drivers/vhost/vringh.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Helpers for the host side of a virtio ring.
   4  *
   5  * Since these may be in userspace, we use (inline) accessors.
   6  */
   7 #include <linux/compiler.h>
   8 #include <linux/module.h>
   9 #include <linux/vringh.h>
  10 #include <linux/virtio_ring.h>
  11 #include <linux/kernel.h>
  12 #include <linux/ratelimit.h>
  13 #include <linux/uaccess.h>
  14 #include <linux/slab.h>
  15 #include <linux/export.h>
  16 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)
  17 #include <linux/bvec.h>
  18 #include <linux/highmem.h>
  19 #include <linux/vhost_iotlb.h>
  20 #endif
  21 #include <uapi/linux/virtio_config.h>
  22
  23 static __printf(1,2) __cold void vringh_bad(const char *fmt, ...)
  24 {
  25         static DEFINE_RATELIMIT_STATE(vringh_rs,
  26                                       DEFAULT_RATELIMIT_INTERVAL,
  27                                       DEFAULT_RATELIMIT_BURST);
  28         if (__ratelimit(&vringh_rs)) {
  29                 va_list ap;
  30                 va_start(ap, fmt);
  31                 printk(KERN_NOTICE "vringh:");
  32                 vprintk(fmt, ap);
  33                 va_end(ap);
  34         }
  35 }
  36
  37 /* Returns vring->num if empty, -ve on error. */
  38 static inline int __vringh_get_head(const struct vringh *vrh,
  39                                     int (*getu16)(const struct vringh *vrh,
  40                                                   u16 *val, const __virtio16 *p),
  41                                     u16 *last_avail_idx)
  42 {
  43         u16 avail_idx, i, head;
  44         int err;
  45
  46         err = getu16(vrh, &avail_idx, &vrh->vring.avail->idx);
  47         if (err) {
  48                 vringh_bad("Failed to access avail idx at %p",
  49                            &vrh->vring.avail->idx);
  50                 return err;
  51         }
  52
  53         if (*last_avail_idx == avail_idx)
  54                 return vrh->vring.num;
  55
  56         /* Only get avail ring entries after they have been exposed by guest. */
  57         virtio_rmb(vrh->weak_barriers);
  58
  59         i = *last_avail_idx & (vrh->vring.num - 1);
  60
  61         err = getu16(vrh, &head, &vrh->vring.avail->ring[i]);
  62         if (err) {
  63                 vringh_bad("Failed to read head: idx %d address %p",
  64                            *last_avail_idx, &vrh->vring.avail->ring[i]);
  65                 return err;
  66         }
  67
  68         if (head >= vrh->vring.num) {
  69                 vringh_bad("Guest says index %u > %u is available",
  70                            head, vrh->vring.num);
  71                 return -EINVAL;
  72         }
  73
  74         (*last_avail_idx)++;
  75         return head;
  76 }
  77
  78 /* Copy some bytes to/from the iovec.  Returns num copied. */
  79 static inline ssize_t vringh_iov_xfer(struct vringh *vrh,
  80                                       struct vringh_kiov *iov,
  81                                       void *ptr, size_t len,
  82                                       int (*xfer)(const struct vringh *vrh,
  83                                                   void *addr, void *ptr,
  84                                                   size_t len))
  85 {
  86         int err, done = 0;
  87
  88         while (len && iov->i < iov->used) {
  89                 size_t partlen;
  90
  91                 partlen = min(iov->iov[iov->i].iov_len, len);
  92                 err = xfer(vrh, iov->iov[iov->i].iov_base, ptr, partlen);
  93                 if (err)
  94                         return err;
  95                 done += partlen;
  96                 len -= partlen;
  97                 ptr += partlen;
  98                 iov->consumed += partlen;
  99                 iov->iov[iov->i].iov_len -= partlen;
 100                 iov->iov[iov->i].iov_base += partlen;
 101
 102                 if (!iov->iov[iov->i].iov_len) {
 103                         /* Fix up old iov element then increment. */
 104                         iov->iov[iov->i].iov_len = iov->consumed;
 105                         iov->iov[iov->i].iov_base -= iov->consumed;
 106
 107
 108                         iov->consumed = 0;
 109                         iov->i++;
 110                 }
 111         }
 112         return done;
 113 }
 114
 115 /* May reduce *len if range is shorter. */
 116 static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len,
 117                                struct vringh_range *range,
 118                                bool (*getrange)(struct vringh *,
 119                                                 u64, struct vringh_range *))
 120 {
 121         if (addr < range->start || addr > range->end_incl) {
 122                 if (!getrange(vrh, addr, range))
 123                         return false;
 124         }
 125         BUG_ON(addr < range->start || addr > range->end_incl);
 126
 127         /* To end of memory? */
 128         if (unlikely(addr + *len == 0)) {
 129                 if (range->end_incl == -1ULL)
 130                         return true;
 131                 goto truncate;
 132         }
 133
 134         /* Otherwise, don't wrap. */
 135         if (addr + *len < addr) {
 136                 vringh_bad("Wrapping descriptor %zu@0x%llx",
 137                            *len, (unsigned long long)addr);
 138                 return false;
 139         }
 140
 141         if (unlikely(addr + *len - 1 > range->end_incl))
 142                 goto truncate;
 143         return true;
 144
 145 truncate:
 146         *len = range->end_incl + 1 - addr;
 147         return true;
 148 }
 149
 150 static inline bool no_range_check(struct vringh *vrh, u64 addr, size_t *len,
 151                                   struct vringh_range *range,
 152                                   bool (*getrange)(struct vringh *,
 153                                                    u64, struct vringh_range *))
 154 {
 155         return true;
 156 }
 157
 158 /* No reason for this code to be inline. */
 159 static int move_to_indirect(const struct vringh *vrh,
 160                             int *up_next, u16 *i, void *addr,
 161                             const struct vring_desc *desc,
 162                             struct vring_desc **descs, int *desc_max)
 163 {
 164         u32 len;
 165
 166         /* Indirect tables can't have indirect. */
 167         if (*up_next != -1) {
 168                 vringh_bad("Multilevel indirect %u->%u", *up_next, *i);
 169                 return -EINVAL;
 170         }
 171
 172         len = vringh32_to_cpu(vrh, desc->len);
 173         if (unlikely(len % sizeof(struct vring_desc))) {
 174                 vringh_bad("Strange indirect len %u", desc->len);
 175                 return -EINVAL;
 176         }
 177
 178         /* We will check this when we follow it! */
 179         if (desc->flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT))
 180                 *up_next = vringh16_to_cpu(vrh, desc->next);
 181         else
 182                 *up_next = -2;
 183         *descs = addr;
 184         *desc_max = len / sizeof(struct vring_desc);
 185
 186         /* Now, start at the first indirect. */
 187         *i = 0;
 188         return 0;
 189 }
 190
 191 static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
 192 {
 193         struct kvec *new;
 194         unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
 195
 196         if (new_num < 8)
 197                 new_num = 8;
 198
 199         flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
 200         if (flag)
 201                 new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
 202         else {
 203                 new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
 204                 if (new) {
 205                         memcpy(new, iov->iov,
 206                                iov->max_num * sizeof(struct iovec));
 207                         flag = VRINGH_IOV_ALLOCATED;
 208                 }
 209         }
 210         if (!new)
 211                 return -ENOMEM;
 212         iov->iov = new;
 213         iov->max_num = (new_num | flag);
 214         return 0;
 215 }
 216
 217 static u16 __cold return_from_indirect(const struct vringh *vrh, int *up_next,
 218                                        struct vring_desc **descs, int *desc_max)
 219 {
 220         u16 i = *up_next;
 221
 222         *up_next = -1;
 223         *descs = vrh->vring.desc;
 224         *desc_max = vrh->vring.num;
 225         return i;
 226 }
 227
 228 static int slow_copy(struct vringh *vrh, void *dst, const void *src,
 229                      bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
 230                                     struct vringh_range *range,
 231                                     bool (*getrange)(struct vringh *vrh,
 232                                                      u64,
 233                                                      struct vringh_range *)),
 234                      bool (*getrange)(struct vringh *vrh,
 235                                       u64 addr,
 236                                       struct vringh_range *r),
 237                      struct vringh_range *range,
 238                      int (*copy)(const struct vringh *vrh,
 239                                  void *dst, const void *src, size_t len))
 240 {
 241         size_t part, len = sizeof(struct vring_desc);
 242
 243         do {
 244                 u64 addr;
 245                 int err;
 246
 247                 part = len;
 248                 addr = (u64)(unsigned long)src - range->offset;
 249
 250                 if (!rcheck(vrh, addr, &part, range, getrange))
 251                         return -EINVAL;
 252
 253                 err = copy(vrh, dst, src, part);
 254                 if (err)
 255                         return err;
 256
 257                 dst += part;
 258                 src += part;
 259                 len -= part;
 260         } while (len);
 261         return 0;
 262 }
 263
 264 static inline int
 265 __vringh_iov(struct vringh *vrh, u16 i,
 266              struct vringh_kiov *riov,
 267              struct vringh_kiov *wiov,
 268              bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
 269                             struct vringh_range *range,
 270                             bool (*getrange)(struct vringh *, u64,
 271                                              struct vringh_range *)),
 272              bool (*getrange)(struct vringh *, u64, struct vringh_range *),
 273              gfp_t gfp,
 274              int (*copy)(const struct vringh *vrh,
 275                          void *dst, const void *src, size_t len))
 276 {
 277         int err, count = 0, up_next, desc_max;
 278         struct vring_desc desc, *descs;
 279         struct vringh_range range = { -1ULL, 0 }, slowrange;
 280         bool slow = false;
 281
 282         /* We start traversing vring's descriptor table. */
 283         descs = vrh->vring.desc;
 284         desc_max = vrh->vring.num;
 285         up_next = -1;
 286
 287         if (riov)
 288                 riov->i = riov->used = 0;
 289         else if (wiov)
 290                 wiov->i = wiov->used = 0;
 291         else
 292                 /* You must want something! */
 293                 BUG();
 294
 295         for (;;) {
 296                 void *addr;
 297                 struct vringh_kiov *iov;
 298                 size_t len;
 299
 300                 if (unlikely(slow))
 301                         err = slow_copy(vrh, &desc, &descs[i], rcheck, getrange,
 302                                         &slowrange, copy);
 303                 else
 304                         err = copy(vrh, &desc, &descs[i], sizeof(desc));
 305                 if (unlikely(err))
 306                         goto fail;
 307
 308                 if (unlikely(desc.flags &
 309                              cpu_to_vringh16(vrh, VRING_DESC_F_INDIRECT))) {
 310                         u64 a = vringh64_to_cpu(vrh, desc.addr);
 311
 312                         /* Make sure it's OK, and get offset. */
 313                         len = vringh32_to_cpu(vrh, desc.len);
 314                         if (!rcheck(vrh, a, &len, &range, getrange)) {
 315                                 err = -EINVAL;
 316                                 goto fail;
 317                         }
 318
 319                         if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
 320                                 slow = true;
 321                                 /* We need to save this range to use offset */
 322                                 slowrange = range;
 323                         }
 324
 325                         addr = (void *)(long)(a + range.offset);
 326                         err = move_to_indirect(vrh, &up_next, &i, addr, &desc,
 327                                                &descs, &desc_max);
 328                         if (err)
 329                                 goto fail;
 330                         continue;
 331                 }
 332
 333                 if (count++ == vrh->vring.num) {
 334                         vringh_bad("Descriptor loop in %p", descs);
 335                         err = -ELOOP;
 336                         goto fail;
 337                 }
 338
 339                 if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_WRITE))
 340                         iov = wiov;
 341                 else {
 342                         iov = riov;
 343                         if (unlikely(wiov && wiov->i)) {
 344                                 vringh_bad("Readable desc %p after writable",
 345                                            &descs[i]);
 346                                 err = -EINVAL;
 347                                 goto fail;
 348                         }
 349                 }
 350
 351                 if (!iov) {
 352                         vringh_bad("Unexpected %s desc",
 353                                    !wiov ? "writable" : "readable");
 354                         err = -EPROTO;
 355                         goto fail;
 356                 }
 357
 358         again:
 359                 /* Make sure it's OK, and get offset. */
 360                 len = vringh32_to_cpu(vrh, desc.len);
 361                 if (!rcheck(vrh, vringh64_to_cpu(vrh, desc.addr), &len, &range,
 362                             getrange)) {
 363                         err = -EINVAL;
 364                         goto fail;
 365                 }
 366                 addr = (void *)(unsigned long)(vringh64_to_cpu(vrh, desc.addr) +
 367                                                range.offset);
 368
 369                 if (unlikely(iov->used == (iov->max_num & ~VRINGH_IOV_ALLOCATED))) {
 370                         err = resize_iovec(iov, gfp);
 371                         if (err)
 372                                 goto fail;
 373                 }
 374
 375                 iov->iov[iov->used].iov_base = addr;
 376                 iov->iov[iov->used].iov_len = len;
 377                 iov->used++;
 378
 379                 if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
 380                         desc.len = cpu_to_vringh32(vrh,
 381                                    vringh32_to_cpu(vrh, desc.len) - len);
 382                         desc.addr = cpu_to_vringh64(vrh,
 383                                     vringh64_to_cpu(vrh, desc.addr) + len);
 384                         goto again;
 385                 }
 386
 387                 if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT)) {
 388                         i = vringh16_to_cpu(vrh, desc.next);
 389                 } else {
 390                         /* Just in case we need to finish traversing above. */
 391                         if (unlikely(up_next > 0)) {
 392                                 i = return_from_indirect(vrh, &up_next,
 393                                                          &descs, &desc_max);
 394                                 slow = false;
 395                         } else
 396                                 break;
 397                 }
 398
 399                 if (i >= desc_max) {
 400                         vringh_bad("Chained index %u > %u", i, desc_max);
 401                         err = -EINVAL;
 402                         goto fail;
 403                 }
 404         }
 405
 406         return 0;
 407
 408 fail:
 409         return err;
 410 }
 411
 412 static inline int __vringh_complete(struct vringh *vrh,
 413                                     const struct vring_used_elem *used,
 414                                     unsigned int num_used,
 415                                     int (*putu16)(const struct vringh *vrh,
 416                                                   __virtio16 *p, u16 val),
 417                                     int (*putused)(const struct vringh *vrh,
 418                                                    struct vring_used_elem *dst,
 419                                                    const struct vring_used_elem
 420                                                    *src, unsigned num))
 421 {
 422         struct vring_used *used_ring;
 423         int err;
 424         u16 used_idx, off;
 425
 426         used_ring = vrh->vring.used;
 427         used_idx = vrh->last_used_idx + vrh->completed;
 428
 429         off = used_idx % vrh->vring.num;
 430
 431         /* Compiler knows num_used == 1 sometimes, hence extra check */
 432         if (num_used > 1 && unlikely(off + num_used >= vrh->vring.num)) {
 433                 u16 part = vrh->vring.num - off;
 434                 err = putused(vrh, &used_ring->ring[off], used, part);
 435                 if (!err)
 436                         err = putused(vrh, &used_ring->ring[0], used + part,
 437                                       num_used - part);
 438         } else
 439                 err = putused(vrh, &used_ring->ring[off], used, num_used);
 440
 441         if (err) {
 442                 vringh_bad("Failed to write %u used entries %u at %p",
 443                            num_used, off, &used_ring->ring[off]);
 444                 return err;
 445         }
 446
 447         /* Make sure buffer is written before we update index. */
 448         virtio_wmb(vrh->weak_barriers);
 449
 450         err = putu16(vrh, &vrh->vring.used->idx, used_idx + num_used);
 451         if (err) {
 452                 vringh_bad("Failed to update used index at %p",
 453                            &vrh->vring.used->idx);
 454                 return err;
 455         }
 456
 457         vrh->completed += num_used;
 458         return 0;
 459 }
 460
 461
 462 static inline int __vringh_need_notify(struct vringh *vrh,
 463                                        int (*getu16)(const struct vringh *vrh,
 464                                                      u16 *val,
 465                                                      const __virtio16 *p))
 466 {
 467         bool notify;
 468         u16 used_event;
 469         int err;
 470
 471         /* Flush out used index update. This is paired with the
 472          * barrier that the Guest executes when enabling
 473          * interrupts. */
 474         virtio_mb(vrh->weak_barriers);
 475
 476         /* Old-style, without event indices. */
 477         if (!vrh->event_indices) {
 478                 u16 flags;
 479                 err = getu16(vrh, &flags, &vrh->vring.avail->flags);
 480                 if (err) {
 481                         vringh_bad("Failed to get flags at %p",
 482                                    &vrh->vring.avail->flags);
 483                         return err;
 484                 }
 485                 return (!(flags & VRING_AVAIL_F_NO_INTERRUPT));
 486         }
 487
 488         /* Modern: we know when other side wants to know. */
 489         err = getu16(vrh, &used_event, &vring_used_event(&vrh->vring));
 490         if (err) {
 491                 vringh_bad("Failed to get used event idx at %p",
 492                            &vring_used_event(&vrh->vring));
 493                 return err;
 494         }
 495
 496         /* Just in case we added so many that we wrap. */
 497         if (unlikely(vrh->completed > 0xffff))
 498                 notify = true;
 499         else
 500                 notify = vring_need_event(used_event,
 501                                           vrh->last_used_idx + vrh->completed,
 502                                           vrh->last_used_idx);
 503
 504         vrh->last_used_idx += vrh->completed;
 505         vrh->completed = 0;
 506         return notify;
 507 }
 508
 509 static inline bool __vringh_notify_enable(struct vringh *vrh,
 510                                           int (*getu16)(const struct vringh *vrh,
 511                                                         u16 *val, const __virtio16 *p),
 512                                           int (*putu16)(const struct vringh *vrh,
 513                                                         __virtio16 *p, u16 val))
 514 {
 515         u16 avail;
 516
 517         if (!vrh->event_indices) {
 518                 /* Old-school; update flags. */
 519                 if (putu16(vrh, &vrh->vring.used->flags, 0) != 0) {
 520                         vringh_bad("Clearing used flags %p",
 521                                    &vrh->vring.used->flags);
 522                         return true;
 523                 }
 524         } else {
 525                 if (putu16(vrh, &vring_avail_event(&vrh->vring),
 526                            vrh->last_avail_idx) != 0) {
 527                         vringh_bad("Updating avail event index %p",
 528                                    &vring_avail_event(&vrh->vring));
 529                         return true;
 530                 }
 531         }
 532
 533         /* They could have slipped one in as we were doing that: make
 534          * sure it's written, then check again. */
 535         virtio_mb(vrh->weak_barriers);
 536
 537         if (getu16(vrh, &avail, &vrh->vring.avail->idx) != 0) {
 538                 vringh_bad("Failed to check avail idx at %p",
 539                            &vrh->vring.avail->idx);
 540                 return true;
 541         }
 542
 543         /* This is unlikely, so we just leave notifications enabled
 544          * (if we're using event_indices, we'll only get one
 545          * notification anyway). */
 546         return avail == vrh->last_avail_idx;
 547 }
 548
 549 static inline void __vringh_notify_disable(struct vringh *vrh,
 550                                            int (*putu16)(const struct vringh *vrh,
 551                                                          __virtio16 *p, u16 val))
 552 {
 553         if (!vrh->event_indices) {
 554                 /* Old-school; update flags. */
 555                 if (putu16(vrh, &vrh->vring.used->flags,
 556                            VRING_USED_F_NO_NOTIFY)) {
 557                         vringh_bad("Setting used flags %p",
 558                                    &vrh->vring.used->flags);
 559                 }
 560         }
 561 }
 562
 563 /* Userspace access helpers: in this case, addresses are really userspace. */
 564 static inline int getu16_user(const struct vringh *vrh, u16 *val, const __virtio16 *p)
 565 {
 566         __virtio16 v = 0;
 567         int rc = get_user(v, (__force __virtio16 __user *)p);
 568         *val = vringh16_to_cpu(vrh, v);
 569         return rc;
 570 }
 571
 572 static inline int putu16_user(const struct vringh *vrh, __virtio16 *p, u16 val)
 573 {
 574         __virtio16 v = cpu_to_vringh16(vrh, val);
 575         return put_user(v, (__force __virtio16 __user *)p);
 576 }
 577
 578 static inline int copydesc_user(const struct vringh *vrh,
 579                                 void *dst, const void *src, size_t len)
 580 {
 581         return copy_from_user(dst, (__force void __user *)src, len) ?
 582                 -EFAULT : 0;
 583 }
 584
 585 static inline int putused_user(const struct vringh *vrh,
 586                                struct vring_used_elem *dst,
 587                                const struct vring_used_elem *src,
 588                                unsigned int num)
 589 {
 590         return copy_to_user((__force void __user *)dst, src,
 591                             sizeof(*dst) * num) ? -EFAULT : 0;
 592 }
 593
 594 static inline int xfer_from_user(const struct vringh *vrh, void *src,
 595                                  void *dst, size_t len)
 596 {
 597         return copy_from_user(dst, (__force void __user *)src, len) ?
 598                 -EFAULT : 0;
 599 }
 600
 601 static inline int xfer_to_user(const struct vringh *vrh,
 602                                void *dst, void *src, size_t len)
 603 {
 604         return copy_to_user((__force void __user *)dst, src, len) ?
 605                 -EFAULT : 0;
 606 }
 607
 608 /**
 609  * vringh_init_user - initialize a vringh for a userspace vring.
 610  * @vrh: the vringh to initialize.
 611  * @features: the feature bits for this ring.
 612  * @num: the number of elements.
 613  * @weak_barriers: true if we only need memory barriers, not I/O.
 614  * @desc: the userpace descriptor pointer.
 615  * @avail: the userpace avail pointer.
 616  * @used: the userpace used pointer.
 617  *
 618  * Returns an error if num is invalid: you should check pointers
 619  * yourself!
 620  */
 621 int vringh_init_user(struct vringh *vrh, u64 features,
 622                      unsigned int num, bool weak_barriers,
 623                      struct vring_desc __user *desc,
 624                      struct vring_avail __user *avail,
 625                      struct vring_used __user *used)
 626 {
 627         /* Sane power of 2 please! */
 628         if (!num || num > 0xffff || (num & (num - 1))) {
 629                 vringh_bad("Bad ring size %u", num);
 630                 return -EINVAL;
 631         }
 632
 633         vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
 634         vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
 635         vrh->weak_barriers = weak_barriers;
 636         vrh->completed = 0;
 637         vrh->last_avail_idx = 0;
 638         vrh->last_used_idx = 0;
 639         vrh->vring.num = num;
 640         /* vring expects kernel addresses, but only used via accessors. */
 641         vrh->vring.desc = (__force struct vring_desc *)desc;
 642         vrh->vring.avail = (__force struct vring_avail *)avail;
 643         vrh->vring.used = (__force struct vring_used *)used;
 644         return 0;
 645 }
 646 EXPORT_SYMBOL(vringh_init_user);
 647
 648 /**
 649  * vringh_getdesc_user - get next available descriptor from userspace ring.
 650  * @vrh: the userspace vring.
 651  * @riov: where to put the readable descriptors (or NULL)
 652  * @wiov: where to put the writable descriptors (or NULL)
 653  * @getrange: function to call to check ranges.
 654  * @head: head index we received, for passing to vringh_complete_user().
 655  *
 656  * Returns 0 if there was no descriptor, 1 if there was, or -errno.
 657  *
 658  * Note that on error return, you can tell the difference between an
 659  * invalid ring and a single invalid descriptor: in the former case,
 660  * *head will be vrh->vring.num.  You may be able to ignore an invalid
 661  * descriptor, but there's not much you can do with an invalid ring.
 662  *
 663  * Note that you may need to clean up riov and wiov, even on error!
 664  */
 665 int vringh_getdesc_user(struct vringh *vrh,
 666                         struct vringh_iov *riov,
 667                         struct vringh_iov *wiov,
 668                         bool (*getrange)(struct vringh *vrh,
 669                                          u64 addr, struct vringh_range *r),
 670                         u16 *head)
 671 {
 672         int err;
 673
 674         *head = vrh->vring.num;
 675         err = __vringh_get_head(vrh, getu16_user, &vrh->last_avail_idx);
 676         if (err < 0)
 677                 return err;
 678
 679         /* Empty... */
 680         if (err == vrh->vring.num)
 681                 return 0;
 682
 683         /* We need the layouts to be the identical for this to work */
 684         BUILD_BUG_ON(sizeof(struct vringh_kiov) != sizeof(struct vringh_iov));
 685         BUILD_BUG_ON(offsetof(struct vringh_kiov, iov) !=
 686                      offsetof(struct vringh_iov, iov));
 687         BUILD_BUG_ON(offsetof(struct vringh_kiov, i) !=
 688                      offsetof(struct vringh_iov, i));
 689         BUILD_BUG_ON(offsetof(struct vringh_kiov, used) !=
 690                      offsetof(struct vringh_iov, used));
 691         BUILD_BUG_ON(offsetof(struct vringh_kiov, max_num) !=
 692                      offsetof(struct vringh_iov, max_num));
 693         BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
 694         BUILD_BUG_ON(offsetof(struct iovec, iov_base) !=
 695                      offsetof(struct kvec, iov_base));
 696         BUILD_BUG_ON(offsetof(struct iovec, iov_len) !=
 697                      offsetof(struct kvec, iov_len));
 698         BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_base)
 699                      != sizeof(((struct kvec *)NULL)->iov_base));
 700         BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_len)
 701                      != sizeof(((struct kvec *)NULL)->iov_len));
 702
 703         *head = err;
 704         err = __vringh_iov(vrh, *head, (struct vringh_kiov *)riov,
 705                            (struct vringh_kiov *)wiov,
 706                            range_check, getrange, GFP_KERNEL, copydesc_user);
 707         if (err)
 708                 return err;
 709
 710         return 1;
 711 }
 712 EXPORT_SYMBOL(vringh_getdesc_user);
 713
 714 /**
 715  * vringh_iov_pull_user - copy bytes from vring_iov.
 716  * @riov: the riov as passed to vringh_getdesc_user() (updated as we consume)
 717  * @dst: the place to copy.
 718  * @len: the maximum length to copy.
 719  *
 720  * Returns the bytes copied <= len or a negative errno.
 721  */
 722 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
 723 {
 724         return vringh_iov_xfer(NULL, (struct vringh_kiov *)riov,
 725                                dst, len, xfer_from_user);
 726 }
 727 EXPORT_SYMBOL(vringh_iov_pull_user);
 728
 729 /**
 730  * vringh_iov_push_user - copy bytes into vring_iov.
 731  * @wiov: the wiov as passed to vringh_getdesc_user() (updated as we consume)
 732  * @dst: the place to copy.
 733  * @len: the maximum length to copy.
 734  *
 735  * Returns the bytes copied <= len or a negative errno.
 736  */
 737 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 738                              const void *src, size_t len)
 739 {
 740         return vringh_iov_xfer(NULL, (struct vringh_kiov *)wiov,
 741                                (void *)src, len, xfer_to_user);
 742 }
 743 EXPORT_SYMBOL(vringh_iov_push_user);
 744
 745 /**
 746  * vringh_abandon_user - we've decided not to handle the descriptor(s).
 747  * @vrh: the vring.
 748  * @num: the number of descriptors to put back (ie. num
 749  *       vringh_get_user() to undo).
 750  *
 751  * The next vringh_get_user() will return the old descriptor(s) again.
 752  */
 753 void vringh_abandon_user(struct vringh *vrh, unsigned int num)
 754 {
 755         /* We only update vring_avail_event(vr) when we want to be notified,
 756          * so we haven't changed that yet. */
 757         vrh->last_avail_idx -= num;
 758 }
 759 EXPORT_SYMBOL(vringh_abandon_user);
 760
 761 /**
 762  * vringh_complete_user - we've finished with descriptor, publish it.
 763  * @vrh: the vring.
 764  * @head: the head as filled in by vringh_getdesc_user.
 765  * @len: the length of data we have written.
 766  *
 767  * You should check vringh_need_notify_user() after one or more calls
 768  * to this function.
 769  */
 770 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len)
 771 {
 772         struct vring_used_elem used;
 773
 774         used.id = cpu_to_vringh32(vrh, head);
 775         used.len = cpu_to_vringh32(vrh, len);
 776         return __vringh_complete(vrh, &used, 1, putu16_user, putused_user);
 777 }
 778 EXPORT_SYMBOL(vringh_complete_user);
 779
 780 /**
 781  * vringh_complete_multi_user - we've finished with many descriptors.
 782  * @vrh: the vring.
 783  * @used: the head, length pairs.
 784  * @num_used: the number of used elements.
 785  *
 786  * You should check vringh_need_notify_user() after one or more calls
 787  * to this function.
 788  */
 789 int vringh_complete_multi_user(struct vringh *vrh,
 790                                const struct vring_used_elem used[],
 791                                unsigned num_used)
 792 {
 793         return __vringh_complete(vrh, used, num_used,
 794                                  putu16_user, putused_user);
 795 }
 796 EXPORT_SYMBOL(vringh_complete_multi_user);
 797
 798 /**
 799  * vringh_notify_enable_user - we want to know if something changes.
 800  * @vrh: the vring.
 801  *
 802  * This always enables notifications, but returns false if there are
 803  * now more buffers available in the vring.
 804  */
 805 bool vringh_notify_enable_user(struct vringh *vrh)
 806 {
 807         return __vringh_notify_enable(vrh, getu16_user, putu16_user);
 808 }
 809 EXPORT_SYMBOL(vringh_notify_enable_user);
 810
 811 /**
 812  * vringh_notify_disable_user - don't tell us if something changes.
 813  * @vrh: the vring.
 814  *
 815  * This is our normal running state: we disable and then only enable when
 816  * we're going to sleep.
 817  */
 818 void vringh_notify_disable_user(struct vringh *vrh)
 819 {
 820         __vringh_notify_disable(vrh, putu16_user);
 821 }
 822 EXPORT_SYMBOL(vringh_notify_disable_user);
 823
 824 /**
 825  * vringh_need_notify_user - must we tell the other side about used buffers?
 826  * @vrh: the vring we've called vringh_complete_user() on.
 827  *
 828  * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
 829  */
 830 int vringh_need_notify_user(struct vringh *vrh)
 831 {
 832         return __vringh_need_notify(vrh, getu16_user);
 833 }
 834 EXPORT_SYMBOL(vringh_need_notify_user);
 835
 836 /* Kernelspace access helpers. */
 837 static inline int getu16_kern(const struct vringh *vrh,
 838                               u16 *val, const __virtio16 *p)
 839 {
 840         *val = vringh16_to_cpu(vrh, READ_ONCE(*p));
 841         return 0;
 842 }
 843
 844 static inline int putu16_kern(const struct vringh *vrh, __virtio16 *p, u16 val)
 845 {
 846         WRITE_ONCE(*p, cpu_to_vringh16(vrh, val));
 847         return 0;
 848 }
 849
 850 static inline int copydesc_kern(const struct vringh *vrh,
 851                                 void *dst, const void *src, size_t len)
 852 {
 853         memcpy(dst, src, len);
 854         return 0;
 855 }
 856
 857 static inline int putused_kern(const struct vringh *vrh,
 858                                struct vring_used_elem *dst,
 859                                const struct vring_used_elem *src,
 860                                unsigned int num)
 861 {
 862         memcpy(dst, src, num * sizeof(*dst));
 863         return 0;
 864 }
 865
 866 static inline int xfer_kern(const struct vringh *vrh, void *src,
 867                             void *dst, size_t len)
 868 {
 869         memcpy(dst, src, len);
 870         return 0;
 871 }
 872
 873 static inline int kern_xfer(const struct vringh *vrh, void *dst,
 874                             void *src, size_t len)
 875 {
 876         memcpy(dst, src, len);
 877         return 0;
 878 }
 879
 880 /**
 881  * vringh_init_kern - initialize a vringh for a kernelspace vring.
 882  * @vrh: the vringh to initialize.
 883  * @features: the feature bits for this ring.
 884  * @num: the number of elements.
 885  * @weak_barriers: true if we only need memory barriers, not I/O.
 886  * @desc: the userpace descriptor pointer.
 887  * @avail: the userpace avail pointer.
 888  * @used: the userpace used pointer.
 889  *
 890  * Returns an error if num is invalid.
 891  */
 892 int vringh_init_kern(struct vringh *vrh, u64 features,
 893                      unsigned int num, bool weak_barriers,
 894                      struct vring_desc *desc,
 895                      struct vring_avail *avail,
 896                      struct vring_used *used)
 897 {
 898         /* Sane power of 2 please! */
 899         if (!num || num > 0xffff || (num & (num - 1))) {
 900                 vringh_bad("Bad ring size %u", num);
 901                 return -EINVAL;
 902         }
 903
 904         vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
 905         vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
 906         vrh->weak_barriers = weak_barriers;
 907         vrh->completed = 0;
 908         vrh->last_avail_idx = 0;
 909         vrh->last_used_idx = 0;
 910         vrh->vring.num = num;
 911         vrh->vring.desc = desc;
 912         vrh->vring.avail = avail;
 913         vrh->vring.used = used;
 914         return 0;
 915 }
 916 EXPORT_SYMBOL(vringh_init_kern);
 917
 918 /**
 919  * vringh_getdesc_kern - get next available descriptor from kernelspace ring.
 920  * @vrh: the kernelspace vring.
 921  * @riov: where to put the readable descriptors (or NULL)
 922  * @wiov: where to put the writable descriptors (or NULL)
 923  * @head: head index we received, for passing to vringh_complete_kern().
 924  * @gfp: flags for allocating larger riov/wiov.
 925  *
 926  * Returns 0 if there was no descriptor, 1 if there was, or -errno.
 927  *
 928  * Note that on error return, you can tell the difference between an
 929  * invalid ring and a single invalid descriptor: in the former case,
 930  * *head will be vrh->vring.num.  You may be able to ignore an invalid
 931  * descriptor, but there's not much you can do with an invalid ring.
 932  *
 933  * Note that you may need to clean up riov and wiov, even on error!
 934  */
 935 int vringh_getdesc_kern(struct vringh *vrh,
 936                         struct vringh_kiov *riov,
 937                         struct vringh_kiov *wiov,
 938                         u16 *head,
 939                         gfp_t gfp)
 940 {
 941         int err;
 942
 943         err = __vringh_get_head(vrh, getu16_kern, &vrh->last_avail_idx);
 944         if (err < 0)
 945                 return err;
 946
 947         /* Empty... */
 948         if (err == vrh->vring.num)
 949                 return 0;
 950
 951         *head = err;
 952         err = __vringh_iov(vrh, *head, riov, wiov, no_range_check, NULL,
 953                            gfp, copydesc_kern);
 954         if (err)
 955                 return err;
 956
 957         return 1;
 958 }
 959 EXPORT_SYMBOL(vringh_getdesc_kern);
 960
 961 /**
 962  * vringh_iov_pull_kern - copy bytes from vring_iov.
 963  * @riov: the riov as passed to vringh_getdesc_kern() (updated as we consume)
 964  * @dst: the place to copy.
 965  * @len: the maximum length to copy.
 966  *
 967  * Returns the bytes copied <= len or a negative errno.
 968  */
 969 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len)
 970 {
 971         return vringh_iov_xfer(NULL, riov, dst, len, xfer_kern);
 972 }
 973 EXPORT_SYMBOL(vringh_iov_pull_kern);
 974
 975 /**
 976  * vringh_iov_push_kern - copy bytes into vring_iov.
 977  * @wiov: the wiov as passed to vringh_getdesc_kern() (updated as we consume)
 978  * @dst: the place to copy.
 979  * @len: the maximum length to copy.
 980  *
 981  * Returns the bytes copied <= len or a negative errno.
 982  */
 983 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 984                              const void *src, size_t len)
 985 {
 986         return vringh_iov_xfer(NULL, wiov, (void *)src, len, kern_xfer);
 987 }
 988 EXPORT_SYMBOL(vringh_iov_push_kern);
 989
 990 /**
 991  * vringh_abandon_kern - we've decided not to handle the descriptor(s).
 992  * @vrh: the vring.
 993  * @num: the number of descriptors to put back (ie. num
 994  *       vringh_get_kern() to undo).
 995  *
 996  * The next vringh_get_kern() will return the old descriptor(s) again.
 997  */
 998 void vringh_abandon_kern(struct vringh *vrh, unsigned int num)
 999 {
1000         /* We only update vring_avail_event(vr) when we want to be notified,
1001          * so we haven't changed that yet. */
1002         vrh->last_avail_idx -= num;
1003 }
1004 EXPORT_SYMBOL(vringh_abandon_kern);
1005
1006 /**
1007  * vringh_complete_kern - we've finished with descriptor, publish it.
1008  * @vrh: the vring.
1009  * @head: the head as filled in by vringh_getdesc_kern.
1010  * @len: the length of data we have written.
1011  *
1012  * You should check vringh_need_notify_kern() after one or more calls
1013  * to this function.
1014  */
1015 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len)
1016 {
1017         struct vring_used_elem used;
1018
1019         used.id = cpu_to_vringh32(vrh, head);
1020         used.len = cpu_to_vringh32(vrh, len);
1021
1022         return __vringh_complete(vrh, &used, 1, putu16_kern, putused_kern);
1023 }
1024 EXPORT_SYMBOL(vringh_complete_kern);
1025
1026 /**
1027  * vringh_notify_enable_kern - we want to know if something changes.
1028  * @vrh: the vring.
1029  *
1030  * This always enables notifications, but returns false if there are
1031  * now more buffers available in the vring.
1032  */
1033 bool vringh_notify_enable_kern(struct vringh *vrh)
1034 {
1035         return __vringh_notify_enable(vrh, getu16_kern, putu16_kern);
1036 }
1037 EXPORT_SYMBOL(vringh_notify_enable_kern);
1038
1039 /**
1040  * vringh_notify_disable_kern - don't tell us if something changes.
1041  * @vrh: the vring.
1042  *
1043  * This is our normal running state: we disable and then only enable when
1044  * we're going to sleep.
1045  */
1046 void vringh_notify_disable_kern(struct vringh *vrh)
1047 {
1048         __vringh_notify_disable(vrh, putu16_kern);
1049 }
1050 EXPORT_SYMBOL(vringh_notify_disable_kern);
1051
1052 /**
1053  * vringh_need_notify_kern - must we tell the other side about used buffers?
1054  * @vrh: the vring we've called vringh_complete_kern() on.
1055  *
1056  * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
1057  */
1058 int vringh_need_notify_kern(struct vringh *vrh)
1059 {
1060         return __vringh_need_notify(vrh, getu16_kern);
1061 }
1062 EXPORT_SYMBOL(vringh_need_notify_kern);
1063
1064 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)
1065
1066 static int iotlb_translate(const struct vringh *vrh,
1067                            u64 addr, u64 len, struct bio_vec iov[],
1068                            int iov_size, u32 perm)
1069 {
1070         struct vhost_iotlb_map *map;
1071         struct vhost_iotlb *iotlb = vrh->iotlb;
1072         int ret = 0;
1073         u64 s = 0;
1074
1075         while (len > s) {
1076                 u64 size, pa, pfn;
1077
1078                 if (unlikely(ret >= iov_size)) {
1079                         ret = -ENOBUFS;
1080                         break;
1081                 }
1082
1083                 map = vhost_iotlb_itree_first(iotlb, addr,
1084                                               addr + len - 1);
1085                 if (!map || map->start > addr) {
1086                         ret = -EINVAL;
1087                         break;
1088                 } else if (!(map->perm & perm)) {
1089                         ret = -EPERM;
1090                         break;
1091                 }
1092
1093                 size = map->size - addr + map->start;
1094                 pa = map->addr + addr - map->start;
1095                 pfn = pa >> PAGE_SHIFT;
1096                 iov[ret].bv_page = pfn_to_page(pfn);
1097                 iov[ret].bv_len = min(len - s, size);
1098                 iov[ret].bv_offset = pa & (PAGE_SIZE - 1);
1099                 s += size;
1100                 addr += size;
1101                 ++ret;
1102         }
1103
1104         return ret;
1105 }
1106
1107 static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
1108                                   void *src, size_t len)
1109 {
1110         struct iov_iter iter;
1111         struct bio_vec iov[16];
1112         int ret;
1113
1114         ret = iotlb_translate(vrh, (u64)(uintptr_t)src,
1115                               len, iov, 16, VHOST_MAP_RO);
1116         if (ret < 0)
1117                 return ret;
1118
1119         iov_iter_bvec(&iter, READ, iov, ret, len);
1120
1121         ret = copy_from_iter(dst, len, &iter);
1122
1123         return ret;
1124 }
1125
1126 static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
1127                                 void *src, size_t len)
1128 {
1129         struct iov_iter iter;
1130         struct bio_vec iov[16];
1131         int ret;
1132
1133         ret = iotlb_translate(vrh, (u64)(uintptr_t)dst,
1134                               len, iov, 16, VHOST_MAP_WO);
1135         if (ret < 0)
1136                 return ret;
1137
1138         iov_iter_bvec(&iter, WRITE, iov, ret, len);
1139
1140         return copy_to_iter(src, len, &iter);
1141 }
1142
1143 static inline int getu16_iotlb(const struct vringh *vrh,
1144                                u16 *val, const __virtio16 *p)
1145 {
1146         struct bio_vec iov;
1147         void *kaddr, *from;
1148         int ret;
1149
1150         /* Atomic read is needed for getu16 */
1151         ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
1152                               &iov, 1, VHOST_MAP_RO);
1153         if (ret < 0)
1154                 return ret;
1155
1156         kaddr = kmap_atomic(iov.bv_page);
1157         from = kaddr + iov.bv_offset;
1158         *val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from));
1159         kunmap_atomic(kaddr);
1160
1161         return 0;
1162 }
1163
1164 static inline int putu16_iotlb(const struct vringh *vrh,
1165                                __virtio16 *p, u16 val)
1166 {
1167         struct bio_vec iov;
1168         void *kaddr, *to;
1169         int ret;
1170
1171         /* Atomic write is needed for putu16 */
1172         ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
1173                               &iov, 1, VHOST_MAP_WO);
1174         if (ret < 0)
1175                 return ret;
1176
1177         kaddr = kmap_atomic(iov.bv_page);
1178         to = kaddr + iov.bv_offset;
1179         WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val));
1180         kunmap_atomic(kaddr);
1181
1182         return 0;
1183 }
1184
1185 static inline int copydesc_iotlb(const struct vringh *vrh,
1186                                  void *dst, const void *src, size_t len)
1187 {
1188         int ret;
1189
1190         ret = copy_from_iotlb(vrh, dst, (void *)src, len);
1191         if (ret != len)
1192                 return -EFAULT;
1193
1194         return 0;
1195 }
1196
1197 static inline int xfer_from_iotlb(const struct vringh *vrh, void *src,
1198                                   void *dst, size_t len)
1199 {
1200         int ret;
1201
1202         ret = copy_from_iotlb(vrh, dst, src, len);
1203         if (ret != len)
1204                 return -EFAULT;
1205
1206         return 0;
1207 }
1208
1209 static inline int xfer_to_iotlb(const struct vringh *vrh,
1210                                void *dst, void *src, size_t len)
1211 {
1212         int ret;
1213
1214         ret = copy_to_iotlb(vrh, dst, src, len);
1215         if (ret != len)
1216                 return -EFAULT;
1217
1218         return 0;
1219 }
1220
1221 static inline int putused_iotlb(const struct vringh *vrh,
1222                                 struct vring_used_elem *dst,
1223                                 const struct vring_used_elem *src,
1224                                 unsigned int num)
1225 {
1226         int size = num * sizeof(*dst);
1227         int ret;
1228
1229         ret = copy_to_iotlb(vrh, dst, (void *)src, num * sizeof(*dst));
1230         if (ret != size)
1231                 return -EFAULT;
1232
1233         return 0;
1234 }
1235
1236 /**
1237  * vringh_init_iotlb - initialize a vringh for a ring with IOTLB.
1238  * @vrh: the vringh to initialize.
1239  * @features: the feature bits for this ring.
1240  * @num: the number of elements.
1241  * @weak_barriers: true if we only need memory barriers, not I/O.
1242  * @desc: the userpace descriptor pointer.
1243  * @avail: the userpace avail pointer.
1244  * @used: the userpace used pointer.
1245  *
1246  * Returns an error if num is invalid.
1247  */
1248 int vringh_init_iotlb(struct vringh *vrh, u64 features,
1249                       unsigned int num, bool weak_barriers,
1250                       struct vring_desc *desc,
1251                       struct vring_avail *avail,
1252                       struct vring_used *used)
1253 {
1254         return vringh_init_kern(vrh, features, num, weak_barriers,
1255                                 desc, avail, used);
1256 }
1257 EXPORT_SYMBOL(vringh_init_iotlb);
1258
1259 /**
1260  * vringh_set_iotlb - initialize a vringh for a ring with IOTLB.
1261  * @vrh: the vring
1262  * @iotlb: iotlb associated with this vring
1263  */
1264 void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb)
1265 {
1266         vrh->iotlb = iotlb;
1267 }
1268 EXPORT_SYMBOL(vringh_set_iotlb);
1269
1270 /**
1271  * vringh_getdesc_iotlb - get next available descriptor from ring with
1272  * IOTLB.
1273  * @vrh: the kernelspace vring.
1274  * @riov: where to put the readable descriptors (or NULL)
1275  * @wiov: where to put the writable descriptors (or NULL)
1276  * @head: head index we received, for passing to vringh_complete_iotlb().
1277  * @gfp: flags for allocating larger riov/wiov.
1278  *
1279  * Returns 0 if there was no descriptor, 1 if there was, or -errno.
1280  *
1281  * Note that on error return, you can tell the difference between an
1282  * invalid ring and a single invalid descriptor: in the former case,
1283  * *head will be vrh->vring.num.  You may be able to ignore an invalid
1284  * descriptor, but there's not much you can do with an invalid ring.
1285  *
1286  * Note that you may need to clean up riov and wiov, even on error!
1287  */
1288 int vringh_getdesc_iotlb(struct vringh *vrh,
1289                          struct vringh_kiov *riov,
1290                          struct vringh_kiov *wiov,
1291                          u16 *head,
1292                          gfp_t gfp)
1293 {
1294         int err;
1295
1296         err = __vringh_get_head(vrh, getu16_iotlb, &vrh->last_avail_idx);
1297         if (err < 0)
1298                 return err;
1299
1300         /* Empty... */
1301         if (err == vrh->vring.num)
1302                 return 0;
1303
1304         *head = err;
1305         err = __vringh_iov(vrh, *head, riov, wiov, no_range_check, NULL,
1306                            gfp, copydesc_iotlb);
1307         if (err)
1308                 return err;
1309
1310         return 1;
1311 }
1312 EXPORT_SYMBOL(vringh_getdesc_iotlb);
1313
1314 /**
1315  * vringh_iov_pull_iotlb - copy bytes from vring_iov.
1316  * @vrh: the vring.
1317  * @riov: the riov as passed to vringh_getdesc_iotlb() (updated as we consume)
1318  * @dst: the place to copy.
1319  * @len: the maximum length to copy.
1320  *
1321  * Returns the bytes copied <= len or a negative errno.
1322  */
1323 ssize_t vringh_iov_pull_iotlb(struct vringh *vrh,
1324                               struct vringh_kiov *riov,
1325                               void *dst, size_t len)
1326 {
1327         return vringh_iov_xfer(vrh, riov, dst, len, xfer_from_iotlb);
1328 }
1329 EXPORT_SYMBOL(vringh_iov_pull_iotlb);
1330
1331 /**
1332  * vringh_iov_push_iotlb - copy bytes into vring_iov.
1333  * @vrh: the vring.
1334  * @wiov: the wiov as passed to vringh_getdesc_iotlb() (updated as we consume)
1335  * @dst: the place to copy.
1336  * @len: the maximum length to copy.
1337  *
1338  * Returns the bytes copied <= len or a negative errno.
1339  */
1340 ssize_t vringh_iov_push_iotlb(struct vringh *vrh,
1341                               struct vringh_kiov *wiov,
1342                               const void *src, size_t len)
1343 {
1344         return vringh_iov_xfer(vrh, wiov, (void *)src, len, xfer_to_iotlb);
1345 }
1346 EXPORT_SYMBOL(vringh_iov_push_iotlb);
1347
1348 /**
1349  * vringh_abandon_iotlb - we've decided not to handle the descriptor(s).
1350  * @vrh: the vring.
1351  * @num: the number of descriptors to put back (ie. num
1352  *       vringh_get_iotlb() to undo).
1353  *
1354  * The next vringh_get_iotlb() will return the old descriptor(s) again.
1355  */
1356 void vringh_abandon_iotlb(struct vringh *vrh, unsigned int num)
1357 {
1358         /* We only update vring_avail_event(vr) when we want to be notified,
1359          * so we haven't changed that yet.
1360          */
1361         vrh->last_avail_idx -= num;
1362 }
1363 EXPORT_SYMBOL(vringh_abandon_iotlb);
1364
1365 /**
1366  * vringh_complete_iotlb - we've finished with descriptor, publish it.
1367  * @vrh: the vring.
1368  * @head: the head as filled in by vringh_getdesc_iotlb.
1369  * @len: the length of data we have written.
1370  *
1371  * You should check vringh_need_notify_iotlb() after one or more calls
1372  * to this function.
1373  */
1374 int vringh_complete_iotlb(struct vringh *vrh, u16 head, u32 len)
1375 {
1376         struct vring_used_elem used;
1377
1378         used.id = cpu_to_vringh32(vrh, head);
1379         used.len = cpu_to_vringh32(vrh, len);
1380
1381         return __vringh_complete(vrh, &used, 1, putu16_iotlb, putused_iotlb);
1382 }
1383 EXPORT_SYMBOL(vringh_complete_iotlb);
1384
1385 /**
1386  * vringh_notify_enable_iotlb - we want to know if something changes.
1387  * @vrh: the vring.
1388  *
1389  * This always enables notifications, but returns false if there are
1390  * now more buffers available in the vring.
1391  */
1392 bool vringh_notify_enable_iotlb(struct vringh *vrh)
1393 {
1394         return __vringh_notify_enable(vrh, getu16_iotlb, putu16_iotlb);
1395 }
1396 EXPORT_SYMBOL(vringh_notify_enable_iotlb);
1397
1398 /**
1399  * vringh_notify_disable_iotlb - don't tell us if something changes.
1400  * @vrh: the vring.
1401  *
1402  * This is our normal running state: we disable and then only enable when
1403  * we're going to sleep.
1404  */
1405 void vringh_notify_disable_iotlb(struct vringh *vrh)
1406 {
1407         __vringh_notify_disable(vrh, putu16_iotlb);
1408 }
1409 EXPORT_SYMBOL(vringh_notify_disable_iotlb);
1410
1411 /**
1412  * vringh_need_notify_iotlb - must we tell the other side about used buffers?
1413  * @vrh: the vring we've called vringh_complete_iotlb() on.
1414  *
1415  * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
1416  */
1417 int vringh_need_notify_iotlb(struct vringh *vrh)
1418 {
1419         return __vringh_need_notify(vrh, getu16_iotlb);
1420 }
1421 EXPORT_SYMBOL(vringh_need_notify_iotlb);
1422
1423 #endif
1424
1425 MODULE_LICENSE("GPL");