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