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 static void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  64 {
  65         INIT_LIST_HEAD(&work->node);
  66         work->fn = fn;
  67         init_waitqueue_head(&work->done);
  68         work->flushing = 0;
  69         work->queue_seq = work->done_seq = 0;
  70 }
  71
  72 /* Init poll structure */
  73 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  74                      unsigned long mask, struct vhost_dev *dev)
  75 {
  76         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  77         init_poll_funcptr(&poll->table, vhost_poll_func);
  78         poll->mask = mask;
  79         poll->dev = dev;
  80
  81         vhost_work_init(&poll->work, fn);
  82 }
  83
  84 /* Start polling a file. We add ourselves to file's wait queue. The caller must
  85  * keep a reference to a file until after vhost_poll_stop is called. */
  86 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
  87 {
  88         unsigned long mask;
  89         mask = file->f_op->poll(file, &poll->table);
  90         if (mask)
  91                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  92 }
  93
  94 /* Stop polling a file. After this function returns, it becomes safe to drop the
  95  * file reference. You must also flush afterwards. */
  96 void vhost_poll_stop(struct vhost_poll *poll)
  97 {
  98         remove_wait_queue(poll->wqh, &poll->wait);
  99 }
 100
 101 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 102 {
 103         unsigned seq;
 104         int left;
 105         int flushing;
 106
 107         spin_lock_irq(&dev->work_lock);
 108         seq = work->queue_seq;
 109         work->flushing++;
 110         spin_unlock_irq(&dev->work_lock);
 111         wait_event(work->done, ({
 112                    spin_lock_irq(&dev->work_lock);
 113                    left = seq - work->done_seq <= 0;
 114                    spin_unlock_irq(&dev->work_lock);
 115                    left;
 116         }));
 117         spin_lock_irq(&dev->work_lock);
 118         flushing = --work->flushing;
 119         spin_unlock_irq(&dev->work_lock);
 120         BUG_ON(flushing < 0);
 121 }
 122
 123 /* Flush any work that has been scheduled. When calling this, don't hold any
 124  * locks that are also used by the callback. */
 125 void vhost_poll_flush(struct vhost_poll *poll)
 126 {
 127         vhost_work_flush(poll->dev, &poll->work);
 128 }
 129
 130 static inline void vhost_work_queue(struct vhost_dev *dev,
 131                                     struct vhost_work *work)
 132 {
 133         unsigned long flags;
 134
 135         spin_lock_irqsave(&dev->work_lock, flags);
 136         if (list_empty(&work->node)) {
 137                 list_add_tail(&work->node, &dev->work_list);
 138                 work->queue_seq++;
 139                 wake_up_process(dev->worker);
 140         }
 141         spin_unlock_irqrestore(&dev->work_lock, flags);
 142 }
 143
 144 void vhost_poll_queue(struct vhost_poll *poll)
 145 {
 146         vhost_work_queue(poll->dev, &poll->work);
 147 }
 148
 149 static void vhost_vq_reset(struct vhost_dev *dev,
 150                            struct vhost_virtqueue *vq)
 151 {
 152         vq->num = 1;
 153         vq->desc = NULL;
 154         vq->avail = NULL;
 155         vq->used = NULL;
 156         vq->last_avail_idx = 0;
 157         vq->avail_idx = 0;
 158         vq->last_used_idx = 0;
 159         vq->used_flags = 0;
 160         vq->used_flags = 0;
 161         vq->log_used = false;
 162         vq->log_addr = -1ull;
 163         vq->vhost_hlen = 0;
 164         vq->sock_hlen = 0;
 165         vq->private_data = NULL;
 166         vq->log_base = NULL;
 167         vq->error_ctx = NULL;
 168         vq->error = NULL;
 169         vq->kick = NULL;
 170         vq->call_ctx = NULL;
 171         vq->call = NULL;
 172         vq->log_ctx = NULL;
 173 }
 174
 175 static int vhost_worker(void *data)
 176 {
 177         struct vhost_dev *dev = data;
 178         struct vhost_work *work = NULL;
 179         unsigned uninitialized_var(seq);
 180
 181         for (;;) {
 182                 /* mb paired w/ kthread_stop */
 183                 set_current_state(TASK_INTERRUPTIBLE);
 184
 185                 spin_lock_irq(&dev->work_lock);
 186                 if (work) {
 187                         work->done_seq = seq;
 188                         if (work->flushing)
 189                                 wake_up_all(&work->done);
 190                 }
 191
 192                 if (kthread_should_stop()) {
 193                         spin_unlock_irq(&dev->work_lock);
 194                         __set_current_state(TASK_RUNNING);
 195                         return 0;
 196                 }
 197                 if (!list_empty(&dev->work_list)) {
 198                         work = list_first_entry(&dev->work_list,
 199                                                 struct vhost_work, node);
 200                         list_del_init(&work->node);
 201                         seq = work->queue_seq;
 202                 } else
 203                         work = NULL;
 204                 spin_unlock_irq(&dev->work_lock);
 205
 206                 if (work) {
 207                         __set_current_state(TASK_RUNNING);
 208                         work->fn(work);
 209                 } else
 210                         schedule();
 211
 212         }
 213 }
 214
 215 /* Helper to allocate iovec buffers for all vqs. */
 216 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 217 {
 218         int i;
 219         for (i = 0; i < dev->nvqs; ++i) {
 220                 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
 221                                                UIO_MAXIOV, GFP_KERNEL);
 222                 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
 223                                           GFP_KERNEL);
 224                 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
 225                                             UIO_MAXIOV, GFP_KERNEL);
 226
 227                 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
 228                         !dev->vqs[i].heads)
 229                         goto err_nomem;
 230         }
 231         return 0;
 232 err_nomem:
 233         for (; i >= 0; --i) {
 234                 kfree(dev->vqs[i].indirect);
 235                 kfree(dev->vqs[i].log);
 236                 kfree(dev->vqs[i].heads);
 237         }
 238         return -ENOMEM;
 239 }
 240
 241 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
 242 {
 243         int i;
 244         for (i = 0; i < dev->nvqs; ++i) {
 245                 kfree(dev->vqs[i].indirect);
 246                 dev->vqs[i].indirect = NULL;
 247                 kfree(dev->vqs[i].log);
 248                 dev->vqs[i].log = NULL;
 249                 kfree(dev->vqs[i].heads);
 250                 dev->vqs[i].heads = NULL;
 251         }
 252 }
 253
 254 long vhost_dev_init(struct vhost_dev *dev,
 255                     struct vhost_virtqueue *vqs, int nvqs)
 256 {
 257         int i;
 258
 259         dev->vqs = vqs;
 260         dev->nvqs = nvqs;
 261         mutex_init(&dev->mutex);
 262         dev->log_ctx = NULL;
 263         dev->log_file = NULL;
 264         dev->memory = NULL;
 265         dev->mm = NULL;
 266         spin_lock_init(&dev->work_lock);
 267         INIT_LIST_HEAD(&dev->work_list);
 268         dev->worker = NULL;
 269
 270         for (i = 0; i < dev->nvqs; ++i) {
 271                 dev->vqs[i].log = NULL;
 272                 dev->vqs[i].indirect = NULL;
 273                 dev->vqs[i].heads = NULL;
 274                 dev->vqs[i].dev = dev;
 275                 mutex_init(&dev->vqs[i].mutex);
 276                 vhost_vq_reset(dev, dev->vqs + i);
 277                 if (dev->vqs[i].handle_kick)
 278                         vhost_poll_init(&dev->vqs[i].poll,
 279                                         dev->vqs[i].handle_kick, POLLIN, dev);
 280         }
 281
 282         return 0;
 283 }
 284
 285 /* Caller should have device mutex */
 286 long vhost_dev_check_owner(struct vhost_dev *dev)
 287 {
 288         /* Are you the owner? If not, I don't think you mean to do that */
 289         return dev->mm == current->mm ? 0 : -EPERM;
 290 }
 291
 292 struct vhost_attach_cgroups_struct {
 293         struct vhost_work work;
 294         struct task_struct *owner;
 295         int ret;
 296 };
 297
 298 static void vhost_attach_cgroups_work(struct vhost_work *work)
 299 {
 300         struct vhost_attach_cgroups_struct *s;
 301         s = container_of(work, struct vhost_attach_cgroups_struct, work);
 302         s->ret = cgroup_attach_task_all(s->owner, current);
 303 }
 304
 305 static int vhost_attach_cgroups(struct vhost_dev *dev)
 306 {
 307         struct vhost_attach_cgroups_struct attach;
 308         attach.owner = current;
 309         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 310         vhost_work_queue(dev, &attach.work);
 311         vhost_work_flush(dev, &attach.work);
 312         return attach.ret;
 313 }
 314
 315 /* Caller should have device mutex */
 316 static long vhost_dev_set_owner(struct vhost_dev *dev)
 317 {
 318         struct task_struct *worker;
 319         int err;
 320         /* Is there an owner already? */
 321         if (dev->mm) {
 322                 err = -EBUSY;
 323                 goto err_mm;
 324         }
 325         /* No owner, become one */
 326         dev->mm = get_task_mm(current);
 327         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 328         if (IS_ERR(worker)) {
 329                 err = PTR_ERR(worker);
 330                 goto err_worker;
 331         }
 332
 333         dev->worker = worker;
 334         wake_up_process(worker);        /* avoid contributing to loadavg */
 335
 336         err = vhost_attach_cgroups(dev);
 337         if (err)
 338                 goto err_cgroup;
 339
 340         err = vhost_dev_alloc_iovecs(dev);
 341         if (err)
 342                 goto err_cgroup;
 343
 344         return 0;
 345 err_cgroup:
 346         kthread_stop(worker);
 347         dev->worker = NULL;
 348 err_worker:
 349         if (dev->mm)
 350                 mmput(dev->mm);
 351         dev->mm = NULL;
 352 err_mm:
 353         return err;
 354 }
 355
 356 /* Caller should have device mutex */
 357 long vhost_dev_reset_owner(struct vhost_dev *dev)
 358 {
 359         struct vhost_memory *memory;
 360
 361         /* Restore memory to default empty mapping. */
 362         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 363         if (!memory)
 364                 return -ENOMEM;
 365
 366         vhost_dev_cleanup(dev);
 367
 368         memory->nregions = 0;
 369         dev->memory = memory;
 370         return 0;
 371 }
 372
 373 /* Caller should have device mutex */
 374 void vhost_dev_cleanup(struct vhost_dev *dev)
 375 {
 376         int i;
 377         for (i = 0; i < dev->nvqs; ++i) {
 378                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
 379                         vhost_poll_stop(&dev->vqs[i].poll);
 380                         vhost_poll_flush(&dev->vqs[i].poll);
 381                 }
 382                 if (dev->vqs[i].error_ctx)
 383                         eventfd_ctx_put(dev->vqs[i].error_ctx);
 384                 if (dev->vqs[i].error)
 385                         fput(dev->vqs[i].error);
 386                 if (dev->vqs[i].kick)
 387                         fput(dev->vqs[i].kick);
 388                 if (dev->vqs[i].call_ctx)
 389                         eventfd_ctx_put(dev->vqs[i].call_ctx);
 390                 if (dev->vqs[i].call)
 391                         fput(dev->vqs[i].call);
 392                 vhost_vq_reset(dev, dev->vqs + i);
 393         }
 394         vhost_dev_free_iovecs(dev);
 395         if (dev->log_ctx)
 396                 eventfd_ctx_put(dev->log_ctx);
 397         dev->log_ctx = NULL;
 398         if (dev->log_file)
 399                 fput(dev->log_file);
 400         dev->log_file = NULL;
 401         /* No one will access memory at this point */
 402         kfree(dev->memory);
 403         dev->memory = NULL;
 404         if (dev->mm)
 405                 mmput(dev->mm);
 406         dev->mm = NULL;
 407
 408         WARN_ON(!list_empty(&dev->work_list));
 409         if (dev->worker) {
 410                 kthread_stop(dev->worker);
 411                 dev->worker = NULL;
 412         }
 413 }
 414
 415 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 416 {
 417         u64 a = addr / VHOST_PAGE_SIZE / 8;
 418         /* Make sure 64 bit math will not overflow. */
 419         if (a > ULONG_MAX - (unsigned long)log_base ||
 420             a + (unsigned long)log_base > ULONG_MAX)
 421                 return 0;
 422
 423         return access_ok(VERIFY_WRITE, log_base + a,
 424                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 425 }
 426
 427 /* Caller should have vq mutex and device mutex. */
 428 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 429                                int log_all)
 430 {
 431         int i;
 432
 433         if (!mem)
 434                 return 0;
 435
 436         for (i = 0; i < mem->nregions; ++i) {
 437                 struct vhost_memory_region *m = mem->regions + i;
 438                 unsigned long a = m->userspace_addr;
 439                 if (m->memory_size > ULONG_MAX)
 440                         return 0;
 441                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 442                                     m->memory_size))
 443                         return 0;
 444                 else if (log_all && !log_access_ok(log_base,
 445                                                    m->guest_phys_addr,
 446                                                    m->memory_size))
 447                         return 0;
 448         }
 449         return 1;
 450 }
 451
 452 /* Can we switch to this memory table? */
 453 /* Caller should have device mutex but not vq mutex */
 454 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 455                             int log_all)
 456 {
 457         int i;
 458         for (i = 0; i < d->nvqs; ++i) {
 459                 int ok;
 460                 mutex_lock(&d->vqs[i].mutex);
 461                 /* If ring is inactive, will check when it's enabled. */
 462                 if (d->vqs[i].private_data)
 463                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
 464                                                  log_all);
 465                 else
 466                         ok = 1;
 467                 mutex_unlock(&d->vqs[i].mutex);
 468                 if (!ok)
 469                         return 0;
 470         }
 471         return 1;
 472 }
 473
 474 static int vq_access_ok(unsigned int num,
 475                         struct vring_desc __user *desc,
 476                         struct vring_avail __user *avail,
 477                         struct vring_used __user *used)
 478 {
 479         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 480                access_ok(VERIFY_READ, avail,
 481                          sizeof *avail + num * sizeof *avail->ring) &&
 482                access_ok(VERIFY_WRITE, used,
 483                         sizeof *used + num * sizeof *used->ring);
 484 }
 485
 486 /* Can we log writes? */
 487 /* Caller should have device mutex but not vq mutex */
 488 int vhost_log_access_ok(struct vhost_dev *dev)
 489 {
 490         return memory_access_ok(dev, dev->memory, 1);
 491 }
 492
 493 /* Verify access for write logging. */
 494 /* Caller should have vq mutex and device mutex */
 495 static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
 496 {
 497         return vq_memory_access_ok(log_base, vq->dev->memory,
 498                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 499                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 500                                         sizeof *vq->used +
 501                                         vq->num * sizeof *vq->used->ring));
 502 }
 503
 504 /* Can we start vq? */
 505 /* Caller should have vq mutex and device mutex */
 506 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 507 {
 508         return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
 509                 vq_log_access_ok(vq, vq->log_base);
 510 }
 511
 512 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 513 {
 514         struct vhost_memory mem, *newmem, *oldmem;
 515         unsigned long size = offsetof(struct vhost_memory, regions);
 516         if (copy_from_user(&mem, m, size))
 517                 return -EFAULT;
 518         if (mem.padding)
 519                 return -EOPNOTSUPP;
 520         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 521                 return -E2BIG;
 522         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 523         if (!newmem)
 524                 return -ENOMEM;
 525
 526         memcpy(newmem, &mem, size);
 527         if (copy_from_user(newmem->regions, m->regions,
 528                            mem.nregions * sizeof *m->regions)) {
 529                 kfree(newmem);
 530                 return -EFAULT;
 531         }
 532
 533         if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 534                 kfree(newmem);
 535                 return -EFAULT;
 536         }
 537         oldmem = d->memory;
 538         rcu_assign_pointer(d->memory, newmem);
 539         synchronize_rcu();
 540         kfree(oldmem);
 541         return 0;
 542 }
 543
 544 static int init_used(struct vhost_virtqueue *vq,
 545                      struct vring_used __user *used)
 546 {
 547         int r = put_user(vq->used_flags, &used->flags);
 548         if (r)
 549                 return r;
 550         return get_user(vq->last_used_idx, &used->idx);
 551 }
 552
 553 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 554 {
 555         struct file *eventfp, *filep = NULL,
 556                     *pollstart = NULL, *pollstop = NULL;
 557         struct eventfd_ctx *ctx = NULL;
 558         u32 __user *idxp = argp;
 559         struct vhost_virtqueue *vq;
 560         struct vhost_vring_state s;
 561         struct vhost_vring_file f;
 562         struct vhost_vring_addr a;
 563         u32 idx;
 564         long r;
 565
 566         r = get_user(idx, idxp);
 567         if (r < 0)
 568                 return r;
 569         if (idx >= d->nvqs)
 570                 return -ENOBUFS;
 571
 572         vq = d->vqs + idx;
 573
 574         mutex_lock(&vq->mutex);
 575
 576         switch (ioctl) {
 577         case VHOST_SET_VRING_NUM:
 578                 /* Resizing ring with an active backend?
 579                  * You don't want to do that. */
 580                 if (vq->private_data) {
 581                         r = -EBUSY;
 582                         break;
 583                 }
 584                 if (copy_from_user(&s, argp, sizeof s)) {
 585                         r = -EFAULT;
 586                         break;
 587                 }
 588                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 589                         r = -EINVAL;
 590                         break;
 591                 }
 592                 vq->num = s.num;
 593                 break;
 594         case VHOST_SET_VRING_BASE:
 595                 /* Moving base with an active backend?
 596                  * You don't want to do that. */
 597                 if (vq->private_data) {
 598                         r = -EBUSY;
 599                         break;
 600                 }
 601                 if (copy_from_user(&s, argp, sizeof s)) {
 602                         r = -EFAULT;
 603                         break;
 604                 }
 605                 if (s.num > 0xffff) {
 606                         r = -EINVAL;
 607                         break;
 608                 }
 609                 vq->last_avail_idx = s.num;
 610                 /* Forget the cached index value. */
 611                 vq->avail_idx = vq->last_avail_idx;
 612                 break;
 613         case VHOST_GET_VRING_BASE:
 614                 s.index = idx;
 615                 s.num = vq->last_avail_idx;
 616                 if (copy_to_user(argp, &s, sizeof s))
 617                         r = -EFAULT;
 618                 break;
 619         case VHOST_SET_VRING_ADDR:
 620                 if (copy_from_user(&a, argp, sizeof a)) {
 621                         r = -EFAULT;
 622                         break;
 623                 }
 624                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 625                         r = -EOPNOTSUPP;
 626                         break;
 627                 }
 628                 /* For 32bit, verify that the top 32bits of the user
 629                    data are set to zero. */
 630                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 631                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 632                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 633                         r = -EFAULT;
 634                         break;
 635                 }
 636                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 637                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 638                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 639                         r = -EINVAL;
 640                         break;
 641                 }
 642
 643                 /* We only verify access here if backend is configured.
 644                  * If it is not, we don't as size might not have been setup.
 645                  * We will verify when backend is configured. */
 646                 if (vq->private_data) {
 647                         if (!vq_access_ok(vq->num,
 648                                 (void __user *)(unsigned long)a.desc_user_addr,
 649                                 (void __user *)(unsigned long)a.avail_user_addr,
 650                                 (void __user *)(unsigned long)a.used_user_addr)) {
 651                                 r = -EINVAL;
 652                                 break;
 653                         }
 654
 655                         /* Also validate log access for used ring if enabled. */
 656                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 657                             !log_access_ok(vq->log_base, a.log_guest_addr,
 658                                            sizeof *vq->used +
 659                                            vq->num * sizeof *vq->used->ring)) {
 660                                 r = -EINVAL;
 661                                 break;
 662                         }
 663                 }
 664
 665                 r = init_used(vq, (struct vring_used __user *)(unsigned long)
 666                               a.used_user_addr);
 667                 if (r)
 668                         break;
 669                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 670                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 671                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 672                 vq->log_addr = a.log_guest_addr;
 673                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 674                 break;
 675         case VHOST_SET_VRING_KICK:
 676                 if (copy_from_user(&f, argp, sizeof f)) {
 677                         r = -EFAULT;
 678                         break;
 679                 }
 680                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 681                 if (IS_ERR(eventfp)) {
 682                         r = PTR_ERR(eventfp);
 683                         break;
 684                 }
 685                 if (eventfp != vq->kick) {
 686                         pollstop = filep = vq->kick;
 687                         pollstart = vq->kick = eventfp;
 688                 } else
 689                         filep = eventfp;
 690                 break;
 691         case VHOST_SET_VRING_CALL:
 692                 if (copy_from_user(&f, argp, sizeof f)) {
 693                         r = -EFAULT;
 694                         break;
 695                 }
 696                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 697                 if (IS_ERR(eventfp)) {
 698                         r = PTR_ERR(eventfp);
 699                         break;
 700                 }
 701                 if (eventfp != vq->call) {
 702                         filep = vq->call;
 703                         ctx = vq->call_ctx;
 704                         vq->call = eventfp;
 705                         vq->call_ctx = eventfp ?
 706                                 eventfd_ctx_fileget(eventfp) : NULL;
 707                 } else
 708                         filep = eventfp;
 709                 break;
 710         case VHOST_SET_VRING_ERR:
 711                 if (copy_from_user(&f, argp, sizeof f)) {
 712                         r = -EFAULT;
 713                         break;
 714                 }
 715                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 716                 if (IS_ERR(eventfp)) {
 717                         r = PTR_ERR(eventfp);
 718                         break;
 719                 }
 720                 if (eventfp != vq->error) {
 721                         filep = vq->error;
 722                         vq->error = eventfp;
 723                         ctx = vq->error_ctx;
 724                         vq->error_ctx = eventfp ?
 725                                 eventfd_ctx_fileget(eventfp) : NULL;
 726                 } else
 727                         filep = eventfp;
 728                 break;
 729         default:
 730                 r = -ENOIOCTLCMD;
 731         }
 732
 733         if (pollstop && vq->handle_kick)
 734                 vhost_poll_stop(&vq->poll);
 735
 736         if (ctx)
 737                 eventfd_ctx_put(ctx);
 738         if (filep)
 739                 fput(filep);
 740
 741         if (pollstart && vq->handle_kick)
 742                 vhost_poll_start(&vq->poll, vq->kick);
 743
 744         mutex_unlock(&vq->mutex);
 745
 746         if (pollstop && vq->handle_kick)
 747                 vhost_poll_flush(&vq->poll);
 748         return r;
 749 }
 750
 751 /* Caller must have device mutex */
 752 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 753 {
 754         void __user *argp = (void __user *)arg;
 755         struct file *eventfp, *filep = NULL;
 756         struct eventfd_ctx *ctx = NULL;
 757         u64 p;
 758         long r;
 759         int i, fd;
 760
 761         /* If you are not the owner, you can become one */
 762         if (ioctl == VHOST_SET_OWNER) {
 763                 r = vhost_dev_set_owner(d);
 764                 goto done;
 765         }
 766
 767         /* You must be the owner to do anything else */
 768         r = vhost_dev_check_owner(d);
 769         if (r)
 770                 goto done;
 771
 772         switch (ioctl) {
 773         case VHOST_SET_MEM_TABLE:
 774                 r = vhost_set_memory(d, argp);
 775                 break;
 776         case VHOST_SET_LOG_BASE:
 777                 if (copy_from_user(&p, argp, sizeof p)) {
 778                         r = -EFAULT;
 779                         break;
 780                 }
 781                 if ((u64)(unsigned long)p != p) {
 782                         r = -EFAULT;
 783                         break;
 784                 }
 785                 for (i = 0; i < d->nvqs; ++i) {
 786                         struct vhost_virtqueue *vq;
 787                         void __user *base = (void __user *)(unsigned long)p;
 788                         vq = d->vqs + i;
 789                         mutex_lock(&vq->mutex);
 790                         /* If ring is inactive, will check when it's enabled. */
 791                         if (vq->private_data && !vq_log_access_ok(vq, base))
 792                                 r = -EFAULT;
 793                         else
 794                                 vq->log_base = base;
 795                         mutex_unlock(&vq->mutex);
 796                 }
 797                 break;
 798         case VHOST_SET_LOG_FD:
 799                 r = get_user(fd, (int __user *)argp);
 800                 if (r < 0)
 801                         break;
 802                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 803                 if (IS_ERR(eventfp)) {
 804                         r = PTR_ERR(eventfp);
 805                         break;
 806                 }
 807                 if (eventfp != d->log_file) {
 808                         filep = d->log_file;
 809                         ctx = d->log_ctx;
 810                         d->log_ctx = eventfp ?
 811                                 eventfd_ctx_fileget(eventfp) : NULL;
 812                 } else
 813                         filep = eventfp;
 814                 for (i = 0; i < d->nvqs; ++i) {
 815                         mutex_lock(&d->vqs[i].mutex);
 816                         d->vqs[i].log_ctx = d->log_ctx;
 817                         mutex_unlock(&d->vqs[i].mutex);
 818                 }
 819                 if (ctx)
 820                         eventfd_ctx_put(ctx);
 821                 if (filep)
 822                         fput(filep);
 823                 break;
 824         default:
 825                 r = vhost_set_vring(d, ioctl, argp);
 826                 break;
 827         }
 828 done:
 829         return r;
 830 }
 831
 832 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 833                                                      __u64 addr, __u32 len)
 834 {
 835         struct vhost_memory_region *reg;
 836         int i;
 837         /* linear search is not brilliant, but we really have on the order of 6
 838          * regions in practice */
 839         for (i = 0; i < mem->nregions; ++i) {
 840                 reg = mem->regions + i;
 841                 if (reg->guest_phys_addr <= addr &&
 842                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 843                         return reg;
 844         }
 845         return NULL;
 846 }
 847
 848 /* TODO: This is really inefficient.  We need something like get_user()
 849  * (instruction directly accesses the data, with an exception table entry
 850  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 851  */
 852 static int set_bit_to_user(int nr, void __user *addr)
 853 {
 854         unsigned long log = (unsigned long)addr;
 855         struct page *page;
 856         void *base;
 857         int bit = nr + (log % PAGE_SIZE) * 8;
 858         int r;
 859         r = get_user_pages_fast(log, 1, 1, &page);
 860         if (r < 0)
 861                 return r;
 862         BUG_ON(r != 1);
 863         base = kmap_atomic(page, KM_USER0);
 864         set_bit(bit, base);
 865         kunmap_atomic(base, KM_USER0);
 866         set_page_dirty_lock(page);
 867         put_page(page);
 868         return 0;
 869 }
 870
 871 static int log_write(void __user *log_base,
 872                      u64 write_address, u64 write_length)
 873 {
 874         int r;
 875         if (!write_length)
 876                 return 0;
 877         write_address /= VHOST_PAGE_SIZE;
 878         for (;;) {
 879                 u64 base = (u64)(unsigned long)log_base;
 880                 u64 log = base + write_address / 8;
 881                 int bit = write_address % 8;
 882                 if ((u64)(unsigned long)log != log)
 883                         return -EFAULT;
 884                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 885                 if (r < 0)
 886                         return r;
 887                 if (write_length <= VHOST_PAGE_SIZE)
 888                         break;
 889                 write_length -= VHOST_PAGE_SIZE;
 890                 write_address += VHOST_PAGE_SIZE;
 891         }
 892         return r;
 893 }
 894
 895 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 896                     unsigned int log_num, u64 len)
 897 {
 898         int i, r;
 899
 900         /* Make sure data written is seen before log. */
 901         smp_wmb();
 902         for (i = 0; i < log_num; ++i) {
 903                 u64 l = min(log[i].len, len);
 904                 r = log_write(vq->log_base, log[i].addr, l);
 905                 if (r < 0)
 906                         return r;
 907                 len -= l;
 908                 if (!len) {
 909                         if (vq->log_ctx)
 910                                 eventfd_signal(vq->log_ctx, 1);
 911                         return 0;
 912                 }
 913         }
 914         /* Length written exceeds what we have stored. This is a bug. */
 915         BUG();
 916         return 0;
 917 }
 918
 919 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
 920                           struct iovec iov[], int iov_size)
 921 {
 922         const struct vhost_memory_region *reg;
 923         struct vhost_memory *mem;
 924         struct iovec *_iov;
 925         u64 s = 0;
 926         int ret = 0;
 927
 928         rcu_read_lock();
 929
 930         mem = rcu_dereference(dev->memory);
 931         while ((u64)len > s) {
 932                 u64 size;
 933                 if (unlikely(ret >= iov_size)) {
 934                         ret = -ENOBUFS;
 935                         break;
 936                 }
 937                 reg = find_region(mem, addr, len);
 938                 if (unlikely(!reg)) {
 939                         ret = -EFAULT;
 940                         break;
 941                 }
 942                 _iov = iov + ret;
 943                 size = reg->memory_size - addr + reg->guest_phys_addr;
 944                 _iov->iov_len = min((u64)len, size);
 945                 _iov->iov_base = (void __user *)(unsigned long)
 946                         (reg->userspace_addr + addr - reg->guest_phys_addr);
 947                 s += size;
 948                 addr += size;
 949                 ++ret;
 950         }
 951
 952         rcu_read_unlock();
 953         return ret;
 954 }
 955
 956 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
 957  * function returns the next descriptor in the chain,
 958  * or -1U if we're at the end. */
 959 static unsigned next_desc(struct vring_desc *desc)
 960 {
 961         unsigned int next;
 962
 963         /* If this descriptor says it doesn't chain, we're done. */
 964         if (!(desc->flags & VRING_DESC_F_NEXT))
 965                 return -1U;
 966
 967         /* Check they're not leading us off end of descriptors. */
 968         next = desc->next;
 969         /* Make sure compiler knows to grab that: we don't want it changing! */
 970         /* We will use the result as an index in an array, so most
 971          * architectures only need a compiler barrier here. */
 972         read_barrier_depends();
 973
 974         return next;
 975 }
 976
 977 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
 978                         struct iovec iov[], unsigned int iov_size,
 979                         unsigned int *out_num, unsigned int *in_num,
 980                         struct vhost_log *log, unsigned int *log_num,
 981                         struct vring_desc *indirect)
 982 {
 983         struct vring_desc desc;
 984         unsigned int i = 0, count, found = 0;
 985         int ret;
 986
 987         /* Sanity check */
 988         if (unlikely(indirect->len % sizeof desc)) {
 989                 vq_err(vq, "Invalid length in indirect descriptor: "
 990                        "len 0x%llx not multiple of 0x%zx\n",
 991                        (unsigned long long)indirect->len,
 992                        sizeof desc);
 993                 return -EINVAL;
 994         }
 995
 996         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
 997                              UIO_MAXIOV);
 998         if (unlikely(ret < 0)) {
 999                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1000                 return ret;
1001         }
1002
1003         /* We will use the result as an address to read from, so most
1004          * architectures only need a compiler barrier here. */
1005         read_barrier_depends();
1006
1007         count = indirect->len / sizeof desc;
1008         /* Buffers are chained via a 16 bit next field, so
1009          * we can have at most 2^16 of these. */
1010         if (unlikely(count > USHRT_MAX + 1)) {
1011                 vq_err(vq, "Indirect buffer length too big: %d\n",
1012                        indirect->len);
1013                 return -E2BIG;
1014         }
1015
1016         do {
1017                 unsigned iov_count = *in_num + *out_num;
1018                 if (unlikely(++found > count)) {
1019                         vq_err(vq, "Loop detected: last one at %u "
1020                                "indirect size %u\n",
1021                                i, count);
1022                         return -EINVAL;
1023                 }
1024                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
1025                                               sizeof desc))) {
1026                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1027                                i, (size_t)indirect->addr + i * sizeof desc);
1028                         return -EINVAL;
1029                 }
1030                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1031                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1032                                i, (size_t)indirect->addr + i * sizeof desc);
1033                         return -EINVAL;
1034                 }
1035
1036                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1037                                      iov_size - iov_count);
1038                 if (unlikely(ret < 0)) {
1039                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1040                                ret, i);
1041                         return ret;
1042                 }
1043                 /* If this is an input descriptor, increment that count. */
1044                 if (desc.flags & VRING_DESC_F_WRITE) {
1045                         *in_num += ret;
1046                         if (unlikely(log)) {
1047                                 log[*log_num].addr = desc.addr;
1048                                 log[*log_num].len = desc.len;
1049                                 ++*log_num;
1050                         }
1051                 } else {
1052                         /* If it's an output descriptor, they're all supposed
1053                          * to come before any input descriptors. */
1054                         if (unlikely(*in_num)) {
1055                                 vq_err(vq, "Indirect descriptor "
1056                                        "has out after in: idx %d\n", i);
1057                                 return -EINVAL;
1058                         }
1059                         *out_num += ret;
1060                 }
1061         } while ((i = next_desc(&desc)) != -1);
1062         return 0;
1063 }
1064
1065 /* This looks in the virtqueue and for the first available buffer, and converts
1066  * it to an iovec for convenient access.  Since descriptors consist of some
1067  * number of output then some number of input descriptors, it's actually two
1068  * iovecs, but we pack them into one and note how many of each there were.
1069  *
1070  * This function returns the descriptor number found, or vq->num (which is
1071  * never a valid descriptor number) if none was found.  A negative code is
1072  * returned on error. */
1073 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1074                       struct iovec iov[], unsigned int iov_size,
1075                       unsigned int *out_num, unsigned int *in_num,
1076                       struct vhost_log *log, unsigned int *log_num)
1077 {
1078         struct vring_desc desc;
1079         unsigned int i, head, found = 0;
1080         u16 last_avail_idx;
1081         int ret;
1082
1083         /* Check it isn't doing very strange things with descriptor numbers. */
1084         last_avail_idx = vq->last_avail_idx;
1085         if (unlikely(get_user(vq->avail_idx, &vq->avail->idx))) {
1086                 vq_err(vq, "Failed to access avail idx at %p\n",
1087                        &vq->avail->idx);
1088                 return -EFAULT;
1089         }
1090
1091         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1092                 vq_err(vq, "Guest moved used index from %u to %u",
1093                        last_avail_idx, vq->avail_idx);
1094                 return -EFAULT;
1095         }
1096
1097         /* If there's nothing new since last we looked, return invalid. */
1098         if (vq->avail_idx == last_avail_idx)
1099                 return vq->num;
1100
1101         /* Only get avail ring entries after they have been exposed by guest. */
1102         smp_rmb();
1103
1104         /* Grab the next descriptor number they're advertising, and increment
1105          * the index we've seen. */
1106         if (unlikely(get_user(head,
1107                               &vq->avail->ring[last_avail_idx % vq->num]))) {
1108                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1109                        last_avail_idx,
1110                        &vq->avail->ring[last_avail_idx % vq->num]);
1111                 return -EFAULT;
1112         }
1113
1114         /* If their number is silly, that's an error. */
1115         if (unlikely(head >= vq->num)) {
1116                 vq_err(vq, "Guest says index %u > %u is available",
1117                        head, vq->num);
1118                 return -EINVAL;
1119         }
1120
1121         /* When we start there are none of either input nor output. */
1122         *out_num = *in_num = 0;
1123         if (unlikely(log))
1124                 *log_num = 0;
1125
1126         i = head;
1127         do {
1128                 unsigned iov_count = *in_num + *out_num;
1129                 if (unlikely(i >= vq->num)) {
1130                         vq_err(vq, "Desc index is %u > %u, head = %u",
1131                                i, vq->num, head);
1132                         return -EINVAL;
1133                 }
1134                 if (unlikely(++found > vq->num)) {
1135                         vq_err(vq, "Loop detected: last one at %u "
1136                                "vq size %u head %u\n",
1137                                i, vq->num, head);
1138                         return -EINVAL;
1139                 }
1140                 ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
1141                 if (unlikely(ret)) {
1142                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1143                                i, vq->desc + i);
1144                         return -EFAULT;
1145                 }
1146                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1147                         ret = get_indirect(dev, vq, iov, iov_size,
1148                                            out_num, in_num,
1149                                            log, log_num, &desc);
1150                         if (unlikely(ret < 0)) {
1151                                 vq_err(vq, "Failure detected "
1152                                        "in indirect descriptor at idx %d\n", i);
1153                                 return ret;
1154                         }
1155                         continue;
1156                 }
1157
1158                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1159                                      iov_size - iov_count);
1160                 if (unlikely(ret < 0)) {
1161                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1162                                ret, i);
1163                         return ret;
1164                 }
1165                 if (desc.flags & VRING_DESC_F_WRITE) {
1166                         /* If this is an input descriptor,
1167                          * increment that count. */
1168                         *in_num += ret;
1169                         if (unlikely(log)) {
1170                                 log[*log_num].addr = desc.addr;
1171                                 log[*log_num].len = desc.len;
1172                                 ++*log_num;
1173                         }
1174                 } else {
1175                         /* If it's an output descriptor, they're all supposed
1176                          * to come before any input descriptors. */
1177                         if (unlikely(*in_num)) {
1178                                 vq_err(vq, "Descriptor has out after in: "
1179                                        "idx %d\n", i);
1180                                 return -EINVAL;
1181                         }
1182                         *out_num += ret;
1183                 }
1184         } while ((i = next_desc(&desc)) != -1);
1185
1186         /* On success, increment avail index. */
1187         vq->last_avail_idx++;
1188         return head;
1189 }
1190
1191 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1192 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1193 {
1194         vq->last_avail_idx -= n;
1195 }
1196
1197 /* After we've used one of their buffers, we tell them about it.  We'll then
1198  * want to notify the guest, using eventfd. */
1199 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1200 {
1201         struct vring_used_elem __user *used;
1202
1203         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1204          * next entry in that used ring. */
1205         used = &vq->used->ring[vq->last_used_idx % vq->num];
1206         if (put_user(head, &used->id)) {
1207                 vq_err(vq, "Failed to write used id");
1208                 return -EFAULT;
1209         }
1210         if (put_user(len, &used->len)) {
1211                 vq_err(vq, "Failed to write used len");
1212                 return -EFAULT;
1213         }
1214         /* Make sure buffer is written before we update index. */
1215         smp_wmb();
1216         if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1217                 vq_err(vq, "Failed to increment used idx");
1218                 return -EFAULT;
1219         }
1220         if (unlikely(vq->log_used)) {
1221                 /* Make sure data is seen before log. */
1222                 smp_wmb();
1223                 /* Log used ring entry write. */
1224                 log_write(vq->log_base,
1225                           vq->log_addr +
1226                            ((void __user *)used - (void __user *)vq->used),
1227                           sizeof *used);
1228                 /* Log used index update. */
1229                 log_write(vq->log_base,
1230                           vq->log_addr + offsetof(struct vring_used, idx),
1231                           sizeof vq->used->idx);
1232                 if (vq->log_ctx)
1233                         eventfd_signal(vq->log_ctx, 1);
1234         }
1235         vq->last_used_idx++;
1236         return 0;
1237 }
1238
1239 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1240                             struct vring_used_elem *heads,
1241                             unsigned count)
1242 {
1243         struct vring_used_elem __user *used;
1244         int start;
1245
1246         start = vq->last_used_idx % vq->num;
1247         used = vq->used->ring + start;
1248         if (copy_to_user(used, heads, count * sizeof *used)) {
1249                 vq_err(vq, "Failed to write used");
1250                 return -EFAULT;
1251         }
1252         if (unlikely(vq->log_used)) {
1253                 /* Make sure data is seen before log. */
1254                 smp_wmb();
1255                 /* Log used ring entry write. */
1256                 log_write(vq->log_base,
1257                           vq->log_addr +
1258                            ((void __user *)used - (void __user *)vq->used),
1259                           count * sizeof *used);
1260         }
1261         vq->last_used_idx += count;
1262         return 0;
1263 }
1264
1265 /* After we've used one of their buffers, we tell them about it.  We'll then
1266  * want to notify the guest, using eventfd. */
1267 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1268                      unsigned count)
1269 {
1270         int start, n, r;
1271
1272         start = vq->last_used_idx % vq->num;
1273         n = vq->num - start;
1274         if (n < count) {
1275                 r = __vhost_add_used_n(vq, heads, n);
1276                 if (r < 0)
1277                         return r;
1278                 heads += n;
1279                 count -= n;
1280         }
1281         r = __vhost_add_used_n(vq, heads, count);
1282
1283         /* Make sure buffer is written before we update index. */
1284         smp_wmb();
1285         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1286                 vq_err(vq, "Failed to increment used idx");
1287                 return -EFAULT;
1288         }
1289         if (unlikely(vq->log_used)) {
1290                 /* Log used index update. */
1291                 log_write(vq->log_base,
1292                           vq->log_addr + offsetof(struct vring_used, idx),
1293                           sizeof vq->used->idx);
1294                 if (vq->log_ctx)
1295                         eventfd_signal(vq->log_ctx, 1);
1296         }
1297         return r;
1298 }
1299
1300 /* This actually signals the guest, using eventfd. */
1301 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1302 {
1303         __u16 flags;
1304         /* Flush out used index updates. This is paired
1305          * with the barrier that the Guest executes when enabling
1306          * interrupts. */
1307         smp_mb();
1308
1309         if (get_user(flags, &vq->avail->flags)) {
1310                 vq_err(vq, "Failed to get flags");
1311                 return;
1312         }
1313
1314         /* If they don't want an interrupt, don't signal, unless empty. */
1315         if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1316             (vq->avail_idx != vq->last_avail_idx ||
1317              !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1318                 return;
1319
1320         /* Signal the Guest tell them we used something up. */
1321         if (vq->call_ctx)
1322                 eventfd_signal(vq->call_ctx, 1);
1323 }
1324
1325 /* And here's the combo meal deal.  Supersize me! */
1326 void vhost_add_used_and_signal(struct vhost_dev *dev,
1327                                struct vhost_virtqueue *vq,
1328                                unsigned int head, int len)
1329 {
1330         vhost_add_used(vq, head, len);
1331         vhost_signal(dev, vq);
1332 }
1333
1334 /* multi-buffer version of vhost_add_used_and_signal */
1335 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1336                                  struct vhost_virtqueue *vq,
1337                                  struct vring_used_elem *heads, unsigned count)
1338 {
1339         vhost_add_used_n(vq, heads, count);
1340         vhost_signal(dev, vq);
1341 }
1342
1343 /* OK, now we need to know about added descriptors. */
1344 bool vhost_enable_notify(struct vhost_virtqueue *vq)
1345 {
1346         u16 avail_idx;
1347         int r;
1348         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1349                 return false;
1350         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1351         r = put_user(vq->used_flags, &vq->used->flags);
1352         if (r) {
1353                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1354                        &vq->used->flags, r);
1355                 return false;
1356         }
1357         /* They could have slipped one in as we were doing that: make
1358          * sure it's written, then check again. */
1359         smp_mb();
1360         r = get_user(avail_idx, &vq->avail->idx);
1361         if (r) {
1362                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1363                        &vq->avail->idx, r);
1364                 return false;
1365         }
1366
1367         return avail_idx != vq->avail_idx;
1368 }
1369
1370 /* We don't need to be notified again. */
1371 void vhost_disable_notify(struct vhost_virtqueue *vq)
1372 {
1373         int r;
1374         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1375                 return;
1376         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1377         r = put_user(vq->used_flags, &vq->used->flags);
1378         if (r)
1379                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1380                        &vq->used->flags, r);
1381 }