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