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/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/miscdevice.h>
  19 #include <linux/mutex.h>
  20 #include <linux/rcupdate.h>
  21 #include <linux/poll.h>
  22 #include <linux/file.h>
  23 #include <linux/highmem.h>
  24 #include <linux/slab.h>
  25 #include <linux/kthread.h>
  26 #include <linux/cgroup.h>
  27
  28 #include <linux/net.h>
  29 #include <linux/if_packet.h>
  30 #include <linux/if_arp.h>
  31
  32 #include <net/sock.h>
  33
  34 #include "vhost.h"
  35
  36 enum {
  37         VHOST_MEMORY_MAX_NREGIONS = 64,
  38         VHOST_MEMORY_F_LOG = 0x1,
  39 };
  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         poll = container_of(pt, struct vhost_poll, table);
  46
  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 static 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         mask = file->f_op->poll(file, &poll->table);
  90         if (mask)
  91                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  92 }
  93
  94 /* Stop polling a file. After this function returns, it becomes safe to drop the
  95  * file reference. You must also flush afterwards. */
  96 void vhost_poll_stop(struct vhost_poll *poll)
  97 {
  98         remove_wait_queue(poll->wqh, &poll->wait);
  99 }
 100
 101 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 102 {
 103         unsigned seq;
 104         int left;
 105         int flushing;
 106
 107         spin_lock_irq(&dev->work_lock);
 108         seq = work->queue_seq;
 109         work->flushing++;
 110         spin_unlock_irq(&dev->work_lock);
 111         wait_event(work->done, ({
 112                    spin_lock_irq(&dev->work_lock);
 113                    left = seq - work->done_seq <= 0;
 114                    spin_unlock_irq(&dev->work_lock);
 115                    left;
 116         }));
 117         spin_lock_irq(&dev->work_lock);
 118         flushing = --work->flushing;
 119         spin_unlock_irq(&dev->work_lock);
 120         BUG_ON(flushing < 0);
 121 }
 122
 123 /* Flush any work that has been scheduled. When calling this, don't hold any
 124  * locks that are also used by the callback. */
 125 void vhost_poll_flush(struct vhost_poll *poll)
 126 {
 127         vhost_work_flush(poll->dev, &poll->work);
 128 }
 129
 130 static inline void vhost_work_queue(struct vhost_dev *dev,
 131                                     struct vhost_work *work)
 132 {
 133         unsigned long flags;
 134
 135         spin_lock_irqsave(&dev->work_lock, flags);
 136         if (list_empty(&work->node)) {
 137                 list_add_tail(&work->node, &dev->work_list);
 138                 work->queue_seq++;
 139                 wake_up_process(dev->worker);
 140         }
 141         spin_unlock_irqrestore(&dev->work_lock, flags);
 142 }
 143
 144 void vhost_poll_queue(struct vhost_poll *poll)
 145 {
 146         vhost_work_queue(poll->dev, &poll->work);
 147 }
 148
 149 static void vhost_vq_reset(struct vhost_dev *dev,
 150                            struct vhost_virtqueue *vq)
 151 {
 152         vq->num = 1;
 153         vq->desc = NULL;
 154         vq->avail = NULL;
 155         vq->used = NULL;
 156         vq->last_avail_idx = 0;
 157         vq->avail_idx = 0;
 158         vq->last_used_idx = 0;
 159         vq->used_flags = 0;
 160         vq->used_flags = 0;
 161         vq->log_used = false;
 162         vq->log_addr = -1ull;
 163         vq->vhost_hlen = 0;
 164         vq->sock_hlen = 0;
 165         vq->private_data = NULL;
 166         vq->log_base = NULL;
 167         vq->error_ctx = NULL;
 168         vq->error = NULL;
 169         vq->kick = NULL;
 170         vq->call_ctx = NULL;
 171         vq->call = NULL;
 172         vq->log_ctx = NULL;
 173 }
 174
 175 static int vhost_worker(void *data)
 176 {
 177         struct vhost_dev *dev = data;
 178         struct vhost_work *work = NULL;
 179         unsigned uninitialized_var(seq);
 180
 181         for (;;) {
 182                 /* mb paired w/ kthread_stop */
 183                 set_current_state(TASK_INTERRUPTIBLE);
 184
 185                 spin_lock_irq(&dev->work_lock);
 186                 if (work) {
 187                         work->done_seq = seq;
 188                         if (work->flushing)
 189                                 wake_up_all(&work->done);
 190                 }
 191
 192                 if (kthread_should_stop()) {
 193                         spin_unlock_irq(&dev->work_lock);
 194                         __set_current_state(TASK_RUNNING);
 195                         return 0;
 196                 }
 197                 if (!list_empty(&dev->work_list)) {
 198                         work = list_first_entry(&dev->work_list,
 199                                                 struct vhost_work, node);
 200                         list_del_init(&work->node);
 201                         seq = work->queue_seq;
 202                 } else
 203                         work = NULL;
 204                 spin_unlock_irq(&dev->work_lock);
 205
 206                 if (work) {
 207                         __set_current_state(TASK_RUNNING);
 208                         work->fn(work);
 209                 } else
 210                         schedule();
 211
 212         }
 213 }
 214
 215 long vhost_dev_init(struct vhost_dev *dev,
 216                     struct vhost_virtqueue *vqs, int nvqs)
 217 {
 218         int i;
 219
 220         dev->vqs = vqs;
 221         dev->nvqs = nvqs;
 222         mutex_init(&dev->mutex);
 223         dev->log_ctx = NULL;
 224         dev->log_file = NULL;
 225         dev->memory = NULL;
 226         dev->mm = NULL;
 227         spin_lock_init(&dev->work_lock);
 228         INIT_LIST_HEAD(&dev->work_list);
 229         dev->worker = NULL;
 230
 231         for (i = 0; i < dev->nvqs; ++i) {
 232                 dev->vqs[i].dev = dev;
 233                 mutex_init(&dev->vqs[i].mutex);
 234                 vhost_vq_reset(dev, dev->vqs + i);
 235                 if (dev->vqs[i].handle_kick)
 236                         vhost_poll_init(&dev->vqs[i].poll,
 237                                         dev->vqs[i].handle_kick, POLLIN, dev);
 238         }
 239
 240         return 0;
 241 }
 242
 243 /* Caller should have device mutex */
 244 long vhost_dev_check_owner(struct vhost_dev *dev)
 245 {
 246         /* Are you the owner? If not, I don't think you mean to do that */
 247         return dev->mm == current->mm ? 0 : -EPERM;
 248 }
 249
 250 struct vhost_attach_cgroups_struct {
 251         struct vhost_work work;
 252         struct task_struct *owner;
 253         int ret;
 254 };
 255
 256 static void vhost_attach_cgroups_work(struct vhost_work *work)
 257 {
 258         struct vhost_attach_cgroups_struct *s;
 259         s = container_of(work, struct vhost_attach_cgroups_struct, work);
 260         s->ret = cgroup_attach_task_all(s->owner, current);
 261 }
 262
 263 static int vhost_attach_cgroups(struct vhost_dev *dev)
 264 {
 265         struct vhost_attach_cgroups_struct attach;
 266         attach.owner = current;
 267         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 268         vhost_work_queue(dev, &attach.work);
 269         vhost_work_flush(dev, &attach.work);
 270         return attach.ret;
 271 }
 272
 273 /* Caller should have device mutex */
 274 static long vhost_dev_set_owner(struct vhost_dev *dev)
 275 {
 276         struct task_struct *worker;
 277         int err;
 278         /* Is there an owner already? */
 279         if (dev->mm) {
 280                 err = -EBUSY;
 281                 goto err_mm;
 282         }
 283         /* No owner, become one */
 284         dev->mm = get_task_mm(current);
 285         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 286         if (IS_ERR(worker)) {
 287                 err = PTR_ERR(worker);
 288                 goto err_worker;
 289         }
 290
 291         dev->worker = worker;
 292         wake_up_process(worker);        /* avoid contributing to loadavg */
 293
 294         err = vhost_attach_cgroups(dev);
 295         if (err)
 296                 goto err_cgroup;
 297
 298         return 0;
 299 err_cgroup:
 300         kthread_stop(worker);
 301         dev->worker = NULL;
 302 err_worker:
 303         if (dev->mm)
 304                 mmput(dev->mm);
 305         dev->mm = NULL;
 306 err_mm:
 307         return err;
 308 }
 309
 310 /* Caller should have device mutex */
 311 long vhost_dev_reset_owner(struct vhost_dev *dev)
 312 {
 313         struct vhost_memory *memory;
 314
 315         /* Restore memory to default empty mapping. */
 316         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 317         if (!memory)
 318                 return -ENOMEM;
 319
 320         vhost_dev_cleanup(dev);
 321
 322         memory->nregions = 0;
 323         RCU_INIT_POINTER(dev->memory, memory);
 324         return 0;
 325 }
 326
 327 /* Caller should have device mutex */
 328 void vhost_dev_cleanup(struct vhost_dev *dev)
 329 {
 330         int i;
 331         for (i = 0; i < dev->nvqs; ++i) {
 332                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
 333                         vhost_poll_stop(&dev->vqs[i].poll);
 334                         vhost_poll_flush(&dev->vqs[i].poll);
 335                 }
 336                 if (dev->vqs[i].error_ctx)
 337                         eventfd_ctx_put(dev->vqs[i].error_ctx);
 338                 if (dev->vqs[i].error)
 339                         fput(dev->vqs[i].error);
 340                 if (dev->vqs[i].kick)
 341                         fput(dev->vqs[i].kick);
 342                 if (dev->vqs[i].call_ctx)
 343                         eventfd_ctx_put(dev->vqs[i].call_ctx);
 344                 if (dev->vqs[i].call)
 345                         fput(dev->vqs[i].call);
 346                 vhost_vq_reset(dev, dev->vqs + i);
 347         }
 348         if (dev->log_ctx)
 349                 eventfd_ctx_put(dev->log_ctx);
 350         dev->log_ctx = NULL;
 351         if (dev->log_file)
 352                 fput(dev->log_file);
 353         dev->log_file = NULL;
 354         /* No one will access memory at this point */
 355         kfree(rcu_dereference_protected(dev->memory,
 356                                         lockdep_is_held(&dev->mutex)));
 357         RCU_INIT_POINTER(dev->memory, NULL);
 358         if (dev->mm)
 359                 mmput(dev->mm);
 360         dev->mm = NULL;
 361
 362         WARN_ON(!list_empty(&dev->work_list));
 363         if (dev->worker) {
 364                 kthread_stop(dev->worker);
 365                 dev->worker = NULL;
 366         }
 367 }
 368
 369 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 370 {
 371         u64 a = addr / VHOST_PAGE_SIZE / 8;
 372         /* Make sure 64 bit math will not overflow. */
 373         if (a > ULONG_MAX - (unsigned long)log_base ||
 374             a + (unsigned long)log_base > ULONG_MAX)
 375                 return -EFAULT;
 376
 377         return access_ok(VERIFY_WRITE, log_base + a,
 378                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 379 }
 380
 381 /* Caller should have vq mutex and device mutex. */
 382 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 383                                int log_all)
 384 {
 385         int i;
 386
 387         if (!mem)
 388                 return 0;
 389
 390         for (i = 0; i < mem->nregions; ++i) {
 391                 struct vhost_memory_region *m = mem->regions + i;
 392                 unsigned long a = m->userspace_addr;
 393                 if (m->memory_size > ULONG_MAX)
 394                         return 0;
 395                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 396                                     m->memory_size))
 397                         return 0;
 398                 else if (log_all && !log_access_ok(log_base,
 399                                                    m->guest_phys_addr,
 400                                                    m->memory_size))
 401                         return 0;
 402         }
 403         return 1;
 404 }
 405
 406 /* Can we switch to this memory table? */
 407 /* Caller should have device mutex but not vq mutex */
 408 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 409                             int log_all)
 410 {
 411         int i;
 412         for (i = 0; i < d->nvqs; ++i) {
 413                 int ok;
 414                 mutex_lock(&d->vqs[i].mutex);
 415                 /* If ring is inactive, will check when it's enabled. */
 416                 if (d->vqs[i].private_data)
 417                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
 418                                                  log_all);
 419                 else
 420                         ok = 1;
 421                 mutex_unlock(&d->vqs[i].mutex);
 422                 if (!ok)
 423                         return 0;
 424         }
 425         return 1;
 426 }
 427
 428 static int vq_access_ok(unsigned int num,
 429                         struct vring_desc __user *desc,
 430                         struct vring_avail __user *avail,
 431                         struct vring_used __user *used)
 432 {
 433         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 434                access_ok(VERIFY_READ, avail,
 435                          sizeof *avail + num * sizeof *avail->ring) &&
 436                access_ok(VERIFY_WRITE, used,
 437                         sizeof *used + num * sizeof *used->ring);
 438 }
 439
 440 /* Can we log writes? */
 441 /* Caller should have device mutex but not vq mutex */
 442 int vhost_log_access_ok(struct vhost_dev *dev)
 443 {
 444         struct vhost_memory *mp;
 445
 446         mp = rcu_dereference_protected(dev->memory,
 447                                        lockdep_is_held(&dev->mutex));
 448         return memory_access_ok(dev, mp, 1);
 449 }
 450
 451 /* Verify access for write logging. */
 452 /* Caller should have vq mutex and device mutex */
 453 static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
 454 {
 455         struct vhost_memory *mp;
 456
 457         mp = rcu_dereference_protected(vq->dev->memory,
 458                                        lockdep_is_held(&vq->mutex));
 459         return vq_memory_access_ok(log_base, mp,
 460                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 461                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 462                                         sizeof *vq->used +
 463                                         vq->num * sizeof *vq->used->ring));
 464 }
 465
 466 /* Can we start vq? */
 467 /* Caller should have vq mutex and device mutex */
 468 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 469 {
 470         return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
 471                 vq_log_access_ok(vq, vq->log_base);
 472 }
 473
 474 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 475 {
 476         struct vhost_memory mem, *newmem, *oldmem;
 477         unsigned long size = offsetof(struct vhost_memory, regions);
 478         if (copy_from_user(&mem, m, size))
 479                 return -EFAULT;
 480         if (mem.padding)
 481                 return -EOPNOTSUPP;
 482         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 483                 return -E2BIG;
 484         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 485         if (!newmem)
 486                 return -ENOMEM;
 487
 488         memcpy(newmem, &mem, size);
 489         if (copy_from_user(newmem->regions, m->regions,
 490                            mem.nregions * sizeof *m->regions)) {
 491                 kfree(newmem);
 492                 return -EFAULT;
 493         }
 494
 495         if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 496                 kfree(newmem);
 497                 return -EFAULT;
 498         }
 499         oldmem = rcu_dereference_protected(d->memory,
 500                                            lockdep_is_held(&d->mutex));
 501         rcu_assign_pointer(d->memory, newmem);
 502         synchronize_rcu();
 503         kfree(oldmem);
 504         return 0;
 505 }
 506
 507 static int init_used(struct vhost_virtqueue *vq,
 508                      struct vring_used __user *used)
 509 {
 510         int r = put_user(vq->used_flags, &used->flags);
 511         if (r)
 512                 return r;
 513         return get_user(vq->last_used_idx, &used->idx);
 514 }
 515
 516 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 517 {
 518         struct file *eventfp, *filep = NULL,
 519                     *pollstart = NULL, *pollstop = NULL;
 520         struct eventfd_ctx *ctx = NULL;
 521         u32 __user *idxp = argp;
 522         struct vhost_virtqueue *vq;
 523         struct vhost_vring_state s;
 524         struct vhost_vring_file f;
 525         struct vhost_vring_addr a;
 526         u32 idx;
 527         long r;
 528
 529         r = get_user(idx, idxp);
 530         if (r < 0)
 531                 return r;
 532         if (idx >= d->nvqs)
 533                 return -ENOBUFS;
 534
 535         vq = d->vqs + idx;
 536
 537         mutex_lock(&vq->mutex);
 538
 539         switch (ioctl) {
 540         case VHOST_SET_VRING_NUM:
 541                 /* Resizing ring with an active backend?
 542                  * You don't want to do that. */
 543                 if (vq->private_data) {
 544                         r = -EBUSY;
 545                         break;
 546                 }
 547                 if (copy_from_user(&s, argp, sizeof s)) {
 548                         r = -EFAULT;
 549                         break;
 550                 }
 551                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 552                         r = -EINVAL;
 553                         break;
 554                 }
 555                 vq->num = s.num;
 556                 break;
 557         case VHOST_SET_VRING_BASE:
 558                 /* Moving base with an active backend?
 559                  * You don't want to do that. */
 560                 if (vq->private_data) {
 561                         r = -EBUSY;
 562                         break;
 563                 }
 564                 if (copy_from_user(&s, argp, sizeof s)) {
 565                         r = -EFAULT;
 566                         break;
 567                 }
 568                 if (s.num > 0xffff) {
 569                         r = -EINVAL;
 570                         break;
 571                 }
 572                 vq->last_avail_idx = s.num;
 573                 /* Forget the cached index value. */
 574                 vq->avail_idx = vq->last_avail_idx;
 575                 break;
 576         case VHOST_GET_VRING_BASE:
 577                 s.index = idx;
 578                 s.num = vq->last_avail_idx;
 579                 if (copy_to_user(argp, &s, sizeof s))
 580                         r = -EFAULT;
 581                 break;
 582         case VHOST_SET_VRING_ADDR:
 583                 if (copy_from_user(&a, argp, sizeof a)) {
 584                         r = -EFAULT;
 585                         break;
 586                 }
 587                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 588                         r = -EOPNOTSUPP;
 589                         break;
 590                 }
 591                 /* For 32bit, verify that the top 32bits of the user
 592                    data are set to zero. */
 593                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 594                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 595                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 596                         r = -EFAULT;
 597                         break;
 598                 }
 599                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 600                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 601                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 602                         r = -EINVAL;
 603                         break;
 604                 }
 605
 606                 /* We only verify access here if backend is configured.
 607                  * If it is not, we don't as size might not have been setup.
 608                  * We will verify when backend is configured. */
 609                 if (vq->private_data) {
 610                         if (!vq_access_ok(vq->num,
 611                                 (void __user *)(unsigned long)a.desc_user_addr,
 612                                 (void __user *)(unsigned long)a.avail_user_addr,
 613                                 (void __user *)(unsigned long)a.used_user_addr)) {
 614                                 r = -EINVAL;
 615                                 break;
 616                         }
 617
 618                         /* Also validate log access for used ring if enabled. */
 619                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 620                             !log_access_ok(vq->log_base, a.log_guest_addr,
 621                                            sizeof *vq->used +
 622                                            vq->num * sizeof *vq->used->ring)) {
 623                                 r = -EINVAL;
 624                                 break;
 625                         }
 626                 }
 627
 628                 r = init_used(vq, (struct vring_used __user *)(unsigned long)
 629                               a.used_user_addr);
 630                 if (r)
 631                         break;
 632                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 633                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 634                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 635                 vq->log_addr = a.log_guest_addr;
 636                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 637                 break;
 638         case VHOST_SET_VRING_KICK:
 639                 if (copy_from_user(&f, argp, sizeof f)) {
 640                         r = -EFAULT;
 641                         break;
 642                 }
 643                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 644                 if (IS_ERR(eventfp)) {
 645                         r = PTR_ERR(eventfp);
 646                         break;
 647                 }
 648                 if (eventfp != vq->kick) {
 649                         pollstop = filep = vq->kick;
 650                         pollstart = vq->kick = eventfp;
 651                 } else
 652                         filep = eventfp;
 653                 break;
 654         case VHOST_SET_VRING_CALL:
 655                 if (copy_from_user(&f, argp, sizeof f)) {
 656                         r = -EFAULT;
 657                         break;
 658                 }
 659                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 660                 if (IS_ERR(eventfp)) {
 661                         r = PTR_ERR(eventfp);
 662                         break;
 663                 }
 664                 if (eventfp != vq->call) {
 665                         filep = vq->call;
 666                         ctx = vq->call_ctx;
 667                         vq->call = eventfp;
 668                         vq->call_ctx = eventfp ?
 669                                 eventfd_ctx_fileget(eventfp) : NULL;
 670                 } else
 671                         filep = eventfp;
 672                 break;
 673         case VHOST_SET_VRING_ERR:
 674                 if (copy_from_user(&f, argp, sizeof f)) {
 675                         r = -EFAULT;
 676                         break;
 677                 }
 678                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 679                 if (IS_ERR(eventfp)) {
 680                         r = PTR_ERR(eventfp);
 681                         break;
 682                 }
 683                 if (eventfp != vq->error) {
 684                         filep = vq->error;
 685                         vq->error = eventfp;
 686                         ctx = vq->error_ctx;
 687                         vq->error_ctx = eventfp ?
 688                                 eventfd_ctx_fileget(eventfp) : NULL;
 689                 } else
 690                         filep = eventfp;
 691                 break;
 692         default:
 693                 r = -ENOIOCTLCMD;
 694         }
 695
 696         if (pollstop && vq->handle_kick)
 697                 vhost_poll_stop(&vq->poll);
 698
 699         if (ctx)
 700                 eventfd_ctx_put(ctx);
 701         if (filep)
 702                 fput(filep);
 703
 704         if (pollstart && vq->handle_kick)
 705                 vhost_poll_start(&vq->poll, vq->kick);
 706
 707         mutex_unlock(&vq->mutex);
 708
 709         if (pollstop && vq->handle_kick)
 710                 vhost_poll_flush(&vq->poll);
 711         return r;
 712 }
 713
 714 /* Caller must have device mutex */
 715 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 716 {
 717         void __user *argp = (void __user *)arg;
 718         struct file *eventfp, *filep = NULL;
 719         struct eventfd_ctx *ctx = NULL;
 720         u64 p;
 721         long r;
 722         int i, fd;
 723
 724         /* If you are not the owner, you can become one */
 725         if (ioctl == VHOST_SET_OWNER) {
 726                 r = vhost_dev_set_owner(d);
 727                 goto done;
 728         }
 729
 730         /* You must be the owner to do anything else */
 731         r = vhost_dev_check_owner(d);
 732         if (r)
 733                 goto done;
 734
 735         switch (ioctl) {
 736         case VHOST_SET_MEM_TABLE:
 737                 r = vhost_set_memory(d, argp);
 738                 break;
 739         case VHOST_SET_LOG_BASE:
 740                 if (copy_from_user(&p, argp, sizeof p)) {
 741                         r = -EFAULT;
 742                         break;
 743                 }
 744                 if ((u64)(unsigned long)p != p) {
 745                         r = -EFAULT;
 746                         break;
 747                 }
 748                 for (i = 0; i < d->nvqs; ++i) {
 749                         struct vhost_virtqueue *vq;
 750                         void __user *base = (void __user *)(unsigned long)p;
 751                         vq = d->vqs + i;
 752                         mutex_lock(&vq->mutex);
 753                         /* If ring is inactive, will check when it's enabled. */
 754                         if (vq->private_data && !vq_log_access_ok(vq, base))
 755                                 r = -EFAULT;
 756                         else
 757                                 vq->log_base = base;
 758                         mutex_unlock(&vq->mutex);
 759                 }
 760                 break;
 761         case VHOST_SET_LOG_FD:
 762                 r = get_user(fd, (int __user *)argp);
 763                 if (r < 0)
 764                         break;
 765                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 766                 if (IS_ERR(eventfp)) {
 767                         r = PTR_ERR(eventfp);
 768                         break;
 769                 }
 770                 if (eventfp != d->log_file) {
 771                         filep = d->log_file;
 772                         ctx = d->log_ctx;
 773                         d->log_ctx = eventfp ?
 774                                 eventfd_ctx_fileget(eventfp) : NULL;
 775                 } else
 776                         filep = eventfp;
 777                 for (i = 0; i < d->nvqs; ++i) {
 778                         mutex_lock(&d->vqs[i].mutex);
 779                         d->vqs[i].log_ctx = d->log_ctx;
 780                         mutex_unlock(&d->vqs[i].mutex);
 781                 }
 782                 if (ctx)
 783                         eventfd_ctx_put(ctx);
 784                 if (filep)
 785                         fput(filep);
 786                 break;
 787         default:
 788                 r = vhost_set_vring(d, ioctl, argp);
 789                 break;
 790         }
 791 done:
 792         return r;
 793 }
 794
 795 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 796                                                      __u64 addr, __u32 len)
 797 {
 798         struct vhost_memory_region *reg;
 799         int i;
 800         /* linear search is not brilliant, but we really have on the order of 6
 801          * regions in practice */
 802         for (i = 0; i < mem->nregions; ++i) {
 803                 reg = mem->regions + i;
 804                 if (reg->guest_phys_addr <= addr &&
 805                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 806                         return reg;
 807         }
 808         return NULL;
 809 }
 810
 811 /* TODO: This is really inefficient.  We need something like get_user()
 812  * (instruction directly accesses the data, with an exception table entry
 813  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 814  */
 815 static int set_bit_to_user(int nr, void __user *addr)
 816 {
 817         unsigned long log = (unsigned long)addr;
 818         struct page *page;
 819         void *base;
 820         int bit = nr + (log % PAGE_SIZE) * 8;
 821         int r;
 822         r = get_user_pages_fast(log, 1, 1, &page);
 823         if (r < 0)
 824                 return r;
 825         BUG_ON(r != 1);
 826         base = kmap_atomic(page, KM_USER0);
 827         set_bit(bit, base);
 828         kunmap_atomic(base, KM_USER0);
 829         set_page_dirty_lock(page);
 830         put_page(page);
 831         return 0;
 832 }
 833
 834 static int log_write(void __user *log_base,
 835                      u64 write_address, u64 write_length)
 836 {
 837         int r;
 838         if (!write_length)
 839                 return 0;
 840         write_address /= VHOST_PAGE_SIZE;
 841         for (;;) {
 842                 u64 base = (u64)(unsigned long)log_base;
 843                 u64 log = base + write_address / 8;
 844                 int bit = write_address % 8;
 845                 if ((u64)(unsigned long)log != log)
 846                         return -EFAULT;
 847                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 848                 if (r < 0)
 849                         return r;
 850                 if (write_length <= VHOST_PAGE_SIZE)
 851                         break;
 852                 write_length -= VHOST_PAGE_SIZE;
 853                 write_address += VHOST_PAGE_SIZE;
 854         }
 855         return r;
 856 }
 857
 858 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 859                     unsigned int log_num, u64 len)
 860 {
 861         int i, r;
 862
 863         /* Make sure data written is seen before log. */
 864         smp_wmb();
 865         for (i = 0; i < log_num; ++i) {
 866                 u64 l = min(log[i].len, len);
 867                 r = log_write(vq->log_base, log[i].addr, l);
 868                 if (r < 0)
 869                         return r;
 870                 len -= l;
 871                 if (!len) {
 872                         if (vq->log_ctx)
 873                                 eventfd_signal(vq->log_ctx, 1);
 874                         return 0;
 875                 }
 876         }
 877         /* Length written exceeds what we have stored. This is a bug. */
 878         BUG();
 879         return 0;
 880 }
 881
 882 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
 883                           struct iovec iov[], int iov_size)
 884 {
 885         const struct vhost_memory_region *reg;
 886         struct vhost_memory *mem;
 887         struct iovec *_iov;
 888         u64 s = 0;
 889         int ret = 0;
 890
 891         rcu_read_lock();
 892
 893         mem = rcu_dereference(dev->memory);
 894         while ((u64)len > s) {
 895                 u64 size;
 896                 if (unlikely(ret >= iov_size)) {
 897                         ret = -ENOBUFS;
 898                         break;
 899                 }
 900                 reg = find_region(mem, addr, len);
 901                 if (unlikely(!reg)) {
 902                         ret = -EFAULT;
 903                         break;
 904                 }
 905                 _iov = iov + ret;
 906                 size = reg->memory_size - addr + reg->guest_phys_addr;
 907                 _iov->iov_len = min((u64)len, size);
 908                 _iov->iov_base = (void __user *)(unsigned long)
 909                         (reg->userspace_addr + addr - reg->guest_phys_addr);
 910                 s += size;
 911                 addr += size;
 912                 ++ret;
 913         }
 914
 915         rcu_read_unlock();
 916         return ret;
 917 }
 918
 919 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
 920  * function returns the next descriptor in the chain,
 921  * or -1U if we're at the end. */
 922 static unsigned next_desc(struct vring_desc *desc)
 923 {
 924         unsigned int next;
 925
 926         /* If this descriptor says it doesn't chain, we're done. */
 927         if (!(desc->flags & VRING_DESC_F_NEXT))
 928                 return -1U;
 929
 930         /* Check they're not leading us off end of descriptors. */
 931         next = desc->next;
 932         /* Make sure compiler knows to grab that: we don't want it changing! */
 933         /* We will use the result as an index in an array, so most
 934          * architectures only need a compiler barrier here. */
 935         read_barrier_depends();
 936
 937         return next;
 938 }
 939
 940 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
 941                         struct iovec iov[], unsigned int iov_size,
 942                         unsigned int *out_num, unsigned int *in_num,
 943                         struct vhost_log *log, unsigned int *log_num,
 944                         struct vring_desc *indirect)
 945 {
 946         struct vring_desc desc;
 947         unsigned int i = 0, count, found = 0;
 948         int ret;
 949
 950         /* Sanity check */
 951         if (unlikely(indirect->len % sizeof desc)) {
 952                 vq_err(vq, "Invalid length in indirect descriptor: "
 953                        "len 0x%llx not multiple of 0x%zx\n",
 954                        (unsigned long long)indirect->len,
 955                        sizeof desc);
 956                 return -EINVAL;
 957         }
 958
 959         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
 960                              ARRAY_SIZE(vq->indirect));
 961         if (unlikely(ret < 0)) {
 962                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
 963                 return ret;
 964         }
 965
 966         /* We will use the result as an address to read from, so most
 967          * architectures only need a compiler barrier here. */
 968         read_barrier_depends();
 969
 970         count = indirect->len / sizeof desc;
 971         /* Buffers are chained via a 16 bit next field, so
 972          * we can have at most 2^16 of these. */
 973         if (unlikely(count > USHRT_MAX + 1)) {
 974                 vq_err(vq, "Indirect buffer length too big: %d\n",
 975                        indirect->len);
 976                 return -E2BIG;
 977         }
 978
 979         do {
 980                 unsigned iov_count = *in_num + *out_num;
 981                 if (unlikely(++found > count)) {
 982                         vq_err(vq, "Loop detected: last one at %u "
 983                                "indirect size %u\n",
 984                                i, count);
 985                         return -EINVAL;
 986                 }
 987                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
 988                                               sizeof desc))) {
 989                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
 990                                i, (size_t)indirect->addr + i * sizeof desc);
 991                         return -EINVAL;
 992                 }
 993                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
 994                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
 995                                i, (size_t)indirect->addr + i * sizeof desc);
 996                         return -EINVAL;
 997                 }
 998
 999                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1000                                      iov_size - iov_count);
1001                 if (unlikely(ret < 0)) {
1002                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1003                                ret, i);
1004                         return ret;
1005                 }
1006                 /* If this is an input descriptor, increment that count. */
1007                 if (desc.flags & VRING_DESC_F_WRITE) {
1008                         *in_num += ret;
1009                         if (unlikely(log)) {
1010                                 log[*log_num].addr = desc.addr;
1011                                 log[*log_num].len = desc.len;
1012                                 ++*log_num;
1013                         }
1014                 } else {
1015                         /* If it's an output descriptor, they're all supposed
1016                          * to come before any input descriptors. */
1017                         if (unlikely(*in_num)) {
1018                                 vq_err(vq, "Indirect descriptor "
1019                                        "has out after in: idx %d\n", i);
1020                                 return -EINVAL;
1021                         }
1022                         *out_num += ret;
1023                 }
1024         } while ((i = next_desc(&desc)) != -1);
1025         return 0;
1026 }
1027
1028 /* This looks in the virtqueue and for the first available buffer, and converts
1029  * it to an iovec for convenient access.  Since descriptors consist of some
1030  * number of output then some number of input descriptors, it's actually two
1031  * iovecs, but we pack them into one and note how many of each there were.
1032  *
1033  * This function returns the descriptor number found, or vq->num (which is
1034  * never a valid descriptor number) if none was found.  A negative code is
1035  * returned on error. */
1036 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1037                       struct iovec iov[], unsigned int iov_size,
1038                       unsigned int *out_num, unsigned int *in_num,
1039                       struct vhost_log *log, unsigned int *log_num)
1040 {
1041         struct vring_desc desc;
1042         unsigned int i, head, found = 0;
1043         u16 last_avail_idx;
1044         int ret;
1045
1046         /* Check it isn't doing very strange things with descriptor numbers. */
1047         last_avail_idx = vq->last_avail_idx;
1048         if (unlikely(get_user(vq->avail_idx, &vq->avail->idx))) {
1049                 vq_err(vq, "Failed to access avail idx at %p\n",
1050                        &vq->avail->idx);
1051                 return -EFAULT;
1052         }
1053
1054         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1055                 vq_err(vq, "Guest moved used index from %u to %u",
1056                        last_avail_idx, vq->avail_idx);
1057                 return -EFAULT;
1058         }
1059
1060         /* If there's nothing new since last we looked, return invalid. */
1061         if (vq->avail_idx == last_avail_idx)
1062                 return vq->num;
1063
1064         /* Only get avail ring entries after they have been exposed by guest. */
1065         smp_rmb();
1066
1067         /* Grab the next descriptor number they're advertising, and increment
1068          * the index we've seen. */
1069         if (unlikely(get_user(head,
1070                               &vq->avail->ring[last_avail_idx % vq->num]))) {
1071                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1072                        last_avail_idx,
1073                        &vq->avail->ring[last_avail_idx % vq->num]);
1074                 return -EFAULT;
1075         }
1076
1077         /* If their number is silly, that's an error. */
1078         if (unlikely(head >= vq->num)) {
1079                 vq_err(vq, "Guest says index %u > %u is available",
1080                        head, vq->num);
1081                 return -EINVAL;
1082         }
1083
1084         /* When we start there are none of either input nor output. */
1085         *out_num = *in_num = 0;
1086         if (unlikely(log))
1087                 *log_num = 0;
1088
1089         i = head;
1090         do {
1091                 unsigned iov_count = *in_num + *out_num;
1092                 if (unlikely(i >= vq->num)) {
1093                         vq_err(vq, "Desc index is %u > %u, head = %u",
1094                                i, vq->num, head);
1095                         return -EINVAL;
1096                 }
1097                 if (unlikely(++found > vq->num)) {
1098                         vq_err(vq, "Loop detected: last one at %u "
1099                                "vq size %u head %u\n",
1100                                i, vq->num, head);
1101                         return -EINVAL;
1102                 }
1103                 ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
1104                 if (unlikely(ret)) {
1105                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1106                                i, vq->desc + i);
1107                         return -EFAULT;
1108                 }
1109                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1110                         ret = get_indirect(dev, vq, iov, iov_size,
1111                                            out_num, in_num,
1112                                            log, log_num, &desc);
1113                         if (unlikely(ret < 0)) {
1114                                 vq_err(vq, "Failure detected "
1115                                        "in indirect descriptor at idx %d\n", i);
1116                                 return ret;
1117                         }
1118                         continue;
1119                 }
1120
1121                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1122                                      iov_size - iov_count);
1123                 if (unlikely(ret < 0)) {
1124                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1125                                ret, i);
1126                         return ret;
1127                 }
1128                 if (desc.flags & VRING_DESC_F_WRITE) {
1129                         /* If this is an input descriptor,
1130                          * increment that count. */
1131                         *in_num += ret;
1132                         if (unlikely(log)) {
1133                                 log[*log_num].addr = desc.addr;
1134                                 log[*log_num].len = desc.len;
1135                                 ++*log_num;
1136                         }
1137                 } else {
1138                         /* If it's an output descriptor, they're all supposed
1139                          * to come before any input descriptors. */
1140                         if (unlikely(*in_num)) {
1141                                 vq_err(vq, "Descriptor has out after in: "
1142                                        "idx %d\n", i);
1143                                 return -EINVAL;
1144                         }
1145                         *out_num += ret;
1146                 }
1147         } while ((i = next_desc(&desc)) != -1);
1148
1149         /* On success, increment avail index. */
1150         vq->last_avail_idx++;
1151         return head;
1152 }
1153
1154 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1155 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1156 {
1157         vq->last_avail_idx -= n;
1158 }
1159
1160 /* After we've used one of their buffers, we tell them about it.  We'll then
1161  * want to notify the guest, using eventfd. */
1162 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1163 {
1164         struct vring_used_elem __user *used;
1165
1166         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1167          * next entry in that used ring. */
1168         used = &vq->used->ring[vq->last_used_idx % vq->num];
1169         if (put_user(head, &used->id)) {
1170                 vq_err(vq, "Failed to write used id");
1171                 return -EFAULT;
1172         }
1173         if (put_user(len, &used->len)) {
1174                 vq_err(vq, "Failed to write used len");
1175                 return -EFAULT;
1176         }
1177         /* Make sure buffer is written before we update index. */
1178         smp_wmb();
1179         if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1180                 vq_err(vq, "Failed to increment used idx");
1181                 return -EFAULT;
1182         }
1183         if (unlikely(vq->log_used)) {
1184                 /* Make sure data is seen before log. */
1185                 smp_wmb();
1186                 /* Log used ring entry write. */
1187                 log_write(vq->log_base,
1188                           vq->log_addr +
1189                            ((void __user *)used - (void __user *)vq->used),
1190                           sizeof *used);
1191                 /* Log used index update. */
1192                 log_write(vq->log_base,
1193                           vq->log_addr + offsetof(struct vring_used, idx),
1194                           sizeof vq->used->idx);
1195                 if (vq->log_ctx)
1196                         eventfd_signal(vq->log_ctx, 1);
1197         }
1198         vq->last_used_idx++;
1199         return 0;
1200 }
1201
1202 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1203                             struct vring_used_elem *heads,
1204                             unsigned count)
1205 {
1206         struct vring_used_elem __user *used;
1207         int start;
1208
1209         start = vq->last_used_idx % vq->num;
1210         used = vq->used->ring + start;
1211         if (copy_to_user(used, heads, count * sizeof *used)) {
1212                 vq_err(vq, "Failed to write used");
1213                 return -EFAULT;
1214         }
1215         if (unlikely(vq->log_used)) {
1216                 /* Make sure data is seen before log. */
1217                 smp_wmb();
1218                 /* Log used ring entry write. */
1219                 log_write(vq->log_base,
1220                           vq->log_addr +
1221                            ((void __user *)used - (void __user *)vq->used),
1222                           count * sizeof *used);
1223         }
1224         vq->last_used_idx += count;
1225         return 0;
1226 }
1227
1228 /* After we've used one of their buffers, we tell them about it.  We'll then
1229  * want to notify the guest, using eventfd. */
1230 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1231                      unsigned count)
1232 {
1233         int start, n, r;
1234
1235         start = vq->last_used_idx % vq->num;
1236         n = vq->num - start;
1237         if (n < count) {
1238                 r = __vhost_add_used_n(vq, heads, n);
1239                 if (r < 0)
1240                         return r;
1241                 heads += n;
1242                 count -= n;
1243         }
1244         r = __vhost_add_used_n(vq, heads, count);
1245
1246         /* Make sure buffer is written before we update index. */
1247         smp_wmb();
1248         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1249                 vq_err(vq, "Failed to increment used idx");
1250                 return -EFAULT;
1251         }
1252         if (unlikely(vq->log_used)) {
1253                 /* Log used index update. */
1254                 log_write(vq->log_base,
1255                           vq->log_addr + offsetof(struct vring_used, idx),
1256                           sizeof vq->used->idx);
1257                 if (vq->log_ctx)
1258                         eventfd_signal(vq->log_ctx, 1);
1259         }
1260         return r;
1261 }
1262
1263 /* This actually signals the guest, using eventfd. */
1264 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1265 {
1266         __u16 flags;
1267         /* Flush out used index updates. This is paired
1268          * with the barrier that the Guest executes when enabling
1269          * interrupts. */
1270         smp_mb();
1271
1272         if (get_user(flags, &vq->avail->flags)) {
1273                 vq_err(vq, "Failed to get flags");
1274                 return;
1275         }
1276
1277         /* If they don't want an interrupt, don't signal, unless empty. */
1278         if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1279             (vq->avail_idx != vq->last_avail_idx ||
1280              !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1281                 return;
1282
1283         /* Signal the Guest tell them we used something up. */
1284         if (vq->call_ctx)
1285                 eventfd_signal(vq->call_ctx, 1);
1286 }
1287
1288 /* And here's the combo meal deal.  Supersize me! */
1289 void vhost_add_used_and_signal(struct vhost_dev *dev,
1290                                struct vhost_virtqueue *vq,
1291                                unsigned int head, int len)
1292 {
1293         vhost_add_used(vq, head, len);
1294         vhost_signal(dev, vq);
1295 }
1296
1297 /* multi-buffer version of vhost_add_used_and_signal */
1298 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1299                                  struct vhost_virtqueue *vq,
1300                                  struct vring_used_elem *heads, unsigned count)
1301 {
1302         vhost_add_used_n(vq, heads, count);
1303         vhost_signal(dev, vq);
1304 }
1305
1306 /* OK, now we need to know about added descriptors. */
1307 bool vhost_enable_notify(struct vhost_virtqueue *vq)
1308 {
1309         u16 avail_idx;
1310         int r;
1311         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1312                 return false;
1313         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1314         r = put_user(vq->used_flags, &vq->used->flags);
1315         if (r) {
1316                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1317                        &vq->used->flags, r);
1318                 return false;
1319         }
1320         /* They could have slipped one in as we were doing that: make
1321          * sure it's written, then check again. */
1322         smp_mb();
1323         r = get_user(avail_idx, &vq->avail->idx);
1324         if (r) {
1325                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1326                        &vq->avail->idx, r);
1327                 return false;
1328         }
1329
1330         return avail_idx != vq->avail_idx;
1331 }
1332
1333 /* We don't need to be notified again. */
1334 void vhost_disable_notify(struct vhost_virtqueue *vq)
1335 {
1336         int r;
1337         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1338                 return;
1339         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1340         r = put_user(vq->used_flags, &vq->used->flags);
1341         if (r)
1342                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1343                        &vq->used->flags, r);
1344 }