drivers/vhost/vhost.c

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