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/virtual/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/uio.h>
  17 #include <linux/mm.h>
  18 #include <linux/mmu_context.h>
  19 #include <linux/miscdevice.h>
  20 #include <linux/mutex.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 #include <linux/module.h>
  28
  29 #include "vhost.h"
  30
  31 enum {
  32         VHOST_MEMORY_MAX_NREGIONS = 64,
  33         VHOST_MEMORY_F_LOG = 0x1,
  34 };
  35
  36 #define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
  37 #define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
  38
  39 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  40                             poll_table *pt)
  41 {
  42         struct vhost_poll *poll;
  43
  44         poll = container_of(pt, struct vhost_poll, table);
  45         poll->wqh = wqh;
  46         add_wait_queue(wqh, &poll->wait);
  47 }
  48
  49 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
  50                              void *key)
  51 {
  52         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  53
  54         if (!((unsigned long)key & poll->mask))
  55                 return 0;
  56
  57         vhost_poll_queue(poll);
  58         return 0;
  59 }
  60
  61 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  62 {
  63         INIT_LIST_HEAD(&work->node);
  64         work->fn = fn;
  65         init_waitqueue_head(&work->done);
  66         work->flushing = 0;
  67         work->queue_seq = work->done_seq = 0;
  68 }
  69 EXPORT_SYMBOL_GPL(vhost_work_init);
  70
  71 /* Init poll structure */
  72 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  73                      unsigned long mask, struct vhost_dev *dev)
  74 {
  75         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  76         init_poll_funcptr(&poll->table, vhost_poll_func);
  77         poll->mask = mask;
  78         poll->dev = dev;
  79         poll->wqh = NULL;
  80
  81         vhost_work_init(&poll->work, fn);
  82 }
  83 EXPORT_SYMBOL_GPL(vhost_poll_init);
  84
  85 /* Start polling a file. We add ourselves to file's wait queue. The caller must
  86  * keep a reference to a file until after vhost_poll_stop is called. */
  87 int vhost_poll_start(struct vhost_poll *poll, struct file *file)
  88 {
  89         unsigned long mask;
  90         int ret = 0;
  91
  92         if (poll->wqh)
  93                 return 0;
  94
  95         mask = file->f_op->poll(file, &poll->table);
  96         if (mask)
  97                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  98         if (mask & POLLERR) {
  99                 if (poll->wqh)
 100                         remove_wait_queue(poll->wqh, &poll->wait);
 101                 ret = -EINVAL;
 102         }
 103
 104         return ret;
 105 }
 106 EXPORT_SYMBOL_GPL(vhost_poll_start);
 107
 108 /* Stop polling a file. After this function returns, it becomes safe to drop the
 109  * file reference. You must also flush afterwards. */
 110 void vhost_poll_stop(struct vhost_poll *poll)
 111 {
 112         if (poll->wqh) {
 113                 remove_wait_queue(poll->wqh, &poll->wait);
 114                 poll->wqh = NULL;
 115         }
 116 }
 117 EXPORT_SYMBOL_GPL(vhost_poll_stop);
 118
 119 static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
 120                                 unsigned seq)
 121 {
 122         int left;
 123
 124         spin_lock_irq(&dev->work_lock);
 125         left = seq - work->done_seq;
 126         spin_unlock_irq(&dev->work_lock);
 127         return left <= 0;
 128 }
 129
 130 void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 131 {
 132         unsigned seq;
 133         int flushing;
 134
 135         spin_lock_irq(&dev->work_lock);
 136         seq = work->queue_seq;
 137         work->flushing++;
 138         spin_unlock_irq(&dev->work_lock);
 139         wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 140         spin_lock_irq(&dev->work_lock);
 141         flushing = --work->flushing;
 142         spin_unlock_irq(&dev->work_lock);
 143         BUG_ON(flushing < 0);
 144 }
 145 EXPORT_SYMBOL_GPL(vhost_work_flush);
 146
 147 /* Flush any work that has been scheduled. When calling this, don't hold any
 148  * locks that are also used by the callback. */
 149 void vhost_poll_flush(struct vhost_poll *poll)
 150 {
 151         vhost_work_flush(poll->dev, &poll->work);
 152 }
 153 EXPORT_SYMBOL_GPL(vhost_poll_flush);
 154
 155 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 156 {
 157         unsigned long flags;
 158
 159         spin_lock_irqsave(&dev->work_lock, flags);
 160         if (list_empty(&work->node)) {
 161                 list_add_tail(&work->node, &dev->work_list);
 162                 work->queue_seq++;
 163                 spin_unlock_irqrestore(&dev->work_lock, flags);
 164                 wake_up_process(dev->worker);
 165         } else {
 166                 spin_unlock_irqrestore(&dev->work_lock, flags);
 167         }
 168 }
 169 EXPORT_SYMBOL_GPL(vhost_work_queue);
 170
 171 void vhost_poll_queue(struct vhost_poll *poll)
 172 {
 173         vhost_work_queue(poll->dev, &poll->work);
 174 }
 175 EXPORT_SYMBOL_GPL(vhost_poll_queue);
 176
 177 static void vhost_vq_reset(struct vhost_dev *dev,
 178                            struct vhost_virtqueue *vq)
 179 {
 180         vq->num = 1;
 181         vq->desc = NULL;
 182         vq->avail = NULL;
 183         vq->used = NULL;
 184         vq->last_avail_idx = 0;
 185         vq->avail_idx = 0;
 186         vq->last_used_idx = 0;
 187         vq->signalled_used = 0;
 188         vq->signalled_used_valid = false;
 189         vq->used_flags = 0;
 190         vq->log_used = false;
 191         vq->log_addr = -1ull;
 192         vq->private_data = NULL;
 193         vq->acked_features = 0;
 194         vq->log_base = NULL;
 195         vq->error_ctx = NULL;
 196         vq->error = NULL;
 197         vq->kick = NULL;
 198         vq->call_ctx = NULL;
 199         vq->call = NULL;
 200         vq->log_ctx = NULL;
 201         vq->memory = NULL;
 202 }
 203
 204 static int vhost_worker(void *data)
 205 {
 206         struct vhost_dev *dev = data;
 207         struct vhost_work *work = NULL;
 208         unsigned uninitialized_var(seq);
 209         mm_segment_t oldfs = get_fs();
 210
 211         set_fs(USER_DS);
 212         use_mm(dev->mm);
 213
 214         for (;;) {
 215                 /* mb paired w/ kthread_stop */
 216                 set_current_state(TASK_INTERRUPTIBLE);
 217
 218                 spin_lock_irq(&dev->work_lock);
 219                 if (work) {
 220                         work->done_seq = seq;
 221                         if (work->flushing)
 222                                 wake_up_all(&work->done);
 223                 }
 224
 225                 if (kthread_should_stop()) {
 226                         spin_unlock_irq(&dev->work_lock);
 227                         __set_current_state(TASK_RUNNING);
 228                         break;
 229                 }
 230                 if (!list_empty(&dev->work_list)) {
 231                         work = list_first_entry(&dev->work_list,
 232                                                 struct vhost_work, node);
 233                         list_del_init(&work->node);
 234                         seq = work->queue_seq;
 235                 } else
 236                         work = NULL;
 237                 spin_unlock_irq(&dev->work_lock);
 238
 239                 if (work) {
 240                         __set_current_state(TASK_RUNNING);
 241                         work->fn(work);
 242                         if (need_resched())
 243                                 schedule();
 244                 } else
 245                         schedule();
 246
 247         }
 248         unuse_mm(dev->mm);
 249         set_fs(oldfs);
 250         return 0;
 251 }
 252
 253 static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
 254 {
 255         kfree(vq->indirect);
 256         vq->indirect = NULL;
 257         kfree(vq->log);
 258         vq->log = NULL;
 259         kfree(vq->heads);
 260         vq->heads = NULL;
 261 }
 262
 263 /* Helper to allocate iovec buffers for all vqs. */
 264 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 265 {
 266         struct vhost_virtqueue *vq;
 267         int i;
 268
 269         for (i = 0; i < dev->nvqs; ++i) {
 270                 vq = dev->vqs[i];
 271                 vq->indirect = kmalloc(sizeof *vq->indirect * UIO_MAXIOV,
 272                                        GFP_KERNEL);
 273                 vq->log = kmalloc(sizeof *vq->log * UIO_MAXIOV, GFP_KERNEL);
 274                 vq->heads = kmalloc(sizeof *vq->heads * UIO_MAXIOV, GFP_KERNEL);
 275                 if (!vq->indirect || !vq->log || !vq->heads)
 276                         goto err_nomem;
 277         }
 278         return 0;
 279
 280 err_nomem:
 281         for (; i >= 0; --i)
 282                 vhost_vq_free_iovecs(dev->vqs[i]);
 283         return -ENOMEM;
 284 }
 285
 286 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
 287 {
 288         int i;
 289
 290         for (i = 0; i < dev->nvqs; ++i)
 291                 vhost_vq_free_iovecs(dev->vqs[i]);
 292 }
 293
 294 void vhost_dev_init(struct vhost_dev *dev,
 295                     struct vhost_virtqueue **vqs, int nvqs)
 296 {
 297         struct vhost_virtqueue *vq;
 298         int i;
 299
 300         dev->vqs = vqs;
 301         dev->nvqs = nvqs;
 302         mutex_init(&dev->mutex);
 303         dev->log_ctx = NULL;
 304         dev->log_file = NULL;
 305         dev->memory = NULL;
 306         dev->mm = NULL;
 307         spin_lock_init(&dev->work_lock);
 308         INIT_LIST_HEAD(&dev->work_list);
 309         dev->worker = NULL;
 310
 311         for (i = 0; i < dev->nvqs; ++i) {
 312                 vq = dev->vqs[i];
 313                 vq->log = NULL;
 314                 vq->indirect = NULL;
 315                 vq->heads = NULL;
 316                 vq->dev = dev;
 317                 mutex_init(&vq->mutex);
 318                 vhost_vq_reset(dev, vq);
 319                 if (vq->handle_kick)
 320                         vhost_poll_init(&vq->poll, vq->handle_kick,
 321                                         POLLIN, dev);
 322         }
 323 }
 324 EXPORT_SYMBOL_GPL(vhost_dev_init);
 325
 326 /* Caller should have device mutex */
 327 long vhost_dev_check_owner(struct vhost_dev *dev)
 328 {
 329         /* Are you the owner? If not, I don't think you mean to do that */
 330         return dev->mm == current->mm ? 0 : -EPERM;
 331 }
 332 EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
 333
 334 struct vhost_attach_cgroups_struct {
 335         struct vhost_work work;
 336         struct task_struct *owner;
 337         int ret;
 338 };
 339
 340 static void vhost_attach_cgroups_work(struct vhost_work *work)
 341 {
 342         struct vhost_attach_cgroups_struct *s;
 343
 344         s = container_of(work, struct vhost_attach_cgroups_struct, work);
 345         s->ret = cgroup_attach_task_all(s->owner, current);
 346 }
 347
 348 static int vhost_attach_cgroups(struct vhost_dev *dev)
 349 {
 350         struct vhost_attach_cgroups_struct attach;
 351
 352         attach.owner = current;
 353         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 354         vhost_work_queue(dev, &attach.work);
 355         vhost_work_flush(dev, &attach.work);
 356         return attach.ret;
 357 }
 358
 359 /* Caller should have device mutex */
 360 bool vhost_dev_has_owner(struct vhost_dev *dev)
 361 {
 362         return dev->mm;
 363 }
 364 EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
 365
 366 /* Caller should have device mutex */
 367 long vhost_dev_set_owner(struct vhost_dev *dev)
 368 {
 369         struct task_struct *worker;
 370         int err;
 371
 372         /* Is there an owner already? */
 373         if (vhost_dev_has_owner(dev)) {
 374                 err = -EBUSY;
 375                 goto err_mm;
 376         }
 377
 378         /* No owner, become one */
 379         dev->mm = get_task_mm(current);
 380         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 381         if (IS_ERR(worker)) {
 382                 err = PTR_ERR(worker);
 383                 goto err_worker;
 384         }
 385
 386         dev->worker = worker;
 387         wake_up_process(worker);        /* avoid contributing to loadavg */
 388
 389         err = vhost_attach_cgroups(dev);
 390         if (err)
 391                 goto err_cgroup;
 392
 393         err = vhost_dev_alloc_iovecs(dev);
 394         if (err)
 395                 goto err_cgroup;
 396
 397         return 0;
 398 err_cgroup:
 399         kthread_stop(worker);
 400         dev->worker = NULL;
 401 err_worker:
 402         if (dev->mm)
 403                 mmput(dev->mm);
 404         dev->mm = NULL;
 405 err_mm:
 406         return err;
 407 }
 408 EXPORT_SYMBOL_GPL(vhost_dev_set_owner);
 409
 410 struct vhost_memory *vhost_dev_reset_owner_prepare(void)
 411 {
 412         return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 413 }
 414 EXPORT_SYMBOL_GPL(vhost_dev_reset_owner_prepare);
 415
 416 /* Caller should have device mutex */
 417 void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory *memory)
 418 {
 419         int i;
 420
 421         vhost_dev_cleanup(dev, true);
 422
 423         /* Restore memory to default empty mapping. */
 424         memory->nregions = 0;
 425         dev->memory = memory;
 426         /* We don't need VQ locks below since vhost_dev_cleanup makes sure
 427          * VQs aren't running.
 428          */
 429         for (i = 0; i < dev->nvqs; ++i)
 430                 dev->vqs[i]->memory = memory;
 431 }
 432 EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
 433
 434 void vhost_dev_stop(struct vhost_dev *dev)
 435 {
 436         int i;
 437
 438         for (i = 0; i < dev->nvqs; ++i) {
 439                 if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
 440                         vhost_poll_stop(&dev->vqs[i]->poll);
 441                         vhost_poll_flush(&dev->vqs[i]->poll);
 442                 }
 443         }
 444 }
 445 EXPORT_SYMBOL_GPL(vhost_dev_stop);
 446
 447 /* Caller should have device mutex if and only if locked is set */
 448 void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 449 {
 450         int i;
 451
 452         for (i = 0; i < dev->nvqs; ++i) {
 453                 if (dev->vqs[i]->error_ctx)
 454                         eventfd_ctx_put(dev->vqs[i]->error_ctx);
 455                 if (dev->vqs[i]->error)
 456                         fput(dev->vqs[i]->error);
 457                 if (dev->vqs[i]->kick)
 458                         fput(dev->vqs[i]->kick);
 459                 if (dev->vqs[i]->call_ctx)
 460                         eventfd_ctx_put(dev->vqs[i]->call_ctx);
 461                 if (dev->vqs[i]->call)
 462                         fput(dev->vqs[i]->call);
 463                 vhost_vq_reset(dev, dev->vqs[i]);
 464         }
 465         vhost_dev_free_iovecs(dev);
 466         if (dev->log_ctx)
 467                 eventfd_ctx_put(dev->log_ctx);
 468         dev->log_ctx = NULL;
 469         if (dev->log_file)
 470                 fput(dev->log_file);
 471         dev->log_file = NULL;
 472         /* No one will access memory at this point */
 473         kfree(dev->memory);
 474         dev->memory = NULL;
 475         WARN_ON(!list_empty(&dev->work_list));
 476         if (dev->worker) {
 477                 kthread_stop(dev->worker);
 478                 dev->worker = NULL;
 479         }
 480         if (dev->mm)
 481                 mmput(dev->mm);
 482         dev->mm = NULL;
 483 }
 484 EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
 485
 486 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 487 {
 488         u64 a = addr / VHOST_PAGE_SIZE / 8;
 489
 490         /* Make sure 64 bit math will not overflow. */
 491         if (a > ULONG_MAX - (unsigned long)log_base ||
 492             a + (unsigned long)log_base > ULONG_MAX)
 493                 return 0;
 494
 495         return access_ok(VERIFY_WRITE, log_base + a,
 496                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 497 }
 498
 499 /* Caller should have vq mutex and device mutex. */
 500 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 501                                int log_all)
 502 {
 503         int i;
 504
 505         if (!mem)
 506                 return 0;
 507
 508         for (i = 0; i < mem->nregions; ++i) {
 509                 struct vhost_memory_region *m = mem->regions + i;
 510                 unsigned long a = m->userspace_addr;
 511                 if (m->memory_size > ULONG_MAX)
 512                         return 0;
 513                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 514                                     m->memory_size))
 515                         return 0;
 516                 else if (log_all && !log_access_ok(log_base,
 517                                                    m->guest_phys_addr,
 518                                                    m->memory_size))
 519                         return 0;
 520         }
 521         return 1;
 522 }
 523
 524 /* Can we switch to this memory table? */
 525 /* Caller should have device mutex but not vq mutex */
 526 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 527                             int log_all)
 528 {
 529         int i;
 530
 531         for (i = 0; i < d->nvqs; ++i) {
 532                 int ok;
 533                 bool log;
 534
 535                 mutex_lock(&d->vqs[i]->mutex);
 536                 log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
 537                 /* If ring is inactive, will check when it's enabled. */
 538                 if (d->vqs[i]->private_data)
 539                         ok = vq_memory_access_ok(d->vqs[i]->log_base, mem, log);
 540                 else
 541                         ok = 1;
 542                 mutex_unlock(&d->vqs[i]->mutex);
 543                 if (!ok)
 544                         return 0;
 545         }
 546         return 1;
 547 }
 548
 549 static int vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
 550                         struct vring_desc __user *desc,
 551                         struct vring_avail __user *avail,
 552                         struct vring_used __user *used)
 553 {
 554         size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 555         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 556                access_ok(VERIFY_READ, avail,
 557                          sizeof *avail + num * sizeof *avail->ring + s) &&
 558                access_ok(VERIFY_WRITE, used,
 559                         sizeof *used + num * sizeof *used->ring + s);
 560 }
 561
 562 /* Can we log writes? */
 563 /* Caller should have device mutex but not vq mutex */
 564 int vhost_log_access_ok(struct vhost_dev *dev)
 565 {
 566         return memory_access_ok(dev, dev->memory, 1);
 567 }
 568 EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 569
 570 /* Verify access for write logging. */
 571 /* Caller should have vq mutex and device mutex */
 572 static int vq_log_access_ok(struct vhost_virtqueue *vq,
 573                             void __user *log_base)
 574 {
 575         size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 576
 577         return vq_memory_access_ok(log_base, vq->memory,
 578                                    vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
 579                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 580                                         sizeof *vq->used +
 581                                         vq->num * sizeof *vq->used->ring + s));
 582 }
 583
 584 /* Can we start vq? */
 585 /* Caller should have vq mutex and device mutex */
 586 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 587 {
 588         return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used) &&
 589                 vq_log_access_ok(vq, vq->log_base);
 590 }
 591 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
 592
 593 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 594 {
 595         struct vhost_memory mem, *newmem, *oldmem;
 596         unsigned long size = offsetof(struct vhost_memory, regions);
 597         int i;
 598
 599         if (copy_from_user(&mem, m, size))
 600                 return -EFAULT;
 601         if (mem.padding)
 602                 return -EOPNOTSUPP;
 603         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 604                 return -E2BIG;
 605         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 606         if (!newmem)
 607                 return -ENOMEM;
 608
 609         memcpy(newmem, &mem, size);
 610         if (copy_from_user(newmem->regions, m->regions,
 611                            mem.nregions * sizeof *m->regions)) {
 612                 kfree(newmem);
 613                 return -EFAULT;
 614         }
 615
 616         if (!memory_access_ok(d, newmem, 0)) {
 617                 kfree(newmem);
 618                 return -EFAULT;
 619         }
 620         oldmem = d->memory;
 621         d->memory = newmem;
 622
 623         /* All memory accesses are done under some VQ mutex. */
 624         for (i = 0; i < d->nvqs; ++i) {
 625                 mutex_lock(&d->vqs[i]->mutex);
 626                 d->vqs[i]->memory = newmem;
 627                 mutex_unlock(&d->vqs[i]->mutex);
 628         }
 629         kfree(oldmem);
 630         return 0;
 631 }
 632
 633 long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
 634 {
 635         struct file *eventfp, *filep = NULL;
 636         bool pollstart = false, pollstop = false;
 637         struct eventfd_ctx *ctx = NULL;
 638         u32 __user *idxp = argp;
 639         struct vhost_virtqueue *vq;
 640         struct vhost_vring_state s;
 641         struct vhost_vring_file f;
 642         struct vhost_vring_addr a;
 643         u32 idx;
 644         long r;
 645
 646         r = get_user(idx, idxp);
 647         if (r < 0)
 648                 return r;
 649         if (idx >= d->nvqs)
 650                 return -ENOBUFS;
 651
 652         vq = d->vqs[idx];
 653
 654         mutex_lock(&vq->mutex);
 655
 656         switch (ioctl) {
 657         case VHOST_SET_VRING_NUM:
 658                 /* Resizing ring with an active backend?
 659                  * You don't want to do that. */
 660                 if (vq->private_data) {
 661                         r = -EBUSY;
 662                         break;
 663                 }
 664                 if (copy_from_user(&s, argp, sizeof s)) {
 665                         r = -EFAULT;
 666                         break;
 667                 }
 668                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 669                         r = -EINVAL;
 670                         break;
 671                 }
 672                 vq->num = s.num;
 673                 break;
 674         case VHOST_SET_VRING_BASE:
 675                 /* Moving base with an active backend?
 676                  * You don't want to do that. */
 677                 if (vq->private_data) {
 678                         r = -EBUSY;
 679                         break;
 680                 }
 681                 if (copy_from_user(&s, argp, sizeof s)) {
 682                         r = -EFAULT;
 683                         break;
 684                 }
 685                 if (s.num > 0xffff) {
 686                         r = -EINVAL;
 687                         break;
 688                 }
 689                 vq->last_avail_idx = s.num;
 690                 /* Forget the cached index value. */
 691                 vq->avail_idx = vq->last_avail_idx;
 692                 break;
 693         case VHOST_GET_VRING_BASE:
 694                 s.index = idx;
 695                 s.num = vq->last_avail_idx;
 696                 if (copy_to_user(argp, &s, sizeof s))
 697                         r = -EFAULT;
 698                 break;
 699         case VHOST_SET_VRING_ADDR:
 700                 if (copy_from_user(&a, argp, sizeof a)) {
 701                         r = -EFAULT;
 702                         break;
 703                 }
 704                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 705                         r = -EOPNOTSUPP;
 706                         break;
 707                 }
 708                 /* For 32bit, verify that the top 32bits of the user
 709                    data are set to zero. */
 710                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 711                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 712                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 713                         r = -EFAULT;
 714                         break;
 715                 }
 716                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 717                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 718                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 719                         r = -EINVAL;
 720                         break;
 721                 }
 722
 723                 /* We only verify access here if backend is configured.
 724                  * If it is not, we don't as size might not have been setup.
 725                  * We will verify when backend is configured. */
 726                 if (vq->private_data) {
 727                         if (!vq_access_ok(vq, vq->num,
 728                                 (void __user *)(unsigned long)a.desc_user_addr,
 729                                 (void __user *)(unsigned long)a.avail_user_addr,
 730                                 (void __user *)(unsigned long)a.used_user_addr)) {
 731                                 r = -EINVAL;
 732                                 break;
 733                         }
 734
 735                         /* Also validate log access for used ring if enabled. */
 736                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 737                             !log_access_ok(vq->log_base, a.log_guest_addr,
 738                                            sizeof *vq->used +
 739                                            vq->num * sizeof *vq->used->ring)) {
 740                                 r = -EINVAL;
 741                                 break;
 742                         }
 743                 }
 744
 745                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 746                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 747                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 748                 vq->log_addr = a.log_guest_addr;
 749                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 750                 break;
 751         case VHOST_SET_VRING_KICK:
 752                 if (copy_from_user(&f, argp, sizeof f)) {
 753                         r = -EFAULT;
 754                         break;
 755                 }
 756                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 757                 if (IS_ERR(eventfp)) {
 758                         r = PTR_ERR(eventfp);
 759                         break;
 760                 }
 761                 if (eventfp != vq->kick) {
 762                         pollstop = (filep = vq->kick) != NULL;
 763                         pollstart = (vq->kick = eventfp) != NULL;
 764                 } else
 765                         filep = eventfp;
 766                 break;
 767         case VHOST_SET_VRING_CALL:
 768                 if (copy_from_user(&f, argp, sizeof f)) {
 769                         r = -EFAULT;
 770                         break;
 771                 }
 772                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 773                 if (IS_ERR(eventfp)) {
 774                         r = PTR_ERR(eventfp);
 775                         break;
 776                 }
 777                 if (eventfp != vq->call) {
 778                         filep = vq->call;
 779                         ctx = vq->call_ctx;
 780                         vq->call = eventfp;
 781                         vq->call_ctx = eventfp ?
 782                                 eventfd_ctx_fileget(eventfp) : NULL;
 783                 } else
 784                         filep = eventfp;
 785                 break;
 786         case VHOST_SET_VRING_ERR:
 787                 if (copy_from_user(&f, argp, sizeof f)) {
 788                         r = -EFAULT;
 789                         break;
 790                 }
 791                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 792                 if (IS_ERR(eventfp)) {
 793                         r = PTR_ERR(eventfp);
 794                         break;
 795                 }
 796                 if (eventfp != vq->error) {
 797                         filep = vq->error;
 798                         vq->error = eventfp;
 799                         ctx = vq->error_ctx;
 800                         vq->error_ctx = eventfp ?
 801                                 eventfd_ctx_fileget(eventfp) : NULL;
 802                 } else
 803                         filep = eventfp;
 804                 break;
 805         default:
 806                 r = -ENOIOCTLCMD;
 807         }
 808
 809         if (pollstop && vq->handle_kick)
 810                 vhost_poll_stop(&vq->poll);
 811
 812         if (ctx)
 813                 eventfd_ctx_put(ctx);
 814         if (filep)
 815                 fput(filep);
 816
 817         if (pollstart && vq->handle_kick)
 818                 r = vhost_poll_start(&vq->poll, vq->kick);
 819
 820         mutex_unlock(&vq->mutex);
 821
 822         if (pollstop && vq->handle_kick)
 823                 vhost_poll_flush(&vq->poll);
 824         return r;
 825 }
 826 EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
 827
 828 /* Caller must have device mutex */
 829 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
 830 {
 831         struct file *eventfp, *filep = NULL;
 832         struct eventfd_ctx *ctx = NULL;
 833         u64 p;
 834         long r;
 835         int i, fd;
 836
 837         /* If you are not the owner, you can become one */
 838         if (ioctl == VHOST_SET_OWNER) {
 839                 r = vhost_dev_set_owner(d);
 840                 goto done;
 841         }
 842
 843         /* You must be the owner to do anything else */
 844         r = vhost_dev_check_owner(d);
 845         if (r)
 846                 goto done;
 847
 848         switch (ioctl) {
 849         case VHOST_SET_MEM_TABLE:
 850                 r = vhost_set_memory(d, argp);
 851                 break;
 852         case VHOST_SET_LOG_BASE:
 853                 if (copy_from_user(&p, argp, sizeof p)) {
 854                         r = -EFAULT;
 855                         break;
 856                 }
 857                 if ((u64)(unsigned long)p != p) {
 858                         r = -EFAULT;
 859                         break;
 860                 }
 861                 for (i = 0; i < d->nvqs; ++i) {
 862                         struct vhost_virtqueue *vq;
 863                         void __user *base = (void __user *)(unsigned long)p;
 864                         vq = d->vqs[i];
 865                         mutex_lock(&vq->mutex);
 866                         /* If ring is inactive, will check when it's enabled. */
 867                         if (vq->private_data && !vq_log_access_ok(vq, base))
 868                                 r = -EFAULT;
 869                         else
 870                                 vq->log_base = base;
 871                         mutex_unlock(&vq->mutex);
 872                 }
 873                 break;
 874         case VHOST_SET_LOG_FD:
 875                 r = get_user(fd, (int __user *)argp);
 876                 if (r < 0)
 877                         break;
 878                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 879                 if (IS_ERR(eventfp)) {
 880                         r = PTR_ERR(eventfp);
 881                         break;
 882                 }
 883                 if (eventfp != d->log_file) {
 884                         filep = d->log_file;
 885                         ctx = d->log_ctx;
 886                         d->log_ctx = eventfp ?
 887                                 eventfd_ctx_fileget(eventfp) : NULL;
 888                 } else
 889                         filep = eventfp;
 890                 for (i = 0; i < d->nvqs; ++i) {
 891                         mutex_lock(&d->vqs[i]->mutex);
 892                         d->vqs[i]->log_ctx = d->log_ctx;
 893                         mutex_unlock(&d->vqs[i]->mutex);
 894                 }
 895                 if (ctx)
 896                         eventfd_ctx_put(ctx);
 897                 if (filep)
 898                         fput(filep);
 899                 break;
 900         default:
 901                 r = -ENOIOCTLCMD;
 902                 break;
 903         }
 904 done:
 905         return r;
 906 }
 907 EXPORT_SYMBOL_GPL(vhost_dev_ioctl);
 908
 909 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 910                                                      __u64 addr, __u32 len)
 911 {
 912         struct vhost_memory_region *reg;
 913         int i;
 914
 915         /* linear search is not brilliant, but we really have on the order of 6
 916          * regions in practice */
 917         for (i = 0; i < mem->nregions; ++i) {
 918                 reg = mem->regions + i;
 919                 if (reg->guest_phys_addr <= addr &&
 920                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 921                         return reg;
 922         }
 923         return NULL;
 924 }
 925
 926 /* TODO: This is really inefficient.  We need something like get_user()
 927  * (instruction directly accesses the data, with an exception table entry
 928  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 929  */
 930 static int set_bit_to_user(int nr, void __user *addr)
 931 {
 932         unsigned long log = (unsigned long)addr;
 933         struct page *page;
 934         void *base;
 935         int bit = nr + (log % PAGE_SIZE) * 8;
 936         int r;
 937
 938         r = get_user_pages_fast(log, 1, 1, &page);
 939         if (r < 0)
 940                 return r;
 941         BUG_ON(r != 1);
 942         base = kmap_atomic(page);
 943         set_bit(bit, base);
 944         kunmap_atomic(base);
 945         set_page_dirty_lock(page);
 946         put_page(page);
 947         return 0;
 948 }
 949
 950 static int log_write(void __user *log_base,
 951                      u64 write_address, u64 write_length)
 952 {
 953         u64 write_page = write_address / VHOST_PAGE_SIZE;
 954         int r;
 955
 956         if (!write_length)
 957                 return 0;
 958         write_length += write_address % VHOST_PAGE_SIZE;
 959         for (;;) {
 960                 u64 base = (u64)(unsigned long)log_base;
 961                 u64 log = base + write_page / 8;
 962                 int bit = write_page % 8;
 963                 if ((u64)(unsigned long)log != log)
 964                         return -EFAULT;
 965                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 966                 if (r < 0)
 967                         return r;
 968                 if (write_length <= VHOST_PAGE_SIZE)
 969                         break;
 970                 write_length -= VHOST_PAGE_SIZE;
 971                 write_page += 1;
 972         }
 973         return r;
 974 }
 975
 976 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 977                     unsigned int log_num, u64 len)
 978 {
 979         int i, r;
 980
 981         /* Make sure data written is seen before log. */
 982         smp_wmb();
 983         for (i = 0; i < log_num; ++i) {
 984                 u64 l = min(log[i].len, len);
 985                 r = log_write(vq->log_base, log[i].addr, l);
 986                 if (r < 0)
 987                         return r;
 988                 len -= l;
 989                 if (!len) {
 990                         if (vq->log_ctx)
 991                                 eventfd_signal(vq->log_ctx, 1);
 992                         return 0;
 993                 }
 994         }
 995         /* Length written exceeds what we have stored. This is a bug. */
 996         BUG();
 997         return 0;
 998 }
 999 EXPORT_SYMBOL_GPL(vhost_log_write);
1000
1001 static int vhost_update_used_flags(struct vhost_virtqueue *vq)
1002 {
1003         void __user *used;
1004         if (__put_user(vq->used_flags, &vq->used->flags) < 0)
1005                 return -EFAULT;
1006         if (unlikely(vq->log_used)) {
1007                 /* Make sure the flag is seen before log. */
1008                 smp_wmb();
1009                 /* Log used flag write. */
1010                 used = &vq->used->flags;
1011                 log_write(vq->log_base, vq->log_addr +
1012                           (used - (void __user *)vq->used),
1013                           sizeof vq->used->flags);
1014                 if (vq->log_ctx)
1015                         eventfd_signal(vq->log_ctx, 1);
1016         }
1017         return 0;
1018 }
1019
1020 static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
1021 {
1022         if (__put_user(vq->avail_idx, vhost_avail_event(vq)))
1023                 return -EFAULT;
1024         if (unlikely(vq->log_used)) {
1025                 void __user *used;
1026                 /* Make sure the event is seen before log. */
1027                 smp_wmb();
1028                 /* Log avail event write */
1029                 used = vhost_avail_event(vq);
1030                 log_write(vq->log_base, vq->log_addr +
1031                           (used - (void __user *)vq->used),
1032                           sizeof *vhost_avail_event(vq));
1033                 if (vq->log_ctx)
1034                         eventfd_signal(vq->log_ctx, 1);
1035         }
1036         return 0;
1037 }
1038
1039 int vhost_init_used(struct vhost_virtqueue *vq)
1040 {
1041         int r;
1042         if (!vq->private_data)
1043                 return 0;
1044
1045         r = vhost_update_used_flags(vq);
1046         if (r)
1047                 return r;
1048         vq->signalled_used_valid = false;
1049         return get_user(vq->last_used_idx, &vq->used->idx);
1050 }
1051 EXPORT_SYMBOL_GPL(vhost_init_used);
1052
1053 static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
1054                           struct iovec iov[], int iov_size)
1055 {
1056         const struct vhost_memory_region *reg;
1057         struct vhost_memory *mem;
1058         struct iovec *_iov;
1059         u64 s = 0;
1060         int ret = 0;
1061
1062         mem = vq->memory;
1063         while ((u64)len > s) {
1064                 u64 size;
1065                 if (unlikely(ret >= iov_size)) {
1066                         ret = -ENOBUFS;
1067                         break;
1068                 }
1069                 reg = find_region(mem, addr, len);
1070                 if (unlikely(!reg)) {
1071                         ret = -EFAULT;
1072                         break;
1073                 }
1074                 _iov = iov + ret;
1075                 size = reg->memory_size - addr + reg->guest_phys_addr;
1076                 _iov->iov_len = min((u64)len - s, size);
1077                 _iov->iov_base = (void __user *)(unsigned long)
1078                         (reg->userspace_addr + addr - reg->guest_phys_addr);
1079                 s += size;
1080                 addr += size;
1081                 ++ret;
1082         }
1083
1084         return ret;
1085 }
1086
1087 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
1088  * function returns the next descriptor in the chain,
1089  * or -1U if we're at the end. */
1090 static unsigned next_desc(struct vring_desc *desc)
1091 {
1092         unsigned int next;
1093
1094         /* If this descriptor says it doesn't chain, we're done. */
1095         if (!(desc->flags & VRING_DESC_F_NEXT))
1096                 return -1U;
1097
1098         /* Check they're not leading us off end of descriptors. */
1099         next = desc->next;
1100         /* Make sure compiler knows to grab that: we don't want it changing! */
1101         /* We will use the result as an index in an array, so most
1102          * architectures only need a compiler barrier here. */
1103         read_barrier_depends();
1104
1105         return next;
1106 }
1107
1108 static int get_indirect(struct vhost_virtqueue *vq,
1109                         struct iovec iov[], unsigned int iov_size,
1110                         unsigned int *out_num, unsigned int *in_num,
1111                         struct vhost_log *log, unsigned int *log_num,
1112                         struct vring_desc *indirect)
1113 {
1114         struct vring_desc desc;
1115         unsigned int i = 0, count, found = 0;
1116         int ret;
1117
1118         /* Sanity check */
1119         if (unlikely(indirect->len % sizeof desc)) {
1120                 vq_err(vq, "Invalid length in indirect descriptor: "
1121                        "len 0x%llx not multiple of 0x%zx\n",
1122                        (unsigned long long)indirect->len,
1123                        sizeof desc);
1124                 return -EINVAL;
1125         }
1126
1127         ret = translate_desc(vq, indirect->addr, indirect->len, vq->indirect,
1128                              UIO_MAXIOV);
1129         if (unlikely(ret < 0)) {
1130                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1131                 return ret;
1132         }
1133
1134         /* We will use the result as an address to read from, so most
1135          * architectures only need a compiler barrier here. */
1136         read_barrier_depends();
1137
1138         count = indirect->len / sizeof desc;
1139         /* Buffers are chained via a 16 bit next field, so
1140          * we can have at most 2^16 of these. */
1141         if (unlikely(count > USHRT_MAX + 1)) {
1142                 vq_err(vq, "Indirect buffer length too big: %d\n",
1143                        indirect->len);
1144                 return -E2BIG;
1145         }
1146
1147         do {
1148                 unsigned iov_count = *in_num + *out_num;
1149                 if (unlikely(++found > count)) {
1150                         vq_err(vq, "Loop detected: last one at %u "
1151                                "indirect size %u\n",
1152                                i, count);
1153                         return -EINVAL;
1154                 }
1155                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1156                                               vq->indirect, sizeof desc))) {
1157                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1158                                i, (size_t)indirect->addr + i * sizeof desc);
1159                         return -EINVAL;
1160                 }
1161                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1162                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1163                                i, (size_t)indirect->addr + i * sizeof desc);
1164                         return -EINVAL;
1165                 }
1166
1167                 ret = translate_desc(vq, desc.addr, desc.len, iov + iov_count,
1168                                      iov_size - iov_count);
1169                 if (unlikely(ret < 0)) {
1170                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1171                                ret, i);
1172                         return ret;
1173                 }
1174                 /* If this is an input descriptor, increment that count. */
1175                 if (desc.flags & VRING_DESC_F_WRITE) {
1176                         *in_num += ret;
1177                         if (unlikely(log)) {
1178                                 log[*log_num].addr = desc.addr;
1179                                 log[*log_num].len = desc.len;
1180                                 ++*log_num;
1181                         }
1182                 } else {
1183                         /* If it's an output descriptor, they're all supposed
1184                          * to come before any input descriptors. */
1185                         if (unlikely(*in_num)) {
1186                                 vq_err(vq, "Indirect descriptor "
1187                                        "has out after in: idx %d\n", i);
1188                                 return -EINVAL;
1189                         }
1190                         *out_num += ret;
1191                 }
1192         } while ((i = next_desc(&desc)) != -1);
1193         return 0;
1194 }
1195
1196 /* This looks in the virtqueue and for the first available buffer, and converts
1197  * it to an iovec for convenient access.  Since descriptors consist of some
1198  * number of output then some number of input descriptors, it's actually two
1199  * iovecs, but we pack them into one and note how many of each there were.
1200  *
1201  * This function returns the descriptor number found, or vq->num (which is
1202  * never a valid descriptor number) if none was found.  A negative code is
1203  * returned on error. */
1204 int vhost_get_vq_desc(struct vhost_virtqueue *vq,
1205                       struct iovec iov[], unsigned int iov_size,
1206                       unsigned int *out_num, unsigned int *in_num,
1207                       struct vhost_log *log, unsigned int *log_num)
1208 {
1209         struct vring_desc desc;
1210         unsigned int i, head, found = 0;
1211         u16 last_avail_idx;
1212         int ret;
1213
1214         /* Check it isn't doing very strange things with descriptor numbers. */
1215         last_avail_idx = vq->last_avail_idx;
1216         if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1217                 vq_err(vq, "Failed to access avail idx at %p\n",
1218                        &vq->avail->idx);
1219                 return -EFAULT;
1220         }
1221
1222         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1223                 vq_err(vq, "Guest moved used index from %u to %u",
1224                        last_avail_idx, vq->avail_idx);
1225                 return -EFAULT;
1226         }
1227
1228         /* If there's nothing new since last we looked, return invalid. */
1229         if (vq->avail_idx == last_avail_idx)
1230                 return vq->num;
1231
1232         /* Only get avail ring entries after they have been exposed by guest. */
1233         smp_rmb();
1234
1235         /* Grab the next descriptor number they're advertising, and increment
1236          * the index we've seen. */
1237         if (unlikely(__get_user(head,
1238                                 &vq->avail->ring[last_avail_idx % vq->num]))) {
1239                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1240                        last_avail_idx,
1241                        &vq->avail->ring[last_avail_idx % vq->num]);
1242                 return -EFAULT;
1243         }
1244
1245         /* If their number is silly, that's an error. */
1246         if (unlikely(head >= vq->num)) {
1247                 vq_err(vq, "Guest says index %u > %u is available",
1248                        head, vq->num);
1249                 return -EINVAL;
1250         }
1251
1252         /* When we start there are none of either input nor output. */
1253         *out_num = *in_num = 0;
1254         if (unlikely(log))
1255                 *log_num = 0;
1256
1257         i = head;
1258         do {
1259                 unsigned iov_count = *in_num + *out_num;
1260                 if (unlikely(i >= vq->num)) {
1261                         vq_err(vq, "Desc index is %u > %u, head = %u",
1262                                i, vq->num, head);
1263                         return -EINVAL;
1264                 }
1265                 if (unlikely(++found > vq->num)) {
1266                         vq_err(vq, "Loop detected: last one at %u "
1267                                "vq size %u head %u\n",
1268                                i, vq->num, head);
1269                         return -EINVAL;
1270                 }
1271                 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1272                 if (unlikely(ret)) {
1273                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1274                                i, vq->desc + i);
1275                         return -EFAULT;
1276                 }
1277                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1278                         ret = get_indirect(vq, iov, iov_size,
1279                                            out_num, in_num,
1280                                            log, log_num, &desc);
1281                         if (unlikely(ret < 0)) {
1282                                 vq_err(vq, "Failure detected "
1283                                        "in indirect descriptor at idx %d\n", i);
1284                                 return ret;
1285                         }
1286                         continue;
1287                 }
1288
1289                 ret = translate_desc(vq, desc.addr, desc.len, iov + iov_count,
1290                                      iov_size - iov_count);
1291                 if (unlikely(ret < 0)) {
1292                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1293                                ret, i);
1294                         return ret;
1295                 }
1296                 if (desc.flags & VRING_DESC_F_WRITE) {
1297                         /* If this is an input descriptor,
1298                          * increment that count. */
1299                         *in_num += ret;
1300                         if (unlikely(log)) {
1301                                 log[*log_num].addr = desc.addr;
1302                                 log[*log_num].len = desc.len;
1303                                 ++*log_num;
1304                         }
1305                 } else {
1306                         /* If it's an output descriptor, they're all supposed
1307                          * to come before any input descriptors. */
1308                         if (unlikely(*in_num)) {
1309                                 vq_err(vq, "Descriptor has out after in: "
1310                                        "idx %d\n", i);
1311                                 return -EINVAL;
1312                         }
1313                         *out_num += ret;
1314                 }
1315         } while ((i = next_desc(&desc)) != -1);
1316
1317         /* On success, increment avail index. */
1318         vq->last_avail_idx++;
1319
1320         /* Assume notifications from guest are disabled at this point,
1321          * if they aren't we would need to update avail_event index. */
1322         BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1323         return head;
1324 }
1325 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
1326
1327 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1328 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1329 {
1330         vq->last_avail_idx -= n;
1331 }
1332 EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
1333
1334 /* After we've used one of their buffers, we tell them about it.  We'll then
1335  * want to notify the guest, using eventfd. */
1336 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1337 {
1338         struct vring_used_elem heads = { head, len };
1339
1340         return vhost_add_used_n(vq, &heads, 1);
1341 }
1342 EXPORT_SYMBOL_GPL(vhost_add_used);
1343
1344 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1345                             struct vring_used_elem *heads,
1346                             unsigned count)
1347 {
1348         struct vring_used_elem __user *used;
1349         u16 old, new;
1350         int start;
1351
1352         start = vq->last_used_idx % vq->num;
1353         used = vq->used->ring + start;
1354         if (count == 1) {
1355                 if (__put_user(heads[0].id, &used->id)) {
1356                         vq_err(vq, "Failed to write used id");
1357                         return -EFAULT;
1358                 }
1359                 if (__put_user(heads[0].len, &used->len)) {
1360                         vq_err(vq, "Failed to write used len");
1361                         return -EFAULT;
1362                 }
1363         } else if (__copy_to_user(used, heads, count * sizeof *used)) {
1364                 vq_err(vq, "Failed to write used");
1365                 return -EFAULT;
1366         }
1367         if (unlikely(vq->log_used)) {
1368                 /* Make sure data is seen before log. */
1369                 smp_wmb();
1370                 /* Log used ring entry write. */
1371                 log_write(vq->log_base,
1372                           vq->log_addr +
1373                            ((void __user *)used - (void __user *)vq->used),
1374                           count * sizeof *used);
1375         }
1376         old = vq->last_used_idx;
1377         new = (vq->last_used_idx += count);
1378         /* If the driver never bothers to signal in a very long while,
1379          * used index might wrap around. If that happens, invalidate
1380          * signalled_used index we stored. TODO: make sure driver
1381          * signals at least once in 2^16 and remove this. */
1382         if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1383                 vq->signalled_used_valid = false;
1384         return 0;
1385 }
1386
1387 /* After we've used one of their buffers, we tell them about it.  We'll then
1388  * want to notify the guest, using eventfd. */
1389 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1390                      unsigned count)
1391 {
1392         int start, n, r;
1393
1394         start = vq->last_used_idx % vq->num;
1395         n = vq->num - start;
1396         if (n < count) {
1397                 r = __vhost_add_used_n(vq, heads, n);
1398                 if (r < 0)
1399                         return r;
1400                 heads += n;
1401                 count -= n;
1402         }
1403         r = __vhost_add_used_n(vq, heads, count);
1404
1405         /* Make sure buffer is written before we update index. */
1406         smp_wmb();
1407         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1408                 vq_err(vq, "Failed to increment used idx");
1409                 return -EFAULT;
1410         }
1411         if (unlikely(vq->log_used)) {
1412                 /* Log used index update. */
1413                 log_write(vq->log_base,
1414                           vq->log_addr + offsetof(struct vring_used, idx),
1415                           sizeof vq->used->idx);
1416                 if (vq->log_ctx)
1417                         eventfd_signal(vq->log_ctx, 1);
1418         }
1419         return r;
1420 }
1421 EXPORT_SYMBOL_GPL(vhost_add_used_n);
1422
1423 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1424 {
1425         __u16 old, new, event;
1426         bool v;
1427         /* Flush out used index updates. This is paired
1428          * with the barrier that the Guest executes when enabling
1429          * interrupts. */
1430         smp_mb();
1431
1432         if (vhost_has_feature(vq, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1433             unlikely(vq->avail_idx == vq->last_avail_idx))
1434                 return true;
1435
1436         if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
1437                 __u16 flags;
1438                 if (__get_user(flags, &vq->avail->flags)) {
1439                         vq_err(vq, "Failed to get flags");
1440                         return true;
1441                 }
1442                 return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1443         }
1444         old = vq->signalled_used;
1445         v = vq->signalled_used_valid;
1446         new = vq->signalled_used = vq->last_used_idx;
1447         vq->signalled_used_valid = true;
1448
1449         if (unlikely(!v))
1450                 return true;
1451
1452         if (get_user(event, vhost_used_event(vq))) {
1453                 vq_err(vq, "Failed to get used event idx");
1454                 return true;
1455         }
1456         return vring_need_event(event, new, old);
1457 }
1458
1459 /* This actually signals the guest, using eventfd. */
1460 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1461 {
1462         /* Signal the Guest tell them we used something up. */
1463         if (vq->call_ctx && vhost_notify(dev, vq))
1464                 eventfd_signal(vq->call_ctx, 1);
1465 }
1466 EXPORT_SYMBOL_GPL(vhost_signal);
1467
1468 /* And here's the combo meal deal.  Supersize me! */
1469 void vhost_add_used_and_signal(struct vhost_dev *dev,
1470                                struct vhost_virtqueue *vq,
1471                                unsigned int head, int len)
1472 {
1473         vhost_add_used(vq, head, len);
1474         vhost_signal(dev, vq);
1475 }
1476 EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
1477
1478 /* multi-buffer version of vhost_add_used_and_signal */
1479 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1480                                  struct vhost_virtqueue *vq,
1481                                  struct vring_used_elem *heads, unsigned count)
1482 {
1483         vhost_add_used_n(vq, heads, count);
1484         vhost_signal(dev, vq);
1485 }
1486 EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
1487
1488 /* OK, now we need to know about added descriptors. */
1489 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1490 {
1491         u16 avail_idx;
1492         int r;
1493
1494         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1495                 return false;
1496         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1497         if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
1498                 r = vhost_update_used_flags(vq);
1499                 if (r) {
1500                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1501                                &vq->used->flags, r);
1502                         return false;
1503                 }
1504         } else {
1505                 r = vhost_update_avail_event(vq, vq->avail_idx);
1506                 if (r) {
1507                         vq_err(vq, "Failed to update avail event index at %p: %d\n",
1508                                vhost_avail_event(vq), r);
1509                         return false;
1510                 }
1511         }
1512         /* They could have slipped one in as we were doing that: make
1513          * sure it's written, then check again. */
1514         smp_mb();
1515         r = __get_user(avail_idx, &vq->avail->idx);
1516         if (r) {
1517                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1518                        &vq->avail->idx, r);
1519                 return false;
1520         }
1521
1522         return avail_idx != vq->avail_idx;
1523 }
1524 EXPORT_SYMBOL_GPL(vhost_enable_notify);
1525
1526 /* We don't need to be notified again. */
1527 void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1528 {
1529         int r;
1530
1531         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1532                 return;
1533         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1534         if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
1535                 r = vhost_update_used_flags(vq);
1536                 if (r)
1537                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1538                                &vq->used->flags, r);
1539         }
1540 }
1541 EXPORT_SYMBOL_GPL(vhost_disable_notify);
1542
1543 static int __init vhost_init(void)
1544 {
1545         return 0;
1546 }
1547
1548 static void __exit vhost_exit(void)
1549 {
1550 }
1551
1552 module_init(vhost_init);
1553 module_exit(vhost_exit);
1554
1555 MODULE_VERSION("0.0.1");
1556 MODULE_LICENSE("GPL v2");
1557 MODULE_AUTHOR("Michael S. Tsirkin");
1558 MODULE_DESCRIPTION("Host kernel accelerator for virtio");