Pileus Git - ~andy/linux/blob - 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/virtio_net.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
  29 #include "vhost.h"
  30
  31 enum {
  32         VHOST_MEMORY_MAX_NREGIONS = 64,
  33         VHOST_MEMORY_F_LOG = 0x1,
  34 };
  35
  36 static unsigned vhost_zcopy_mask __read_mostly;
  37
  38 #define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
  39 #define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
  40
  41 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  42                             poll_table *pt)
  43 {
  44         struct vhost_poll *poll;
  45
  46         poll = container_of(pt, struct vhost_poll, table);
  47         poll->wqh = wqh;
  48         add_wait_queue(wqh, &poll->wait);
  49 }
  50
  51 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
  52                              void *key)
  53 {
  54         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  55
  56         if (!((unsigned long)key & poll->mask))
  57                 return 0;
  58
  59         vhost_poll_queue(poll);
  60         return 0;
  61 }
  62
  63 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  64 {
  65         INIT_LIST_HEAD(&work->node);
  66         work->fn = fn;
  67         init_waitqueue_head(&work->done);
  68         work->flushing = 0;
  69         work->queue_seq = work->done_seq = 0;
  70 }
  71
  72 /* Init poll structure */
  73 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  74                      unsigned long mask, struct vhost_dev *dev)
  75 {
  76         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  77         init_poll_funcptr(&poll->table, vhost_poll_func);
  78         poll->mask = mask;
  79         poll->dev = dev;
  80
  81         vhost_work_init(&poll->work, fn);
  82 }
  83
  84 /* Start polling a file. We add ourselves to file's wait queue. The caller must
  85  * keep a reference to a file until after vhost_poll_stop is called. */
  86 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
  87 {
  88         unsigned long mask;
  89
  90         mask = file->f_op->poll(file, &poll->table);
  91         if (mask)
  92                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  93 }
  94
  95 /* Stop polling a file. After this function returns, it becomes safe to drop the
  96  * file reference. You must also flush afterwards. */
  97 void vhost_poll_stop(struct vhost_poll *poll)
  98 {
  99         remove_wait_queue(poll->wqh, &poll->wait);
 100 }
 101
 102 static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
 103                                 unsigned seq)
 104 {
 105         int left;
 106
 107         spin_lock_irq(&dev->work_lock);
 108         left = seq - work->done_seq;
 109         spin_unlock_irq(&dev->work_lock);
 110         return left <= 0;
 111 }
 112
 113 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 114 {
 115         unsigned seq;
 116         int flushing;
 117
 118         spin_lock_irq(&dev->work_lock);
 119         seq = work->queue_seq;
 120         work->flushing++;
 121         spin_unlock_irq(&dev->work_lock);
 122         wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 123         spin_lock_irq(&dev->work_lock);
 124         flushing = --work->flushing;
 125         spin_unlock_irq(&dev->work_lock);
 126         BUG_ON(flushing < 0);
 127 }
 128
 129 /* Flush any work that has been scheduled. When calling this, don't hold any
 130  * locks that are also used by the callback. */
 131 void vhost_poll_flush(struct vhost_poll *poll)
 132 {
 133         vhost_work_flush(poll->dev, &poll->work);
 134 }
 135
 136 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 137 {
 138         unsigned long flags;
 139
 140         spin_lock_irqsave(&dev->work_lock, flags);
 141         if (list_empty(&work->node)) {
 142                 list_add_tail(&work->node, &dev->work_list);
 143                 work->queue_seq++;
 144                 wake_up_process(dev->worker);
 145         }
 146         spin_unlock_irqrestore(&dev->work_lock, flags);
 147 }
 148
 149 void vhost_poll_queue(struct vhost_poll *poll)
 150 {
 151         vhost_work_queue(poll->dev, &poll->work);
 152 }
 153
 154 static void vhost_vq_reset(struct vhost_dev *dev,
 155                            struct vhost_virtqueue *vq)
 156 {
 157         vq->num = 1;
 158         vq->desc = NULL;
 159         vq->avail = NULL;
 160         vq->used = NULL;
 161         vq->last_avail_idx = 0;
 162         vq->avail_idx = 0;
 163         vq->last_used_idx = 0;
 164         vq->signalled_used = 0;
 165         vq->signalled_used_valid = false;
 166         vq->used_flags = 0;
 167         vq->log_used = false;
 168         vq->log_addr = -1ull;
 169         vq->vhost_hlen = 0;
 170         vq->sock_hlen = 0;
 171         vq->private_data = NULL;
 172         vq->log_base = NULL;
 173         vq->error_ctx = NULL;
 174         vq->error = NULL;
 175         vq->kick = NULL;
 176         vq->call_ctx = NULL;
 177         vq->call = NULL;
 178         vq->log_ctx = NULL;
 179         vq->upend_idx = 0;
 180         vq->done_idx = 0;
 181         vq->ubufs = NULL;
 182 }
 183
 184 static int vhost_worker(void *data)
 185 {
 186         struct vhost_dev *dev = data;
 187         struct vhost_work *work = NULL;
 188         unsigned uninitialized_var(seq);
 189         mm_segment_t oldfs = get_fs();
 190
 191         set_fs(USER_DS);
 192         use_mm(dev->mm);
 193
 194         for (;;) {
 195                 /* mb paired w/ kthread_stop */
 196                 set_current_state(TASK_INTERRUPTIBLE);
 197
 198                 spin_lock_irq(&dev->work_lock);
 199                 if (work) {
 200                         work->done_seq = seq;
 201                         if (work->flushing)
 202                                 wake_up_all(&work->done);
 203                 }
 204
 205                 if (kthread_should_stop()) {
 206                         spin_unlock_irq(&dev->work_lock);
 207                         __set_current_state(TASK_RUNNING);
 208                         break;
 209                 }
 210                 if (!list_empty(&dev->work_list)) {
 211                         work = list_first_entry(&dev->work_list,
 212                                                 struct vhost_work, node);
 213                         list_del_init(&work->node);
 214                         seq = work->queue_seq;
 215                 } else
 216                         work = NULL;
 217                 spin_unlock_irq(&dev->work_lock);
 218
 219                 if (work) {
 220                         __set_current_state(TASK_RUNNING);
 221                         work->fn(work);
 222                         if (need_resched())
 223                                 schedule();
 224                 } else
 225                         schedule();
 226
 227         }
 228         unuse_mm(dev->mm);
 229         set_fs(oldfs);
 230         return 0;
 231 }
 232
 233 static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
 234 {
 235         kfree(vq->indirect);
 236         vq->indirect = NULL;
 237         kfree(vq->log);
 238         vq->log = NULL;
 239         kfree(vq->heads);
 240         vq->heads = NULL;
 241         kfree(vq->ubuf_info);
 242         vq->ubuf_info = NULL;
 243 }
 244
 245 void vhost_enable_zcopy(int vq)
 246 {
 247         vhost_zcopy_mask |= 0x1 << vq;
 248 }
 249
 250 /* Helper to allocate iovec buffers for all vqs. */
 251 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 252 {
 253         int i;
 254         bool zcopy;
 255
 256         for (i = 0; i < dev->nvqs; ++i) {
 257                 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
 258                                                UIO_MAXIOV, GFP_KERNEL);
 259                 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
 260                                           GFP_KERNEL);
 261                 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
 262                                             UIO_MAXIOV, GFP_KERNEL);
 263                 zcopy = vhost_zcopy_mask & (0x1 << i);
 264                 if (zcopy)
 265                         dev->vqs[i].ubuf_info =
 266                                 kmalloc(sizeof *dev->vqs[i].ubuf_info *
 267                                         UIO_MAXIOV, GFP_KERNEL);
 268                 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
 269                         !dev->vqs[i].heads ||
 270                         (zcopy && !dev->vqs[i].ubuf_info))
 271                         goto err_nomem;
 272         }
 273         return 0;
 274
 275 err_nomem:
 276         for (; i >= 0; --i)
 277                 vhost_vq_free_iovecs(&dev->vqs[i]);
 278         return -ENOMEM;
 279 }
 280
 281 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
 282 {
 283         int i;
 284
 285         for (i = 0; i < dev->nvqs; ++i)
 286                 vhost_vq_free_iovecs(&dev->vqs[i]);
 287 }
 288
 289 long vhost_dev_init(struct vhost_dev *dev,
 290                     struct vhost_virtqueue *vqs, int nvqs)
 291 {
 292         int i;
 293
 294         dev->vqs = vqs;
 295         dev->nvqs = nvqs;
 296         mutex_init(&dev->mutex);
 297         dev->log_ctx = NULL;
 298         dev->log_file = NULL;
 299         dev->memory = NULL;
 300         dev->mm = NULL;
 301         spin_lock_init(&dev->work_lock);
 302         INIT_LIST_HEAD(&dev->work_list);
 303         dev->worker = NULL;
 304
 305         for (i = 0; i < dev->nvqs; ++i) {
 306                 dev->vqs[i].log = NULL;
 307                 dev->vqs[i].indirect = NULL;
 308                 dev->vqs[i].heads = NULL;
 309                 dev->vqs[i].ubuf_info = NULL;
 310                 dev->vqs[i].dev = dev;
 311                 mutex_init(&dev->vqs[i].mutex);
 312                 vhost_vq_reset(dev, dev->vqs + i);
 313                 if (dev->vqs[i].handle_kick)
 314                         vhost_poll_init(&dev->vqs[i].poll,
 315                                         dev->vqs[i].handle_kick, POLLIN, dev);
 316         }
 317
 318         return 0;
 319 }
 320
 321 /* Caller should have device mutex */
 322 long vhost_dev_check_owner(struct vhost_dev *dev)
 323 {
 324         /* Are you the owner? If not, I don't think you mean to do that */
 325         return dev->mm == current->mm ? 0 : -EPERM;
 326 }
 327
 328 struct vhost_attach_cgroups_struct {
 329         struct vhost_work work;
 330         struct task_struct *owner;
 331         int ret;
 332 };
 333
 334 static void vhost_attach_cgroups_work(struct vhost_work *work)
 335 {
 336         struct vhost_attach_cgroups_struct *s;
 337
 338         s = container_of(work, struct vhost_attach_cgroups_struct, work);
 339         s->ret = cgroup_attach_task_all(s->owner, current);
 340 }
 341
 342 static int vhost_attach_cgroups(struct vhost_dev *dev)
 343 {
 344         struct vhost_attach_cgroups_struct attach;
 345
 346         attach.owner = current;
 347         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 348         vhost_work_queue(dev, &attach.work);
 349         vhost_work_flush(dev, &attach.work);
 350         return attach.ret;
 351 }
 352
 353 /* Caller should have device mutex */
 354 static long vhost_dev_set_owner(struct vhost_dev *dev)
 355 {
 356         struct task_struct *worker;
 357         int err;
 358
 359         /* Is there an owner already? */
 360         if (dev->mm) {
 361                 err = -EBUSY;
 362                 goto err_mm;
 363         }
 364
 365         /* No owner, become one */
 366         dev->mm = get_task_mm(current);
 367         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 368         if (IS_ERR(worker)) {
 369                 err = PTR_ERR(worker);
 370                 goto err_worker;
 371         }
 372
 373         dev->worker = worker;
 374         wake_up_process(worker);        /* avoid contributing to loadavg */
 375
 376         err = vhost_attach_cgroups(dev);
 377         if (err)
 378                 goto err_cgroup;
 379
 380         err = vhost_dev_alloc_iovecs(dev);
 381         if (err)
 382                 goto err_cgroup;
 383
 384         return 0;
 385 err_cgroup:
 386         kthread_stop(worker);
 387         dev->worker = NULL;
 388 err_worker:
 389         if (dev->mm)
 390                 mmput(dev->mm);
 391         dev->mm = NULL;
 392 err_mm:
 393         return err;
 394 }
 395
 396 /* Caller should have device mutex */
 397 long vhost_dev_reset_owner(struct vhost_dev *dev)
 398 {
 399         struct vhost_memory *memory;
 400
 401         /* Restore memory to default empty mapping. */
 402         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 403         if (!memory)
 404                 return -ENOMEM;
 405
 406         vhost_dev_cleanup(dev, true);
 407
 408         memory->nregions = 0;
 409         RCU_INIT_POINTER(dev->memory, memory);
 410         return 0;
 411 }
 412
 413 void vhost_dev_stop(struct vhost_dev *dev)
 414 {
 415         int i;
 416
 417         for (i = 0; i < dev->nvqs; ++i) {
 418                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
 419                         vhost_poll_stop(&dev->vqs[i].poll);
 420                         vhost_poll_flush(&dev->vqs[i].poll);
 421                 }
 422         }
 423 }
 424
 425 /* Caller should have device mutex if and only if locked is set */
 426 void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 427 {
 428         int i;
 429
 430         for (i = 0; i < dev->nvqs; ++i) {
 431                 if (dev->vqs[i].error_ctx)
 432                         eventfd_ctx_put(dev->vqs[i].error_ctx);
 433                 if (dev->vqs[i].error)
 434                         fput(dev->vqs[i].error);
 435                 if (dev->vqs[i].kick)
 436                         fput(dev->vqs[i].kick);
 437                 if (dev->vqs[i].call_ctx)
 438                         eventfd_ctx_put(dev->vqs[i].call_ctx);
 439                 if (dev->vqs[i].call)
 440                         fput(dev->vqs[i].call);
 441                 vhost_vq_reset(dev, dev->vqs + i);
 442         }
 443         vhost_dev_free_iovecs(dev);
 444         if (dev->log_ctx)
 445                 eventfd_ctx_put(dev->log_ctx);
 446         dev->log_ctx = NULL;
 447         if (dev->log_file)
 448                 fput(dev->log_file);
 449         dev->log_file = NULL;
 450         /* No one will access memory at this point */
 451         kfree(rcu_dereference_protected(dev->memory,
 452                                         locked ==
 453                                                 lockdep_is_held(&dev->mutex)));
 454         RCU_INIT_POINTER(dev->memory, NULL);
 455         WARN_ON(!list_empty(&dev->work_list));
 456         if (dev->worker) {
 457                 kthread_stop(dev->worker);
 458                 dev->worker = NULL;
 459         }
 460         if (dev->mm)
 461                 mmput(dev->mm);
 462         dev->mm = NULL;
 463 }
 464
 465 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 466 {
 467         u64 a = addr / VHOST_PAGE_SIZE / 8;
 468
 469         /* Make sure 64 bit math will not overflow. */
 470         if (a > ULONG_MAX - (unsigned long)log_base ||
 471             a + (unsigned long)log_base > ULONG_MAX)
 472                 return 0;
 473
 474         return access_ok(VERIFY_WRITE, log_base + a,
 475                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 476 }
 477
 478 /* Caller should have vq mutex and device mutex. */
 479 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 480                                int log_all)
 481 {
 482         int i;
 483
 484         if (!mem)
 485                 return 0;
 486
 487         for (i = 0; i < mem->nregions; ++i) {
 488                 struct vhost_memory_region *m = mem->regions + i;
 489                 unsigned long a = m->userspace_addr;
 490                 if (m->memory_size > ULONG_MAX)
 491                         return 0;
 492                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 493                                     m->memory_size))
 494                         return 0;
 495                 else if (log_all && !log_access_ok(log_base,
 496                                                    m->guest_phys_addr,
 497                                                    m->memory_size))
 498                         return 0;
 499         }
 500         return 1;
 501 }
 502
 503 /* Can we switch to this memory table? */
 504 /* Caller should have device mutex but not vq mutex */
 505 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 506                             int log_all)
 507 {
 508         int i;
 509
 510         for (i = 0; i < d->nvqs; ++i) {
 511                 int ok;
 512                 mutex_lock(&d->vqs[i].mutex);
 513                 /* If ring is inactive, will check when it's enabled. */
 514                 if (d->vqs[i].private_data)
 515                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
 516                                                  log_all);
 517                 else
 518                         ok = 1;
 519                 mutex_unlock(&d->vqs[i].mutex);
 520                 if (!ok)
 521                         return 0;
 522         }
 523         return 1;
 524 }
 525
 526 static int vq_access_ok(struct vhost_dev *d, unsigned int num,
 527                         struct vring_desc __user *desc,
 528                         struct vring_avail __user *avail,
 529                         struct vring_used __user *used)
 530 {
 531         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 532         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 533                access_ok(VERIFY_READ, avail,
 534                          sizeof *avail + num * sizeof *avail->ring + s) &&
 535                access_ok(VERIFY_WRITE, used,
 536                         sizeof *used + num * sizeof *used->ring + s);
 537 }
 538
 539 /* Can we log writes? */
 540 /* Caller should have device mutex but not vq mutex */
 541 int vhost_log_access_ok(struct vhost_dev *dev)
 542 {
 543         struct vhost_memory *mp;
 544
 545         mp = rcu_dereference_protected(dev->memory,
 546                                        lockdep_is_held(&dev->mutex));
 547         return memory_access_ok(dev, mp, 1);
 548 }
 549
 550 /* Verify access for write logging. */
 551 /* Caller should have vq mutex and device mutex */
 552 static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
 553                             void __user *log_base)
 554 {
 555         struct vhost_memory *mp;
 556         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 557
 558         mp = rcu_dereference_protected(vq->dev->memory,
 559                                        lockdep_is_held(&vq->mutex));
 560         return vq_memory_access_ok(log_base, mp,
 561                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 562                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 563                                         sizeof *vq->used +
 564                                         vq->num * sizeof *vq->used->ring + s));
 565 }
 566
 567 /* Can we start vq? */
 568 /* Caller should have vq mutex and device mutex */
 569 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 570 {
 571         return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
 572                 vq_log_access_ok(vq->dev, vq, vq->log_base);
 573 }
 574
 575 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 576 {
 577         struct vhost_memory mem, *newmem, *oldmem;
 578         unsigned long size = offsetof(struct vhost_memory, regions);
 579
 580         if (copy_from_user(&mem, m, size))
 581                 return -EFAULT;
 582         if (mem.padding)
 583                 return -EOPNOTSUPP;
 584         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 585                 return -E2BIG;
 586         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 587         if (!newmem)
 588                 return -ENOMEM;
 589
 590         memcpy(newmem, &mem, size);
 591         if (copy_from_user(newmem->regions, m->regions,
 592                            mem.nregions * sizeof *m->regions)) {
 593                 kfree(newmem);
 594                 return -EFAULT;
 595         }
 596
 597         if (!memory_access_ok(d, newmem,
 598                               vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 599                 kfree(newmem);
 600                 return -EFAULT;
 601         }
 602         oldmem = rcu_dereference_protected(d->memory,
 603                                            lockdep_is_held(&d->mutex));
 604         rcu_assign_pointer(d->memory, newmem);
 605         synchronize_rcu();
 606         kfree(oldmem);
 607         return 0;
 608 }
 609
 610 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 611 {
 612         struct file *eventfp, *filep = NULL;
 613         bool pollstart = false, pollstop = false;
 614         struct eventfd_ctx *ctx = NULL;
 615         u32 __user *idxp = argp;
 616         struct vhost_virtqueue *vq;
 617         struct vhost_vring_state s;
 618         struct vhost_vring_file f;
 619         struct vhost_vring_addr a;
 620         u32 idx;
 621         long r;
 622
 623         r = get_user(idx, idxp);
 624         if (r < 0)
 625                 return r;
 626         if (idx >= d->nvqs)
 627                 return -ENOBUFS;
 628
 629         vq = d->vqs + idx;
 630
 631         mutex_lock(&vq->mutex);
 632
 633         switch (ioctl) {
 634         case VHOST_SET_VRING_NUM:
 635                 /* Resizing ring with an active backend?
 636                  * You don't want to do that. */
 637                 if (vq->private_data) {
 638                         r = -EBUSY;
 639                         break;
 640                 }
 641                 if (copy_from_user(&s, argp, sizeof s)) {
 642                         r = -EFAULT;
 643                         break;
 644                 }
 645                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 646                         r = -EINVAL;
 647                         break;
 648                 }
 649                 vq->num = s.num;
 650                 break;
 651         case VHOST_SET_VRING_BASE:
 652                 /* Moving base with an active backend?
 653                  * You don't want to do that. */
 654                 if (vq->private_data) {
 655                         r = -EBUSY;
 656                         break;
 657                 }
 658                 if (copy_from_user(&s, argp, sizeof s)) {
 659                         r = -EFAULT;
 660                         break;
 661                 }
 662                 if (s.num > 0xffff) {
 663                         r = -EINVAL;
 664                         break;
 665                 }
 666                 vq->last_avail_idx = s.num;
 667                 /* Forget the cached index value. */
 668                 vq->avail_idx = vq->last_avail_idx;
 669                 break;
 670         case VHOST_GET_VRING_BASE:
 671                 s.index = idx;
 672                 s.num = vq->last_avail_idx;
 673                 if (copy_to_user(argp, &s, sizeof s))
 674                         r = -EFAULT;
 675                 break;
 676         case VHOST_SET_VRING_ADDR:
 677                 if (copy_from_user(&a, argp, sizeof a)) {
 678                         r = -EFAULT;
 679                         break;
 680                 }
 681                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 682                         r = -EOPNOTSUPP;
 683                         break;
 684                 }
 685                 /* For 32bit, verify that the top 32bits of the user
 686                    data are set to zero. */
 687                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 688                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 689                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 690                         r = -EFAULT;
 691                         break;
 692                 }
 693                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 694                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 695                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 696                         r = -EINVAL;
 697                         break;
 698                 }
 699
 700                 /* We only verify access here if backend is configured.
 701                  * If it is not, we don't as size might not have been setup.
 702                  * We will verify when backend is configured. */
 703                 if (vq->private_data) {
 704                         if (!vq_access_ok(d, vq->num,
 705                                 (void __user *)(unsigned long)a.desc_user_addr,
 706                                 (void __user *)(unsigned long)a.avail_user_addr,
 707                                 (void __user *)(unsigned long)a.used_user_addr)) {
 708                                 r = -EINVAL;
 709                                 break;
 710                         }
 711
 712                         /* Also validate log access for used ring if enabled. */
 713                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 714                             !log_access_ok(vq->log_base, a.log_guest_addr,
 715                                            sizeof *vq->used +
 716                                            vq->num * sizeof *vq->used->ring)) {
 717                                 r = -EINVAL;
 718                                 break;
 719                         }
 720                 }
 721
 722                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 723                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 724                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 725                 vq->log_addr = a.log_guest_addr;
 726                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 727                 break;
 728         case VHOST_SET_VRING_KICK:
 729                 if (copy_from_user(&f, argp, sizeof f)) {
 730                         r = -EFAULT;
 731                         break;
 732                 }
 733                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 734                 if (IS_ERR(eventfp)) {
 735                         r = PTR_ERR(eventfp);
 736                         break;
 737                 }
 738                 if (eventfp != vq->kick) {
 739                         pollstop = (filep = vq->kick) != NULL;
 740                         pollstart = (vq->kick = eventfp) != NULL;
 741                 } else
 742                         filep = eventfp;
 743                 break;
 744         case VHOST_SET_VRING_CALL:
 745                 if (copy_from_user(&f, argp, sizeof f)) {
 746                         r = -EFAULT;
 747                         break;
 748                 }
 749                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 750                 if (IS_ERR(eventfp)) {
 751                         r = PTR_ERR(eventfp);
 752                         break;
 753                 }
 754                 if (eventfp != vq->call) {
 755                         filep = vq->call;
 756                         ctx = vq->call_ctx;
 757                         vq->call = eventfp;
 758                         vq->call_ctx = eventfp ?
 759                                 eventfd_ctx_fileget(eventfp) : NULL;
 760                 } else
 761                         filep = eventfp;
 762                 break;
 763         case VHOST_SET_VRING_ERR:
 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->error) {
 774                         filep = vq->error;
 775                         vq->error = eventfp;
 776                         ctx = vq->error_ctx;
 777                         vq->error_ctx = eventfp ?
 778                                 eventfd_ctx_fileget(eventfp) : NULL;
 779                 } else
 780                         filep = eventfp;
 781                 break;
 782         default:
 783                 r = -ENOIOCTLCMD;
 784         }
 785
 786         if (pollstop && vq->handle_kick)
 787                 vhost_poll_stop(&vq->poll);
 788
 789         if (ctx)
 790                 eventfd_ctx_put(ctx);
 791         if (filep)
 792                 fput(filep);
 793
 794         if (pollstart && vq->handle_kick)
 795                 vhost_poll_start(&vq->poll, vq->kick);
 796
 797         mutex_unlock(&vq->mutex);
 798
 799         if (pollstop && vq->handle_kick)
 800                 vhost_poll_flush(&vq->poll);
 801         return r;
 802 }
 803
 804 /* Caller must have device mutex */
 805 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 806 {
 807         void __user *argp = (void __user *)arg;
 808         struct file *eventfp, *filep = NULL;
 809         struct eventfd_ctx *ctx = NULL;
 810         u64 p;
 811         long r;
 812         int i, fd;
 813
 814         /* If you are not the owner, you can become one */
 815         if (ioctl == VHOST_SET_OWNER) {
 816                 r = vhost_dev_set_owner(d);
 817                 goto done;
 818         }
 819
 820         /* You must be the owner to do anything else */
 821         r = vhost_dev_check_owner(d);
 822         if (r)
 823                 goto done;
 824
 825         switch (ioctl) {
 826         case VHOST_SET_MEM_TABLE:
 827                 r = vhost_set_memory(d, argp);
 828                 break;
 829         case VHOST_SET_LOG_BASE:
 830                 if (copy_from_user(&p, argp, sizeof p)) {
 831                         r = -EFAULT;
 832                         break;
 833                 }
 834                 if ((u64)(unsigned long)p != p) {
 835                         r = -EFAULT;
 836                         break;
 837                 }
 838                 for (i = 0; i < d->nvqs; ++i) {
 839                         struct vhost_virtqueue *vq;
 840                         void __user *base = (void __user *)(unsigned long)p;
 841                         vq = d->vqs + i;
 842                         mutex_lock(&vq->mutex);
 843                         /* If ring is inactive, will check when it's enabled. */
 844                         if (vq->private_data && !vq_log_access_ok(d, vq, base))
 845                                 r = -EFAULT;
 846                         else
 847                                 vq->log_base = base;
 848                         mutex_unlock(&vq->mutex);
 849                 }
 850                 break;
 851         case VHOST_SET_LOG_FD:
 852                 r = get_user(fd, (int __user *)argp);
 853                 if (r < 0)
 854                         break;
 855                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 856                 if (IS_ERR(eventfp)) {
 857                         r = PTR_ERR(eventfp);
 858                         break;
 859                 }
 860                 if (eventfp != d->log_file) {
 861                         filep = d->log_file;
 862                         ctx = d->log_ctx;
 863                         d->log_ctx = eventfp ?
 864                                 eventfd_ctx_fileget(eventfp) : NULL;
 865                 } else
 866                         filep = eventfp;
 867                 for (i = 0; i < d->nvqs; ++i) {
 868                         mutex_lock(&d->vqs[i].mutex);
 869                         d->vqs[i].log_ctx = d->log_ctx;
 870                         mutex_unlock(&d->vqs[i].mutex);
 871                 }
 872                 if (ctx)
 873                         eventfd_ctx_put(ctx);
 874                 if (filep)
 875                         fput(filep);
 876                 break;
 877         default:
 878                 r = vhost_set_vring(d, ioctl, argp);
 879                 break;
 880         }
 881 done:
 882         return r;
 883 }
 884
 885 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 886                                                      __u64 addr, __u32 len)
 887 {
 888         struct vhost_memory_region *reg;
 889         int i;
 890
 891         /* linear search is not brilliant, but we really have on the order of 6
 892          * regions in practice */
 893         for (i = 0; i < mem->nregions; ++i) {
 894                 reg = mem->regions + i;
 895                 if (reg->guest_phys_addr <= addr &&
 896                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 897                         return reg;
 898         }
 899         return NULL;
 900 }
 901
 902 /* TODO: This is really inefficient.  We need something like get_user()
 903  * (instruction directly accesses the data, with an exception table entry
 904  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 905  */
 906 static int set_bit_to_user(int nr, void __user *addr)
 907 {
 908         unsigned long log = (unsigned long)addr;
 909         struct page *page;
 910         void *base;
 911         int bit = nr + (log % PAGE_SIZE) * 8;
 912         int r;
 913
 914         r = get_user_pages_fast(log, 1, 1, &page);
 915         if (r < 0)
 916                 return r;
 917         BUG_ON(r != 1);
 918         base = kmap_atomic(page);
 919         set_bit(bit, base);
 920         kunmap_atomic(base);
 921         set_page_dirty_lock(page);
 922         put_page(page);
 923         return 0;
 924 }
 925
 926 static int log_write(void __user *log_base,
 927                      u64 write_address, u64 write_length)
 928 {
 929         u64 write_page = write_address / VHOST_PAGE_SIZE;
 930         int r;
 931
 932         if (!write_length)
 933                 return 0;
 934         write_length += write_address % VHOST_PAGE_SIZE;
 935         for (;;) {
 936                 u64 base = (u64)(unsigned long)log_base;
 937                 u64 log = base + write_page / 8;
 938                 int bit = write_page % 8;
 939                 if ((u64)(unsigned long)log != log)
 940                         return -EFAULT;
 941                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 942                 if (r < 0)
 943                         return r;
 944                 if (write_length <= VHOST_PAGE_SIZE)
 945                         break;
 946                 write_length -= VHOST_PAGE_SIZE;
 947                 write_page += 1;
 948         }
 949         return r;
 950 }
 951
 952 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 953                     unsigned int log_num, u64 len)
 954 {
 955         int i, r;
 956
 957         /* Make sure data written is seen before log. */
 958         smp_wmb();
 959         for (i = 0; i < log_num; ++i) {
 960                 u64 l = min(log[i].len, len);
 961                 r = log_write(vq->log_base, log[i].addr, l);
 962                 if (r < 0)
 963                         return r;
 964                 len -= l;
 965                 if (!len) {
 966                         if (vq->log_ctx)
 967                                 eventfd_signal(vq->log_ctx, 1);
 968                         return 0;
 969                 }
 970         }
 971         /* Length written exceeds what we have stored. This is a bug. */
 972         BUG();
 973         return 0;
 974 }
 975
 976 static int vhost_update_used_flags(struct vhost_virtqueue *vq)
 977 {
 978         void __user *used;
 979         if (__put_user(vq->used_flags, &vq->used->flags) < 0)
 980                 return -EFAULT;
 981         if (unlikely(vq->log_used)) {
 982                 /* Make sure the flag is seen before log. */
 983                 smp_wmb();
 984                 /* Log used flag write. */
 985                 used = &vq->used->flags;
 986                 log_write(vq->log_base, vq->log_addr +
 987                           (used - (void __user *)vq->used),
 988                           sizeof vq->used->flags);
 989                 if (vq->log_ctx)
 990                         eventfd_signal(vq->log_ctx, 1);
 991         }
 992         return 0;
 993 }
 994
 995 static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
 996 {
 997         if (__put_user(vq->avail_idx, vhost_avail_event(vq)))
 998                 return -EFAULT;
 999         if (unlikely(vq->log_used)) {
1000                 void __user *used;
1001                 /* Make sure the event is seen before log. */
1002                 smp_wmb();
1003                 /* Log avail event write */
1004                 used = vhost_avail_event(vq);
1005                 log_write(vq->log_base, vq->log_addr +
1006                           (used - (void __user *)vq->used),
1007                           sizeof *vhost_avail_event(vq));
1008                 if (vq->log_ctx)
1009                         eventfd_signal(vq->log_ctx, 1);
1010         }
1011         return 0;
1012 }
1013
1014 int vhost_init_used(struct vhost_virtqueue *vq)
1015 {
1016         int r;
1017         if (!vq->private_data)
1018                 return 0;
1019
1020         r = vhost_update_used_flags(vq);
1021         if (r)
1022                 return r;
1023         vq->signalled_used_valid = false;
1024         return get_user(vq->last_used_idx, &vq->used->idx);
1025 }
1026
1027 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
1028                           struct iovec iov[], int iov_size)
1029 {
1030         const struct vhost_memory_region *reg;
1031         struct vhost_memory *mem;
1032         struct iovec *_iov;
1033         u64 s = 0;
1034         int ret = 0;
1035
1036         rcu_read_lock();
1037
1038         mem = rcu_dereference(dev->memory);
1039         while ((u64)len > s) {
1040                 u64 size;
1041                 if (unlikely(ret >= iov_size)) {
1042                         ret = -ENOBUFS;
1043                         break;
1044                 }
1045                 reg = find_region(mem, addr, len);
1046                 if (unlikely(!reg)) {
1047                         ret = -EFAULT;
1048                         break;
1049                 }
1050                 _iov = iov + ret;
1051                 size = reg->memory_size - addr + reg->guest_phys_addr;
1052                 _iov->iov_len = min((u64)len - s, size);
1053                 _iov->iov_base = (void __user *)(unsigned long)
1054                         (reg->userspace_addr + addr - reg->guest_phys_addr);
1055                 s += size;
1056                 addr += size;
1057                 ++ret;
1058         }
1059
1060         rcu_read_unlock();
1061         return ret;
1062 }
1063
1064 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
1065  * function returns the next descriptor in the chain,
1066  * or -1U if we're at the end. */
1067 static unsigned next_desc(struct vring_desc *desc)
1068 {
1069         unsigned int next;
1070
1071         /* If this descriptor says it doesn't chain, we're done. */
1072         if (!(desc->flags & VRING_DESC_F_NEXT))
1073                 return -1U;
1074
1075         /* Check they're not leading us off end of descriptors. */
1076         next = desc->next;
1077         /* Make sure compiler knows to grab that: we don't want it changing! */
1078         /* We will use the result as an index in an array, so most
1079          * architectures only need a compiler barrier here. */
1080         read_barrier_depends();
1081
1082         return next;
1083 }
1084
1085 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1086                         struct iovec iov[], unsigned int iov_size,
1087                         unsigned int *out_num, unsigned int *in_num,
1088                         struct vhost_log *log, unsigned int *log_num,
1089                         struct vring_desc *indirect)
1090 {
1091         struct vring_desc desc;
1092         unsigned int i = 0, count, found = 0;
1093         int ret;
1094
1095         /* Sanity check */
1096         if (unlikely(indirect->len % sizeof desc)) {
1097                 vq_err(vq, "Invalid length in indirect descriptor: "
1098                        "len 0x%llx not multiple of 0x%zx\n",
1099                        (unsigned long long)indirect->len,
1100                        sizeof desc);
1101                 return -EINVAL;
1102         }
1103
1104         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1105                              UIO_MAXIOV);
1106         if (unlikely(ret < 0)) {
1107                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1108                 return ret;
1109         }
1110
1111         /* We will use the result as an address to read from, so most
1112          * architectures only need a compiler barrier here. */
1113         read_barrier_depends();
1114
1115         count = indirect->len / sizeof desc;
1116         /* Buffers are chained via a 16 bit next field, so
1117          * we can have at most 2^16 of these. */
1118         if (unlikely(count > USHRT_MAX + 1)) {
1119                 vq_err(vq, "Indirect buffer length too big: %d\n",
1120                        indirect->len);
1121                 return -E2BIG;
1122         }
1123
1124         do {
1125                 unsigned iov_count = *in_num + *out_num;
1126                 if (unlikely(++found > count)) {
1127                         vq_err(vq, "Loop detected: last one at %u "
1128                                "indirect size %u\n",
1129                                i, count);
1130                         return -EINVAL;
1131                 }
1132                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1133                                               vq->indirect, sizeof desc))) {
1134                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1135                                i, (size_t)indirect->addr + i * sizeof desc);
1136                         return -EINVAL;
1137                 }
1138                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1139                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1140                                i, (size_t)indirect->addr + i * sizeof desc);
1141                         return -EINVAL;
1142                 }
1143
1144                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1145                                      iov_size - iov_count);
1146                 if (unlikely(ret < 0)) {
1147                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1148                                ret, i);
1149                         return ret;
1150                 }
1151                 /* If this is an input descriptor, increment that count. */
1152                 if (desc.flags & VRING_DESC_F_WRITE) {
1153                         *in_num += ret;
1154                         if (unlikely(log)) {
1155                                 log[*log_num].addr = desc.addr;
1156                                 log[*log_num].len = desc.len;
1157                                 ++*log_num;
1158                         }
1159                 } else {
1160                         /* If it's an output descriptor, they're all supposed
1161                          * to come before any input descriptors. */
1162                         if (unlikely(*in_num)) {
1163                                 vq_err(vq, "Indirect descriptor "
1164                                        "has out after in: idx %d\n", i);
1165                                 return -EINVAL;
1166                         }
1167                         *out_num += ret;
1168                 }
1169         } while ((i = next_desc(&desc)) != -1);
1170         return 0;
1171 }
1172
1173 /* This looks in the virtqueue and for the first available buffer, and converts
1174  * it to an iovec for convenient access.  Since descriptors consist of some
1175  * number of output then some number of input descriptors, it's actually two
1176  * iovecs, but we pack them into one and note how many of each there were.
1177  *
1178  * This function returns the descriptor number found, or vq->num (which is
1179  * never a valid descriptor number) if none was found.  A negative code is
1180  * returned on error. */
1181 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1182                       struct iovec iov[], unsigned int iov_size,
1183                       unsigned int *out_num, unsigned int *in_num,
1184                       struct vhost_log *log, unsigned int *log_num)
1185 {
1186         struct vring_desc desc;
1187         unsigned int i, head, found = 0;
1188         u16 last_avail_idx;
1189         int ret;
1190
1191         /* Check it isn't doing very strange things with descriptor numbers. */
1192         last_avail_idx = vq->last_avail_idx;
1193         if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1194                 vq_err(vq, "Failed to access avail idx at %p\n",
1195                        &vq->avail->idx);
1196                 return -EFAULT;
1197         }
1198
1199         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1200                 vq_err(vq, "Guest moved used index from %u to %u",
1201                        last_avail_idx, vq->avail_idx);
1202                 return -EFAULT;
1203         }
1204
1205         /* If there's nothing new since last we looked, return invalid. */
1206         if (vq->avail_idx == last_avail_idx)
1207                 return vq->num;
1208
1209         /* Only get avail ring entries after they have been exposed by guest. */
1210         smp_rmb();
1211
1212         /* Grab the next descriptor number they're advertising, and increment
1213          * the index we've seen. */
1214         if (unlikely(__get_user(head,
1215                                 &vq->avail->ring[last_avail_idx % vq->num]))) {
1216                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1217                        last_avail_idx,
1218                        &vq->avail->ring[last_avail_idx % vq->num]);
1219                 return -EFAULT;
1220         }
1221
1222         /* If their number is silly, that's an error. */
1223         if (unlikely(head >= vq->num)) {
1224                 vq_err(vq, "Guest says index %u > %u is available",
1225                        head, vq->num);
1226                 return -EINVAL;
1227         }
1228
1229         /* When we start there are none of either input nor output. */
1230         *out_num = *in_num = 0;
1231         if (unlikely(log))
1232                 *log_num = 0;
1233
1234         i = head;
1235         do {
1236                 unsigned iov_count = *in_num + *out_num;
1237                 if (unlikely(i >= vq->num)) {
1238                         vq_err(vq, "Desc index is %u > %u, head = %u",
1239                                i, vq->num, head);
1240                         return -EINVAL;
1241                 }
1242                 if (unlikely(++found > vq->num)) {
1243                         vq_err(vq, "Loop detected: last one at %u "
1244                                "vq size %u head %u\n",
1245                                i, vq->num, head);
1246                         return -EINVAL;
1247                 }
1248                 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1249                 if (unlikely(ret)) {
1250                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1251                                i, vq->desc + i);
1252                         return -EFAULT;
1253                 }
1254                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1255                         ret = get_indirect(dev, vq, iov, iov_size,
1256                                            out_num, in_num,
1257                                            log, log_num, &desc);
1258                         if (unlikely(ret < 0)) {
1259                                 vq_err(vq, "Failure detected "
1260                                        "in indirect descriptor at idx %d\n", i);
1261                                 return ret;
1262                         }
1263                         continue;
1264                 }
1265
1266                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1267                                      iov_size - iov_count);
1268                 if (unlikely(ret < 0)) {
1269                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1270                                ret, i);
1271                         return ret;
1272                 }
1273                 if (desc.flags & VRING_DESC_F_WRITE) {
1274                         /* If this is an input descriptor,
1275                          * increment that count. */
1276                         *in_num += ret;
1277                         if (unlikely(log)) {
1278                                 log[*log_num].addr = desc.addr;
1279                                 log[*log_num].len = desc.len;
1280                                 ++*log_num;
1281                         }
1282                 } else {
1283                         /* If it's an output descriptor, they're all supposed
1284                          * to come before any input descriptors. */
1285                         if (unlikely(*in_num)) {
1286                                 vq_err(vq, "Descriptor has out after in: "
1287                                        "idx %d\n", i);
1288                                 return -EINVAL;
1289                         }
1290                         *out_num += ret;
1291                 }
1292         } while ((i = next_desc(&desc)) != -1);
1293
1294         /* On success, increment avail index. */
1295         vq->last_avail_idx++;
1296
1297         /* Assume notifications from guest are disabled at this point,
1298          * if they aren't we would need to update avail_event index. */
1299         BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1300         return head;
1301 }
1302
1303 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1304 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1305 {
1306         vq->last_avail_idx -= n;
1307 }
1308
1309 /* After we've used one of their buffers, we tell them about it.  We'll then
1310  * want to notify the guest, using eventfd. */
1311 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1312 {
1313         struct vring_used_elem __user *used;
1314
1315         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1316          * next entry in that used ring. */
1317         used = &vq->used->ring[vq->last_used_idx % vq->num];
1318         if (__put_user(head, &used->id)) {
1319                 vq_err(vq, "Failed to write used id");
1320                 return -EFAULT;
1321         }
1322         if (__put_user(len, &used->len)) {
1323                 vq_err(vq, "Failed to write used len");
1324                 return -EFAULT;
1325         }
1326         /* Make sure buffer is written before we update index. */
1327         smp_wmb();
1328         if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1329                 vq_err(vq, "Failed to increment used idx");
1330                 return -EFAULT;
1331         }
1332         if (unlikely(vq->log_used)) {
1333                 /* Make sure data is seen before log. */
1334                 smp_wmb();
1335                 /* Log used ring entry write. */
1336                 log_write(vq->log_base,
1337                           vq->log_addr +
1338                            ((void __user *)used - (void __user *)vq->used),
1339                           sizeof *used);
1340                 /* Log used index update. */
1341                 log_write(vq->log_base,
1342                           vq->log_addr + offsetof(struct vring_used, idx),
1343                           sizeof vq->used->idx);
1344                 if (vq->log_ctx)
1345                         eventfd_signal(vq->log_ctx, 1);
1346         }
1347         vq->last_used_idx++;
1348         /* If the driver never bothers to signal in a very long while,
1349          * used index might wrap around. If that happens, invalidate
1350          * signalled_used index we stored. TODO: make sure driver
1351          * signals at least once in 2^16 and remove this. */
1352         if (unlikely(vq->last_used_idx == vq->signalled_used))
1353                 vq->signalled_used_valid = false;
1354         return 0;
1355 }
1356
1357 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1358                             struct vring_used_elem *heads,
1359                             unsigned count)
1360 {
1361         struct vring_used_elem __user *used;
1362         u16 old, new;
1363         int start;
1364
1365         start = vq->last_used_idx % vq->num;
1366         used = vq->used->ring + start;
1367         if (__copy_to_user(used, heads, count * sizeof *used)) {
1368                 vq_err(vq, "Failed to write used");
1369                 return -EFAULT;
1370         }
1371         if (unlikely(vq->log_used)) {
1372                 /* Make sure data is seen before log. */
1373                 smp_wmb();
1374                 /* Log used ring entry write. */
1375                 log_write(vq->log_base,
1376                           vq->log_addr +
1377                            ((void __user *)used - (void __user *)vq->used),
1378                           count * sizeof *used);
1379         }
1380         old = vq->last_used_idx;
1381         new = (vq->last_used_idx += count);
1382         /* If the driver never bothers to signal in a very long while,
1383          * used index might wrap around. If that happens, invalidate
1384          * signalled_used index we stored. TODO: make sure driver
1385          * signals at least once in 2^16 and remove this. */
1386         if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1387                 vq->signalled_used_valid = false;
1388         return 0;
1389 }
1390
1391 /* After we've used one of their buffers, we tell them about it.  We'll then
1392  * want to notify the guest, using eventfd. */
1393 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1394                      unsigned count)
1395 {
1396         int start, n, r;
1397
1398         start = vq->last_used_idx % vq->num;
1399         n = vq->num - start;
1400         if (n < count) {
1401                 r = __vhost_add_used_n(vq, heads, n);
1402                 if (r < 0)
1403                         return r;
1404                 heads += n;
1405                 count -= n;
1406         }
1407         r = __vhost_add_used_n(vq, heads, count);
1408
1409         /* Make sure buffer is written before we update index. */
1410         smp_wmb();
1411         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1412                 vq_err(vq, "Failed to increment used idx");
1413                 return -EFAULT;
1414         }
1415         if (unlikely(vq->log_used)) {
1416                 /* Log used index update. */
1417                 log_write(vq->log_base,
1418                           vq->log_addr + offsetof(struct vring_used, idx),
1419                           sizeof vq->used->idx);
1420                 if (vq->log_ctx)
1421                         eventfd_signal(vq->log_ctx, 1);
1422         }
1423         return r;
1424 }
1425
1426 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1427 {
1428         __u16 old, new, event;
1429         bool v;
1430         /* Flush out used index updates. This is paired
1431          * with the barrier that the Guest executes when enabling
1432          * interrupts. */
1433         smp_mb();
1434
1435         if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1436             unlikely(vq->avail_idx == vq->last_avail_idx))
1437                 return true;
1438
1439         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1440                 __u16 flags;
1441                 if (__get_user(flags, &vq->avail->flags)) {
1442                         vq_err(vq, "Failed to get flags");
1443                         return true;
1444                 }
1445                 return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1446         }
1447         old = vq->signalled_used;
1448         v = vq->signalled_used_valid;
1449         new = vq->signalled_used = vq->last_used_idx;
1450         vq->signalled_used_valid = true;
1451
1452         if (unlikely(!v))
1453                 return true;
1454
1455         if (get_user(event, vhost_used_event(vq))) {
1456                 vq_err(vq, "Failed to get used event idx");
1457                 return true;
1458         }
1459         return vring_need_event(event, new, old);
1460 }
1461
1462 /* This actually signals the guest, using eventfd. */
1463 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1464 {
1465         /* Signal the Guest tell them we used something up. */
1466         if (vq->call_ctx && vhost_notify(dev, vq))
1467                 eventfd_signal(vq->call_ctx, 1);
1468 }
1469
1470 /* And here's the combo meal deal.  Supersize me! */
1471 void vhost_add_used_and_signal(struct vhost_dev *dev,
1472                                struct vhost_virtqueue *vq,
1473                                unsigned int head, int len)
1474 {
1475         vhost_add_used(vq, head, len);
1476         vhost_signal(dev, vq);
1477 }
1478
1479 /* multi-buffer version of vhost_add_used_and_signal */
1480 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1481                                  struct vhost_virtqueue *vq,
1482                                  struct vring_used_elem *heads, unsigned count)
1483 {
1484         vhost_add_used_n(vq, heads, count);
1485         vhost_signal(dev, vq);
1486 }
1487
1488 /* OK, now we need to know about added descriptors. */
1489 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1490 {
1491         u16 avail_idx;
1492         int r;
1493
1494         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1495                 return false;
1496         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1497         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1498                 r = vhost_update_used_flags(vq);
1499                 if (r) {
1500                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1501                                &vq->used->flags, r);
1502                         return false;
1503                 }
1504         } else {
1505                 r = vhost_update_avail_event(vq, vq->avail_idx);
1506                 if (r) {
1507                         vq_err(vq, "Failed to update avail event index at %p: %d\n",
1508                                vhost_avail_event(vq), r);
1509                         return false;
1510                 }
1511         }
1512         /* They could have slipped one in as we were doing that: make
1513          * sure it's written, then check again. */
1514         smp_mb();
1515         r = __get_user(avail_idx, &vq->avail->idx);
1516         if (r) {
1517                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1518                        &vq->avail->idx, r);
1519                 return false;
1520         }
1521
1522         return avail_idx != vq->avail_idx;
1523 }
1524
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
1541 static void vhost_zerocopy_done_signal(struct kref *kref)
1542 {
1543         struct vhost_ubuf_ref *ubufs = container_of(kref, struct vhost_ubuf_ref,
1544                                                     kref);
1545         wake_up(&ubufs->wait);
1546 }
1547
1548 struct vhost_ubuf_ref *vhost_ubuf_alloc(struct vhost_virtqueue *vq,
1549                                         bool zcopy)
1550 {
1551         struct vhost_ubuf_ref *ubufs;
1552         /* No zero copy backend? Nothing to count. */
1553         if (!zcopy)
1554                 return NULL;
1555         ubufs = kmalloc(sizeof *ubufs, GFP_KERNEL);
1556         if (!ubufs)
1557                 return ERR_PTR(-ENOMEM);
1558         kref_init(&ubufs->kref);
1559         init_waitqueue_head(&ubufs->wait);
1560         ubufs->vq = vq;
1561         return ubufs;
1562 }
1563
1564 void vhost_ubuf_put(struct vhost_ubuf_ref *ubufs)
1565 {
1566         kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1567 }
1568
1569 void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs)
1570 {
1571         kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1572         wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
1573         kfree(ubufs);
1574 }