kernel/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/vmalloc.h>
  26 #include <linux/kthread.h>
  27 #include <linux/cgroup.h>
  28 #include <linux/module.h>
  29 #include <linux/sort.h>
  30
  31 #include "vhost.h"
  32
  33 static ushort max_mem_regions = 64;
  34 module_param(max_mem_regions, ushort, 0444);
  35 MODULE_PARM_DESC(max_mem_regions,
  36         "Maximum number of memory regions in memory map. (default: 64)");
  37
  38 enum {
  39         VHOST_MEMORY_F_LOG = 0x1,
  40 };
  41
  42 #define vhost_used_event(vq) ((__virtio16 __user *)&vq->avail->ring[vq->num])
  43 #define vhost_avail_event(vq) ((__virtio16 __user *)&vq->used->ring[vq->num])
  44
  45 #ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
  46 static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
  47 {
  48         vq->user_be = !virtio_legacy_is_little_endian();
  49 }
  50
  51 static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp)
  52 {
  53         struct vhost_vring_state s;
  54
  55         if (vq->private_data)
  56                 return -EBUSY;
  57
  58         if (copy_from_user(&s, argp, sizeof(s)))
  59                 return -EFAULT;
  60
  61         if (s.num != VHOST_VRING_LITTLE_ENDIAN &&
  62             s.num != VHOST_VRING_BIG_ENDIAN)
  63                 return -EINVAL;
  64
  65         vq->user_be = s.num;
  66
  67         return 0;
  68 }
  69
  70 static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
  71                                    int __user *argp)
  72 {
  73         struct vhost_vring_state s = {
  74                 .index = idx,
  75                 .num = vq->user_be
  76         };
  77
  78         if (copy_to_user(argp, &s, sizeof(s)))
  79                 return -EFAULT;
  80
  81         return 0;
  82 }
  83
  84 static void vhost_init_is_le(struct vhost_virtqueue *vq)
  85 {
  86         /* Note for legacy virtio: user_be is initialized at reset time
  87          * according to the host endianness. If userspace does not set an
  88          * explicit endianness, the default behavior is native endian, as
  89          * expected by legacy virtio.
  90          */
  91         vq->is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq->user_be;
  92 }
  93 #else
  94 static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
  95 {
  96 }
  97
  98 static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp)
  99 {
 100         return -ENOIOCTLCMD;
 101 }
 102
 103 static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
 104                                    int __user *argp)
 105 {
 106         return -ENOIOCTLCMD;
 107 }
 108
 109 static void vhost_init_is_le(struct vhost_virtqueue *vq)
 110 {
 111         if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
 112                 vq->is_le = true;
 113 }
 114 #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
 115
 116 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
 117                             poll_table *pt)
 118 {
 119         struct vhost_poll *poll;
 120
 121         poll = container_of(pt, struct vhost_poll, table);
 122         poll->wqh = wqh;
 123         add_wait_queue(wqh, &poll->wait);
 124 }
 125
 126 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
 127                              void *key)
 128 {
 129         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
 130
 131         if (!((unsigned long)key & poll->mask))
 132                 return 0;
 133
 134         vhost_poll_queue(poll);
 135         return 0;
 136 }
 137
 138 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
 139 {
 140         INIT_LIST_HEAD(&work->node);
 141         work->fn = fn;
 142         init_waitqueue_head(&work->done);
 143         work->flushing = 0;
 144         work->queue_seq = work->done_seq = 0;
 145 }
 146 EXPORT_SYMBOL_GPL(vhost_work_init);
 147
 148 /* Init poll structure */
 149 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
 150                      unsigned long mask, struct vhost_dev *dev)
 151 {
 152         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
 153         init_poll_funcptr(&poll->table, vhost_poll_func);
 154         poll->mask = mask;
 155         poll->dev = dev;
 156         poll->wqh = NULL;
 157
 158         vhost_work_init(&poll->work, fn);
 159 }
 160 EXPORT_SYMBOL_GPL(vhost_poll_init);
 161
 162 /* Start polling a file. We add ourselves to file's wait queue. The caller must
 163  * keep a reference to a file until after vhost_poll_stop is called. */
 164 int vhost_poll_start(struct vhost_poll *poll, struct file *file)
 165 {
 166         unsigned long mask;
 167         int ret = 0;
 168
 169         if (poll->wqh)
 170                 return 0;
 171
 172         mask = file->f_op->poll(file, &poll->table);
 173         if (mask)
 174                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
 175         if (mask & POLLERR) {
 176                 if (poll->wqh)
 177                         remove_wait_queue(poll->wqh, &poll->wait);
 178                 ret = -EINVAL;
 179         }
 180
 181         return ret;
 182 }
 183 EXPORT_SYMBOL_GPL(vhost_poll_start);
 184
 185 /* Stop polling a file. After this function returns, it becomes safe to drop the
 186  * file reference. You must also flush afterwards. */
 187 void vhost_poll_stop(struct vhost_poll *poll)
 188 {
 189         if (poll->wqh) {
 190                 remove_wait_queue(poll->wqh, &poll->wait);
 191                 poll->wqh = NULL;
 192         }
 193 }
 194 EXPORT_SYMBOL_GPL(vhost_poll_stop);
 195
 196 static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
 197                                 unsigned seq)
 198 {
 199         int left;
 200
 201         spin_lock_irq(&dev->work_lock);
 202         left = seq - work->done_seq;
 203         spin_unlock_irq(&dev->work_lock);
 204         return left <= 0;
 205 }
 206
 207 void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 208 {
 209         unsigned seq;
 210         int flushing;
 211
 212         spin_lock_irq(&dev->work_lock);
 213         seq = work->queue_seq;
 214         work->flushing++;
 215         spin_unlock_irq(&dev->work_lock);
 216         wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 217         spin_lock_irq(&dev->work_lock);
 218         flushing = --work->flushing;
 219         spin_unlock_irq(&dev->work_lock);
 220         BUG_ON(flushing < 0);
 221 }
 222 EXPORT_SYMBOL_GPL(vhost_work_flush);
 223
 224 /* Flush any work that has been scheduled. When calling this, don't hold any
 225  * locks that are also used by the callback. */
 226 void vhost_poll_flush(struct vhost_poll *poll)
 227 {
 228         vhost_work_flush(poll->dev, &poll->work);
 229 }
 230 EXPORT_SYMBOL_GPL(vhost_poll_flush);
 231
 232 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 233 {
 234         unsigned long flags;
 235
 236         spin_lock_irqsave(&dev->work_lock, flags);
 237         if (list_empty(&work->node)) {
 238                 list_add_tail(&work->node, &dev->work_list);
 239                 work->queue_seq++;
 240                 spin_unlock_irqrestore(&dev->work_lock, flags);
 241                 wake_up_process(dev->worker);
 242         } else {
 243                 spin_unlock_irqrestore(&dev->work_lock, flags);
 244         }
 245 }
 246 EXPORT_SYMBOL_GPL(vhost_work_queue);
 247
 248 void vhost_poll_queue(struct vhost_poll *poll)
 249 {
 250         vhost_work_queue(poll->dev, &poll->work);
 251 }
 252 EXPORT_SYMBOL_GPL(vhost_poll_queue);
 253
 254 static void vhost_vq_reset(struct vhost_dev *dev,
 255                            struct vhost_virtqueue *vq)
 256 {
 257         vq->num = 1;
 258         vq->desc = NULL;
 259         vq->avail = NULL;
 260         vq->used = NULL;
 261         vq->last_avail_idx = 0;
 262         vq->avail_idx = 0;
 263         vq->last_used_idx = 0;
 264         vq->signalled_used = 0;
 265         vq->signalled_used_valid = false;
 266         vq->used_flags = 0;
 267         vq->log_used = false;
 268         vq->log_addr = -1ull;
 269         vq->private_data = NULL;
 270         vq->acked_features = 0;
 271         vq->log_base = NULL;
 272         vq->error_ctx = NULL;
 273         vq->error = NULL;
 274         vq->kick = NULL;
 275         vq->call_ctx = NULL;
 276         vq->call = NULL;
 277         vq->log_ctx = NULL;
 278         vq->memory = NULL;
 279         vq->is_le = virtio_legacy_is_little_endian();
 280         vhost_vq_reset_user_be(vq);
 281 }
 282
 283 static int vhost_worker(void *data)
 284 {
 285         struct vhost_dev *dev = data;
 286         struct vhost_work *work = NULL;
 287         unsigned uninitialized_var(seq);
 288         mm_segment_t oldfs = get_fs();
 289
 290         set_fs(USER_DS);
 291         use_mm(dev->mm);
 292
 293         for (;;) {
 294                 /* mb paired w/ kthread_stop */
 295                 set_current_state(TASK_INTERRUPTIBLE);
 296
 297                 spin_lock_irq(&dev->work_lock);
 298                 if (work) {
 299                         work->done_seq = seq;
 300                         if (work->flushing)
 301                                 wake_up_all(&work->done);
 302                 }
 303
 304                 if (kthread_should_stop()) {
 305                         spin_unlock_irq(&dev->work_lock);
 306                         __set_current_state(TASK_RUNNING);
 307                         break;
 308                 }
 309                 if (!list_empty(&dev->work_list)) {
 310                         work = list_first_entry(&dev->work_list,
 311                                                 struct vhost_work, node);
 312                         list_del_init(&work->node);
 313                         seq = work->queue_seq;
 314                 } else
 315                         work = NULL;
 316                 spin_unlock_irq(&dev->work_lock);
 317
 318                 if (work) {
 319                         __set_current_state(TASK_RUNNING);
 320                         work->fn(work);
 321                         if (need_resched())
 322                                 schedule();
 323                 } else
 324                         schedule();
 325
 326         }
 327         unuse_mm(dev->mm);
 328         set_fs(oldfs);
 329         return 0;
 330 }
 331
 332 static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
 333 {
 334         kfree(vq->indirect);
 335         vq->indirect = NULL;
 336         kfree(vq->log);
 337         vq->log = NULL;
 338         kfree(vq->heads);
 339         vq->heads = NULL;
 340 }
 341
 342 /* Helper to allocate iovec buffers for all vqs. */
 343 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 344 {
 345         struct vhost_virtqueue *vq;
 346         int i;
 347
 348         for (i = 0; i < dev->nvqs; ++i) {
 349                 vq = dev->vqs[i];
 350                 vq->indirect = kmalloc(sizeof *vq->indirect * UIO_MAXIOV,
 351                                        GFP_KERNEL);
 352                 vq->log = kmalloc(sizeof *vq->log * UIO_MAXIOV, GFP_KERNEL);
 353                 vq->heads = kmalloc(sizeof *vq->heads * UIO_MAXIOV, GFP_KERNEL);
 354                 if (!vq->indirect || !vq->log || !vq->heads)
 355                         goto err_nomem;
 356         }
 357         return 0;
 358
 359 err_nomem:
 360         for (; i >= 0; --i)
 361                 vhost_vq_free_iovecs(dev->vqs[i]);
 362         return -ENOMEM;
 363 }
 364
 365 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
 366 {
 367         int i;
 368
 369         for (i = 0; i < dev->nvqs; ++i)
 370                 vhost_vq_free_iovecs(dev->vqs[i]);
 371 }
 372
 373 void vhost_dev_init(struct vhost_dev *dev,
 374                     struct vhost_virtqueue **vqs, int nvqs)
 375 {
 376         struct vhost_virtqueue *vq;
 377         int i;
 378
 379         dev->vqs = vqs;
 380         dev->nvqs = nvqs;
 381         mutex_init(&dev->mutex);
 382         dev->log_ctx = NULL;
 383         dev->log_file = NULL;
 384         dev->memory = NULL;
 385         dev->mm = NULL;
 386         spin_lock_init(&dev->work_lock);
 387         INIT_LIST_HEAD(&dev->work_list);
 388         dev->worker = NULL;
 389
 390         for (i = 0; i < dev->nvqs; ++i) {
 391                 vq = dev->vqs[i];
 392                 vq->log = NULL;
 393                 vq->indirect = NULL;
 394                 vq->heads = NULL;
 395                 vq->dev = dev;
 396                 mutex_init(&vq->mutex);
 397                 vhost_vq_reset(dev, vq);
 398                 if (vq->handle_kick)
 399                         vhost_poll_init(&vq->poll, vq->handle_kick,
 400                                         POLLIN, dev);
 401         }
 402 }
 403 EXPORT_SYMBOL_GPL(vhost_dev_init);
 404
 405 /* Caller should have device mutex */
 406 long vhost_dev_check_owner(struct vhost_dev *dev)
 407 {
 408         /* Are you the owner? If not, I don't think you mean to do that */
 409         return dev->mm == current->mm ? 0 : -EPERM;
 410 }
 411 EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
 412
 413 struct vhost_attach_cgroups_struct {
 414         struct vhost_work work;
 415         struct task_struct *owner;
 416         int ret;
 417 };
 418
 419 static void vhost_attach_cgroups_work(struct vhost_work *work)
 420 {
 421         struct vhost_attach_cgroups_struct *s;
 422
 423         s = container_of(work, struct vhost_attach_cgroups_struct, work);
 424         s->ret = cgroup_attach_task_all(s->owner, current);
 425 }
 426
 427 static int vhost_attach_cgroups(struct vhost_dev *dev)
 428 {
 429         struct vhost_attach_cgroups_struct attach;
 430
 431         attach.owner = current;
 432         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 433         vhost_work_queue(dev, &attach.work);
 434         vhost_work_flush(dev, &attach.work);
 435         return attach.ret;
 436 }
 437
 438 /* Caller should have device mutex */
 439 bool vhost_dev_has_owner(struct vhost_dev *dev)
 440 {
 441         return dev->mm;
 442 }
 443 EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
 444
 445 /* Caller should have device mutex */
 446 long vhost_dev_set_owner(struct vhost_dev *dev)
 447 {
 448         struct task_struct *worker;
 449         int err;
 450
 451         /* Is there an owner already? */
 452         if (vhost_dev_has_owner(dev)) {
 453                 err = -EBUSY;
 454                 goto err_mm;
 455         }
 456
 457         /* No owner, become one */
 458         dev->mm = get_task_mm(current);
 459         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 460         if (IS_ERR(worker)) {
 461                 err = PTR_ERR(worker);
 462                 goto err_worker;
 463         }
 464
 465         dev->worker = worker;
 466         wake_up_process(worker);        /* avoid contributing to loadavg */
 467
 468         err = vhost_attach_cgroups(dev);
 469         if (err)
 470                 goto err_cgroup;
 471
 472         err = vhost_dev_alloc_iovecs(dev);
 473         if (err)
 474                 goto err_cgroup;
 475
 476         return 0;
 477 err_cgroup:
 478         kthread_stop(worker);
 479         dev->worker = NULL;
 480 err_worker:
 481         if (dev->mm)
 482                 mmput(dev->mm);
 483         dev->mm = NULL;
 484 err_mm:
 485         return err;
 486 }
 487 EXPORT_SYMBOL_GPL(vhost_dev_set_owner);
 488
 489 struct vhost_memory *vhost_dev_reset_owner_prepare(void)
 490 {
 491         return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 492 }
 493 EXPORT_SYMBOL_GPL(vhost_dev_reset_owner_prepare);
 494
 495 /* Caller should have device mutex */
 496 void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory *memory)
 497 {
 498         int i;
 499
 500         vhost_dev_cleanup(dev, true);
 501
 502         /* Restore memory to default empty mapping. */
 503         memory->nregions = 0;
 504         dev->memory = memory;
 505         /* We don't need VQ locks below since vhost_dev_cleanup makes sure
 506          * VQs aren't running.
 507          */
 508         for (i = 0; i < dev->nvqs; ++i)
 509                 dev->vqs[i]->memory = memory;
 510 }
 511 EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
 512
 513 void vhost_dev_stop(struct vhost_dev *dev)
 514 {
 515         int i;
 516
 517         for (i = 0; i < dev->nvqs; ++i) {
 518                 if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
 519                         vhost_poll_stop(&dev->vqs[i]->poll);
 520                         vhost_poll_flush(&dev->vqs[i]->poll);
 521                 }
 522         }
 523 }
 524 EXPORT_SYMBOL_GPL(vhost_dev_stop);
 525
 526 /* Caller should have device mutex if and only if locked is set */
 527 void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 528 {
 529         int i;
 530
 531         for (i = 0; i < dev->nvqs; ++i) {
 532                 if (dev->vqs[i]->error_ctx)
 533                         eventfd_ctx_put(dev->vqs[i]->error_ctx);
 534                 if (dev->vqs[i]->error)
 535                         fput(dev->vqs[i]->error);
 536                 if (dev->vqs[i]->kick)
 537                         fput(dev->vqs[i]->kick);
 538                 if (dev->vqs[i]->call_ctx)
 539                         eventfd_ctx_put(dev->vqs[i]->call_ctx);
 540                 if (dev->vqs[i]->call)
 541                         fput(dev->vqs[i]->call);
 542                 vhost_vq_reset(dev, dev->vqs[i]);
 543         }
 544         vhost_dev_free_iovecs(dev);
 545         if (dev->log_ctx)
 546                 eventfd_ctx_put(dev->log_ctx);
 547         dev->log_ctx = NULL;
 548         if (dev->log_file)
 549                 fput(dev->log_file);
 550         dev->log_file = NULL;
 551         /* No one will access memory at this point */
 552         kvfree(dev->memory);
 553         dev->memory = NULL;
 554         WARN_ON(!list_empty(&dev->work_list));
 555         if (dev->worker) {
 556                 kthread_stop(dev->worker);
 557                 dev->worker = NULL;
 558         }
 559         if (dev->mm)
 560                 mmput(dev->mm);
 561         dev->mm = NULL;
 562 }
 563 EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
 564
 565 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 566 {
 567         u64 a = addr / VHOST_PAGE_SIZE / 8;
 568
 569         /* Make sure 64 bit math will not overflow. */
 570         if (a > ULONG_MAX - (unsigned long)log_base ||
 571             a + (unsigned long)log_base > ULONG_MAX)
 572                 return 0;
 573
 574         return access_ok(VERIFY_WRITE, log_base + a,
 575                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 576 }
 577
 578 /* Caller should have vq mutex and device mutex. */
 579 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 580                                int log_all)
 581 {
 582         int i;
 583
 584         if (!mem)
 585                 return 0;
 586
 587         for (i = 0; i < mem->nregions; ++i) {
 588                 struct vhost_memory_region *m = mem->regions + i;
 589                 unsigned long a = m->userspace_addr;
 590                 if (m->memory_size > ULONG_MAX)
 591                         return 0;
 592                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 593                                     m->memory_size))
 594                         return 0;
 595                 else if (log_all && !log_access_ok(log_base,
 596                                                    m->guest_phys_addr,
 597                                                    m->memory_size))
 598                         return 0;
 599         }
 600         return 1;
 601 }
 602
 603 /* Can we switch to this memory table? */
 604 /* Caller should have device mutex but not vq mutex */
 605 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 606                             int log_all)
 607 {
 608         int i;
 609
 610         for (i = 0; i < d->nvqs; ++i) {
 611                 int ok;
 612                 bool log;
 613
 614                 mutex_lock(&d->vqs[i]->mutex);
 615                 log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
 616                 /* If ring is inactive, will check when it's enabled. */
 617                 if (d->vqs[i]->private_data)
 618                         ok = vq_memory_access_ok(d->vqs[i]->log_base, mem, log);
 619                 else
 620                         ok = 1;
 621                 mutex_unlock(&d->vqs[i]->mutex);
 622                 if (!ok)
 623                         return 0;
 624         }
 625         return 1;
 626 }
 627
 628 static int vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
 629                         struct vring_desc __user *desc,
 630                         struct vring_avail __user *avail,
 631                         struct vring_used __user *used)
 632 {
 633         size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 634         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 635                access_ok(VERIFY_READ, avail,
 636                          sizeof *avail + num * sizeof *avail->ring + s) &&
 637                access_ok(VERIFY_WRITE, used,
 638                         sizeof *used + num * sizeof *used->ring + s);
 639 }
 640
 641 /* Can we log writes? */
 642 /* Caller should have device mutex but not vq mutex */
 643 int vhost_log_access_ok(struct vhost_dev *dev)
 644 {
 645         return memory_access_ok(dev, dev->memory, 1);
 646 }
 647 EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 648
 649 /* Verify access for write logging. */
 650 /* Caller should have vq mutex and device mutex */
 651 static int vq_log_access_ok(struct vhost_virtqueue *vq,
 652                             void __user *log_base)
 653 {
 654         size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 655
 656         return vq_memory_access_ok(log_base, vq->memory,
 657                                    vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
 658                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 659                                         sizeof *vq->used +
 660                                         vq->num * sizeof *vq->used->ring + s));
 661 }
 662
 663 /* Can we start vq? */
 664 /* Caller should have vq mutex and device mutex */
 665 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 666 {
 667         return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used) &&
 668                 vq_log_access_ok(vq, vq->log_base);
 669 }
 670 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
 671
 672 static int vhost_memory_reg_sort_cmp(const void *p1, const void *p2)
 673 {
 674         const struct vhost_memory_region *r1 = p1, *r2 = p2;
 675         if (r1->guest_phys_addr < r2->guest_phys_addr)
 676                 return 1;
 677         if (r1->guest_phys_addr > r2->guest_phys_addr)
 678                 return -1;
 679         return 0;
 680 }
 681
 682 static void *vhost_kvzalloc(unsigned long size)
 683 {
 684         void *n = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
 685
 686         if (!n)
 687                 n = vzalloc(size);
 688         return n;
 689 }
 690
 691 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 692 {
 693         struct vhost_memory mem, *newmem, *oldmem;
 694         unsigned long size = offsetof(struct vhost_memory, regions);
 695         int i;
 696
 697         if (copy_from_user(&mem, m, size))
 698                 return -EFAULT;
 699         if (mem.padding)
 700                 return -EOPNOTSUPP;
 701         if (mem.nregions > max_mem_regions)
 702                 return -E2BIG;
 703         newmem = vhost_kvzalloc(size + mem.nregions * sizeof(*m->regions));
 704         if (!newmem)
 705                 return -ENOMEM;
 706
 707         memcpy(newmem, &mem, size);
 708         if (copy_from_user(newmem->regions, m->regions,
 709                            mem.nregions * sizeof *m->regions)) {
 710                 kvfree(newmem);
 711                 return -EFAULT;
 712         }
 713         sort(newmem->regions, newmem->nregions, sizeof(*newmem->regions),
 714                 vhost_memory_reg_sort_cmp, NULL);
 715
 716         if (!memory_access_ok(d, newmem, 0)) {
 717                 kvfree(newmem);
 718                 return -EFAULT;
 719         }
 720         oldmem = d->memory;
 721         d->memory = newmem;
 722
 723         /* All memory accesses are done under some VQ mutex. */
 724         for (i = 0; i < d->nvqs; ++i) {
 725                 mutex_lock(&d->vqs[i]->mutex);
 726                 d->vqs[i]->memory = newmem;
 727                 mutex_unlock(&d->vqs[i]->mutex);
 728         }
 729         kvfree(oldmem);
 730         return 0;
 731 }
 732
 733 long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
 734 {
 735         struct file *eventfp, *filep = NULL;
 736         bool pollstart = false, pollstop = false;
 737         struct eventfd_ctx *ctx = NULL;
 738         u32 __user *idxp = argp;
 739         struct vhost_virtqueue *vq;
 740         struct vhost_vring_state s;
 741         struct vhost_vring_file f;
 742         struct vhost_vring_addr a;
 743         u32 idx;
 744         long r;
 745
 746         r = get_user(idx, idxp);
 747         if (r < 0)
 748                 return r;
 749         if (idx >= d->nvqs)
 750                 return -ENOBUFS;
 751
 752         vq = d->vqs[idx];
 753
 754         mutex_lock(&vq->mutex);
 755
 756         switch (ioctl) {
 757         case VHOST_SET_VRING_NUM:
 758                 /* Resizing ring with an active backend?
 759                  * You don't want to do that. */
 760                 if (vq->private_data) {
 761                         r = -EBUSY;
 762                         break;
 763                 }
 764                 if (copy_from_user(&s, argp, sizeof s)) {
 765                         r = -EFAULT;
 766                         break;
 767                 }
 768                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 769                         r = -EINVAL;
 770                         break;
 771                 }
 772                 vq->num = s.num;
 773                 break;
 774         case VHOST_SET_VRING_BASE:
 775                 /* Moving base with an active backend?
 776                  * You don't want to do that. */
 777                 if (vq->private_data) {
 778                         r = -EBUSY;
 779                         break;
 780                 }
 781                 if (copy_from_user(&s, argp, sizeof s)) {
 782                         r = -EFAULT;
 783                         break;
 784                 }
 785                 if (s.num > 0xffff) {
 786                         r = -EINVAL;
 787                         break;
 788                 }
 789                 vq->last_avail_idx = s.num;
 790                 /* Forget the cached index value. */
 791                 vq->avail_idx = vq->last_avail_idx;
 792                 break;
 793         case VHOST_GET_VRING_BASE:
 794                 s.index = idx;
 795                 s.num = vq->last_avail_idx;
 796                 if (copy_to_user(argp, &s, sizeof s))
 797                         r = -EFAULT;
 798                 break;
 799         case VHOST_SET_VRING_ADDR:
 800                 if (copy_from_user(&a, argp, sizeof a)) {
 801                         r = -EFAULT;
 802                         break;
 803                 }
 804                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 805                         r = -EOPNOTSUPP;
 806                         break;
 807                 }
 808                 /* For 32bit, verify that the top 32bits of the user
 809                    data are set to zero. */
 810                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 811                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 812                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 813                         r = -EFAULT;
 814                         break;
 815                 }
 816
 817                 /* Make sure it's safe to cast pointers to vring types. */
 818                 BUILD_BUG_ON(__alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE);
 819                 BUILD_BUG_ON(__alignof__ *vq->used > VRING_USED_ALIGN_SIZE);
 820                 if ((a.avail_user_addr & (VRING_AVAIL_ALIGN_SIZE - 1)) ||
 821                     (a.used_user_addr & (VRING_USED_ALIGN_SIZE - 1)) ||
 822                     (a.log_guest_addr & (VRING_USED_ALIGN_SIZE - 1))) {
 823                         r = -EINVAL;
 824                         break;
 825                 }
 826
 827                 /* We only verify access here if backend is configured.
 828                  * If it is not, we don't as size might not have been setup.
 829                  * We will verify when backend is configured. */
 830                 if (vq->private_data) {
 831                         if (!vq_access_ok(vq, vq->num,
 832                                 (void __user *)(unsigned long)a.desc_user_addr,
 833                                 (void __user *)(unsigned long)a.avail_user_addr,
 834                                 (void __user *)(unsigned long)a.used_user_addr)) {
 835                                 r = -EINVAL;
 836                                 break;
 837                         }
 838
 839                         /* Also validate log access for used ring if enabled. */
 840                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 841                             !log_access_ok(vq->log_base, a.log_guest_addr,
 842                                            sizeof *vq->used +
 843                                            vq->num * sizeof *vq->used->ring)) {
 844                                 r = -EINVAL;
 845                                 break;
 846                         }
 847                 }
 848
 849                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 850                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 851                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 852                 vq->log_addr = a.log_guest_addr;
 853                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 854                 break;
 855         case VHOST_SET_VRING_KICK:
 856                 if (copy_from_user(&f, argp, sizeof f)) {
 857                         r = -EFAULT;
 858                         break;
 859                 }
 860                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 861                 if (IS_ERR(eventfp)) {
 862                         r = PTR_ERR(eventfp);
 863                         break;
 864                 }
 865                 if (eventfp != vq->kick) {
 866                         pollstop = (filep = vq->kick) != NULL;
 867                         pollstart = (vq->kick = eventfp) != NULL;
 868                 } else
 869                         filep = eventfp;
 870                 break;
 871         case VHOST_SET_VRING_CALL:
 872                 if (copy_from_user(&f, argp, sizeof f)) {
 873                         r = -EFAULT;
 874                         break;
 875                 }
 876                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 877                 if (IS_ERR(eventfp)) {
 878                         r = PTR_ERR(eventfp);
 879                         break;
 880                 }
 881                 if (eventfp != vq->call) {
 882                         filep = vq->call;
 883                         ctx = vq->call_ctx;
 884                         vq->call = eventfp;
 885                         vq->call_ctx = eventfp ?
 886                                 eventfd_ctx_fileget(eventfp) : NULL;
 887                 } else
 888                         filep = eventfp;
 889                 break;
 890         case VHOST_SET_VRING_ERR:
 891                 if (copy_from_user(&f, argp, sizeof f)) {
 892                         r = -EFAULT;
 893                         break;
 894                 }
 895                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 896                 if (IS_ERR(eventfp)) {
 897                         r = PTR_ERR(eventfp);
 898                         break;
 899                 }
 900                 if (eventfp != vq->error) {
 901                         filep = vq->error;
 902                         vq->error = eventfp;
 903                         ctx = vq->error_ctx;
 904                         vq->error_ctx = eventfp ?
 905                                 eventfd_ctx_fileget(eventfp) : NULL;
 906                 } else
 907                         filep = eventfp;
 908                 break;
 909         case VHOST_SET_VRING_ENDIAN:
 910                 r = vhost_set_vring_endian(vq, argp);
 911                 break;
 912         case VHOST_GET_VRING_ENDIAN:
 913                 r = vhost_get_vring_endian(vq, idx, argp);
 914                 break;
 915         default:
 916                 r = -ENOIOCTLCMD;
 917         }
 918
 919         if (pollstop && vq->handle_kick)
 920                 vhost_poll_stop(&vq->poll);
 921
 922         if (ctx)
 923                 eventfd_ctx_put(ctx);
 924         if (filep)
 925                 fput(filep);
 926
 927         if (pollstart && vq->handle_kick)
 928                 r = vhost_poll_start(&vq->poll, vq->kick);
 929
 930         mutex_unlock(&vq->mutex);
 931
 932         if (pollstop && vq->handle_kick)
 933                 vhost_poll_flush(&vq->poll);
 934         return r;
 935 }
 936 EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
 937
 938 /* Caller must have device mutex */
 939 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
 940 {
 941         struct file *eventfp, *filep = NULL;
 942         struct eventfd_ctx *ctx = NULL;
 943         u64 p;
 944         long r;
 945         int i, fd;
 946
 947         /* If you are not the owner, you can become one */
 948         if (ioctl == VHOST_SET_OWNER) {
 949                 r = vhost_dev_set_owner(d);
 950                 goto done;
 951         }
 952
 953         /* You must be the owner to do anything else */
 954         r = vhost_dev_check_owner(d);
 955         if (r)
 956                 goto done;
 957
 958         switch (ioctl) {
 959         case VHOST_SET_MEM_TABLE:
 960                 r = vhost_set_memory(d, argp);
 961                 break;
 962         case VHOST_SET_LOG_BASE:
 963                 if (copy_from_user(&p, argp, sizeof p)) {
 964                         r = -EFAULT;
 965                         break;
 966                 }
 967                 if ((u64)(unsigned long)p != p) {
 968                         r = -EFAULT;
 969                         break;
 970                 }
 971                 for (i = 0; i < d->nvqs; ++i) {
 972                         struct vhost_virtqueue *vq;
 973                         void __user *base = (void __user *)(unsigned long)p;
 974                         vq = d->vqs[i];
 975                         mutex_lock(&vq->mutex);
 976                         /* If ring is inactive, will check when it's enabled. */
 977                         if (vq->private_data && !vq_log_access_ok(vq, base))
 978                                 r = -EFAULT;
 979                         else
 980                                 vq->log_base = base;
 981                         mutex_unlock(&vq->mutex);
 982                 }
 983                 break;
 984         case VHOST_SET_LOG_FD:
 985                 r = get_user(fd, (int __user *)argp);
 986                 if (r < 0)
 987                         break;
 988                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 989                 if (IS_ERR(eventfp)) {
 990                         r = PTR_ERR(eventfp);
 991                         break;
 992                 }
 993                 if (eventfp != d->log_file) {
 994                         filep = d->log_file;
 995                         d->log_file = eventfp;
 996                         ctx = d->log_ctx;
 997                         d->log_ctx = eventfp ?
 998                                 eventfd_ctx_fileget(eventfp) : NULL;
 999                 } else
1000                         filep = eventfp;
1001                 for (i = 0; i < d->nvqs; ++i) {
1002                         mutex_lock(&d->vqs[i]->mutex);
1003                         d->vqs[i]->log_ctx = d->log_ctx;
1004                         mutex_unlock(&d->vqs[i]->mutex);
1005                 }
1006                 if (ctx)
1007                         eventfd_ctx_put(ctx);
1008                 if (filep)
1009                         fput(filep);
1010                 break;
1011         default:
1012                 r = -ENOIOCTLCMD;
1013                 break;
1014         }
1015 done:
1016         return r;
1017 }
1018 EXPORT_SYMBOL_GPL(vhost_dev_ioctl);
1019
1020 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
1021                                                      __u64 addr, __u32 len)
1022 {
1023         const struct vhost_memory_region *reg;
1024         int start = 0, end = mem->nregions;
1025
1026         while (start < end) {
1027                 int slot = start + (end - start) / 2;
1028                 reg = mem->regions + slot;
1029                 if (addr >= reg->guest_phys_addr)
1030                         end = slot;
1031                 else
1032                         start = slot + 1;
1033         }
1034
1035         reg = mem->regions + start;
1036         if (addr >= reg->guest_phys_addr &&
1037                 reg->guest_phys_addr + reg->memory_size > addr)
1038                 return reg;
1039         return NULL;
1040 }
1041
1042 /* TODO: This is really inefficient.  We need something like get_user()
1043  * (instruction directly accesses the data, with an exception table entry
1044  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
1045  */
1046 static int set_bit_to_user(int nr, void __user *addr)
1047 {
1048         unsigned long log = (unsigned long)addr;
1049         struct page *page;
1050         void *base;
1051         int bit = nr + (log % PAGE_SIZE) * 8;
1052         int r;
1053
1054         r = get_user_pages_fast(log, 1, 1, &page);
1055         if (r < 0)
1056                 return r;
1057         BUG_ON(r != 1);
1058         base = kmap_atomic(page);
1059         set_bit(bit, base);
1060         kunmap_atomic(base);
1061         set_page_dirty_lock(page);
1062         put_page(page);
1063         return 0;
1064 }
1065
1066 static int log_write(void __user *log_base,
1067                      u64 write_address, u64 write_length)
1068 {
1069         u64 write_page = write_address / VHOST_PAGE_SIZE;
1070         int r;
1071
1072         if (!write_length)
1073                 return 0;
1074         write_length += write_address % VHOST_PAGE_SIZE;
1075         for (;;) {
1076                 u64 base = (u64)(unsigned long)log_base;
1077                 u64 log = base + write_page / 8;
1078                 int bit = write_page % 8;
1079                 if ((u64)(unsigned long)log != log)
1080                         return -EFAULT;
1081                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
1082                 if (r < 0)
1083                         return r;
1084                 if (write_length <= VHOST_PAGE_SIZE)
1085                         break;
1086                 write_length -= VHOST_PAGE_SIZE;
1087                 write_page += 1;
1088         }
1089         return r;
1090 }
1091
1092 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
1093                     unsigned int log_num, u64 len)
1094 {
1095         int i, r;
1096
1097         /* Make sure data written is seen before log. */
1098         smp_wmb();
1099         for (i = 0; i < log_num; ++i) {
1100                 u64 l = min(log[i].len, len);
1101                 r = log_write(vq->log_base, log[i].addr, l);
1102                 if (r < 0)
1103                         return r;
1104                 len -= l;
1105                 if (!len) {
1106                         if (vq->log_ctx)
1107                                 eventfd_signal(vq->log_ctx, 1);
1108                         return 0;
1109                 }
1110         }
1111         /* Length written exceeds what we have stored. This is a bug. */
1112         BUG();
1113         return 0;
1114 }
1115 EXPORT_SYMBOL_GPL(vhost_log_write);
1116
1117 static int vhost_update_used_flags(struct vhost_virtqueue *vq)
1118 {
1119         void __user *used;
1120         if (__put_user(cpu_to_vhost16(vq, vq->used_flags), &vq->used->flags) < 0)
1121                 return -EFAULT;
1122         if (unlikely(vq->log_used)) {
1123                 /* Make sure the flag is seen before log. */
1124                 smp_wmb();
1125                 /* Log used flag write. */
1126                 used = &vq->used->flags;
1127                 log_write(vq->log_base, vq->log_addr +
1128                           (used - (void __user *)vq->used),
1129                           sizeof vq->used->flags);
1130                 if (vq->log_ctx)
1131                         eventfd_signal(vq->log_ctx, 1);
1132         }
1133         return 0;
1134 }
1135
1136 static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
1137 {
1138         if (__put_user(cpu_to_vhost16(vq, vq->avail_idx), vhost_avail_event(vq)))
1139                 return -EFAULT;
1140         if (unlikely(vq->log_used)) {
1141                 void __user *used;
1142                 /* Make sure the event is seen before log. */
1143                 smp_wmb();
1144                 /* Log avail event write */
1145                 used = vhost_avail_event(vq);
1146                 log_write(vq->log_base, vq->log_addr +
1147                           (used - (void __user *)vq->used),
1148                           sizeof *vhost_avail_event(vq));
1149                 if (vq->log_ctx)
1150                         eventfd_signal(vq->log_ctx, 1);
1151         }
1152         return 0;
1153 }
1154
1155 int vhost_init_used(struct vhost_virtqueue *vq)
1156 {
1157         __virtio16 last_used_idx;
1158         int r;
1159         if (!vq->private_data) {
1160                 vq->is_le = virtio_legacy_is_little_endian();
1161                 return 0;
1162         }
1163
1164         vhost_init_is_le(vq);
1165
1166         r = vhost_update_used_flags(vq);
1167         if (r)
1168                 return r;
1169         vq->signalled_used_valid = false;
1170         if (!access_ok(VERIFY_READ, &vq->used->idx, sizeof vq->used->idx))
1171                 return -EFAULT;
1172         r = __get_user(last_used_idx, &vq->used->idx);
1173         if (r)
1174                 return r;
1175         vq->last_used_idx = vhost16_to_cpu(vq, last_used_idx);
1176         return 0;
1177 }
1178 EXPORT_SYMBOL_GPL(vhost_init_used);
1179
1180 static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
1181                           struct iovec iov[], int iov_size)
1182 {
1183         const struct vhost_memory_region *reg;
1184         struct vhost_memory *mem;
1185         struct iovec *_iov;
1186         u64 s = 0;
1187         int ret = 0;
1188
1189         mem = vq->memory;
1190         while ((u64)len > s) {
1191                 u64 size;
1192                 if (unlikely(ret >= iov_size)) {
1193                         ret = -ENOBUFS;
1194                         break;
1195                 }
1196                 reg = find_region(mem, addr, len);
1197                 if (unlikely(!reg)) {
1198                         ret = -EFAULT;
1199                         break;
1200                 }
1201                 _iov = iov + ret;
1202                 size = reg->memory_size - addr + reg->guest_phys_addr;
1203                 _iov->iov_len = min((u64)len - s, size);
1204                 _iov->iov_base = (void __user *)(unsigned long)
1205                         (reg->userspace_addr + addr - reg->guest_phys_addr);
1206                 s += size;
1207                 addr += size;
1208                 ++ret;
1209         }
1210
1211         return ret;
1212 }
1213
1214 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
1215  * function returns the next descriptor in the chain,
1216  * or -1U if we're at the end. */
1217 static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc)
1218 {
1219         unsigned int next;
1220
1221         /* If this descriptor says it doesn't chain, we're done. */
1222         if (!(desc->flags & cpu_to_vhost16(vq, VRING_DESC_F_NEXT)))
1223                 return -1U;
1224
1225         /* Check they're not leading us off end of descriptors. */
1226         next = vhost16_to_cpu(vq, desc->next);
1227         /* Make sure compiler knows to grab that: we don't want it changing! */
1228         /* We will use the result as an index in an array, so most
1229          * architectures only need a compiler barrier here. */
1230         read_barrier_depends();
1231
1232         return next;
1233 }
1234
1235 static int get_indirect(struct vhost_virtqueue *vq,
1236                         struct iovec iov[], unsigned int iov_size,
1237                         unsigned int *out_num, unsigned int *in_num,
1238                         struct vhost_log *log, unsigned int *log_num,
1239                         struct vring_desc *indirect)
1240 {
1241         struct vring_desc desc;
1242         unsigned int i = 0, count, found = 0;
1243         u32 len = vhost32_to_cpu(vq, indirect->len);
1244         struct iov_iter from;
1245         int ret;
1246
1247         /* Sanity check */
1248         if (unlikely(len % sizeof desc)) {
1249                 vq_err(vq, "Invalid length in indirect descriptor: "
1250                        "len 0x%llx not multiple of 0x%zx\n",
1251                        (unsigned long long)len,
1252                        sizeof desc);
1253                 return -EINVAL;
1254         }
1255
1256         ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len, vq->indirect,
1257                              UIO_MAXIOV);
1258         if (unlikely(ret < 0)) {
1259                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1260                 return ret;
1261         }
1262         iov_iter_init(&from, READ, vq->indirect, ret, len);
1263
1264         /* We will use the result as an address to read from, so most
1265          * architectures only need a compiler barrier here. */
1266         read_barrier_depends();
1267
1268         count = len / sizeof desc;
1269         /* Buffers are chained via a 16 bit next field, so
1270          * we can have at most 2^16 of these. */
1271         if (unlikely(count > USHRT_MAX + 1)) {
1272                 vq_err(vq, "Indirect buffer length too big: %d\n",
1273                        indirect->len);
1274                 return -E2BIG;
1275         }
1276
1277         do {
1278                 unsigned iov_count = *in_num + *out_num;
1279                 if (unlikely(++found > count)) {
1280                         vq_err(vq, "Loop detected: last one at %u "
1281                                "indirect size %u\n",
1282                                i, count);
1283                         return -EINVAL;
1284                 }
1285                 if (unlikely(copy_from_iter(&desc, sizeof(desc), &from) !=
1286                              sizeof(desc))) {
1287                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1288                                i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
1289                         return -EINVAL;
1290                 }
1291                 if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) {
1292                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1293                                i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
1294                         return -EINVAL;
1295                 }
1296
1297                 ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
1298                                      vhost32_to_cpu(vq, desc.len), iov + iov_count,
1299                                      iov_size - iov_count);
1300                 if (unlikely(ret < 0)) {
1301                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1302                                ret, i);
1303                         return ret;
1304                 }
1305                 /* If this is an input descriptor, increment that count. */
1306                 if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) {
1307                         *in_num += ret;
1308                         if (unlikely(log)) {
1309                                 log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
1310                                 log[*log_num].len = vhost32_to_cpu(vq, desc.len);
1311                                 ++*log_num;
1312                         }
1313                 } else {
1314                         /* If it's an output descriptor, they're all supposed
1315                          * to come before any input descriptors. */
1316                         if (unlikely(*in_num)) {
1317                                 vq_err(vq, "Indirect descriptor "
1318                                        "has out after in: idx %d\n", i);
1319                                 return -EINVAL;
1320                         }
1321                         *out_num += ret;
1322                 }
1323         } while ((i = next_desc(vq, &desc)) != -1);
1324         return 0;
1325 }
1326
1327 /* This looks in the virtqueue and for the first available buffer, and converts
1328  * it to an iovec for convenient access.  Since descriptors consist of some
1329  * number of output then some number of input descriptors, it's actually two
1330  * iovecs, but we pack them into one and note how many of each there were.
1331  *
1332  * This function returns the descriptor number found, or vq->num (which is
1333  * never a valid descriptor number) if none was found.  A negative code is
1334  * returned on error. */
1335 int vhost_get_vq_desc(struct vhost_virtqueue *vq,
1336                       struct iovec iov[], unsigned int iov_size,
1337                       unsigned int *out_num, unsigned int *in_num,
1338                       struct vhost_log *log, unsigned int *log_num)
1339 {
1340         struct vring_desc desc;
1341         unsigned int i, head, found = 0;
1342         u16 last_avail_idx;
1343         __virtio16 avail_idx;
1344         __virtio16 ring_head;
1345         int ret;
1346
1347         /* Check it isn't doing very strange things with descriptor numbers. */
1348         last_avail_idx = vq->last_avail_idx;
1349         if (unlikely(__get_user(avail_idx, &vq->avail->idx))) {
1350                 vq_err(vq, "Failed to access avail idx at %p\n",
1351                        &vq->avail->idx);
1352                 return -EFAULT;
1353         }
1354         vq->avail_idx = vhost16_to_cpu(vq, avail_idx);
1355
1356         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1357                 vq_err(vq, "Guest moved used index from %u to %u",
1358                        last_avail_idx, vq->avail_idx);
1359                 return -EFAULT;
1360         }
1361
1362         /* If there's nothing new since last we looked, return invalid. */
1363         if (vq->avail_idx == last_avail_idx)
1364                 return vq->num;
1365
1366         /* Only get avail ring entries after they have been exposed by guest. */
1367         smp_rmb();
1368
1369         /* Grab the next descriptor number they're advertising, and increment
1370          * the index we've seen. */
1371         if (unlikely(__get_user(ring_head,
1372                                 &vq->avail->ring[last_avail_idx & (vq->num - 1)]))) {
1373                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1374                        last_avail_idx,
1375                        &vq->avail->ring[last_avail_idx % vq->num]);
1376                 return -EFAULT;
1377         }
1378
1379         head = vhost16_to_cpu(vq, ring_head);
1380
1381         /* If their number is silly, that's an error. */
1382         if (unlikely(head >= vq->num)) {
1383                 vq_err(vq, "Guest says index %u > %u is available",
1384                        head, vq->num);
1385                 return -EINVAL;
1386         }
1387
1388         /* When we start there are none of either input nor output. */
1389         *out_num = *in_num = 0;
1390         if (unlikely(log))
1391                 *log_num = 0;
1392
1393         i = head;
1394         do {
1395                 unsigned iov_count = *in_num + *out_num;
1396                 if (unlikely(i >= vq->num)) {
1397                         vq_err(vq, "Desc index is %u > %u, head = %u",
1398                                i, vq->num, head);
1399                         return -EINVAL;
1400                 }
1401                 if (unlikely(++found > vq->num)) {
1402                         vq_err(vq, "Loop detected: last one at %u "
1403                                "vq size %u head %u\n",
1404                                i, vq->num, head);
1405                         return -EINVAL;
1406                 }
1407                 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1408                 if (unlikely(ret)) {
1409                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1410                                i, vq->desc + i);
1411                         return -EFAULT;
1412                 }
1413                 if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
1414                         ret = get_indirect(vq, iov, iov_size,
1415                                            out_num, in_num,
1416                                            log, log_num, &desc);
1417                         if (unlikely(ret < 0)) {
1418                                 vq_err(vq, "Failure detected "
1419                                        "in indirect descriptor at idx %d\n", i);
1420                                 return ret;
1421                         }
1422                         continue;
1423                 }
1424
1425                 ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
1426                                      vhost32_to_cpu(vq, desc.len), iov + iov_count,
1427                                      iov_size - iov_count);
1428                 if (unlikely(ret < 0)) {
1429                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1430                                ret, i);
1431                         return ret;
1432                 }
1433                 if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) {
1434                         /* If this is an input descriptor,
1435                          * increment that count. */
1436                         *in_num += ret;
1437                         if (unlikely(log)) {
1438                                 log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
1439                                 log[*log_num].len = vhost32_to_cpu(vq, desc.len);
1440                                 ++*log_num;
1441                         }
1442                 } else {
1443                         /* If it's an output descriptor, they're all supposed
1444                          * to come before any input descriptors. */
1445                         if (unlikely(*in_num)) {
1446                                 vq_err(vq, "Descriptor has out after in: "
1447                                        "idx %d\n", i);
1448                                 return -EINVAL;
1449                         }
1450                         *out_num += ret;
1451                 }
1452         } while ((i = next_desc(vq, &desc)) != -1);
1453
1454         /* On success, increment avail index. */
1455         vq->last_avail_idx++;
1456
1457         /* Assume notifications from guest are disabled at this point,
1458          * if they aren't we would need to update avail_event index. */
1459         BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1460         return head;
1461 }
1462 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
1463
1464 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1465 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1466 {
1467         vq->last_avail_idx -= n;
1468 }
1469 EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
1470
1471 /* After we've used one of their buffers, we tell them about it.  We'll then
1472  * want to notify the guest, using eventfd. */
1473 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1474 {
1475         struct vring_used_elem heads = {
1476                 cpu_to_vhost32(vq, head),
1477                 cpu_to_vhost32(vq, len)
1478         };
1479
1480         return vhost_add_used_n(vq, &heads, 1);
1481 }
1482 EXPORT_SYMBOL_GPL(vhost_add_used);
1483
1484 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1485                             struct vring_used_elem *heads,
1486                             unsigned count)
1487 {
1488         struct vring_used_elem __user *used;
1489         u16 old, new;
1490         int start;
1491
1492         start = vq->last_used_idx & (vq->num - 1);
1493         used = vq->used->ring + start;
1494         if (count == 1) {
1495                 if (__put_user(heads[0].id, &used->id)) {
1496                         vq_err(vq, "Failed to write used id");
1497                         return -EFAULT;
1498                 }
1499                 if (__put_user(heads[0].len, &used->len)) {
1500                         vq_err(vq, "Failed to write used len");
1501                         return -EFAULT;
1502                 }
1503         } else if (__copy_to_user(used, heads, count * sizeof *used)) {
1504                 vq_err(vq, "Failed to write used");
1505                 return -EFAULT;
1506         }
1507         if (unlikely(vq->log_used)) {
1508                 /* Make sure data is seen before log. */
1509                 smp_wmb();
1510                 /* Log used ring entry write. */
1511                 log_write(vq->log_base,
1512                           vq->log_addr +
1513                            ((void __user *)used - (void __user *)vq->used),
1514                           count * sizeof *used);
1515         }
1516         old = vq->last_used_idx;
1517         new = (vq->last_used_idx += count);
1518         /* If the driver never bothers to signal in a very long while,
1519          * used index might wrap around. If that happens, invalidate
1520          * signalled_used index we stored. TODO: make sure driver
1521          * signals at least once in 2^16 and remove this. */
1522         if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1523                 vq->signalled_used_valid = false;
1524         return 0;
1525 }
1526
1527 /* After we've used one of their buffers, we tell them about it.  We'll then
1528  * want to notify the guest, using eventfd. */
1529 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1530                      unsigned count)
1531 {
1532         int start, n, r;
1533
1534         start = vq->last_used_idx & (vq->num - 1);
1535         n = vq->num - start;
1536         if (n < count) {
1537                 r = __vhost_add_used_n(vq, heads, n);
1538                 if (r < 0)
1539                         return r;
1540                 heads += n;
1541                 count -= n;
1542         }
1543         r = __vhost_add_used_n(vq, heads, count);
1544
1545         /* Make sure buffer is written before we update index. */
1546         smp_wmb();
1547         if (__put_user(cpu_to_vhost16(vq, vq->last_used_idx), &vq->used->idx)) {
1548                 vq_err(vq, "Failed to increment used idx");
1549                 return -EFAULT;
1550         }
1551         if (unlikely(vq->log_used)) {
1552                 /* Log used index update. */
1553                 log_write(vq->log_base,
1554                           vq->log_addr + offsetof(struct vring_used, idx),
1555                           sizeof vq->used->idx);
1556                 if (vq->log_ctx)
1557                         eventfd_signal(vq->log_ctx, 1);
1558         }
1559         return r;
1560 }
1561 EXPORT_SYMBOL_GPL(vhost_add_used_n);
1562
1563 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1564 {
1565         __u16 old, new;
1566         __virtio16 event;
1567         bool v;
1568         /* Flush out used index updates. This is paired
1569          * with the barrier that the Guest executes when enabling
1570          * interrupts. */
1571         smp_mb();
1572
1573         if (vhost_has_feature(vq, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1574             unlikely(vq->avail_idx == vq->last_avail_idx))
1575                 return true;
1576
1577         if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
1578                 __virtio16 flags;
1579                 if (__get_user(flags, &vq->avail->flags)) {
1580                         vq_err(vq, "Failed to get flags");
1581                         return true;
1582                 }
1583                 return !(flags & cpu_to_vhost16(vq, VRING_AVAIL_F_NO_INTERRUPT));
1584         }
1585         old = vq->signalled_used;
1586         v = vq->signalled_used_valid;
1587         new = vq->signalled_used = vq->last_used_idx;
1588         vq->signalled_used_valid = true;
1589
1590         if (unlikely(!v))
1591                 return true;
1592
1593         if (__get_user(event, vhost_used_event(vq))) {
1594                 vq_err(vq, "Failed to get used event idx");
1595                 return true;
1596         }
1597         return vring_need_event(vhost16_to_cpu(vq, event), new, old);
1598 }
1599
1600 /* This actually signals the guest, using eventfd. */
1601 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1602 {
1603         /* Signal the Guest tell them we used something up. */
1604         if (vq->call_ctx && vhost_notify(dev, vq))
1605                 eventfd_signal(vq->call_ctx, 1);
1606 }
1607 EXPORT_SYMBOL_GPL(vhost_signal);
1608
1609 /* And here's the combo meal deal.  Supersize me! */
1610 void vhost_add_used_and_signal(struct vhost_dev *dev,
1611                                struct vhost_virtqueue *vq,
1612                                unsigned int head, int len)
1613 {
1614         vhost_add_used(vq, head, len);
1615         vhost_signal(dev, vq);
1616 }
1617 EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
1618
1619 /* multi-buffer version of vhost_add_used_and_signal */
1620 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1621                                  struct vhost_virtqueue *vq,
1622                                  struct vring_used_elem *heads, unsigned count)
1623 {
1624         vhost_add_used_n(vq, heads, count);
1625         vhost_signal(dev, vq);
1626 }
1627 EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
1628
1629 /* OK, now we need to know about added descriptors. */
1630 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1631 {
1632         __virtio16 avail_idx;
1633         int r;
1634
1635         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1636                 return false;
1637         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1638         if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
1639                 r = vhost_update_used_flags(vq);
1640                 if (r) {
1641                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1642                                &vq->used->flags, r);
1643                         return false;
1644                 }
1645         } else {
1646                 r = vhost_update_avail_event(vq, vq->avail_idx);
1647                 if (r) {
1648                         vq_err(vq, "Failed to update avail event index at %p: %d\n",
1649                                vhost_avail_event(vq), r);
1650                         return false;
1651                 }
1652         }
1653         /* They could have slipped one in as we were doing that: make
1654          * sure it's written, then check again. */
1655         smp_mb();
1656         r = __get_user(avail_idx, &vq->avail->idx);
1657         if (r) {
1658                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1659                        &vq->avail->idx, r);
1660                 return false;
1661         }
1662
1663         return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx;
1664 }
1665 EXPORT_SYMBOL_GPL(vhost_enable_notify);
1666
1667 /* We don't need to be notified again. */
1668 void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1669 {
1670         int r;
1671
1672         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1673                 return;
1674         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1675         if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
1676                 r = vhost_update_used_flags(vq);
1677                 if (r)
1678                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1679                                &vq->used->flags, r);
1680         }
1681 }
1682 EXPORT_SYMBOL_GPL(vhost_disable_notify);
1683
1684 static int __init vhost_init(void)
1685 {
1686         return 0;
1687 }
1688
1689 static void __exit vhost_exit(void)
1690 {
1691 }
1692
1693 module_init(vhost_init);
1694 module_exit(vhost_exit);
1695
1696 MODULE_VERSION("0.0.1");
1697 MODULE_LICENSE("GPL v2");
1698 MODULE_AUTHOR("Michael S. Tsirkin");
1699 MODULE_DESCRIPTION("Host kernel accelerator for virtio");