq->sock_hlen = 0;
 154         vq->private_data = NULL;
 155         vq->log_base = NULL;
 156         vq->error_ctx = NULL;
 157         vq->error = NULL;
 158         vq->kick = NULL;
 159         vq->call_ctx = NULL;
 160         vq->call = NULL;
 161         vq->log_ctx = NULL;
 162 }
 163
 164 static int vhost_worker(void *data)
 165 {
 166         struct vhost_dev *dev = data;
 167         struct vhost_work *work = NULL;
 168         unsigned uninitialized_var(seq);
 169
 170         for (;;) {
 171                 /* mb paired w/ kthread_stop */
 172                 set_current_state(TASK_INTERRUPTIBLE);
 173
 174                 spin_lock_irq(&dev->work_lock);
 175                 if (work) {
 176                         work->done_seq = seq;
 177                         if (work->flushing)
 178                                 wake_up_all(&work->done);
 179                 }
 180
 181                 if (kthread_should_stop()) {
 182                         spin_unlock_irq(&dev->work_lock);
 183                         __set_current_state(TASK_RUNNING);
 184                         return 0;
 185                 }
 186                 if (!list_empty(&dev->work_list)) {
 187                         work = list_first_entry(&dev->work_list,
 188                                                 struct vhost_work, node);
 189                         list_del_init(&work->node);
 190                         seq = work->queue_seq;
 191                 } else
 192                         work = NULL;
 193                 spin_unlock_irq(&dev->work_lock);
 194
 195                 if (work) {
 196                         __set_current_state(TASK_RUNNING);
 197                         work->fn(work);
 198                 } else
 199                         schedule();
 200
 201         }
 202 }
 203
 204 long vhost_dev_init(struct vhost_dev *dev,
 205                     struct vhost_virtqueue *vqs, int nvqs)
 206 {
 207         int i;
 208
 209         dev->vqs = vqs;
 210         dev->nvqs = nvqs;
 211         mutex_init(&dev->mutex);
 212         dev->log_ctx = NULL;
 213         dev->log_file = NULL;
 214         dev->memory = NULL;
 215         dev->mm = NULL;
 216         spin_lock_init(&dev->work_lock);
 217         INIT_LIST_HEAD(&dev->work_list);
 218         dev->worker = NULL;
 219
 220         for (i = 0; i < dev->nvqs; ++i) {
 221                 dev->vqs[i].dev = dev;
 222                 mutex_init(&dev->vqs[i].mutex);
 223                 vhost_vq_reset(dev, dev->vqs + i);
 224                 if (dev->vqs[i].handle_kick)
 225                         vhost_poll_init(&dev->vqs[i].poll,
 226                                         dev->vqs[i].handle_kick, POLLIN, dev);
 227         }
 228
 229         return 0;
 230 }
 231
 232 /* Caller should have device mutex */
 233 long vhost_dev_check_owner(struct vhost_dev *dev)
 234 {
 235         /* Are you the owner? If not, I don't think you mean to do that */
 236         return dev->mm == current->mm ? 0 : -EPERM;
 237 }
 238
 239 /* Caller should have device mutex */
 240 static long vhost_dev_set_owner(struct vhost_dev *dev)
 241 {
 242         struct task_struct *worker;
 243         int err;
 244         /* Is there an owner already? */
 245         if (dev->mm) {
 246                 err = -EBUSY;
 247                 goto err_mm;
 248         }
 249         /* No owner, become one */
 250         dev->mm = get_task_mm(current);
 251         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 252         if (IS_ERR(worker)) {
 253                 err = PTR_ERR(worker);
 254                 goto err_worker;
 255         }
 256
 257         dev->worker = worker;
 258         err = cgroup_attach_task_current_cg(worker);
 259         if (err)
 260                 goto err_cgroup;
 261         wake_up_process(worker);        /* avoid contributing to loadavg */
 262
 263         return 0;
 264 err_cgroup:
 265         kthread_stop(worker);
 266 err_worker:
 267         if (dev->mm)
 268                 mmput(dev->mm);
 269         dev->mm = NULL;
 270 err_mm:
 271         return err;
 272 }
 273
 274 /* Caller should have device mutex */
 275 long vhost_dev_reset_owner(struct vhost_dev *dev)
 276 {
 277         struct vhost_memory *memory;
 278
 279         /* Restore memory to default empty mapping. */
 280         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 281         if (!memory)
 282                 return -ENOMEM;
 283
 284         vhost_dev_cleanup(dev);
 285
 286         memory->nregions = 0;
 287         RCU_INIT_POINTER(dev->memory, memory);
 288         return 0;
 289 }
 290
 291 /* Caller should have device mutex */
 292 void vhost_dev_cleanup(struct vhost_dev *dev)
 293 {
 294         int i;
 295         for (i = 0; i < dev->nvqs; ++i) {
 296                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
 297                         vhost_poll_stop(&dev->vqs[i].poll);
 298                         vhost_poll_flush(&dev->vqs[i].poll);
 299                 }
 300                 if (dev->vqs[i].error_ctx)
 301                         eventfd_ctx_put(dev->vqs[i].error_ctx);
 302                 if (dev->vqs[i].error)
 303                         fput(dev->vqs[i].error);
 304                 if (dev->vqs[i].kick)
 305                         fput(dev->vqs[i].kick);
 306                 if (dev->vqs[i].call_ctx)
 307                         eventfd_ctx_put(dev->vqs[i].call_ctx);
 308                 if (dev->vqs[i].call)
 309                         fput(dev->vqs[i].call);
 310                 vhost_vq_reset(dev, dev->vqs + i);
 311         }
 312         if (dev->log_ctx)
 313                 eventfd_ctx_put(dev->log_ctx);
 314         dev->log_ctx = NULL;
 315         if (dev->log_file)
 316                 fput(dev->log_file);
 317         dev->log_file = NULL;
 318         /* No one will access memory at this point */
 319         kfree(rcu_dereference_protected(dev->memory,
 320                                         lockdep_is_held(&dev->mutex)));
 321         RCU_INIT_POINTER(dev->memory, NULL);
 322         if (dev->mm)
 323                 mmput(dev->mm);
 324         dev->mm = NULL;
 325
 326         WARN_ON(!list_empty(&dev->work_list));
 327         if (dev->worker) {
 328                 kthread_stop(dev->worker);
 329                 dev->worker = NULL;
 330         }
 331 }
 332
 333 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 334 {
 335         u64 a = addr / VHOST_PAGE_SIZE / 8;
 336         /* Make sure 64 bit math will not overflow. */
 337         if (a > ULONG_MAX - (unsigned long)log_base ||
 338             a + (unsigned long)log_base > ULONG_MAX)
 339                 return -EFAULT;
 340
 341         return access_ok(VERIFY_WRITE, log_base + a,
 342                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 343 }
 344
 345 /* Caller should have vq mutex and device mutex. */
 346 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 347                                int log_all)
 348 {
 349         int i;
 350
 351         if (!mem)
 352                 return 0;
 353
 354         for (i = 0; i < mem->nregions; ++i) {
 355                 struct vhost_memory_region *m = mem->regions + i;
 356                 unsigned long a = m->userspace_addr;
 357                 if (m->memory_size > ULONG_MAX)
 358                         return 0;
 359                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 360                                     m->memory_size))
 361                         return 0;
 362                 else if (log_all && !log_access_ok(log_base,
 363                                                    m->guest_phys_addr,
 364                                                    m->memory_size))
 365                         return 0;
 366         }
 367         return 1;
 368 }
 369
 370 /* Can we switch to this memory table? */
 371 /* Caller should have device mutex but not vq mutex */
 372 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 373                             int log_all)
 374 {
 375         int i;
 376         for (i = 0; i < d->nvqs; ++i) {
 377                 int ok;
 378                 mutex_lock(&d->vqs[i].mutex);
 379                 /* If ring is inactive, will check when it's enabled. */
 380                 if (d->vqs[i].private_data)
 381                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
 382                                                  log_all);
 383                 else
 384                         ok = 1;
 385                 mutex_unlock(&d->vqs[i].mutex);
 386                 if (!ok)
 387                         return 0;
 388         }
 389         return 1;
 390 }
 391
 392 static int vq_access_ok(unsigned int num,
 393                         struct vring_desc __user *desc,
 394                         struct vring_avail __user *avail,
 395                         struct vring_used __user *used)
 396 {
 397         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 398                access_ok(VERIFY_READ, avail,
 399                          sizeof *avail + num * sizeof *avail->ring) &&
 400                access_ok(VERIFY_WRITE, used,
 401                         sizeof *used + num * sizeof *used->ring);
 402 }
 403
 404 /* Can we log writes? */
 405 /* Caller should have device mutex but not vq mutex */
 406 int vhost_log_access_ok(struct vhost_dev *dev)
 407 {
 408         struct vhost_memory *mp;
 409
 410         mp = rcu_dereference_protected(dev->memory,
 411                                        lockdep_is_held(&dev->mutex));
 412         return memory_access_ok(dev, mp, 1);
 413 }
 414
 415 /* Verify access for write logging. */
 416 /* Caller should have vq mutex and device mutex */
 417 static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
 418 {
 419         struct vhost_memory *mp;
 420
 421         mp = rcu_dereference_protected(vq->dev->memory,
 422                                        lockdep_is_held(&vq->mutex));
 423         return vq_memory_access_ok(log_base, mp,
 424                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 425                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 426                                         sizeof *vq->used +
 427                                         vq->num * sizeof *vq->used->ring));
 428 }
 429
 430 /* Can we start vq? */
 431 /* Caller should have vq mutex and device mutex */
 432 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 433 {
 434         return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
 435                 vq_log_access_ok(vq, vq->log_base);
 436 }
 437
 438 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 439 {
 440         struct vhost_memory mem, *newmem, *oldmem;
 441         unsigned long size = offsetof(struct vhost_memory, regions);
 442         if (copy_from_user(&mem, m, size))
 443                 return -EFAULT;
 444         if (mem.padding)
 445                 return -EOPNOTSUPP;
 446         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 447                 return -E2BIG;
 448         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 449         if (!newmem)
 450                 return -ENOMEM;
 451
 452         memcpy(newmem, &mem, size);
 453         if (copy_from_user(newmem->regions, m->regions,
 454                            mem.nregions * sizeof *m->regions)) {
 455                 kfree(newmem);
 456                 return -EFAULT;
 457         }
 458
 459         if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 460                 kfree(newmem);
 461                 return -EFAULT;
 462         }
 463         oldmem = rcu_dereference_protected(d->memory,
 464                                            lockdep_is_held(&d->mutex));
 465         rcu_assign_pointer(d->memory, newmem);
 466         synchronize_rcu();
 467         kfree(oldmem);
 468         return 0;
 469 }
 470
 471 static int init_used(struct vhost_virtqueue *vq,
 472                      struct vring_used __user *used)
 473 {
 474         int r = put_user(vq->used_flags, &used->flags);
 475         if (r)
 476                 return r;
 477         return get_user(vq->last_used_idx, &used->idx);
 478 }
 479
 480 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 481 {
 482         struct file *eventfp, *filep = NULL,
 483                     *pollstart = NULL, *pollstop = NULL;
 484         struct eventfd_ctx *ctx = NULL;
 485         u32 __user *idxp = argp;
 486         struct vhost_virtqueue *vq;
 487         struct vhost_vring_state s;
 488         struct vhost_vring_file f;
 489         struct vhost_vring_addr a;
 490         u32 idx;
 491         long r;
 492
 493         r = get_user(idx, idxp);
 494         if (r < 0)
 495                 return r;
 496         if (idx >= d->nvqs)
 497                 return -ENOBUFS;
 498
 499         vq = d->vqs + idx;
 500
 501         mutex_lock(&vq->mutex);
 502
 503         switch (ioctl) {
 504         case VHOST_SET_VRING_NUM:
 505                 /* Resizing ring with an active backend?
 506                  * You don't want to do that. */
 507                 if (vq->private_data) {
 508                         r = -EBUSY;
 509                         break;
 510                 }
 511                 if (copy_from_user(&s, argp, sizeof s)) {
 512                         r = -EFAULT;
 513                         break;
 514                 }
 515                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 516                         r = -EINVAL;
 517                         break;
 518                 }
 519                 vq->num = s.num;
 520                 break;
 521         case VHOST_SET_VRING_BASE:
 522                 /* Moving base with an active backend?
 523                  * You don't want to do that. */
 524                 if (vq->private_data) {
 525                         r = -EBUSY;
 526                         break;
 527                 }
 528                 if (copy_from_user(&s, argp, sizeof s)) {
 529                         r = -EFAULT;
 530                         break;
 531                 }
 532                 if (s.num > 0xffff) {
 533                         r = -EINVAL;
 534                         break;
 535                 }
 536                 vq->last_avail_idx = s.num;
 537                 /* Forget the cached index value. */
 538                 vq->avail_idx = vq->last_avail_idx;
 539                 break;
 540         case VHOST_GET_VRING_BASE:
 541                 s.index = idx;
 542                 s.num = vq->last_avail_idx;
 543                 if (copy_to_user(argp, &s, sizeof s))
 544                         r = -EFAULT;
 545                 break;
 546         case VHOST_SET_VRING_ADDR:
 547                 if (copy_from_user(&a, argp, sizeof a)) {
 548                         r = -EFAULT;
 549                         break;
 550                 }
 551                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 552                         r = -EOPNOTSUPP;
 553                         break;
 554                 }
 555                 /* For 32bit, verify that the top 32bits of the user
 556                    data are set to zero. */
 557                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 558                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 559                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 560                         r = -EFAULT;
 561                         break;
 562                 }
 563                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 564                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 565                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 566                         r = -EINVAL;
 567                         break;
 568                 }
 569
 570                 /* We only verify access here if backend is configured.
 571                  * If it is not, we don't as size might not have been setup.
 572                  * We will verify when backend is configured. */
 573                 if (vq->private_data) {
 574                         if (!vq_access_ok(vq->num,
 575                                 (void __user *)(unsigned long)a.desc_user_addr,
 576                                 (void __user *)(unsigned long)a.avail_user_addr,
 577                                 (void __user *)(unsigned long)a.used_user_addr)) {
 578                                 r = -EINVAL;
 579                                 break;
 580                         }
 581
 582                         /* Also validate log access for used ring if enabled. */
 583                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 584                             !log_access_ok(vq->log_base, a.log_guest_addr,
 585                                            sizeof *vq->used +
 586                                            vq->num * sizeof *vq->used->ring)) {
 587                                 r = -EINVAL;
 588                                 break;
 589                         }
 590                 }
 591
 592                 r = init_used(vq, (struct vring_used __user *)(unsigned long)
 593                               a.used_user_addr);
 594                 if (r)
 595                         break;
 596                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 597                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 598                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 599                 vq->log_addr = a.log_guest_addr;
 600                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 601                 break;
 602         case VHOST_SET_VRING_KICK:
 603                 if (copy_from_user(&f, argp, sizeof f)) {
 604                         r = -EFAULT;
 605                         break;
 606                 }
 607                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 608                 if (IS_ERR(eventfp)) {
 609                         r = PTR_ERR(eventfp);
 610                         break;
 611                 }
 612                 if (eventfp != vq->kick) {
 613                         pollstop = filep = vq->kick;
 614                         pollstart = vq->kick = eventfp;
 615                 } else
 616                         filep = eventfp;
 617                 break;
 618         case VHOST_SET_VRING_CALL:
 619                 if (copy_from_user(&f, argp, sizeof f)) {
 620                         r = -EFAULT;
 621                         break;
 622                 }
 623                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 624                 if (IS_ERR(eventfp)) {
 625                         r = PTR_ERR(eventfp);
 626                         break;
 627                 }
 628                 if (eventfp != vq->call) {
 629                         filep = vq->call;
 630                         ctx = vq->call_ctx;
 631                         vq->call = eventfp;
 632                         vq->call_ctx = eventfp ?
 633                                 eventfd_ctx_fileget(eventfp) : NULL;
 634                 } else
 635                         filep = eventfp;
 636                 break;
 637         case VHOST_SET_VRING_ERR:
 638                 if (copy_from_user(&f, argp, sizeof f)) {
 639                         r = -EFAULT;
 640                         break;
 641                 }
 642                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 643                 if (IS_ERR(eventfp)) {
 644                         r = PTR_ERR(eventfp);
 645                         break;
 646                 }
 647                 if (eventfp != vq->error) {
 648                         filep = vq->error;
 649                         vq->error = eventfp;
 650                         ctx = vq->error_ctx;
 651                         vq->error_ctx = eventfp ?
 652                                 eventfd_ctx_fileget(eventfp) : NULL;
 653                 } else
 654                         filep = eventfp;
 655                 break;
 656         default:
 657                 r = -ENOIOCTLCMD;
 658         }
 659
 660         if (pollstop && vq->handle_kick)
 661                 vhost_poll_stop(&vq->poll);
 662
 663         if (ctx)
 664                 eventfd_ctx_put(ctx);
 665         if (filep)
 666                 fput(filep);
 667
 668         if (pollstart && vq->handle_kick)
 669                 vhost_poll_start(&vq->poll, vq->kick);
 670
 671         mutex_unlock(&vq->mutex);
 672
 673         if (pollstop && vq->handle_kick)
 674                 vhost_poll_flush(&vq->poll);
 675         return r;
 676 }
 677
 678 /* Caller must have device mutex */
 679 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 680 {
 681         void __user *argp = (void __user *)arg;
 682         struct file *eventfp, *filep = NULL;
 683         struct eventfd_ctx *ctx = NULL;
 684         u64 p;
 685         long r;
 686         int i, fd;
 687
 688         /* If you are not the owner, you can become one */
 689         if (ioctl == VHOST_SET_OWNER) {
 690                 r = vhost_dev_set_owner(d);
 691                 goto done;
 692         }
 693
 694         /* You must be the owner to do anything else */
 695         r = vhost_dev_check_owner(d);
 696         if (r)
 697                 goto done;
 698
 699         switch (ioctl) {
 700         case VHOST_SET_MEM_TABLE:
 701                 r = vhost_set_memory(d, argp);
 702                 break;
 703         case VHOST_SET_LOG_BASE:
 704                 if (copy_from_user(&p, argp, sizeof p)) {
 705                         r = -EFAULT;
 706                         break;
 707                 }
 708                 if ((u64)(unsigned long)p != p) {
 709                         r = -EFAULT;
 710                         break;
 711                 }
 712                 for (i = 0; i < d->nvqs; ++i) {
 713                         struct vhost_virtqueue *vq;
 714                         void __user *base = (void __user *)(unsigned long)p;
 715                         vq = d->vqs + i;
 716                         mutex_lock(&vq->mutex);
 717                         /* If ring is inactive, will check when it's enabled. */
 718                         if (vq->private_data && !vq_log_access_ok(vq, base))
 719                                 r = -EFAULT;
 720                         else
 721                                 vq->log_base = base;
 722                         mutex_unlock(&vq->mutex);
 723                 }
 724                 break;
 725         case VHOST_SET_LOG_FD:
 726                 r = get_user(fd, (int __user *)argp);
 727                 if (r < 0)
 728                         break;
 729                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 730                 if (IS_ERR(eventfp)) {
 731                         r = PTR_ERR(eventfp);
 732                         break;
 733                 }
 734                 if (eventfp != d->log_file) {
 735                         filep = d->log_file;
 736                         ctx = d->log_ctx;
 737                         d->log_ctx = eventfp ?
 738                                 eventfd_ctx_fileget(eventfp) : NULL;
 739                 } else
 740                         filep = eventfp;
 741                 for (i = 0; i < d->nvqs; ++i) {
 742                         mutex_lock(&d->vqs[i].mutex);
 743                         d->vqs[i].log_ctx = d->log_ctx;
 744                         mutex_unlock(&d->vqs[i].mutex);
 745                 }
 746                 if (ctx)
 747                         eventfd_ctx_put(ctx);
 748                 if (filep)
 749                         fput(filep);
 750                 break;
 751         default:
 752                 r = vhost_set_vring(d, ioctl, argp);
 753                 break;
 754         }
 755 done:
 756         return r;
 757 }
 758
 759 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 760                                                      __u64 addr, __u32 len)
 761 {
 762         struct vhost_memory_region *reg;
 763         int i;
 764         /* linear search is not brilliant, but we really have on the order of 6
 765          * regions in practice */
 766         for (i = 0; i < mem->nregions; ++i) {
 767                 reg = mem->regions + i;
 768                 if (reg->guest_phys_addr <= addr &&
 769                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 770                         return reg;
 771         }
 772         return NULL;
 773 }
 774
 775 /* TODO: This is really inefficient.  We need something like get_user()
 776  * (instruction directly accesses the data, with an exception table entry
 777  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 778  */
 779 static int set_bit_to_user(int nr, void __user *addr)
 780 {
 781         unsigned long log = (unsigned long)addr;
 782         struct page *page;
 783         void *base;
 784         int bit = nr + (log % PAGE_SIZE) * 8;
 785         int r;
 786         r = get_user_pages_fast(log, 1, 1, &page);
 787         if (r < 0)
 788                 return r;
 789         BUG_ON(r != 1);
 790         base = kmap_atomic(page, KM_USER0);
 791         set_bit(bit, base);
 792         kunmap_atomic(base, KM_USER0);
 793         set_page_dirty_lock(page);
 794         put_page(page);
 795         return 0;
 796 }
 797
 798 static int log_write(void __user *log_base,
 799                      u64 write_address, u64 write_length)
 800 {
 801         int r;
 802         if (!write_length)
 803                 return 0;
 804         write_address /= VHOST_PAGE_SIZE;
 805         for (;;) {
 806                 u64 base = (u64)(unsigned long)log_base;
 807                 u64 log = base + write_address / 8;
 808                 int bit = write_address % 8;
 809                 if ((u64)(unsigned long)log != log)
 810                         return -EFAULT;
 811                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 812                 if (r < 0)
 813                         return r;
 814                 if (write_length <= VHOST_PAGE_SIZE)
 815                         break;
 816                 write_length -= VHOST_PAGE_SIZE;
 817                 write_address += VHOST_PAGE_SIZE;
 818         }
 819         return r;
 820 }
 821
 822 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 823                     unsigned int log_num, u64 len)
 824 {
 825         int i, r;
 826
 827         /* Make sure data written is seen before log. */
 828         smp_wmb();
 829         for (i = 0; i < log_num; ++i) {
 830                 u64 l = min(log[i].len, len);
 831                 r = log_write(vq->log_base, log[i].addr, l);
 832                 if (r < 0)
 833                         return r;
 834                 len -= l;
 835                 if (!len)
 836                         return 0;
 837         }
 838         if (vq->log_ctx)
 839                 eventfd_signal(vq->log_ctx, 1);
 840         /* Length written exceeds what we have stored. This is a bug. */
 841         BUG();
 842         return 0;
 843 }
 844
 845 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
 846                           struct iovec iov[], int iov_size)
 847 {
 848         const struct vhost_memory_region *reg;
 849         struct vhost_memory *mem;
 850         struct iovec *_iov;
 851         u64 s = 0;
 852         int ret = 0;
 853
 854         rcu_read_lock();
 855
 856         mem = rcu_dereference(dev->memory);
 857         while ((u64)len > s) {
 858                 u64 size;
 859                 if (unlikely(ret >= iov_size)) {
 860                         ret = -ENOBUFS;
 861                         break;
 862                 }
 863                 reg = find_region(mem, addr, len);
 864                 if (unlikely(!reg)) {
 865                         ret = -EFAULT;
 866                         break;
 867                 }
 868                 _iov = iov + ret;
 869                 size = reg->memory_size - addr + reg->guest_phys_addr;
 870                 _iov->iov_len = min((u64)len, size);
 871                 _iov->iov_base = (void __user *)(unsigned long)
 872                         (reg->userspace_addr + addr - reg->guest_phys_addr);
 873                 s += size;
 874                 addr += size;
 875                 ++ret;
 876         }
 877
 878         rcu_read_unlock();
 879         return ret;
 880 }
 881
 882 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
 883  * function returns the next descriptor in the chain,
 884  * or -1U if we're at the end. */
 885 static unsigned next_desc(struct vring_desc *desc)
 886 {
 887         unsigned int next;
 888
 889         /* If this descriptor says it doesn't chain, we're done. */
 890         if (!(desc->flags & VRING_DESC_F_NEXT))
 891                 return -1U;
 892
 893         /* Check they're not leading us off end of descriptors. */
 894         next = desc->next;
 895         /* Make sure compiler knows to grab that: we don't want it changing! */
 896         /* We will use the result as an index in an array, so most
 897          * architectures only need a compiler barrier here. */
 898         read_barrier_depends();
 899
 900         return next;
 901 }
 902
 903 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
 904                         struct iovec iov[], unsigned int iov_size,
 905                         unsigned int *out_num, unsigned int *in_num,
 906                         struct vhost_log *log, unsigned int *log_num,
 907                         struct vring_desc *indirect)
 908 {
 909         struct vring_desc desc;
 910         unsigned int i = 0, count, found = 0;
 911         int ret;
 912
 913         /* Sanity check */
 914         if (unlikely(indirect->len % sizeof desc)) {
 915                 vq_err(vq, "Invalid length in indirect descriptor: "
 916                        "len 0x%llx not multiple of 0x%zx\n",
 917                        (unsigned long long)indirect->len,
 918                        sizeof desc);
 919                 return -EINVAL;
 920         }
 921
 922         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
 923                              ARRAY_SIZE(vq->indirect));
 924         if (unlikely(ret < 0)) {
 925                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
 926                 return ret;
 927         }
 928
 929         /* We will use the result as an address to read from, so most
 930          * architectures only need a compiler barrier here. */
 931         read_barrier_depends();
 932
 933         count = indirect->len / sizeof desc;
 934         /* Buffers are chained via a 16 bit next field, so
 935          * we can have at most 2^16 of these. */
 936         if (unlikely(count > USHRT_MAX + 1)) {
 937                 vq_err(vq, "Indirect buffer length too big: %d\n",
 938                        indirect->len);
 939                 return -E2BIG;
 940         }
 941
 942         do {
 943                 unsigned iov_count = *in_num + *out_num;
 944                 if (unlikely(++found > count)) {
 945                         vq_err(vq, "Loop detected: last one at %u "
 946                                "indirect size %u\n",
 947                                i, count);
 948                         return -EINVAL;
 949                 }
 950                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
 951                                               sizeof desc))) {
 952                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
 953                                i, (size_t)indirect->addr + i * sizeof desc);
 954                         return -EINVAL;
 955                 }
 956                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
 957                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
 958                                i, (size_t)indirect->addr + i * sizeof desc);
 959                         return -EINVAL;
 960                 }
 961
 962                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
 963                                      iov_size - iov_count);
 964                 if (unlikely(ret < 0)) {
 965                         vq_err(vq, "Translation failure %d indirect idx %d\n",
 966                                ret, i);
 967                         return ret;
 968                 }
 969                 /* If this is an input descriptor, increment that count. */
 970                 if (desc.flags & VRING_DESC_F_WRITE) {
 971                         *in_num += ret;
 972                         if (unlikely(log)) {
 973                                 log[*log_num].addr = desc.addr;
 974                                 log[*log_num].len = desc.len;
 975                                 ++*log_num;
 976                         }
 977                 } else {
 978                         /* If it's an output descriptor, they're all supposed
 979                          * to come before any input descriptors. */
 980                         if (unlikely(*in_num)) {
 981                                 vq_err(vq, "Indirect descriptor "
 982                                        "has out after in: idx %d\n", i);
 983                                 return -EINVAL;
 984                         }
 985                         *out_num += ret;
 986                 }
 987         } while ((i = next_desc(&desc)) != -1);
 988         return 0;
 989 }
 990
 991 /* This looks in the virtqueue and for the first available buffer, and converts
 992  * it to an iovec for convenient access.  Since descriptors consist of some
 993  * number of output then some number of input descriptors, it's actually two
 994  * iovecs, but we pack them into one and note how many of each there were.
 995  *
 996  * This function returns the descriptor number found, or vq->num (which is
 997  * never a valid descriptor number) if none was found.  A negative code is
 998  * returned on error. */
 999 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1000                       struct iovec iov[], unsigned int iov_size,
1001                       unsigned int *out_num, unsigned int *in_num,
1002                       struct vhost_log *log, unsigned int *log_num)
1003 {
1004         struct vring_desc desc;
1005         unsigned int i, head, found = 0;
1006         u16 last_avail_idx;
1007         int ret;
1008
1009         /* Check it isn't doing very strange things with descriptor numbers. */
1010         last_avail_idx = vq->last_avail_idx;
1011         if (unlikely(get_user(vq->avail_idx, &vq->avail->idx))) {
1012                 vq_err(vq, "Failed to access avail idx at %p\n",
1013                        &vq->avail->idx);
1014                 return -EFAULT;
1015         }
1016
1017         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1018                 vq_err(vq, "Guest moved used index from %u to %u",
1019                        last_avail_idx, vq->avail_idx);
1020                 return -EFAULT;
1021         }
1022
1023         /* If there's nothing new since last we looked, return invalid. */
1024         if (vq->avail_idx == last_avail_idx)
1025                 return vq->num;
1026
1027         /* Only get avail ring entries after they have been exposed by guest. */
1028         smp_rmb();
1029
1030         /* Grab the next descriptor number they're advertising, and increment
1031          * the index we've seen. */
1032         if (unlikely(get_user(head,
1033                               &vq->avail->ring[last_avail_idx % vq->num]))) {
1034                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1035                        last_avail_idx,
1036                        &vq->avail->ring[last_avail_idx % vq->num]);
1037                 return -EFAULT;
1038         }
1039
1040         /* If their number is silly, that's an error. */
1041         if (unlikely(head >= vq->num)) {
1042                 vq_err(vq, "Guest says index %u > %u is available",
1043                        head, vq->num);
1044                 return -EINVAL;
1045         }
1046
1047         /* When we start there are none of either input nor output. */
1048         *out_num = *in_num = 0;
1049         if (unlikely(log))
1050                 *log_num = 0;
1051
1052         i = head;
1053         do {
1054                 unsigned iov_count = *in_num + *out_num;
1055                 if (unlikely(i >= vq->num)) {
1056                         vq_err(vq, "Desc index is %u > %u, head = %u",
1057                                i, vq->num, head);
1058                         return -EINVAL;
1059                 }
1060                 if (unlikely(++found > vq->num)) {
1061                         vq_err(vq, "Loop detected: last one at %u "
1062                                "vq size %u head %u\n",
1063                                i, vq->num, head);
1064                         return -EINVAL;
1065                 }
1066                 ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
1067                 if (unlikely(ret)) {
1068                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1069                                i, vq->desc + i);
1070                         return -EFAULT;
1071                 }
1072                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1073                         ret = get_indirect(dev, vq, iov, iov_size,
1074                                            out_num, in_num,
1075                                            log, log_num, &desc);
1076                         if (unlikely(ret < 0)) {
1077                                 vq_err(vq, "Failure detected "
1078                                        "in indirect descriptor at idx %d\n", i);
1079                                 return ret;
1080                         }
1081                         continue;
1082                 }
1083
1084                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1085                                      iov_size - iov_count);
1086                 if (unlikely(ret < 0)) {
1087                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1088                                ret, i);
1089                         return ret;
1090                 }
1091                 if (desc.flags & VRING_DESC_F_WRITE) {
1092                         /* If this is an input descriptor,
1093                          * increment that count. */
1094                         *in_num += ret;
1095                         if (unlikely(log)) {
1096                                 log[*log_num].addr = desc.addr;
1097                                 log[*log_num].len = desc.len;
1098                                 ++*log_num;
1099                         }
1100                 } else {
1101                         /* If it's an output descriptor, they're all supposed
1102                          * to come before any input descriptors. */
1103                         if (unlikely(*in_num)) {
1104                                 vq_err(vq, "Descriptor has out after in: "
1105                                        "idx %d\n", i);
1106                                 return -EINVAL;
1107                         }
1108                         *out_num += ret;
1109                 }
1110         } while ((i = next_desc(&desc)) != -1);
1111
1112         /* On success, increment avail index. */
1113         vq->last_avail_idx++;
1114         return head;
1115 }
1116
1117 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1118 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1119 {
1120         vq->last_avail_idx -= n;
1121 }
1122
1123 /* After we've used one of their buffers, we tell them about it.  We'll then
1124  * want to notify the guest, using eventfd. */
1125 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1126 {
1127         struct vring_used_elem __user *used;
1128
1129         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1130          * next entry in that used ring. */
1131         used = &vq->used->ring[vq->last_used_idx % vq->num];
1132         if (put_user(head, &used->id)) {
1133                 vq_err(vq, "Failed to write used id");
1134                 return -EFAULT;
1135         }
1136         if (put_user(len, &used->len)) {
1137                 vq_err(vq, "Failed to write used len");
1138                 return -EFAULT;
1139         }
1140         /* Make sure buffer is written before we update index. */
1141         smp_wmb();
1142         if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1143                 vq_err(vq, "Failed to increment used idx");
1144                 return -EFAULT;
1145         }
1146         if (unlikely(vq->log_used)) {
1147                 /* Make sure data is seen before log. */
1148                 smp_wmb();
1149                 /* Log used ring entry write. */
1150                 log_write(vq->log_base,
1151                           vq->log_addr +
1152                            ((void __user *)used - (void __user *)vq->used),
1153                           sizeof *used);
1154                 /* Log used index update. */
1155                 log_write(vq->log_base,
1156                           vq->log_addr + offsetof(struct vring_used, idx),
1157                           sizeof vq->used->idx);
1158                 if (vq->log_ctx)
1159                         eventfd_signal(vq->log_ctx, 1);
1160         }
1161         vq->last_used_idx++;
1162         return 0;
1163 }
1164
1165 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1166                             struct vring_used_elem *heads,
1167                             unsigned count)
1168 {
1169         struct vring_used_elem __user *used;
1170         int start;
1171
1172         start = vq->last_used_idx % vq->num;
1173         used = vq->used->ring + start;
1174         if (copy_to_user(used, heads, count * sizeof *used)) {
1175                 vq_err(vq, "Failed to write used");
1176                 return -EFAULT;
1177         }
1178         if (unlikely(vq->log_used)) {
1179                 /* Make sure data is seen before log. */
1180                 smp_wmb();
1181                 /* Log used ring entry write. */
1182                 log_write(vq->log_base,
1183                           vq->log_addr +
1184                            ((void __user *)used - (void __user *)vq->used),
1185                           count * sizeof *used);
1186         }
1187         vq->last_used_idx += count;
1188         return 0;
1189 }
1190
1191 /* After we've used one of their buffers, we tell them about it.  We'll then
1192  * want to notify the guest, using eventfd. */
1193 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1194                      unsigned count)
1195 {
1196         int start, n, r;
1197
1198         start = vq->last_used_idx % vq->num;
1199         n = vq->num - start;
1200         if (n < count) {
1201                 r = __vhost_add_used_n(vq, heads, n);
1202                 if (r < 0)
1203                         return r;
1204                 heads += n;
1205                 count -= n;
1206         }
1207         r = __vhost_add_used_n(vq, heads, count);
1208
1209         /* Make sure buffer is written before we update index. */
1210         smp_wmb();
1211         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1212                 vq_err(vq, "Failed to increment used idx");
1213                 return -EFAULT;
1214         }
1215         if (unlikely(vq->log_used)) {
1216                 /* Log used index update. */
1217                 log_write(vq->log_base,
1218                           vq->log_addr + offsetof(struct vring_used, idx),
1219                           sizeof vq->used->idx);
1220                 if (vq->log_ctx)
1221                         eventfd_signal(vq->log_ctx, 1);
1222         }
1223         return r;
1224 }
1225
1226 /* This actually signals the guest, using eventfd. */
1227 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1228 {
1229         __u16 flags;
1230         /* Flush out used index updates. This is paired
1231          * with the barrier that the Guest executes when enabling
1232          * interrupts. */
1233         smp_mb();
1234
1235         if (get_user(flags, &vq->avail->flags)) {
1236                 vq_err(vq, "Failed to get flags");
1237                 return;
1238         }
1239
1240         /* If they don't want an interrupt, don't signal, unless empty. */
1241         if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1242             (vq->avail_idx != vq->last_avail_idx ||
1243              !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1244                 return;
1245
1246         /* Signal the Guest tell them we used something up. */
1247         if (vq->call_ctx)
1248                 eventfd_signal(vq->call_ctx, 1);
1249 }
1250
1251 /* And here's the combo meal deal.  Supersize me! */
1252 void vhost_add_used_and_signal(struct vhost_dev *dev,
1253                                struct vhost_virtqueue *vq,
1254                                unsigned int head, int len)
1255 {
1256         vhost_add_used(vq, head, len);
1257         vhost_signal(dev, vq);
1258 }
1259
1260 /* multi-buffer version of vhost_add_used_and_signal */
1261 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1262                                  struct vhost_virtqueue *vq,
1263                                  struct vring_used_elem *heads, unsigned count)
1264 {
1265         vhost_add_used_n(vq, heads, count);
1266         vhost_signal(dev, vq);
1267 }
1268
1269 /* OK, now we need to know about added descriptors. */
1270 bool vhost_enable_notify(struct vhost_virtqueue *vq)
1271 {
1272         u16 avail_idx;
1273         int r;
1274         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1275                 return false;
1276         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1277         r = put_user(vq->used_flags, &vq->used->flags);
1278         if (r) {
1279                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1280                        &vq->used->flags, r);
1281                 return false;
1282         }
1283         /* They could have slipped one in as we were doing that: make
1284          * sure it's written, then check again. */
1285         smp_mb();
1286         r = get_user(avail_idx, &vq->avail->idx);
1287         if (r) {
1288                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1289                        &vq->avail->idx, r);
1290                 return false;
1291         }
1292
1293         return avail_idx != vq->avail_idx;
1294 }
1295
1296 /* We don't need to be notified again. */
1297 void vhost_disable_notify(struct vhost_virtqueue *vq)
1298 {
1299         int r;
1300         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1301                 return;
1302         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1303         r = put_user(vq->used_flags, &vq->used->flags);
1304         if (r)
1305                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1306                        &vq->used->flags, r);
1307 }