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 <linux/net.h>
  30 #include <linux/if_packet.h>
  31 #include <linux/if_arp.h>
  32
  33 #include "vhost.h"
  34
  35 enum {
  36         VHOST_MEMORY_MAX_NREGIONS = 64,
  37         VHOST_MEMORY_F_LOG = 0x1,
  38 };
  39
  40 static unsigned vhost_zcopy_mask __read_mostly;
  41
  42 #define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
  43 #define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
  44
  45 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  46                             poll_table *pt)
  47 {
  48         struct vhost_poll *poll;
  49
  50         poll = container_of(pt, struct vhost_poll, table);
  51         poll->wqh = wqh;
  52         add_wait_queue(wqh, &poll->wait);
  53 }
  54
  55 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
  56                              void *key)
  57 {
  58         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  59
  60         if (!((unsigned long)key & poll->mask))
  61                 return 0;
  62
  63         vhost_poll_queue(poll);
  64         return 0;
  65 }
  66
  67 static void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  68 {
  69         INIT_LIST_HEAD(&work->node);
  70         work->fn = fn;
  71         init_waitqueue_head(&work->done);
  72         work->flushing = 0;
  73         work->queue_seq = work->done_seq = 0;
  74 }
  75
  76 /* Init poll structure */
  77 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  78                      unsigned long mask, struct vhost_dev *dev)
  79 {
  80         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  81         init_poll_funcptr(&poll->table, vhost_poll_func);
  82         poll->mask = mask;
  83         poll->dev = dev;
  84
  85         vhost_work_init(&poll->work, fn);
  86 }
  87
  88 /* Start polling a file. We add ourselves to file's wait queue. The caller must
  89  * keep a reference to a file until after vhost_poll_stop is called. */
  90 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
  91 {
  92         unsigned long mask;
  93
  94         mask = file->f_op->poll(file, &poll->table);
  95         if (mask)
  96                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  97 }
  98
  99 /* Stop polling a file. After this function returns, it becomes safe to drop the
 100  * file reference. You must also flush afterwards. */
 101 void vhost_poll_stop(struct vhost_poll *poll)
 102 {
 103         remove_wait_queue(poll->wqh, &poll->wait);
 104 }
 105
 106 static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
 107                                 unsigned seq)
 108 {
 109         int left;
 110
 111         spin_lock_irq(&dev->work_lock);
 112         left = seq - work->done_seq;
 113         spin_unlock_irq(&dev->work_lock);
 114         return left <= 0;
 115 }
 116
 117 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 118 {
 119         unsigned seq;
 120         int flushing;
 121
 122         spin_lock_irq(&dev->work_lock);
 123         seq = work->queue_seq;
 124         work->flushing++;
 125         spin_unlock_irq(&dev->work_lock);
 126         wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 127         spin_lock_irq(&dev->work_lock);
 128         flushing = --work->flushing;
 129         spin_unlock_irq(&dev->work_lock);
 130         BUG_ON(flushing < 0);
 131 }
 132
 133 /* Flush any work that has been scheduled. When calling this, don't hold any
 134  * locks that are also used by the callback. */
 135 void vhost_poll_flush(struct vhost_poll *poll)
 136 {
 137         vhost_work_flush(poll->dev, &poll->work);
 138 }
 139
 140 static inline void vhost_work_queue(struct vhost_dev *dev,
 141                                     struct vhost_work *work)
 142 {
 143         unsigned long flags;
 144
 145         spin_lock_irqsave(&dev->work_lock, flags);
 146         if (list_empty(&work->node)) {
 147                 list_add_tail(&work->node, &dev->work_list);
 148                 work->queue_seq++;
 149                 wake_up_process(dev->worker);
 150         }
 151         spin_unlock_irqrestore(&dev->work_lock, flags);
 152 }
 153
 154 void vhost_poll_queue(struct vhost_poll *poll)
 155 {
 156         vhost_work_queue(poll->dev, &poll->work);
 157 }
 158
 159 static void vhost_vq_reset(struct vhost_dev *dev,
 160                            struct vhost_virtqueue *vq)
 161 {
 162         vq->num = 1;
 163         vq->desc = NULL;
 164         vq->avail = NULL;
 165         vq->used = NULL;
 166         vq->last_avail_idx = 0;
 167         vq->avail_idx = 0;
 168         vq->last_used_idx = 0;
 169         vq->signalled_used = 0;
 170         vq->signalled_used_valid = false;
 171         vq->used_flags = 0;
 172         vq->log_used = false;
 173         vq->log_addr = -1ull;
 174         vq->vhost_hlen = 0;
 175         vq->sock_hlen = 0;
 176         vq->private_data = NULL;
 177         vq->log_base = NULL;
 178         vq->error_ctx = NULL;
 179         vq->error = NULL;
 180         vq->kick = NULL;
 181         vq->call_ctx = NULL;
 182         vq->call = NULL;
 183         vq->log_ctx = NULL;
 184         vq->upend_idx = 0;
 185         vq->done_idx = 0;
 186         vq->ubufs = NULL;
 187 }
 188
 189 static int vhost_worker(void *data)
 190 {
 191         struct vhost_dev *dev = data;
 192         struct vhost_work *work = NULL;
 193         unsigned uninitialized_var(seq);
 194
 195         use_mm(dev->mm);
 196
 197         for (;;) {
 198                 /* mb paired w/ kthread_stop */
 199                 set_current_state(TASK_INTERRUPTIBLE);
 200
 201                 spin_lock_irq(&dev->work_lock);
 202                 if (work) {
 203                         work->done_seq = seq;
 204                         if (work->flushing)
 205                                 wake_up_all(&work->done);
 206                 }
 207
 208                 if (kthread_should_stop()) {
 209                         spin_unlock_irq(&dev->work_lock);
 210                         __set_current_state(TASK_RUNNING);
 211                         break;
 212                 }
 213                 if (!list_empty(&dev->work_list)) {
 214                         work = list_first_entry(&dev->work_list,
 215                                                 struct vhost_work, node);
 216                         list_del_init(&work->node);
 217                         seq = work->queue_seq;
 218                 } else
 219                         work = NULL;
 220                 spin_unlock_irq(&dev->work_lock);
 221
 222                 if (work) {
 223                         __set_current_state(TASK_RUNNING);
 224                         work->fn(work);
 225                         if (need_resched())
 226                                 schedule();
 227                 } else
 228                         schedule();
 229
 230         }
 231         unuse_mm(dev->mm);
 232         return 0;
 233 }
 234
 235 static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
 236 {
 237         kfree(vq->indirect);
 238         vq->indirect = NULL;
 239         kfree(vq->log);
 240         vq->log = NULL;
 241         kfree(vq->heads);
 242         vq->heads = NULL;
 243         kfree(vq->ubuf_info);
 244         vq->ubuf_info = NULL;
 245 }
 246
 247 void vhost_enable_zcopy(int vq)
 248 {
 249         vhost_zcopy_mask |= 0x1 << vq;
 250 }
 251
 252 /* Helper to allocate iovec buffers for all vqs. */
 253 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 254 {
 255         int i;
 256         bool zcopy;
 257
 258         for (i = 0; i < dev->nvqs; ++i) {
 259                 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
 260                                                UIO_MAXIOV, GFP_KERNEL);
 261                 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
 262                                           GFP_KERNEL);
 263                 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
 264                                             UIO_MAXIOV, GFP_KERNEL);
 265                 zcopy = vhost_zcopy_mask & (0x1 << i);
 266                 if (zcopy)
 267                         dev->vqs[i].ubuf_info =
 268                                 kmalloc(sizeof *dev->vqs[i].ubuf_info *
 269                                         UIO_MAXIOV, GFP_KERNEL);
 270                 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
 271                         !dev->vqs[i].heads ||
 272                         (zcopy && !dev->vqs[i].ubuf_info))
 273                         goto err_nomem;
 274         }
 275         return 0;
 276
 277 err_nomem:
 278         for (; i >= 0; --i)
 279                 vhost_vq_free_iovecs(&dev->vqs[i]);
 280         return -ENOMEM;
 281 }
 282
 283 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
 284 {
 285         int i;
 286
 287         for (i = 0; i < dev->nvqs; ++i)
 288                 vhost_vq_free_iovecs(&dev->vqs[i]);
 289 }
 290
 291 long vhost_dev_init(struct vhost_dev *dev,
 292                     struct vhost_virtqueue *vqs, int nvqs)
 293 {
 294         int i;
 295
 296         dev->vqs = vqs;
 297         dev->nvqs = nvqs;
 298         mutex_init(&dev->mutex);
 299         dev->log_ctx = NULL;
 300         dev->log_file = NULL;
 301         dev->memory = NULL;
 302         dev->mm = NULL;
 303         spin_lock_init(&dev->work_lock);
 304         INIT_LIST_HEAD(&dev->work_list);
 305         dev->worker = NULL;
 306
 307         for (i = 0; i < dev->nvqs; ++i) {
 308                 dev->vqs[i].log = NULL;
 309                 dev->vqs[i].indirect = NULL;
 310                 dev->vqs[i].heads = NULL;
 311                 dev->vqs[i].ubuf_info = NULL;
 312                 dev->vqs[i].dev = dev;
 313                 mutex_init(&dev->vqs[i].mutex);
 314                 vhost_vq_reset(dev, dev->vqs + i);
 315                 if (dev->vqs[i].handle_kick)
 316                         vhost_poll_init(&dev->vqs[i].poll,
 317                                         dev->vqs[i].handle_kick, POLLIN, dev);
 318         }
 319
 320         return 0;
 321 }
 322
 323 /* Caller should have device mutex */
 324 long vhost_dev_check_owner(struct vhost_dev *dev)
 325 {
 326         /* Are you the owner? If not, I don't think you mean to do that */
 327         return dev->mm == current->mm ? 0 : -EPERM;
 328 }
 329
 330 struct vhost_attach_cgroups_struct {
 331         struct vhost_work work;
 332         struct task_struct *owner;
 333         int ret;
 334 };
 335
 336 static void vhost_attach_cgroups_work(struct vhost_work *work)
 337 {
 338         struct vhost_attach_cgroups_struct *s;
 339
 340         s = container_of(work, struct vhost_attach_cgroups_struct, work);
 341         s->ret = cgroup_attach_task_all(s->owner, current);
 342 }
 343
 344 static int vhost_attach_cgroups(struct vhost_dev *dev)
 345 {
 346         struct vhost_attach_cgroups_struct attach;
 347
 348         attach.owner = current;
 349         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 350         vhost_work_queue(dev, &attach.work);
 351         vhost_work_flush(dev, &attach.work);
 352         return attach.ret;
 353 }
 354
 355 /* Caller should have device mutex */
 356 static long vhost_dev_set_owner(struct vhost_dev *dev)
 357 {
 358         struct task_struct *worker;
 359         int err;
 360
 361         /* Is there an owner already? */
 362         if (dev->mm) {
 363                 err = -EBUSY;
 364                 goto err_mm;
 365         }
 366
 367         /* No owner, become one */
 368         dev->mm = get_task_mm(current);
 369         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 370         if (IS_ERR(worker)) {
 371                 err = PTR_ERR(worker);
 372                 goto err_worker;
 373         }
 374
 375         dev->worker = worker;
 376         wake_up_process(worker);        /* avoid contributing to loadavg */
 377
 378         err = vhost_attach_cgroups(dev);
 379         if (err)
 380                 goto err_cgroup;
 381
 382         err = vhost_dev_alloc_iovecs(dev);
 383         if (err)
 384                 goto err_cgroup;
 385
 386         return 0;
 387 err_cgroup:
 388         kthread_stop(worker);
 389         dev->worker = NULL;
 390 err_worker:
 391         if (dev->mm)
 392                 mmput(dev->mm);
 393         dev->mm = NULL;
 394 err_mm:
 395         return err;
 396 }
 397
 398 /* Caller should have device mutex */
 399 long vhost_dev_reset_owner(struct vhost_dev *dev)
 400 {
 401         struct vhost_memory *memory;
 402
 403         /* Restore memory to default empty mapping. */
 404         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 405         if (!memory)
 406                 return -ENOMEM;
 407
 408         vhost_dev_cleanup(dev);
 409
 410         memory->nregions = 0;
 411         RCU_INIT_POINTER(dev->memory, memory);
 412         return 0;
 413 }
 414
 415 /* In case of DMA done not in order in lower device driver for some reason.
 416  * upend_idx is used to track end of used idx, done_idx is used to track head
 417  * of used idx. Once lower device DMA done contiguously, we will signal KVM
 418  * guest used idx.
 419  */
 420 int vhost_zerocopy_signal_used(struct vhost_virtqueue *vq)
 421 {
 422         int i;
 423         int j = 0;
 424
 425         for (i = vq->done_idx; i != vq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
 426                 if ((vq->heads[i].len == VHOST_DMA_DONE_LEN)) {
 427                         vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
 428                         vhost_add_used_and_signal(vq->dev, vq,
 429                                                   vq->heads[i].id, 0);
 430                         ++j;
 431                 } else
 432                         break;
 433         }
 434         if (j)
 435                 vq->done_idx = i;
 436         return j;
 437 }
 438
 439 /* Caller should have device mutex */
 440 void vhost_dev_cleanup(struct vhost_dev *dev)
 441 {
 442         int i;
 443
 444         for (i = 0; i < dev->nvqs; ++i) {
 445                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
 446                         vhost_poll_stop(&dev->vqs[i].poll);
 447                         vhost_poll_flush(&dev->vqs[i].poll);
 448                 }
 449                 /* Wait for all lower device DMAs done. */
 450                 if (dev->vqs[i].ubufs)
 451                         vhost_ubuf_put_and_wait(dev->vqs[i].ubufs);
 452
 453                 /* Signal guest as appropriate. */
 454                 vhost_zerocopy_signal_used(&dev->vqs[i]);
 455
 456                 if (dev->vqs[i].error_ctx)
 457                         eventfd_ctx_put(dev->vqs[i].error_ctx);
 458                 if (dev->vqs[i].error)
 459                         fput(dev->vqs[i].error);
 460                 if (dev->vqs[i].kick)
 461                         fput(dev->vqs[i].kick);
 462                 if (dev->vqs[i].call_ctx)
 463                         eventfd_ctx_put(dev->vqs[i].call_ctx);
 464                 if (dev->vqs[i].call)
 465                         fput(dev->vqs[i].call);
 466                 vhost_vq_reset(dev, dev->vqs + i);
 467         }
 468         vhost_dev_free_iovecs(dev);
 469         if (dev->log_ctx)
 470                 eventfd_ctx_put(dev->log_ctx);
 471         dev->log_ctx = NULL;
 472         if (dev->log_file)
 473                 fput(dev->log_file);
 474         dev->log_file = NULL;
 475         /* No one will access memory at this point */
 476         kfree(rcu_dereference_protected(dev->memory,
 477                                         lockdep_is_held(&dev->mutex)));
 478         RCU_INIT_POINTER(dev->memory, NULL);
 479         WARN_ON(!list_empty(&dev->work_list));
 480         if (dev->worker) {
 481                 kthread_stop(dev->worker);
 482                 dev->worker = NULL;
 483         }
 484         if (dev->mm)
 485                 mmput(dev->mm);
 486         dev->mm = NULL;
 487 }
 488
 489 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 490 {
 491         u64 a = addr / VHOST_PAGE_SIZE / 8;
 492
 493         /* Make sure 64 bit math will not overflow. */
 494         if (a > ULONG_MAX - (unsigned long)log_base ||
 495             a + (unsigned long)log_base > ULONG_MAX)
 496                 return 0;
 497
 498         return access_ok(VERIFY_WRITE, log_base + a,
 499                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 500 }
 501
 502 /* Caller should have vq mutex and device mutex. */
 503 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 504                                int log_all)
 505 {
 506         int i;
 507
 508         if (!mem)
 509                 return 0;
 510
 511         for (i = 0; i < mem->nregions; ++i) {
 512                 struct vhost_memory_region *m = mem->regions + i;
 513                 unsigned long a = m->userspace_addr;
 514                 if (m->memory_size > ULONG_MAX)
 515                         return 0;
 516                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 517                                     m->memory_size))
 518                         return 0;
 519                 else if (log_all && !log_access_ok(log_base,
 520                                                    m->guest_phys_addr,
 521                                                    m->memory_size))
 522                         return 0;
 523         }
 524         return 1;
 525 }
 526
 527 /* Can we switch to this memory table? */
 528 /* Caller should have device mutex but not vq mutex */
 529 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 530                             int log_all)
 531 {
 532         int i;
 533
 534         for (i = 0; i < d->nvqs; ++i) {
 535                 int ok;
 536                 mutex_lock(&d->vqs[i].mutex);
 537                 /* If ring is inactive, will check when it's enabled. */
 538                 if (d->vqs[i].private_data)
 539                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
 540                                                  log_all);
 541                 else
 542                         ok = 1;
 543                 mutex_unlock(&d->vqs[i].mutex);
 544                 if (!ok)
 545                         return 0;
 546         }
 547         return 1;
 548 }
 549
 550 static int vq_access_ok(struct vhost_dev *d, unsigned int num,
 551                         struct vring_desc __user *desc,
 552                         struct vring_avail __user *avail,
 553                         struct vring_used __user *used)
 554 {
 555         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 556         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 557                access_ok(VERIFY_READ, avail,
 558                          sizeof *avail + num * sizeof *avail->ring + s) &&
 559                access_ok(VERIFY_WRITE, used,
 560                         sizeof *used + num * sizeof *used->ring + s);
 561 }
 562
 563 /* Can we log writes? */
 564 /* Caller should have device mutex but not vq mutex */
 565 int vhost_log_access_ok(struct vhost_dev *dev)
 566 {
 567         struct vhost_memory *mp;
 568
 569         mp = rcu_dereference_protected(dev->memory,
 570                                        lockdep_is_held(&dev->mutex));
 571         return memory_access_ok(dev, mp, 1);
 572 }
 573
 574 /* Verify access for write logging. */
 575 /* Caller should have vq mutex and device mutex */
 576 static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
 577                             void __user *log_base)
 578 {
 579         struct vhost_memory *mp;
 580         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 581
 582         mp = rcu_dereference_protected(vq->dev->memory,
 583                                        lockdep_is_held(&vq->mutex));
 584         return vq_memory_access_ok(log_base, mp,
 585                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 586                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 587                                         sizeof *vq->used +
 588                                         vq->num * sizeof *vq->used->ring + s));
 589 }
 590
 591 /* Can we start vq? */
 592 /* Caller should have vq mutex and device mutex */
 593 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 594 {
 595         return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
 596                 vq_log_access_ok(vq->dev, vq, vq->log_base);
 597 }
 598
 599 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 600 {
 601         struct vhost_memory mem, *newmem, *oldmem;
 602         unsigned long size = offsetof(struct vhost_memory, regions);
 603
 604         if (copy_from_user(&mem, m, size))
 605                 return -EFAULT;
 606         if (mem.padding)
 607                 return -EOPNOTSUPP;
 608         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 609                 return -E2BIG;
 610         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 611         if (!newmem)
 612                 return -ENOMEM;
 613
 614         memcpy(newmem, &mem, size);
 615         if (copy_from_user(newmem->regions, m->regions,
 616                            mem.nregions * sizeof *m->regions)) {
 617                 kfree(newmem);
 618                 return -EFAULT;
 619         }
 620
 621         if (!memory_access_ok(d, newmem,
 622                               vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 623                 kfree(newmem);
 624                 return -EFAULT;
 625         }
 626         oldmem = rcu_dereference_protected(d->memory,
 627                                            lockdep_is_held(&d->mutex));
 628         rcu_assign_pointer(d->memory, newmem);
 629         synchronize_rcu();
 630         kfree(oldmem);
 631         return 0;
 632 }
 633
 634 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 635 {
 636         struct file *eventfp, *filep = NULL,
 637                     *pollstart = NULL, *pollstop = NULL;
 638         struct eventfd_ctx *ctx = NULL;
 639         u32 __user *idxp = argp;
 640         struct vhost_virtqueue *vq;
 641         struct vhost_vring_state s;
 642         struct vhost_vring_file f;
 643         struct vhost_vring_addr a;
 644         u32 idx;
 645         long r;
 646
 647         r = get_user(idx, idxp);
 648         if (r < 0)
 649                 return r;
 650         if (idx >= d->nvqs)
 651                 return -ENOBUFS;
 652
 653         vq = d->vqs + idx;
 654
 655         mutex_lock(&vq->mutex);
 656
 657         switch (ioctl) {
 658         case VHOST_SET_VRING_NUM:
 659                 /* Resizing ring with an active backend?
 660                  * You don't want to do that. */
 661                 if (vq->private_data) {
 662                         r = -EBUSY;
 663                         break;
 664                 }
 665                 if (copy_from_user(&s, argp, sizeof s)) {
 666                         r = -EFAULT;
 667                         break;
 668                 }
 669                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 670                         r = -EINVAL;
 671                         break;
 672                 }
 673                 vq->num = s.num;
 674                 break;
 675         case VHOST_SET_VRING_BASE:
 676                 /* Moving base with an active backend?
 677                  * You don't want to do that. */
 678                 if (vq->private_data) {
 679                         r = -EBUSY;
 680                         break;
 681                 }
 682                 if (copy_from_user(&s, argp, sizeof s)) {
 683                         r = -EFAULT;
 684                         break;
 685                 }
 686                 if (s.num > 0xffff) {
 687                         r = -EINVAL;
 688                         break;
 689                 }
 690                 vq->last_avail_idx = s.num;
 691                 /* Forget the cached index value. */
 692                 vq->avail_idx = vq->last_avail_idx;
 693                 break;
 694         case VHOST_GET_VRING_BASE:
 695                 s.index = idx;
 696                 s.num = vq->last_avail_idx;
 697                 if (copy_to_user(argp, &s, sizeof s))
 698                         r = -EFAULT;
 699                 break;
 700         case VHOST_SET_VRING_ADDR:
 701                 if (copy_from_user(&a, argp, sizeof a)) {
 702                         r = -EFAULT;
 703                         break;
 704                 }
 705                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 706                         r = -EOPNOTSUPP;
 707                         break;
 708                 }
 709                 /* For 32bit, verify that the top 32bits of the user
 710                    data are set to zero. */
 711                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 712                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 713                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 714                         r = -EFAULT;
 715                         break;
 716                 }
 717                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 718                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 719                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 720                         r = -EINVAL;
 721                         break;
 722                 }
 723
 724                 /* We only verify access here if backend is configured.
 725                  * If it is not, we don't as size might not have been setup.
 726                  * We will verify when backend is configured. */
 727                 if (vq->private_data) {
 728                         if (!vq_access_ok(d, vq->num,
 729                                 (void __user *)(unsigned long)a.desc_user_addr,
 730                                 (void __user *)(unsigned long)a.avail_user_addr,
 731                                 (void __user *)(unsigned long)a.used_user_addr)) {
 732                                 r = -EINVAL;
 733                                 break;
 734                         }
 735
 736                         /* Also validate log access for used ring if enabled. */
 737                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 738                             !log_access_ok(vq->log_base, a.log_guest_addr,
 739                                            sizeof *vq->used +
 740                                            vq->num * sizeof *vq->used->ring)) {
 741                                 r = -EINVAL;
 742                                 break;
 743                         }
 744                 }
 745
 746                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 747                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 748                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 749                 vq->log_addr = a.log_guest_addr;
 750                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 751                 break;
 752         case VHOST_SET_VRING_KICK:
 753                 if (copy_from_user(&f, argp, sizeof f)) {
 754                         r = -EFAULT;
 755                         break;
 756                 }
 757                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 758                 if (IS_ERR(eventfp)) {
 759                         r = PTR_ERR(eventfp);
 760                         break;
 761                 }
 762                 if (eventfp != vq->kick) {
 763                         pollstop = filep = vq->kick;
 764                         pollstart = vq->kick = eventfp;
 765                 } else
 766                         filep = eventfp;
 767                 break;
 768         case VHOST_SET_VRING_CALL:
 769                 if (copy_from_user(&f, argp, sizeof f)) {
 770                         r = -EFAULT;
 771                         break;
 772                 }
 773                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 774                 if (IS_ERR(eventfp)) {
 775                         r = PTR_ERR(eventfp);
 776                         break;
 777                 }
 778                 if (eventfp != vq->call) {
 779                         filep = vq->call;
 780                         ctx = vq->call_ctx;
 781                         vq->call = eventfp;
 782                         vq->call_ctx = eventfp ?
 783                                 eventfd_ctx_fileget(eventfp) : NULL;
 784                 } else
 785                         filep = eventfp;
 786                 break;
 787         case VHOST_SET_VRING_ERR:
 788                 if (copy_from_user(&f, argp, sizeof f)) {
 789                         r = -EFAULT;
 790                         break;
 791                 }
 792                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 793                 if (IS_ERR(eventfp)) {
 794                         r = PTR_ERR(eventfp);
 795                         break;
 796                 }
 797                 if (eventfp != vq->error) {
 798                         filep = vq->error;
 799                         vq->error = eventfp;
 800                         ctx = vq->error_ctx;
 801                         vq->error_ctx = eventfp ?
 802                                 eventfd_ctx_fileget(eventfp) : NULL;
 803                 } else
 804                         filep = eventfp;
 805                 break;
 806         default:
 807                 r = -ENOIOCTLCMD;
 808         }
 809
 810         if (pollstop && vq->handle_kick)
 811                 vhost_poll_stop(&vq->poll);
 812
 813         if (ctx)
 814                 eventfd_ctx_put(ctx);
 815         if (filep)
 816                 fput(filep);
 817
 818         if (pollstart && vq->handle_kick)
 819                 vhost_poll_start(&vq->poll, vq->kick);
 820
 821         mutex_unlock(&vq->mutex);
 822
 823         if (pollstop && vq->handle_kick)
 824                 vhost_poll_flush(&vq->poll);
 825         return r;
 826 }
 827
 828 /* Caller must have device mutex */
 829 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 830 {
 831         void __user *argp = (void __user *)arg;
 832         struct file *eventfp, *filep = NULL;
 833         struct eventfd_ctx *ctx = NULL;
 834         u64 p;
 835         long r;
 836         int i, fd;
 837
 838         /* If you are not the owner, you can become one */
 839         if (ioctl == VHOST_SET_OWNER) {
 840                 r = vhost_dev_set_owner(d);
 841                 goto done;
 842         }
 843
 844         /* You must be the owner to do anything else */
 845         r = vhost_dev_check_owner(d);
 846         if (r)
 847                 goto done;
 848
 849         switch (ioctl) {
 850         case VHOST_SET_MEM_TABLE:
 851                 r = vhost_set_memory(d, argp);
 852                 break;
 853         case VHOST_SET_LOG_BASE:
 854                 if (copy_from_user(&p, argp, sizeof p)) {
 855                         r = -EFAULT;
 856                         break;
 857                 }
 858                 if ((u64)(unsigned long)p != p) {
 859                         r = -EFAULT;
 860                         break;
 861                 }
 862                 for (i = 0; i < d->nvqs; ++i) {
 863                         struct vhost_virtqueue *vq;
 864                         void __user *base = (void __user *)(unsigned long)p;
 865                         vq = d->vqs + i;
 866                         mutex_lock(&vq->mutex);
 867                         /* If ring is inactive, will check when it's enabled. */
 868                         if (vq->private_data && !vq_log_access_ok(d, vq, base))
 869                                 r = -EFAULT;
 870                         else
 871                                 vq->log_base = base;
 872                         mutex_unlock(&vq->mutex);
 873                 }
 874                 break;
 875         case VHOST_SET_LOG_FD:
 876                 r = get_user(fd, (int __user *)argp);
 877                 if (r < 0)
 878                         break;
 879                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 880                 if (IS_ERR(eventfp)) {
 881                         r = PTR_ERR(eventfp);
 882                         break;
 883                 }
 884                 if (eventfp != d->log_file) {
 885                         filep = d->log_file;
 886                         ctx = d->log_ctx;
 887                         d->log_ctx = eventfp ?
 888                                 eventfd_ctx_fileget(eventfp) : NULL;
 889                 } else
 890                         filep = eventfp;
 891                 for (i = 0; i < d->nvqs; ++i) {
 892                         mutex_lock(&d->vqs[i].mutex);
 893                         d->vqs[i].log_ctx = d->log_ctx;
 894                         mutex_unlock(&d->vqs[i].mutex);
 895                 }
 896                 if (ctx)
 897                         eventfd_ctx_put(ctx);
 898                 if (filep)
 899                         fput(filep);
 900                 break;
 901         default:
 902                 r = vhost_set_vring(d, ioctl, argp);
 903                 break;
 904         }
 905 done:
 906         return r;
 907 }
 908
 909 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 910                                                      __u64 addr, __u32 len)
 911 {
 912         struct vhost_memory_region *reg;
 913         int i;
 914
 915         /* linear search is not brilliant, but we really have on the order of 6
 916          * regions in practice */
 917         for (i = 0; i < mem->nregions; ++i) {
 918                 reg = mem->regions + i;
 919                 if (reg->guest_phys_addr <= addr &&
 920                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 921                         return reg;
 922         }
 923         return NULL;
 924 }
 925
 926 /* TODO: This is really inefficient.  We need something like get_user()
 927  * (instruction directly accesses the data, with an exception table entry
 928  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 929  */
 930 static int set_bit_to_user(int nr, void __user *addr)
 931 {
 932         unsigned long log = (unsigned long)addr;
 933         struct page *page;
 934         void *base;
 935         int bit = nr + (log % PAGE_SIZE) * 8;
 936         int r;
 937
 938         r = get_user_pages_fast(log, 1, 1, &page);
 939         if (r < 0)
 940                 return r;
 941         BUG_ON(r != 1);
 942         base = kmap_atomic(page, KM_USER0);
 943         set_bit(bit, base);
 944         kunmap_atomic(base, KM_USER0);
 945         set_page_dirty_lock(page);
 946         put_page(page);
 947         return 0;
 948 }
 949
 950 static int log_write(void __user *log_base,
 951                      u64 write_address, u64 write_length)
 952 {
 953         u64 write_page = write_address / VHOST_PAGE_SIZE;
 954         int r;
 955
 956         if (!write_length)
 957                 return 0;
 958         write_length += write_address % VHOST_PAGE_SIZE;
 959         for (;;) {
 960                 u64 base = (u64)(unsigned long)log_base;
 961                 u64 log = base + write_page / 8;
 962                 int bit = write_page % 8;
 963                 if ((u64)(unsigned long)log != log)
 964                         return -EFAULT;
 965                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 966                 if (r < 0)
 967                         return r;
 968                 if (write_length <= VHOST_PAGE_SIZE)
 969                         break;
 970                 write_length -= VHOST_PAGE_SIZE;
 971                 write_page += 1;
 972         }
 973         return r;
 974 }
 975
 976 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 977                     unsigned int log_num, u64 len)
 978 {
 979         int i, r;
 980
 981         /* Make sure data written is seen before log. */
 982         smp_wmb();
 983         for (i = 0; i < log_num; ++i) {
 984                 u64 l = min(log[i].len, len);
 985                 r = log_write(vq->log_base, log[i].addr, l);
 986                 if (r < 0)
 987                         return r;
 988                 len -= l;
 989                 if (!len) {
 990                         if (vq->log_ctx)
 991                                 eventfd_signal(vq->log_ctx, 1);
 992                         return 0;
 993                 }
 994         }
 995         /* Length written exceeds what we have stored. This is a bug. */
 996         BUG();
 997         return 0;
 998 }
 999
1000 static int vhost_update_used_flags(struct vhost_virtqueue *vq)
1001 {
1002         void __user *used;
1003         if (__put_user(vq->used_flags, &vq->used->flags) < 0)
1004                 return -EFAULT;
1005         if (unlikely(vq->log_used)) {
1006                 /* Make sure the flag is seen before log. */
1007                 smp_wmb();
1008                 /* Log used flag write. */
1009                 used = &vq->used->flags;
1010                 log_write(vq->log_base, vq->log_addr +
1011                           (used - (void __user *)vq->used),
1012                           sizeof vq->used->flags);
1013                 if (vq->log_ctx)
1014                         eventfd_signal(vq->log_ctx, 1);
1015         }
1016         return 0;
1017 }
1018
1019 static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
1020 {
1021         if (__put_user(vq->avail_idx, vhost_avail_event(vq)))
1022                 return -EFAULT;
1023         if (unlikely(vq->log_used)) {
1024                 void __user *used;
1025                 /* Make sure the event is seen before log. */
1026                 smp_wmb();
1027                 /* Log avail event write */
1028                 used = vhost_avail_event(vq);
1029                 log_write(vq->log_base, vq->log_addr +
1030                           (used - (void __user *)vq->used),
1031                           sizeof *vhost_avail_event(vq));
1032                 if (vq->log_ctx)
1033                         eventfd_signal(vq->log_ctx, 1);
1034         }
1035         return 0;
1036 }
1037
1038 int vhost_init_used(struct vhost_virtqueue *vq)
1039 {
1040         int r;
1041         if (!vq->private_data)
1042                 return 0;
1043
1044         r = vhost_update_used_flags(vq);
1045         if (r)
1046                 return r;
1047         vq->signalled_used_valid = false;
1048         return get_user(vq->last_used_idx, &vq->used->idx);
1049 }
1050
1051 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
1052                           struct iovec iov[], int iov_size)
1053 {
1054         const struct vhost_memory_region *reg;
1055         struct vhost_memory *mem;
1056         struct iovec *_iov;
1057         u64 s = 0;
1058         int ret = 0;
1059
1060         rcu_read_lock();
1061
1062         mem = rcu_dereference(dev->memory);
1063         while ((u64)len > s) {
1064                 u64 size;
1065                 if (unlikely(ret >= iov_size)) {
1066                         ret = -ENOBUFS;
1067                         break;
1068                 }
1069                 reg = find_region(mem, addr, len);
1070                 if (unlikely(!reg)) {
1071                         ret = -EFAULT;
1072                         break;
1073                 }
1074                 _iov = iov + ret;
1075                 size = reg->memory_size - addr + reg->guest_phys_addr;
1076                 _iov->iov_len = min((u64)len, size);
1077                 _iov->iov_base = (void __user *)(unsigned long)
1078                         (reg->userspace_addr + addr - reg->guest_phys_addr);
1079                 s += size;
1080                 addr += size;
1081                 ++ret;
1082         }
1083
1084         rcu_read_unlock();
1085         return ret;
1086 }
1087
1088 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
1089  * function returns the next descriptor in the chain,
1090  * or -1U if we're at the end. */
1091 static unsigned next_desc(struct vring_desc *desc)
1092 {
1093         unsigned int next;
1094
1095         /* If this descriptor says it doesn't chain, we're done. */
1096         if (!(desc->flags & VRING_DESC_F_NEXT))
1097                 return -1U;
1098
1099         /* Check they're not leading us off end of descriptors. */
1100         next = desc->next;
1101         /* Make sure compiler knows to grab that: we don't want it changing! */
1102         /* We will use the result as an index in an array, so most
1103          * architectures only need a compiler barrier here. */
1104         read_barrier_depends();
1105
1106         return next;
1107 }
1108
1109 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1110                         struct iovec iov[], unsigned int iov_size,
1111                         unsigned int *out_num, unsigned int *in_num,
1112                         struct vhost_log *log, unsigned int *log_num,
1113                         struct vring_desc *indirect)
1114 {
1115         struct vring_desc desc;
1116         unsigned int i = 0, count, found = 0;
1117         int ret;
1118
1119         /* Sanity check */
1120         if (unlikely(indirect->len % sizeof desc)) {
1121                 vq_err(vq, "Invalid length in indirect descriptor: "
1122                        "len 0x%llx not multiple of 0x%zx\n",
1123                        (unsigned long long)indirect->len,
1124                        sizeof desc);
1125                 return -EINVAL;
1126         }
1127
1128         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1129                              UIO_MAXIOV);
1130         if (unlikely(ret < 0)) {
1131                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1132                 return ret;
1133         }
1134
1135         /* We will use the result as an address to read from, so most
1136          * architectures only need a compiler barrier here. */
1137         read_barrier_depends();
1138
1139         count = indirect->len / sizeof desc;
1140         /* Buffers are chained via a 16 bit next field, so
1141          * we can have at most 2^16 of these. */
1142         if (unlikely(count > USHRT_MAX + 1)) {
1143                 vq_err(vq, "Indirect buffer length too big: %d\n",
1144                        indirect->len);
1145                 return -E2BIG;
1146         }
1147
1148         do {
1149                 unsigned iov_count = *in_num + *out_num;
1150                 if (unlikely(++found > count)) {
1151                         vq_err(vq, "Loop detected: last one at %u "
1152                                "indirect size %u\n",
1153                                i, count);
1154                         return -EINVAL;
1155                 }
1156                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1157                                               vq->indirect, sizeof desc))) {
1158                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1159                                i, (size_t)indirect->addr + i * sizeof desc);
1160                         return -EINVAL;
1161                 }
1162                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1163                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1164                                i, (size_t)indirect->addr + i * sizeof desc);
1165                         return -EINVAL;
1166                 }
1167
1168                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1169                                      iov_size - iov_count);
1170                 if (unlikely(ret < 0)) {
1171                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1172                                ret, i);
1173                         return ret;
1174                 }
1175                 /* If this is an input descriptor, increment that count. */
1176                 if (desc.flags & VRING_DESC_F_WRITE) {
1177                         *in_num += ret;
1178                         if (unlikely(log)) {
1179                                 log[*log_num].addr = desc.addr;
1180                                 log[*log_num].len = desc.len;
1181                                 ++*log_num;
1182                         }
1183                 } else {
1184                         /* If it's an output descriptor, they're all supposed
1185                          * to come before any input descriptors. */
1186                         if (unlikely(*in_num)) {
1187                                 vq_err(vq, "Indirect descriptor "
1188                                        "has out after in: idx %d\n", i);
1189                                 return -EINVAL;
1190                         }
1191                         *out_num += ret;
1192                 }
1193         } while ((i = next_desc(&desc)) != -1);
1194         return 0;
1195 }
1196
1197 /* This looks in the virtqueue and for the first available buffer, and converts
1198  * it to an iovec for convenient access.  Since descriptors consist of some
1199  * number of output then some number of input descriptors, it's actually two
1200  * iovecs, but we pack them into one and note how many of each there were.
1201  *
1202  * This function returns the descriptor number found, or vq->num (which is
1203  * never a valid descriptor number) if none was found.  A negative code is
1204  * returned on error. */
1205 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1206                       struct iovec iov[], unsigned int iov_size,
1207                       unsigned int *out_num, unsigned int *in_num,
1208                       struct vhost_log *log, unsigned int *log_num)
1209 {
1210         struct vring_desc desc;
1211         unsigned int i, head, found = 0;
1212         u16 last_avail_idx;
1213         int ret;
1214
1215         /* Check it isn't doing very strange things with descriptor numbers. */
1216         last_avail_idx = vq->last_avail_idx;
1217         if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1218                 vq_err(vq, "Failed to access avail idx at %p\n",
1219                        &vq->avail->idx);
1220                 return -EFAULT;
1221         }
1222
1223         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1224                 vq_err(vq, "Guest moved used index from %u to %u",
1225                        last_avail_idx, vq->avail_idx);
1226                 return -EFAULT;
1227         }
1228
1229         /* If there's nothing new since last we looked, return invalid. */
1230         if (vq->avail_idx == last_avail_idx)
1231                 return vq->num;
1232
1233         /* Only get avail ring entries after they have been exposed by guest. */
1234         smp_rmb();
1235
1236         /* Grab the next descriptor number they're advertising, and increment
1237          * the index we've seen. */
1238         if (unlikely(__get_user(head,
1239                                 &vq->avail->ring[last_avail_idx % vq->num]))) {
1240                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1241                        last_avail_idx,
1242                        &vq->avail->ring[last_avail_idx % vq->num]);
1243                 return -EFAULT;
1244         }
1245
1246         /* If their number is silly, that's an error. */
1247         if (unlikely(head >= vq->num)) {
1248                 vq_err(vq, "Guest says index %u > %u is available",
1249                        head, vq->num);
1250                 return -EINVAL;
1251         }
1252
1253         /* When we start there are none of either input nor output. */
1254         *out_num = *in_num = 0;
1255         if (unlikely(log))
1256                 *log_num = 0;
1257
1258         i = head;
1259         do {
1260                 unsigned iov_count = *in_num + *out_num;
1261                 if (unlikely(i >= vq->num)) {
1262                         vq_err(vq, "Desc index is %u > %u, head = %u",
1263                                i, vq->num, head);
1264                         return -EINVAL;
1265                 }
1266                 if (unlikely(++found > vq->num)) {
1267                         vq_err(vq, "Loop detected: last one at %u "
1268                                "vq size %u head %u\n",
1269                                i, vq->num, head);
1270                         return -EINVAL;
1271                 }
1272                 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1273                 if (unlikely(ret)) {
1274                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1275                                i, vq->desc + i);
1276                         return -EFAULT;
1277                 }
1278                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1279                         ret = get_indirect(dev, vq, iov, iov_size,
1280                                            out_num, in_num,
1281                                            log, log_num, &desc);
1282                         if (unlikely(ret < 0)) {
1283                                 vq_err(vq, "Failure detected "
1284                                        "in indirect descriptor at idx %d\n", i);
1285                                 return ret;
1286                         }
1287                         continue;
1288                 }
1289
1290                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1291                                      iov_size - iov_count);
1292                 if (unlikely(ret < 0)) {
1293                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1294                                ret, i);
1295                         return ret;
1296                 }
1297                 if (desc.flags & VRING_DESC_F_WRITE) {
1298                         /* If this is an input descriptor,
1299                          * increment that count. */
1300                         *in_num += ret;
1301                         if (unlikely(log)) {
1302                                 log[*log_num].addr = desc.addr;
1303                                 log[*log_num].len = desc.len;
1304                                 ++*log_num;
1305                         }
1306                 } else {
1307                         /* If it's an output descriptor, they're all supposed
1308                          * to come before any input descriptors. */
1309                         if (unlikely(*in_num)) {
1310                                 vq_err(vq, "Descriptor has out after in: "
1311                                        "idx %d\n", i);
1312                                 return -EINVAL;
1313                         }
1314                         *out_num += ret;
1315                 }
1316         } while ((i = next_desc(&desc)) != -1);
1317
1318         /* On success, increment avail index. */
1319         vq->last_avail_idx++;
1320
1321         /* Assume notifications from guest are disabled at this point,
1322          * if they aren't we would need to update avail_event index. */
1323         BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1324         return head;
1325 }
1326
1327 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1328 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1329 {
1330         vq->last_avail_idx -= n;
1331 }
1332
1333 /* After we've used one of their buffers, we tell them about it.  We'll then
1334  * want to notify the guest, using eventfd. */
1335 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1336 {
1337         struct vring_used_elem __user *used;
1338
1339         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1340          * next entry in that used ring. */
1341         used = &vq->used->ring[vq->last_used_idx % vq->num];
1342         if (__put_user(head, &used->id)) {
1343                 vq_err(vq, "Failed to write used id");
1344                 return -EFAULT;
1345         }
1346         if (__put_user(len, &used->len)) {
1347                 vq_err(vq, "Failed to write used len");
1348                 return -EFAULT;
1349         }
1350         /* Make sure buffer is written before we update index. */
1351         smp_wmb();
1352         if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1353                 vq_err(vq, "Failed to increment used idx");
1354                 return -EFAULT;
1355         }
1356         if (unlikely(vq->log_used)) {
1357                 /* Make sure data is seen before log. */
1358                 smp_wmb();
1359                 /* Log used ring entry write. */
1360                 log_write(vq->log_base,
1361                           vq->log_addr +
1362                            ((void __user *)used - (void __user *)vq->used),
1363                           sizeof *used);
1364                 /* Log used index update. */
1365                 log_write(vq->log_base,
1366                           vq->log_addr + offsetof(struct vring_used, idx),
1367                           sizeof vq->used->idx);
1368                 if (vq->log_ctx)
1369                         eventfd_signal(vq->log_ctx, 1);
1370         }
1371         vq->last_used_idx++;
1372         /* If the driver never bothers to signal in a very long while,
1373          * used index might wrap around. If that happens, invalidate
1374          * signalled_used index we stored. TODO: make sure driver
1375          * signals at least once in 2^16 and remove this. */
1376         if (unlikely(vq->last_used_idx == vq->signalled_used))
1377                 vq->signalled_used_valid = false;
1378         return 0;
1379 }
1380
1381 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1382                             struct vring_used_elem *heads,
1383                             unsigned count)
1384 {
1385         struct vring_used_elem __user *used;
1386         u16 old, new;
1387         int start;
1388
1389         start = vq->last_used_idx % vq->num;
1390         used = vq->used->ring + start;
1391         if (__copy_to_user(used, heads, count * sizeof *used)) {
1392                 vq_err(vq, "Failed to write used");
1393                 return -EFAULT;
1394         }
1395         if (unlikely(vq->log_used)) {
1396                 /* Make sure data is seen before log. */
1397                 smp_wmb();
1398                 /* Log used ring entry write. */
1399                 log_write(vq->log_base,
1400                           vq->log_addr +
1401                            ((void __user *)used - (void __user *)vq->used),
1402                           count * sizeof *used);
1403         }
1404         old = vq->last_used_idx;
1405         new = (vq->last_used_idx += count);
1406         /* If the driver never bothers to signal in a very long while,
1407          * used index might wrap around. If that happens, invalidate
1408          * signalled_used index we stored. TODO: make sure driver
1409          * signals at least once in 2^16 and remove this. */
1410         if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1411                 vq->signalled_used_valid = false;
1412         return 0;
1413 }
1414
1415 /* After we've used one of their buffers, we tell them about it.  We'll then
1416  * want to notify the guest, using eventfd. */
1417 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1418                      unsigned count)
1419 {
1420         int start, n, r;
1421
1422         start = vq->last_used_idx % vq->num;
1423         n = vq->num - start;
1424         if (n < count) {
1425                 r = __vhost_add_used_n(vq, heads, n);
1426                 if (r < 0)
1427                         return r;
1428                 heads += n;
1429                 count -= n;
1430         }
1431         r = __vhost_add_used_n(vq, heads, count);
1432
1433         /* Make sure buffer is written before we update index. */
1434         smp_wmb();
1435         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1436                 vq_err(vq, "Failed to increment used idx");
1437                 return -EFAULT;
1438         }
1439         if (unlikely(vq->log_used)) {
1440                 /* Log used index update. */
1441                 log_write(vq->log_base,
1442                           vq->log_addr + offsetof(struct vring_used, idx),
1443                           sizeof vq->used->idx);
1444                 if (vq->log_ctx)
1445                         eventfd_signal(vq->log_ctx, 1);
1446         }
1447         return r;
1448 }
1449
1450 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1451 {
1452         __u16 old, new, event;
1453         bool v;
1454         /* Flush out used index updates. This is paired
1455          * with the barrier that the Guest executes when enabling
1456          * interrupts. */
1457         smp_mb();
1458
1459         if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1460             unlikely(vq->avail_idx == vq->last_avail_idx))
1461                 return true;
1462
1463         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1464                 __u16 flags;
1465                 if (__get_user(flags, &vq->avail->flags)) {
1466                         vq_err(vq, "Failed to get flags");
1467                         return true;
1468                 }
1469                 return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1470         }
1471         old = vq->signalled_used;
1472         v = vq->signalled_used_valid;
1473         new = vq->signalled_used = vq->last_used_idx;
1474         vq->signalled_used_valid = true;
1475
1476         if (unlikely(!v))
1477                 return true;
1478
1479         if (get_user(event, vhost_used_event(vq))) {
1480                 vq_err(vq, "Failed to get used event idx");
1481                 return true;
1482         }
1483         return vring_need_event(event, new, old);
1484 }
1485
1486 /* This actually signals the guest, using eventfd. */
1487 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1488 {
1489         /* Signal the Guest tell them we used something up. */
1490         if (vq->call_ctx && vhost_notify(dev, vq))
1491                 eventfd_signal(vq->call_ctx, 1);
1492 }
1493
1494 /* And here's the combo meal deal.  Supersize me! */
1495 void vhost_add_used_and_signal(struct vhost_dev *dev,
1496                                struct vhost_virtqueue *vq,
1497                                unsigned int head, int len)
1498 {
1499         vhost_add_used(vq, head, len);
1500         vhost_signal(dev, vq);
1501 }
1502
1503 /* multi-buffer version of vhost_add_used_and_signal */
1504 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1505                                  struct vhost_virtqueue *vq,
1506                                  struct vring_used_elem *heads, unsigned count)
1507 {
1508         vhost_add_used_n(vq, heads, count);
1509         vhost_signal(dev, vq);
1510 }
1511
1512 /* OK, now we need to know about added descriptors. */
1513 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1514 {
1515         u16 avail_idx;
1516         int r;
1517
1518         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1519                 return false;
1520         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1521         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1522                 r = vhost_update_used_flags(vq);
1523                 if (r) {
1524                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1525                                &vq->used->flags, r);
1526                         return false;
1527                 }
1528         } else {
1529                 r = vhost_update_avail_event(vq, vq->avail_idx);
1530                 if (r) {
1531                         vq_err(vq, "Failed to update avail event index at %p: %d\n",
1532                                vhost_avail_event(vq), r);
1533                         return false;
1534                 }
1535         }
1536         /* They could have slipped one in as we were doing that: make
1537          * sure it's written, then check again. */
1538         smp_mb();
1539         r = __get_user(avail_idx, &vq->avail->idx);
1540         if (r) {
1541                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1542                        &vq->avail->idx, r);
1543                 return false;
1544         }
1545
1546         return avail_idx != vq->avail_idx;
1547 }
1548
1549 /* We don't need to be notified again. */
1550 void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1551 {
1552         int r;
1553
1554         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1555                 return;
1556         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1557         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1558                 r = vhost_update_used_flags(vq);
1559                 if (r)
1560                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1561                                &vq->used->flags, r);
1562         }
1563 }
1564
1565 static void vhost_zerocopy_done_signal(struct kref *kref)
1566 {
1567         struct vhost_ubuf_ref *ubufs = container_of(kref, struct vhost_ubuf_ref,
1568                                                     kref);
1569         wake_up(&ubufs->wait);
1570 }
1571
1572 struct vhost_ubuf_ref *vhost_ubuf_alloc(struct vhost_virtqueue *vq,
1573                                         bool zcopy)
1574 {
1575         struct vhost_ubuf_ref *ubufs;
1576         /* No zero copy backend? Nothing to count. */
1577         if (!zcopy)
1578                 return NULL;
1579         ubufs = kmalloc(sizeof *ubufs, GFP_KERNEL);
1580         if (!ubufs)
1581                 return ERR_PTR(-ENOMEM);
1582         kref_init(&ubufs->kref);
1583         init_waitqueue_head(&ubufs->wait);
1584         ubufs->vq = vq;
1585         return ubufs;
1586 }
1587
1588 void vhost_ubuf_put(struct vhost_ubuf_ref *ubufs)
1589 {
1590         kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1591 }
1592
1593 void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs)
1594 {
1595         kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1596         wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
1597         kfree(ubufs);
1598 }
1599
1600 void vhost_zerocopy_callback(void *arg)
1601 {
1602         struct ubuf_info *ubuf = arg;
1603         struct vhost_ubuf_ref *ubufs = ubuf->arg;
1604         struct vhost_virtqueue *vq = ubufs->vq;
1605
1606         /* set len = 1 to mark this desc buffers done DMA */
1607         vq->heads[ubuf->desc].len = VHOST_DMA_DONE_LEN;
1608         kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1609 }