drivers/vhost/vhost.c

   1 /* Copyright (C) 2009 Red Hat, Inc.
   2  * Copyright (C) 2006 Rusty Russell IBM Corporation
   3  *
   4  * Author: Michael S. Tsirkin <mst@redhat.com>
   5  *
   6  * Inspiration, some code, and most witty comments come from
   7  * Documentation/virtual/lguest/lguest.c, by Rusty Russell
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.
  10  *
  11  * Generic code for virtio server in host kernel.
  12  */
  13
  14 #include <linux/eventfd.h>
  15 #include <linux/vhost.h>
  16 #include <linux/virtio_net.h>
  17 #include <linux/mm.h>
  18 #include <linux/mmu_context.h>
  19 #include <linux/miscdevice.h>
  20 #include <linux/mutex.h>
  21 #include <linux/rcupdate.h>
  22 #include <linux/poll.h>
  23 #include <linux/file.h>
  24 #include <linux/highmem.h>
  25 #include <linux/slab.h>
  26 #include <linux/kthread.h>
  27 #include <linux/cgroup.h>
  28
  29 #include <linux/net.h>
  30 #include <linux/if_packet.h>
  31 #include <linux/if_arp.h>
  32
  33 #include "vhost.h"
  34
  35 enum {
  36         VHOST_MEMORY_MAX_NREGIONS = 64,
  37         VHOST_MEMORY_F_LOG = 0x1,
  38 };
  39
  40 #define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
  41 #define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
  42
  43 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  44                             poll_table *pt)
  45 {
  46         struct vhost_poll *poll;
  47
  48         poll = container_of(pt, struct vhost_poll, table);
  49         poll->wqh = wqh;
  50         add_wait_queue(wqh, &poll->wait);
  51 }
  52
  53 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
  54                              void *key)
  55 {
  56         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  57
  58         if (!((unsigned long)key & poll->mask))
  59                 return 0;
  60
  61         vhost_poll_queue(poll);
  62         return 0;
  63 }
  64
  65 static void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  66 {
  67         INIT_LIST_HEAD(&work->node);
  68         work->fn = fn;
  69         init_waitqueue_head(&work->done);
  70         work->flushing = 0;
  71         work->queue_seq = work->done_seq = 0;
  72 }
  73
  74 /* Init poll structure */
  75 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  76                      unsigned long mask, struct vhost_dev *dev)
  77 {
  78         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  79         init_poll_funcptr(&poll->table, vhost_poll_func);
  80         poll->mask = mask;
  81         poll->dev = dev;
  82
  83         vhost_work_init(&poll->work, fn);
  84 }
  85
  86 /* Start polling a file. We add ourselves to file's wait queue. The caller must
  87  * keep a reference to a file until after vhost_poll_stop is called. */
  88 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
  89 {
  90         unsigned long mask;
  91
  92         mask = file->f_op->poll(file, &poll->table);
  93         if (mask)
  94                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  95 }
  96
  97 /* Stop polling a file. After this function returns, it becomes safe to drop the
  98  * file reference. You must also flush afterwards. */
  99 void vhost_poll_stop(struct vhost_poll *poll)
 100 {
 101         remove_wait_queue(poll->wqh, &poll->wait);
 102 }
 103
 104 static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
 105                                 unsigned seq)
 106 {
 107         int left;
 108
 109         spin_lock_irq(&dev->work_lock);
 110         left = seq - work->done_seq;
 111         spin_unlock_irq(&dev->work_lock);
 112         return left <= 0;
 113 }
 114
 115 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 116 {
 117         unsigned seq;
 118         int flushing;
 119
 120         spin_lock_irq(&dev->work_lock);
 121         seq = work->queue_seq;
 122         work->flushing++;
 123         spin_unlock_irq(&dev->work_lock);
 124         wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 125         spin_lock_irq(&dev->work_lock);
 126         flushing = --work->flushing;
 127         spin_unlock_irq(&dev->work_lock);
 128         BUG_ON(flushing < 0);
 129 }
 130
 131 /* Flush any work that has been scheduled. When calling this, don't hold any
 132  * locks that are also used by the callback. */
 133 void vhost_poll_flush(struct vhost_poll *poll)
 134 {
 135         vhost_work_flush(poll->dev, &poll->work);
 136 }
 137
 138 static inline void vhost_work_queue(struct vhost_dev *dev,
 139                                     struct vhost_work *work)
 140 {
 141         unsigned long flags;
 142
 143         spin_lock_irqsave(&dev->work_lock, flags);
 144         if (list_empty(&work->node)) {
 145                 list_add_tail(&work->node, &dev->work_list);
 146                 work->queue_seq++;
 147                 wake_up_process(dev->worker);
 148         }
 149         spin_unlock_irqrestore(&dev->work_lock, flags);
 150 }
 151
 152 void vhost_poll_queue(struct vhost_poll *poll)
 153 {
 154         vhost_work_queue(poll->dev, &poll->work);
 155 }
 156
 157 static void vhost_vq_reset(struct vhost_dev *dev,
 158                            struct vhost_virtqueue *vq)
 159 {
 160         vq->num = 1;
 161         vq->desc = NULL;
 162         vq->avail = NULL;
 163         vq->used = NULL;
 164         vq->last_avail_idx = 0;
 165         vq->avail_idx = 0;
 166         vq->last_used_idx = 0;
 167         vq->signalled_used = 0;
 168         vq->signalled_used_valid = false;
 169         vq->used_flags = 0;
 170         vq->log_used = false;
 171         vq->log_addr = -1ull;
 172         vq->vhost_hlen = 0;
 173         vq->sock_hlen = 0;
 174         vq->private_data = NULL;
 175         vq->log_base = NULL;
 176         vq->error_ctx = NULL;
 177         vq->error = NULL;
 178         vq->kick = NULL;
 179         vq->call_ctx = NULL;
 180         vq->call = NULL;
 181         vq->log_ctx = NULL;
 182 }
 183
 184 static int vhost_worker(void *data)
 185 {
 186         struct vhost_dev *dev = data;
 187         struct vhost_work *work = NULL;
 188         unsigned uninitialized_var(seq);
 189
 190         use_mm(dev->mm);
 191
 192         for (;;) {
 193                 /* mb paired w/ kthread_stop */
 194                 set_current_state(TASK_INTERRUPTIBLE);
 195
 196                 spin_lock_irq(&dev->work_lock);
 197                 if (work) {
 198                         work->done_seq = seq;
 199                         if (work->flushing)
 200                                 wake_up_all(&work->done);
 201                 }
 202
 203                 if (kthread_should_stop()) {
 204                         spin_unlock_irq(&dev->work_lock);
 205                         __set_current_state(TASK_RUNNING);
 206                         break;
 207                 }
 208                 if (!list_empty(&dev->work_list)) {
 209                         work = list_first_entry(&dev->work_list,
 210                                                 struct vhost_work, node);
 211                         list_del_init(&work->node);
 212                         seq = work->queue_seq;
 213                 } else
 214                         work = NULL;
 215                 spin_unlock_irq(&dev->work_lock);
 216
 217                 if (work) {
 218                         __set_current_state(TASK_RUNNING);
 219                         work->fn(work);
 220                 } else
 221                         schedule();
 222
 223         }
 224         unuse_mm(dev->mm);
 225         return 0;
 226 }
 227
 228 /* Helper to allocate iovec buffers for all vqs. */
 229 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 230 {
 231         int i;
 232
 233         for (i = 0; i < dev->nvqs; ++i) {
 234                 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
 235                                                UIO_MAXIOV, GFP_KERNEL);
 236                 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
 237                                           GFP_KERNEL);
 238                 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
 239                                             UIO_MAXIOV, GFP_KERNEL);
 240
 241                 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
 242                         !dev->vqs[i].heads)
 243                         goto err_nomem;
 244         }
 245         return 0;
 246
 247 err_nomem:
 248         for (; i >= 0; --i) {
 249                 kfree(dev->vqs[i].indirect);
 250                 kfree(dev->vqs[i].log);
 251                 kfree(dev->vqs[i].heads);
 252         }
 253         return -ENOMEM;
 254 }
 255
 256 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
 257 {
 258         int i;
 259
 260         for (i = 0; i < dev->nvqs; ++i) {
 261                 kfree(dev->vqs[i].indirect);
 262                 dev->vqs[i].indirect = NULL;
 263                 kfree(dev->vqs[i].log);
 264                 dev->vqs[i].log = NULL;
 265                 kfree(dev->vqs[i].heads);
 266                 dev->vqs[i].heads = NULL;
 267         }
 268 }
 269
 270 long vhost_dev_init(struct vhost_dev *dev,
 271                     struct vhost_virtqueue *vqs, int nvqs)
 272 {
 273         int i;
 274
 275         dev->vqs = vqs;
 276         dev->nvqs = nvqs;
 277         mutex_init(&dev->mutex);
 278         dev->log_ctx = NULL;
 279         dev->log_file = NULL;
 280         dev->memory = NULL;
 281         dev->mm = NULL;
 282         spin_lock_init(&dev->work_lock);
 283         INIT_LIST_HEAD(&dev->work_list);
 284         dev->worker = NULL;
 285
 286         for (i = 0; i < dev->nvqs; ++i) {
 287                 dev->vqs[i].log = NULL;
 288                 dev->vqs[i].indirect = NULL;
 289                 dev->vqs[i].heads = NULL;
 290                 dev->vqs[i].dev = dev;
 291                 mutex_init(&dev->vqs[i].mutex);
 292                 vhost_vq_reset(dev, dev->vqs + i);
 293                 if (dev->vqs[i].handle_kick)
 294                         vhost_poll_init(&dev->vqs[i].poll,
 295                                         dev->vqs[i].handle_kick, POLLIN, dev);
 296         }
 297
 298         return 0;
 299 }
 300
 301 /* Caller should have device mutex */
 302 long vhost_dev_check_owner(struct vhost_dev *dev)
 303 {
 304         /* Are you the owner? If not, I don't think you mean to do that */
 305         return dev->mm == current->mm ? 0 : -EPERM;
 306 }
 307
 308 struct vhost_attach_cgroups_struct {
 309         struct vhost_work work;
 310         struct task_struct *owner;
 311         int ret;
 312 };
 313
 314 static void vhost_attach_cgroups_work(struct vhost_work *work)
 315 {
 316         struct vhost_attach_cgroups_struct *s;
 317
 318         s = container_of(work, struct vhost_attach_cgroups_struct, work);
 319         s->ret = cgroup_attach_task_all(s->owner, current);
 320 }
 321
 322 static int vhost_attach_cgroups(struct vhost_dev *dev)
 323 {
 324         struct vhost_attach_cgroups_struct attach;
 325
 326         attach.owner = current;
 327         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 328         vhost_work_queue(dev, &attach.work);
 329         vhost_work_flush(dev, &attach.work);
 330         return attach.ret;
 331 }
 332
 333 /* Caller should have device mutex */
 334 static long vhost_dev_set_owner(struct vhost_dev *dev)
 335 {
 336         struct task_struct *worker;
 337         int err;
 338
 339         /* Is there an owner already? */
 340         if (dev->mm) {
 341                 err = -EBUSY;
 342                 goto err_mm;
 343         }
 344
 345         /* No owner, become one */
 346         dev->mm = get_task_mm(current);
 347         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 348         if (IS_ERR(worker)) {
 349                 err = PTR_ERR(worker);
 350                 goto err_worker;
 351         }
 352
 353         dev->worker = worker;
 354         wake_up_process(worker);        /* avoid contributing to loadavg */
 355
 356         err = vhost_attach_cgroups(dev);
 357         if (err)
 358                 goto err_cgroup;
 359
 360         err = vhost_dev_alloc_iovecs(dev);
 361         if (err)
 362                 goto err_cgroup;
 363
 364         return 0;
 365 err_cgroup:
 366         kthread_stop(worker);
 367         dev->worker = NULL;
 368 err_worker:
 369         if (dev->mm)
 370                 mmput(dev->mm);
 371         dev->mm = NULL;
 372 err_mm:
 373         return err;
 374 }
 375
 376 /* Caller should have device mutex */
 377 long vhost_dev_reset_owner(struct vhost_dev *dev)
 378 {
 379         struct vhost_memory *memory;
 380
 381         /* Restore memory to default empty mapping. */
 382         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 383         if (!memory)
 384                 return -ENOMEM;
 385
 386         vhost_dev_cleanup(dev);
 387
 388         memory->nregions = 0;
 389         RCU_INIT_POINTER(dev->memory, memory);
 390         return 0;
 391 }
 392
 393 /* Caller should have device mutex */
 394 void vhost_dev_cleanup(struct vhost_dev *dev)
 395 {
 396         int i;
 397
 398         for (i = 0; i < dev->nvqs; ++i) {
 399                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
 400                         vhost_poll_stop(&dev->vqs[i].poll);
 401                         vhost_poll_flush(&dev->vqs[i].poll);
 402                 }
 403                 if (dev->vqs[i].error_ctx)
 404                         eventfd_ctx_put(dev->vqs[i].error_ctx);
 405                 if (dev->vqs[i].error)
 406                         fput(dev->vqs[i].error);
 407                 if (dev->vqs[i].kick)
 408                         fput(dev->vqs[i].kick);
 409                 if (dev->vqs[i].call_ctx)
 410                         eventfd_ctx_put(dev->vqs[i].call_ctx);
 411                 if (dev->vqs[i].call)
 412                         fput(dev->vqs[i].call);
 413                 vhost_vq_reset(dev, dev->vqs + i);
 414         }
 415         vhost_dev_free_iovecs(dev);
 416         if (dev->log_ctx)
 417                 eventfd_ctx_put(dev->log_ctx);
 418         dev->log_ctx = NULL;
 419         if (dev->log_file)
 420                 fput(dev->log_file);
 421         dev->log_file = NULL;
 422         /* No one will access memory at this point */
 423         kfree(rcu_dereference_protected(dev->memory,
 424                                         lockdep_is_held(&dev->mutex)));
 425         RCU_INIT_POINTER(dev->memory, NULL);
 426         WARN_ON(!list_empty(&dev->work_list));
 427         if (dev->worker) {
 428                 kthread_stop(dev->worker);
 429                 dev->worker = NULL;
 430         }
 431         if (dev->mm)
 432                 mmput(dev->mm);
 433         dev->mm = NULL;
 434 }
 435
 436 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 437 {
 438         u64 a = addr / VHOST_PAGE_SIZE / 8;
 439
 440         /* Make sure 64 bit math will not overflow. */
 441         if (a > ULONG_MAX - (unsigned long)log_base ||
 442             a + (unsigned long)log_base > ULONG_MAX)
 443                 return 0;
 444
 445         return access_ok(VERIFY_WRITE, log_base + a,
 446                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 447 }
 448
 449 /* Caller should have vq mutex and device mutex. */
 450 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 451                                int log_all)
 452 {
 453         int i;
 454
 455         if (!mem)
 456                 return 0;
 457
 458         for (i = 0; i < mem->nregions; ++i) {
 459                 struct vhost_memory_region *m = mem->regions + i;
 460                 unsigned long a = m->userspace_addr;
 461                 if (m->memory_size > ULONG_MAX)
 462                         return 0;
 463                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 464                                     m->memory_size))
 465                         return 0;
 466                 else if (log_all && !log_access_ok(log_base,
 467                                                    m->guest_phys_addr,
 468                                                    m->memory_size))
 469                         return 0;
 470         }
 471         return 1;
 472 }
 473
 474 /* Can we switch to this memory table? */
 475 /* Caller should have device mutex but not vq mutex */
 476 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 477                             int log_all)
 478 {
 479         int i;
 480
 481         for (i = 0; i < d->nvqs; ++i) {
 482                 int ok;
 483                 mutex_lock(&d->vqs[i].mutex);
 484                 /* If ring is inactive, will check when it's enabled. */
 485                 if (d->vqs[i].private_data)
 486                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
 487                                                  log_all);
 488                 else
 489                         ok = 1;
 490                 mutex_unlock(&d->vqs[i].mutex);
 491                 if (!ok)
 492                         return 0;
 493         }
 494         return 1;
 495 }
 496
 497 static int vq_access_ok(struct vhost_dev *d, unsigned int num,
 498                         struct vring_desc __user *desc,
 499                         struct vring_avail __user *avail,
 500                         struct vring_used __user *used)
 501 {
 502         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 503         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 504                access_ok(VERIFY_READ, avail,
 505                          sizeof *avail + num * sizeof *avail->ring + s) &&
 506                access_ok(VERIFY_WRITE, used,
 507                         sizeof *used + num * sizeof *used->ring + s);
 508 }
 509
 510 /* Can we log writes? */
 511 /* Caller should have device mutex but not vq mutex */
 512 int vhost_log_access_ok(struct vhost_dev *dev)
 513 {
 514         struct vhost_memory *mp;
 515
 516         mp = rcu_dereference_protected(dev->memory,
 517                                        lockdep_is_held(&dev->mutex));
 518         return memory_access_ok(dev, mp, 1);
 519 }
 520
 521 /* Verify access for write logging. */
 522 /* Caller should have vq mutex and device mutex */
 523 static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
 524                             void __user *log_base)
 525 {
 526         struct vhost_memory *mp;
 527         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 528
 529         mp = rcu_dereference_protected(vq->dev->memory,
 530                                        lockdep_is_held(&vq->mutex));
 531         return vq_memory_access_ok(log_base, mp,
 532                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 533                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 534                                         sizeof *vq->used +
 535                                         vq->num * sizeof *vq->used->ring + s));
 536 }
 537
 538 /* Can we start vq? */
 539 /* Caller should have vq mutex and device mutex */
 540 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 541 {
 542         return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
 543                 vq_log_access_ok(vq->dev, vq, vq->log_base);
 544 }
 545
 546 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 547 {
 548         struct vhost_memory mem, *newmem, *oldmem;
 549         unsigned long size = offsetof(struct vhost_memory, regions);
 550
 551         if (copy_from_user(&mem, m, size))
 552                 return -EFAULT;
 553         if (mem.padding)
 554                 return -EOPNOTSUPP;
 555         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 556                 return -E2BIG;
 557         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 558         if (!newmem)
 559                 return -ENOMEM;
 560
 561         memcpy(newmem, &mem, size);
 562         if (copy_from_user(newmem->regions, m->regions,
 563                            mem.nregions * sizeof *m->regions)) {
 564                 kfree(newmem);
 565                 return -EFAULT;
 566         }
 567
 568         if (!memory_access_ok(d, newmem,
 569                               vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 570                 kfree(newmem);
 571                 return -EFAULT;
 572         }
 573         oldmem = rcu_dereference_protected(d->memory,
 574                                            lockdep_is_held(&d->mutex));
 575         rcu_assign_pointer(d->memory, newmem);
 576         synchronize_rcu();
 577         kfree(oldmem);
 578         return 0;
 579 }
 580
 581 static int init_used(struct vhost_virtqueue *vq,
 582                      struct vring_used __user *used)
 583 {
 584         int r = put_user(vq->used_flags, &used->flags);
 585
 586         if (r)
 587                 return r;
 588         vq->signalled_used_valid = false;
 589         return get_user(vq->last_used_idx, &used->idx);
 590 }
 591
 592 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 593 {
 594         struct file *eventfp, *filep = NULL,
 595                     *pollstart = NULL, *pollstop = NULL;
 596         struct eventfd_ctx *ctx = NULL;
 597         u32 __user *idxp = argp;
 598         struct vhost_virtqueue *vq;
 599         struct vhost_vring_state s;
 600         struct vhost_vring_file f;
 601         struct vhost_vring_addr a;
 602         u32 idx;
 603         long r;
 604
 605         r = get_user(idx, idxp);
 606         if (r < 0)
 607                 return r;
 608         if (idx >= d->nvqs)
 609                 return -ENOBUFS;
 610
 611         vq = d->vqs + idx;
 612
 613         mutex_lock(&vq->mutex);
 614
 615         switch (ioctl) {
 616         case VHOST_SET_VRING_NUM:
 617                 /* Resizing ring with an active backend?
 618                  * You don't want to do that. */
 619                 if (vq->private_data) {
 620                         r = -EBUSY;
 621                         break;
 622                 }
 623                 if (copy_from_user(&s, argp, sizeof s)) {
 624                         r = -EFAULT;
 625                         break;
 626                 }
 627                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 628                         r = -EINVAL;
 629                         break;
 630                 }
 631                 vq->num = s.num;
 632                 break;
 633         case VHOST_SET_VRING_BASE:
 634                 /* Moving base with an active backend?
 635                  * You don't want to do that. */
 636                 if (vq->private_data) {
 637                         r = -EBUSY;
 638                         break;
 639                 }
 640                 if (copy_from_user(&s, argp, sizeof s)) {
 641                         r = -EFAULT;
 642                         break;
 643                 }
 644                 if (s.num > 0xffff) {
 645                         r = -EINVAL;
 646                         break;
 647                 }
 648                 vq->last_avail_idx = s.num;
 649                 /* Forget the cached index value. */
 650                 vq->avail_idx = vq->last_avail_idx;
 651                 break;
 652         case VHOST_GET_VRING_BASE:
 653                 s.index = idx;
 654                 s.num = vq->last_avail_idx;
 655                 if (copy_to_user(argp, &s, sizeof s))
 656                         r = -EFAULT;
 657                 break;
 658         case VHOST_SET_VRING_ADDR:
 659                 if (copy_from_user(&a, argp, sizeof a)) {
 660                         r = -EFAULT;
 661                         break;
 662                 }
 663                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 664                         r = -EOPNOTSUPP;
 665                         break;
 666                 }
 667                 /* For 32bit, verify that the top 32bits of the user
 668                    data are set to zero. */
 669                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 670                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 671                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 672                         r = -EFAULT;
 673                         break;
 674                 }
 675                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 676                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 677                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 678                         r = -EINVAL;
 679                         break;
 680                 }
 681
 682                 /* We only verify access here if backend is configured.
 683                  * If it is not, we don't as size might not have been setup.
 684                  * We will verify when backend is configured. */
 685                 if (vq->private_data) {
 686                         if (!vq_access_ok(d, vq->num,
 687                                 (void __user *)(unsigned long)a.desc_user_addr,
 688                                 (void __user *)(unsigned long)a.avail_user_addr,
 689                                 (void __user *)(unsigned long)a.used_user_addr)) {
 690                                 r = -EINVAL;
 691                                 break;
 692                         }
 693
 694                         /* Also validate log access for used ring if enabled. */
 695                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 696                             !log_access_ok(vq->log_base, a.log_guest_addr,
 697                                            sizeof *vq->used +
 698                                            vq->num * sizeof *vq->used->ring)) {
 699                                 r = -EINVAL;
 700                                 break;
 701                         }
 702                 }
 703
 704                 r = init_used(vq, (struct vring_used __user *)(unsigned long)
 705                               a.used_user_addr);
 706                 if (r)
 707                         break;
 708                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 709                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 710                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 711                 vq->log_addr = a.log_guest_addr;
 712                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
 713                 break;
 714         case VHOST_SET_VRING_KICK:
 715                 if (copy_from_user(&f, argp, sizeof f)) {
 716                         r = -EFAULT;
 717                         break;
 718                 }
 719                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 720                 if (IS_ERR(eventfp)) {
 721                         r = PTR_ERR(eventfp);
 722                         break;
 723                 }
 724                 if (eventfp != vq->kick) {
 725                         pollstop = filep = vq->kick;
 726                         pollstart = vq->kick = eventfp;
 727                 } else
 728                         filep = eventfp;
 729                 break;
 730         case VHOST_SET_VRING_CALL:
 731                 if (copy_from_user(&f, argp, sizeof f)) {
 732                         r = -EFAULT;
 733                         break;
 734                 }
 735                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 736                 if (IS_ERR(eventfp)) {
 737                         r = PTR_ERR(eventfp);
 738                         break;
 739                 }
 740                 if (eventfp != vq->call) {
 741                         filep = vq->call;
 742                         ctx = vq->call_ctx;
 743                         vq->call = eventfp;
 744                         vq->call_ctx = eventfp ?
 745                                 eventfd_ctx_fileget(eventfp) : NULL;
 746                 } else
 747                         filep = eventfp;
 748                 break;
 749         case VHOST_SET_VRING_ERR:
 750                 if (copy_from_user(&f, argp, sizeof f)) {
 751                         r = -EFAULT;
 752                         break;
 753                 }
 754                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 755                 if (IS_ERR(eventfp)) {
 756                         r = PTR_ERR(eventfp);
 757                         break;
 758                 }
 759                 if (eventfp != vq->error) {
 760                         filep = vq->error;
 761                         vq->error = eventfp;
 762                         ctx = vq->error_ctx;
 763                         vq->error_ctx = eventfp ?
 764                                 eventfd_ctx_fileget(eventfp) : NULL;
 765                 } else
 766                         filep = eventfp;
 767                 break;
 768         default:
 769                 r = -ENOIOCTLCMD;
 770         }
 771
 772         if (pollstop && vq->handle_kick)
 773                 vhost_poll_stop(&vq->poll);
 774
 775         if (ctx)
 776                 eventfd_ctx_put(ctx);
 777         if (filep)
 778                 fput(filep);
 779
 780         if (pollstart && vq->handle_kick)
 781                 vhost_poll_start(&vq->poll, vq->kick);
 782
 783         mutex_unlock(&vq->mutex);
 784
 785         if (pollstop && vq->handle_kick)
 786                 vhost_poll_flush(&vq->poll);
 787         return r;
 788 }
 789
 790 /* Caller must have device mutex */
 791 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 792 {
 793         void __user *argp = (void __user *)arg;
 794         struct file *eventfp, *filep = NULL;
 795         struct eventfd_ctx *ctx = NULL;
 796         u64 p;
 797         long r;
 798         int i, fd;
 799
 800         /* If you are not the owner, you can become one */
 801         if (ioctl == VHOST_SET_OWNER) {
 802                 r = vhost_dev_set_owner(d);
 803                 goto done;
 804         }
 805
 806         /* You must be the owner to do anything else */
 807         r = vhost_dev_check_owner(d);
 808         if (r)
 809                 goto done;
 810
 811         switch (ioctl) {
 812         case VHOST_SET_MEM_TABLE:
 813                 r = vhost_set_memory(d, argp);
 814                 break;
 815         case VHOST_SET_LOG_BASE:
 816                 if (copy_from_user(&p, argp, sizeof p)) {
 817                         r = -EFAULT;
 818                         break;
 819                 }
 820                 if ((u64)(unsigned long)p != p) {
 821                         r = -EFAULT;
 822                         break;
 823                 }
 824                 for (i = 0; i < d->nvqs; ++i) {
 825                         struct vhost_virtqueue *vq;
 826                         void __user *base = (void __user *)(unsigned long)p;
 827                         vq = d->vqs + i;
 828                         mutex_lock(&vq->mutex);
 829                         /* If ring is inactive, will check when it's enabled. */
 830                         if (vq->private_data && !vq_log_access_ok(d, vq, base))
 831                                 r = -EFAULT;
 832                         else
 833                                 vq->log_base = base;
 834                         mutex_unlock(&vq->mutex);
 835                 }
 836                 break;
 837         case VHOST_SET_LOG_FD:
 838                 r = get_user(fd, (int __user *)argp);
 839                 if (r < 0)
 840                         break;
 841                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 842                 if (IS_ERR(eventfp)) {
 843                         r = PTR_ERR(eventfp);
 844                         break;
 845                 }
 846                 if (eventfp != d->log_file) {
 847                         filep = d->log_file;
 848                         ctx = d->log_ctx;
 849                         d->log_ctx = eventfp ?
 850                                 eventfd_ctx_fileget(eventfp) : NULL;
 851                 } else
 852                         filep = eventfp;
 853                 for (i = 0; i < d->nvqs; ++i) {
 854                         mutex_lock(&d->vqs[i].mutex);
 855                         d->vqs[i].log_ctx = d->log_ctx;
 856                         mutex_unlock(&d->vqs[i].mutex);
 857                 }
 858                 if (ctx)
 859                         eventfd_ctx_put(ctx);
 860                 if (filep)
 861                         fput(filep);
 862                 break;
 863         default:
 864                 r = vhost_set_vring(d, ioctl, argp);
 865                 break;
 866         }
 867 done:
 868         return r;
 869 }
 870
 871 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 872                                                      __u64 addr, __u32 len)
 873 {
 874         struct vhost_memory_region *reg;
 875         int i;
 876
 877         /* linear search is not brilliant, but we really have on the order of 6
 878          * regions in practice */
 879         for (i = 0; i < mem->nregions; ++i) {
 880                 reg = mem->regions + i;
 881                 if (reg->guest_phys_addr <= addr &&
 882                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 883                         return reg;
 884         }
 885         return NULL;
 886 }
 887
 888 /* TODO: This is really inefficient.  We need something like get_user()
 889  * (instruction directly accesses the data, with an exception table entry
 890  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 891  */
 892 static int set_bit_to_user(int nr, void __user *addr)
 893 {
 894         unsigned long log = (unsigned long)addr;
 895         struct page *page;
 896         void *base;
 897         int bit = nr + (log % PAGE_SIZE) * 8;
 898         int r;
 899
 900         r = get_user_pages_fast(log, 1, 1, &page);
 901         if (r < 0)
 902                 return r;
 903         BUG_ON(r != 1);
 904         base = kmap_atomic(page, KM_USER0);
 905         set_bit(bit, base);
 906         kunmap_atomic(base, KM_USER0);
 907         set_page_dirty_lock(page);
 908         put_page(page);
 909         return 0;
 910 }
 911
 912 static int log_write(void __user *log_base,
 913                      u64 write_address, u64 write_length)
 914 {
 915         u64 write_page = write_address / VHOST_PAGE_SIZE;
 916         int r;
 917
 918         if (!write_length)
 919                 return 0;
 920         write_length += write_address % VHOST_PAGE_SIZE;
 921         for (;;) {
 922                 u64 base = (u64)(unsigned long)log_base;
 923                 u64 log = base + write_page / 8;
 924                 int bit = write_page % 8;
 925                 if ((u64)(unsigned long)log != log)
 926                         return -EFAULT;
 927                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 928                 if (r < 0)
 929                         return r;
 930                 if (write_length <= VHOST_PAGE_SIZE)
 931                         break;
 932                 write_length -= VHOST_PAGE_SIZE;
 933                 write_page += 1;
 934         }
 935         return r;
 936 }
 937
 938 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 939                     unsigned int log_num, u64 len)
 940 {
 941         int i, r;
 942
 943         /* Make sure data written is seen before log. */
 944         smp_wmb();
 945         for (i = 0; i < log_num; ++i) {
 946                 u64 l = min(log[i].len, len);
 947                 r = log_write(vq->log_base, log[i].addr, l);
 948                 if (r < 0)
 949                         return r;
 950                 len -= l;
 951                 if (!len) {
 952                         if (vq->log_ctx)
 953                                 eventfd_signal(vq->log_ctx, 1);
 954                         return 0;
 955                 }
 956         }
 957         /* Length written exceeds what we have stored. This is a bug. */
 958         BUG();
 959         return 0;
 960 }
 961
 962 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
 963                           struct iovec iov[], int iov_size)
 964 {
 965         const struct vhost_memory_region *reg;
 966         struct vhost_memory *mem;
 967         struct iovec *_iov;
 968         u64 s = 0;
 969         int ret = 0;
 970
 971         rcu_read_lock();
 972
 973         mem = rcu_dereference(dev->memory);
 974         while ((u64)len > s) {
 975                 u64 size;
 976                 if (unlikely(ret >= iov_size)) {
 977                         ret = -ENOBUFS;
 978                         break;
 979                 }
 980                 reg = find_region(mem, addr, len);
 981                 if (unlikely(!reg)) {
 982                         ret = -EFAULT;
 983                         break;
 984                 }
 985                 _iov = iov + ret;
 986                 size = reg->memory_size - addr + reg->guest_phys_addr;
 987                 _iov->iov_len = min((u64)len, size);
 988                 _iov->iov_base = (void __user *)(unsigned long)
 989                         (reg->userspace_addr + addr - reg->guest_phys_addr);
 990                 s += size;
 991                 addr += size;
 992                 ++ret;
 993         }
 994
 995         rcu_read_unlock();
 996         return ret;
 997 }
 998
 999 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
1000  * function returns the next descriptor in the chain,
1001  * or -1U if we're at the end. */
1002 static unsigned next_desc(struct vring_desc *desc)
1003 {
1004         unsigned int next;
1005
1006         /* If this descriptor says it doesn't chain, we're done. */
1007         if (!(desc->flags & VRING_DESC_F_NEXT))
1008                 return -1U;
1009
1010         /* Check they're not leading us off end of descriptors. */
1011         next = desc->next;
1012         /* Make sure compiler knows to grab that: we don't want it changing! */
1013         /* We will use the result as an index in an array, so most
1014          * architectures only need a compiler barrier here. */
1015         read_barrier_depends();
1016
1017         return next;
1018 }
1019
1020 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1021                         struct iovec iov[], unsigned int iov_size,
1022                         unsigned int *out_num, unsigned int *in_num,
1023                         struct vhost_log *log, unsigned int *log_num,
1024                         struct vring_desc *indirect)
1025 {
1026         struct vring_desc desc;
1027         unsigned int i = 0, count, found = 0;
1028         int ret;
1029
1030         /* Sanity check */
1031         if (unlikely(indirect->len % sizeof desc)) {
1032                 vq_err(vq, "Invalid length in indirect descriptor: "
1033                        "len 0x%llx not multiple of 0x%zx\n",
1034                        (unsigned long long)indirect->len,
1035                        sizeof desc);
1036                 return -EINVAL;
1037         }
1038
1039         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1040                              UIO_MAXIOV);
1041         if (unlikely(ret < 0)) {
1042                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1043                 return ret;
1044         }
1045
1046         /* We will use the result as an address to read from, so most
1047          * architectures only need a compiler barrier here. */
1048         read_barrier_depends();
1049
1050         count = indirect->len / sizeof desc;
1051         /* Buffers are chained via a 16 bit next field, so
1052          * we can have at most 2^16 of these. */
1053         if (unlikely(count > USHRT_MAX + 1)) {
1054                 vq_err(vq, "Indirect buffer length too big: %d\n",
1055                        indirect->len);
1056                 return -E2BIG;
1057         }
1058
1059         do {
1060                 unsigned iov_count = *in_num + *out_num;
1061                 if (unlikely(++found > count)) {
1062                         vq_err(vq, "Loop detected: last one at %u "
1063                                "indirect size %u\n",
1064                                i, count);
1065                         return -EINVAL;
1066                 }
1067                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1068                                               vq->indirect, sizeof desc))) {
1069                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1070                                i, (size_t)indirect->addr + i * sizeof desc);
1071                         return -EINVAL;
1072                 }
1073                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1074                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1075                                i, (size_t)indirect->addr + i * sizeof desc);
1076                         return -EINVAL;
1077                 }
1078
1079                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1080                                      iov_size - iov_count);
1081                 if (unlikely(ret < 0)) {
1082                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1083                                ret, i);
1084                         return ret;
1085                 }
1086                 /* If this is an input descriptor, increment that count. */
1087                 if (desc.flags & VRING_DESC_F_WRITE) {
1088                         *in_num += ret;
1089                         if (unlikely(log)) {
1090                                 log[*log_num].addr = desc.addr;
1091                                 log[*log_num].len = desc.len;
1092                                 ++*log_num;
1093                         }
1094                 } else {
1095                         /* If it's an output descriptor, they're all supposed
1096                          * to come before any input descriptors. */
1097                         if (unlikely(*in_num)) {
1098                                 vq_err(vq, "Indirect descriptor "
1099                                        "has out after in: idx %d\n", i);
1100                                 return -EINVAL;
1101                         }
1102                         *out_num += ret;
1103                 }
1104         } while ((i = next_desc(&desc)) != -1);
1105         return 0;
1106 }
1107
1108 /* This looks in the virtqueue and for the first available buffer, and converts
1109  * it to an iovec for convenient access.  Since descriptors consist of some
1110  * number of output then some number of input descriptors, it's actually two
1111  * iovecs, but we pack them into one and note how many of each there were.
1112  *
1113  * This function returns the descriptor number found, or vq->num (which is
1114  * never a valid descriptor number) if none was found.  A negative code is
1115  * returned on error. */
1116 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1117                       struct iovec iov[], unsigned int iov_size,
1118                       unsigned int *out_num, unsigned int *in_num,
1119                       struct vhost_log *log, unsigned int *log_num)
1120 {
1121         struct vring_desc desc;
1122         unsigned int i, head, found = 0;
1123         u16 last_avail_idx;
1124         int ret;
1125
1126         /* Check it isn't doing very strange things with descriptor numbers. */
1127         last_avail_idx = vq->last_avail_idx;
1128         if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1129                 vq_err(vq, "Failed to access avail idx at %p\n",
1130                        &vq->avail->idx);
1131                 return -EFAULT;
1132         }
1133
1134         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1135                 vq_err(vq, "Guest moved used index from %u to %u",
1136                        last_avail_idx, vq->avail_idx);
1137                 return -EFAULT;
1138         }
1139
1140         /* If there's nothing new since last we looked, return invalid. */
1141         if (vq->avail_idx == last_avail_idx)
1142                 return vq->num;
1143
1144         /* Only get avail ring entries after they have been exposed by guest. */
1145         smp_rmb();
1146
1147         /* Grab the next descriptor number they're advertising, and increment
1148          * the index we've seen. */
1149         if (unlikely(__get_user(head,
1150                                 &vq->avail->ring[last_avail_idx % vq->num]))) {
1151                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1152                        last_avail_idx,
1153                        &vq->avail->ring[last_avail_idx % vq->num]);
1154                 return -EFAULT;
1155         }
1156
1157         /* If their number is silly, that's an error. */
1158         if (unlikely(head >= vq->num)) {
1159                 vq_err(vq, "Guest says index %u > %u is available",
1160                        head, vq->num);
1161                 return -EINVAL;
1162         }
1163
1164         /* When we start there are none of either input nor output. */
1165         *out_num = *in_num = 0;
1166         if (unlikely(log))
1167                 *log_num = 0;
1168
1169         i = head;
1170         do {
1171                 unsigned iov_count = *in_num + *out_num;
1172                 if (unlikely(i >= vq->num)) {
1173                         vq_err(vq, "Desc index is %u > %u, head = %u",
1174                                i, vq->num, head);
1175                         return -EINVAL;
1176                 }
1177                 if (unlikely(++found > vq->num)) {
1178                         vq_err(vq, "Loop detected: last one at %u "
1179                                "vq size %u head %u\n",
1180                                i, vq->num, head);
1181                         return -EINVAL;
1182                 }
1183                 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1184                 if (unlikely(ret)) {
1185                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1186                                i, vq->desc + i);
1187                         return -EFAULT;
1188                 }
1189                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1190                         ret = get_indirect(dev, vq, iov, iov_size,
1191                                            out_num, in_num,
1192                                            log, log_num, &desc);
1193                         if (unlikely(ret < 0)) {
1194                                 vq_err(vq, "Failure detected "
1195                                        "in indirect descriptor at idx %d\n", i);
1196                                 return ret;
1197                         }
1198                         continue;
1199                 }
1200
1201                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1202                                      iov_size - iov_count);
1203                 if (unlikely(ret < 0)) {
1204                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1205                                ret, i);
1206                         return ret;
1207                 }
1208                 if (desc.flags & VRING_DESC_F_WRITE) {
1209                         /* If this is an input descriptor,
1210                          * increment that count. */
1211                         *in_num += ret;
1212                         if (unlikely(log)) {
1213                                 log[*log_num].addr = desc.addr;
1214                                 log[*log_num].len = desc.len;
1215                                 ++*log_num;
1216                         }
1217                 } else {
1218                         /* If it's an output descriptor, they're all supposed
1219                          * to come before any input descriptors. */
1220                         if (unlikely(*in_num)) {
1221                                 vq_err(vq, "Descriptor has out after in: "
1222                                        "idx %d\n", i);
1223                                 return -EINVAL;
1224                         }
1225                         *out_num += ret;
1226                 }
1227         } while ((i = next_desc(&desc)) != -1);
1228
1229         /* On success, increment avail index. */
1230         vq->last_avail_idx++;
1231
1232         /* Assume notifications from guest are disabled at this point,
1233          * if they aren't we would need to update avail_event index. */
1234         BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1235         return head;
1236 }
1237
1238 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1239 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1240 {
1241         vq->last_avail_idx -= n;
1242 }
1243
1244 /* After we've used one of their buffers, we tell them about it.  We'll then
1245  * want to notify the guest, using eventfd. */
1246 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1247 {
1248         struct vring_used_elem __user *used;
1249
1250         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1251          * next entry in that used ring. */
1252         used = &vq->used->ring[vq->last_used_idx % vq->num];
1253         if (__put_user(head, &used->id)) {
1254                 vq_err(vq, "Failed to write used id");
1255                 return -EFAULT;
1256         }
1257         if (__put_user(len, &used->len)) {
1258                 vq_err(vq, "Failed to write used len");
1259                 return -EFAULT;
1260         }
1261         /* Make sure buffer is written before we update index. */
1262         smp_wmb();
1263         if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1264                 vq_err(vq, "Failed to increment used idx");
1265                 return -EFAULT;
1266         }
1267         if (unlikely(vq->log_used)) {
1268                 /* Make sure data is seen before log. */
1269                 smp_wmb();
1270                 /* Log used ring entry write. */
1271                 log_write(vq->log_base,
1272                           vq->log_addr +
1273                            ((void __user *)used - (void __user *)vq->used),
1274                           sizeof *used);
1275                 /* Log used index update. */
1276                 log_write(vq->log_base,
1277                           vq->log_addr + offsetof(struct vring_used, idx),
1278                           sizeof vq->used->idx);
1279                 if (vq->log_ctx)
1280                         eventfd_signal(vq->log_ctx, 1);
1281         }
1282         vq->last_used_idx++;
1283         /* If the driver never bothers to signal in a very long while,
1284          * used index might wrap around. If that happens, invalidate
1285          * signalled_used index we stored. TODO: make sure driver
1286          * signals at least once in 2^16 and remove this. */
1287         if (unlikely(vq->last_used_idx == vq->signalled_used))
1288                 vq->signalled_used_valid = false;
1289         return 0;
1290 }
1291
1292 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1293                             struct vring_used_elem *heads,
1294                             unsigned count)
1295 {
1296         struct vring_used_elem __user *used;
1297         u16 old, new;
1298         int start;
1299
1300         start = vq->last_used_idx % vq->num;
1301         used = vq->used->ring + start;
1302         if (__copy_to_user(used, heads, count * sizeof *used)) {
1303                 vq_err(vq, "Failed to write used");
1304                 return -EFAULT;
1305         }
1306         if (unlikely(vq->log_used)) {
1307                 /* Make sure data is seen before log. */
1308                 smp_wmb();
1309                 /* Log used ring entry write. */
1310                 log_write(vq->log_base,
1311                           vq->log_addr +
1312                            ((void __user *)used - (void __user *)vq->used),
1313                           count * sizeof *used);
1314         }
1315         old = vq->last_used_idx;
1316         new = (vq->last_used_idx += count);
1317         /* If the driver never bothers to signal in a very long while,
1318          * used index might wrap around. If that happens, invalidate
1319          * signalled_used index we stored. TODO: make sure driver
1320          * signals at least once in 2^16 and remove this. */
1321         if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1322                 vq->signalled_used_valid = false;
1323         return 0;
1324 }
1325
1326 /* After we've used one of their buffers, we tell them about it.  We'll then
1327  * want to notify the guest, using eventfd. */
1328 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1329                      unsigned count)
1330 {
1331         int start, n, r;
1332
1333         start = vq->last_used_idx % vq->num;
1334         n = vq->num - start;
1335         if (n < count) {
1336                 r = __vhost_add_used_n(vq, heads, n);
1337                 if (r < 0)
1338                         return r;
1339                 heads += n;
1340                 count -= n;
1341         }
1342         r = __vhost_add_used_n(vq, heads, count);
1343
1344         /* Make sure buffer is written before we update index. */
1345         smp_wmb();
1346         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1347                 vq_err(vq, "Failed to increment used idx");
1348                 return -EFAULT;
1349         }
1350         if (unlikely(vq->log_used)) {
1351                 /* Log used index update. */
1352                 log_write(vq->log_base,
1353                           vq->log_addr + offsetof(struct vring_used, idx),
1354                           sizeof vq->used->idx);
1355                 if (vq->log_ctx)
1356                         eventfd_signal(vq->log_ctx, 1);
1357         }
1358         return r;
1359 }
1360
1361 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1362 {
1363         __u16 old, new, event;
1364         bool v;
1365         /* Flush out used index updates. This is paired
1366          * with the barrier that the Guest executes when enabling
1367          * interrupts. */
1368         smp_mb();
1369
1370         if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1371             unlikely(vq->avail_idx == vq->last_avail_idx))
1372                 return true;
1373
1374         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1375                 __u16 flags;
1376                 if (__get_user(flags, &vq->avail->flags)) {
1377                         vq_err(vq, "Failed to get flags");
1378                         return true;
1379                 }
1380                 return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1381         }
1382         old = vq->signalled_used;
1383         v = vq->signalled_used_valid;
1384         new = vq->signalled_used = vq->last_used_idx;
1385         vq->signalled_used_valid = true;
1386
1387         if (unlikely(!v))
1388                 return true;
1389
1390         if (get_user(event, vhost_used_event(vq))) {
1391                 vq_err(vq, "Failed to get used event idx");
1392                 return true;
1393         }
1394         return vring_need_event(event, new, old);
1395 }
1396
1397 /* This actually signals the guest, using eventfd. */
1398 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1399 {
1400         /* Signal the Guest tell them we used something up. */
1401         if (vq->call_ctx && vhost_notify(dev, vq))
1402                 eventfd_signal(vq->call_ctx, 1);
1403 }
1404
1405 /* And here's the combo meal deal.  Supersize me! */
1406 void vhost_add_used_and_signal(struct vhost_dev *dev,
1407                                struct vhost_virtqueue *vq,
1408                                unsigned int head, int len)
1409 {
1410         vhost_add_used(vq, head, len);
1411         vhost_signal(dev, vq);
1412 }
1413
1414 /* multi-buffer version of vhost_add_used_and_signal */
1415 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1416                                  struct vhost_virtqueue *vq,
1417                                  struct vring_used_elem *heads, unsigned count)
1418 {
1419         vhost_add_used_n(vq, heads, count);
1420         vhost_signal(dev, vq);
1421 }
1422
1423 /* OK, now we need to know about added descriptors. */
1424 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1425 {
1426         u16 avail_idx;
1427         int r;
1428
1429         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1430                 return false;
1431         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1432         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1433                 r = put_user(vq->used_flags, &vq->used->flags);
1434                 if (r) {
1435                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1436                                &vq->used->flags, r);
1437                         return false;
1438                 }
1439         } else {
1440                 r = put_user(vq->avail_idx, vhost_avail_event(vq));
1441                 if (r) {
1442                         vq_err(vq, "Failed to update avail event index at %p: %d\n",
1443                                vhost_avail_event(vq), r);
1444                         return false;
1445                 }
1446         }
1447         if (unlikely(vq->log_used)) {
1448                 void __user *used;
1449                 /* Make sure data is seen before log. */
1450                 smp_wmb();
1451                 used = vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX) ?
1452                         &vq->used->flags : vhost_avail_event(vq);
1453                 /* Log used flags or event index entry write. Both are 16 bit
1454                  * fields. */
1455                 log_write(vq->log_base, vq->log_addr +
1456                            (used - (void __user *)vq->used),
1457                           sizeof(u16));
1458                 if (vq->log_ctx)
1459                         eventfd_signal(vq->log_ctx, 1);
1460         }
1461         /* They could have slipped one in as we were doing that: make
1462          * sure it's written, then check again. */
1463         smp_mb();
1464         r = __get_user(avail_idx, &vq->avail->idx);
1465         if (r) {
1466                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1467                        &vq->avail->idx, r);
1468                 return false;
1469         }
1470
1471         return avail_idx != vq->avail_idx;
1472 }
1473
1474 /* We don't need to be notified again. */
1475 void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1476 {
1477         int r;
1478
1479         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1480                 return;
1481         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1482         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1483                 r = put_user(vq->used_flags, &vq->used->flags);
1484                 if (r)
1485                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1486                                &vq->used->flags, r);
1487         }
1488 }