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