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