mm/hmm.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 2013 Red Hat Inc.
   4  *
   5  * Authors: Jérôme Glisse <jglisse@redhat.com>
   6  */
   7 /*
   8  * Refer to include/linux/hmm.h for information about heterogeneous memory
   9  * management or HMM for short.
  10  */
  11 #include <linux/mm.h>
  12 #include <linux/hmm.h>
  13 #include <linux/init.h>
  14 #include <linux/rmap.h>
  15 #include <linux/swap.h>
  16 #include <linux/slab.h>
  17 #include <linux/sched.h>
  18 #include <linux/mmzone.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/swapops.h>
  21 #include <linux/hugetlb.h>
  22 #include <linux/memremap.h>
  23 #include <linux/jump_label.h>
  24 #include <linux/dma-mapping.h>
  25 #include <linux/mmu_notifier.h>
  26 #include <linux/memory_hotplug.h>
  27
  28 #define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
  29
  30 #if IS_ENABLED(CONFIG_HMM_MIRROR)
  31 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
  32
  33 static inline struct hmm *mm_get_hmm(struct mm_struct *mm)
  34 {
  35         struct hmm *hmm = READ_ONCE(mm->hmm);
  36
  37         if (hmm && kref_get_unless_zero(&hmm->kref))
  38                 return hmm;
  39
  40         return NULL;
  41 }
  42
  43 /**
  44  * hmm_get_or_create - register HMM against an mm (HMM internal)
  45  *
  46  * @mm: mm struct to attach to
  47  * Returns: returns an HMM object, either by referencing the existing
  48  *          (per-process) object, or by creating a new one.
  49  *
  50  * This is not intended to be used directly by device drivers. If mm already
  51  * has an HMM struct then it get a reference on it and returns it. Otherwise
  52  * it allocates an HMM struct, initializes it, associate it with the mm and
  53  * returns it.
  54  */
  55 static struct hmm *hmm_get_or_create(struct mm_struct *mm)
  56 {
  57         struct hmm *hmm = mm_get_hmm(mm);
  58         bool cleanup = false;
  59
  60         if (hmm)
  61                 return hmm;
  62
  63         hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
  64         if (!hmm)
  65                 return NULL;
  66         init_waitqueue_head(&hmm->wq);
  67         INIT_LIST_HEAD(&hmm->mirrors);
  68         init_rwsem(&hmm->mirrors_sem);
  69         hmm->mmu_notifier.ops = NULL;
  70         INIT_LIST_HEAD(&hmm->ranges);
  71         mutex_init(&hmm->lock);
  72         kref_init(&hmm->kref);
  73         hmm->notifiers = 0;
  74         hmm->dead = false;
  75         hmm->mm = mm;
  76
  77         spin_lock(&mm->page_table_lock);
  78         if (!mm->hmm)
  79                 mm->hmm = hmm;
  80         else
  81                 cleanup = true;
  82         spin_unlock(&mm->page_table_lock);
  83
  84         if (cleanup)
  85                 goto error;
  86
  87         /*
  88          * We should only get here if hold the mmap_sem in write mode ie on
  89          * registration of first mirror through hmm_mirror_register()
  90          */
  91         hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
  92         if (__mmu_notifier_register(&hmm->mmu_notifier, mm))
  93                 goto error_mm;
  94
  95         return hmm;
  96
  97 error_mm:
  98         spin_lock(&mm->page_table_lock);
  99         if (mm->hmm == hmm)
 100                 mm->hmm = NULL;
 101         spin_unlock(&mm->page_table_lock);
 102 error:
 103         kfree(hmm);
 104         return NULL;
 105 }
 106
 107 static void hmm_free(struct kref *kref)
 108 {
 109         struct hmm *hmm = container_of(kref, struct hmm, kref);
 110         struct mm_struct *mm = hmm->mm;
 111
 112         mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
 113
 114         spin_lock(&mm->page_table_lock);
 115         if (mm->hmm == hmm)
 116                 mm->hmm = NULL;
 117         spin_unlock(&mm->page_table_lock);
 118
 119         kfree(hmm);
 120 }
 121
 122 static inline void hmm_put(struct hmm *hmm)
 123 {
 124         kref_put(&hmm->kref, hmm_free);
 125 }
 126
 127 void hmm_mm_destroy(struct mm_struct *mm)
 128 {
 129         struct hmm *hmm;
 130
 131         spin_lock(&mm->page_table_lock);
 132         hmm = mm_get_hmm(mm);
 133         mm->hmm = NULL;
 134         if (hmm) {
 135                 hmm->mm = NULL;
 136                 hmm->dead = true;
 137                 spin_unlock(&mm->page_table_lock);
 138                 hmm_put(hmm);
 139                 return;
 140         }
 141
 142         spin_unlock(&mm->page_table_lock);
 143 }
 144
 145 static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 146 {
 147         struct hmm *hmm = mm_get_hmm(mm);
 148         struct hmm_mirror *mirror;
 149         struct hmm_range *range;
 150
 151         /* Report this HMM as dying. */
 152         hmm->dead = true;
 153
 154         /* Wake-up everyone waiting on any range. */
 155         mutex_lock(&hmm->lock);
 156         list_for_each_entry(range, &hmm->ranges, list) {
 157                 range->valid = false;
 158         }
 159         wake_up_all(&hmm->wq);
 160         mutex_unlock(&hmm->lock);
 161
 162         down_write(&hmm->mirrors_sem);
 163         mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
 164                                           list);
 165         while (mirror) {
 166                 list_del_init(&mirror->list);
 167                 if (mirror->ops->release) {
 168                         /*
 169                          * Drop mirrors_sem so callback can wait on any pending
 170                          * work that might itself trigger mmu_notifier callback
 171                          * and thus would deadlock with us.
 172                          */
 173                         up_write(&hmm->mirrors_sem);
 174                         mirror->ops->release(mirror);
 175                         down_write(&hmm->mirrors_sem);
 176                 }
 177                 mirror = list_first_entry_or_null(&hmm->mirrors,
 178                                                   struct hmm_mirror, list);
 179         }
 180         up_write(&hmm->mirrors_sem);
 181
 182         hmm_put(hmm);
 183 }
 184
 185 static int hmm_invalidate_range_start(struct mmu_notifier *mn,
 186                         const struct mmu_notifier_range *nrange)
 187 {
 188         struct hmm *hmm = mm_get_hmm(nrange->mm);
 189         struct hmm_mirror *mirror;
 190         struct hmm_update update;
 191         struct hmm_range *range;
 192         int ret = 0;
 193
 194         VM_BUG_ON(!hmm);
 195
 196         update.start = nrange->start;
 197         update.end = nrange->end;
 198         update.event = HMM_UPDATE_INVALIDATE;
 199         update.blockable = mmu_notifier_range_blockable(nrange);
 200
 201         if (mmu_notifier_range_blockable(nrange))
 202                 mutex_lock(&hmm->lock);
 203         else if (!mutex_trylock(&hmm->lock)) {
 204                 ret = -EAGAIN;
 205                 goto out;
 206         }
 207         hmm->notifiers++;
 208         list_for_each_entry(range, &hmm->ranges, list) {
 209                 if (update.end < range->start || update.start >= range->end)
 210                         continue;
 211
 212                 range->valid = false;
 213         }
 214         mutex_unlock(&hmm->lock);
 215
 216         if (mmu_notifier_range_blockable(nrange))
 217                 down_read(&hmm->mirrors_sem);
 218         else if (!down_read_trylock(&hmm->mirrors_sem)) {
 219                 ret = -EAGAIN;
 220                 goto out;
 221         }
 222         list_for_each_entry(mirror, &hmm->mirrors, list) {
 223                 int ret;
 224
 225                 ret = mirror->ops->sync_cpu_device_pagetables(mirror, &update);
 226                 if (!update.blockable && ret == -EAGAIN) {
 227                         up_read(&hmm->mirrors_sem);
 228                         ret = -EAGAIN;
 229                         goto out;
 230                 }
 231         }
 232         up_read(&hmm->mirrors_sem);
 233
 234 out:
 235         hmm_put(hmm);
 236         return ret;
 237 }
 238
 239 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
 240                         const struct mmu_notifier_range *nrange)
 241 {
 242         struct hmm *hmm = mm_get_hmm(nrange->mm);
 243
 244         VM_BUG_ON(!hmm);
 245
 246         mutex_lock(&hmm->lock);
 247         hmm->notifiers--;
 248         if (!hmm->notifiers) {
 249                 struct hmm_range *range;
 250
 251                 list_for_each_entry(range, &hmm->ranges, list) {
 252                         if (range->valid)
 253                                 continue;
 254                         range->valid = true;
 255                 }
 256                 wake_up_all(&hmm->wq);
 257         }
 258         mutex_unlock(&hmm->lock);
 259
 260         hmm_put(hmm);
 261 }
 262
 263 static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
 264         .release                = hmm_release,
 265         .invalidate_range_start = hmm_invalidate_range_start,
 266         .invalidate_range_end   = hmm_invalidate_range_end,
 267 };
 268
 269 /*
 270  * hmm_mirror_register() - register a mirror against an mm
 271  *
 272  * @mirror: new mirror struct to register
 273  * @mm: mm to register against
 274  *
 275  * To start mirroring a process address space, the device driver must register
 276  * an HMM mirror struct.
 277  *
 278  * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
 279  */
 280 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
 281 {
 282         /* Sanity check */
 283         if (!mm || !mirror || !mirror->ops)
 284                 return -EINVAL;
 285
 286         mirror->hmm = hmm_get_or_create(mm);
 287         if (!mirror->hmm)
 288                 return -ENOMEM;
 289
 290         down_write(&mirror->hmm->mirrors_sem);
 291         list_add(&mirror->list, &mirror->hmm->mirrors);
 292         up_write(&mirror->hmm->mirrors_sem);
 293
 294         return 0;
 295 }
 296 EXPORT_SYMBOL(hmm_mirror_register);
 297
 298 /*
 299  * hmm_mirror_unregister() - unregister a mirror
 300  *
 301  * @mirror: new mirror struct to register
 302  *
 303  * Stop mirroring a process address space, and cleanup.
 304  */
 305 void hmm_mirror_unregister(struct hmm_mirror *mirror)
 306 {
 307         struct hmm *hmm = READ_ONCE(mirror->hmm);
 308
 309         if (hmm == NULL)
 310                 return;
 311
 312         down_write(&hmm->mirrors_sem);
 313         list_del_init(&mirror->list);
 314         /* To protect us against double unregister ... */
 315         mirror->hmm = NULL;
 316         up_write(&hmm->mirrors_sem);
 317
 318         hmm_put(hmm);
 319 }
 320 EXPORT_SYMBOL(hmm_mirror_unregister);
 321
 322 struct hmm_vma_walk {
 323         struct hmm_range        *range;
 324         struct dev_pagemap      *pgmap;
 325         unsigned long           last;
 326         bool                    fault;
 327         bool                    block;
 328 };
 329
 330 static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
 331                             bool write_fault, uint64_t *pfn)
 332 {
 333         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
 334         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 335         struct hmm_range *range = hmm_vma_walk->range;
 336         struct vm_area_struct *vma = walk->vma;
 337         vm_fault_t ret;
 338
 339         flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
 340         flags |= write_fault ? FAULT_FLAG_WRITE : 0;
 341         ret = handle_mm_fault(vma, addr, flags);
 342         if (ret & VM_FAULT_RETRY)
 343                 return -EAGAIN;
 344         if (ret & VM_FAULT_ERROR) {
 345                 *pfn = range->values[HMM_PFN_ERROR];
 346                 return -EFAULT;
 347         }
 348
 349         return -EBUSY;
 350 }
 351
 352 static int hmm_pfns_bad(unsigned long addr,
 353                         unsigned long end,
 354                         struct mm_walk *walk)
 355 {
 356         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 357         struct hmm_range *range = hmm_vma_walk->range;
 358         uint64_t *pfns = range->pfns;
 359         unsigned long i;
 360
 361         i = (addr - range->start) >> PAGE_SHIFT;
 362         for (; addr < end; addr += PAGE_SIZE, i++)
 363                 pfns[i] = range->values[HMM_PFN_ERROR];
 364
 365         return 0;
 366 }
 367
 368 /*
 369  * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
 370  * @start: range virtual start address (inclusive)
 371  * @end: range virtual end address (exclusive)
 372  * @fault: should we fault or not ?
 373  * @write_fault: write fault ?
 374  * @walk: mm_walk structure
 375  * Returns: 0 on success, -EBUSY after page fault, or page fault error
 376  *
 377  * This function will be called whenever pmd_none() or pte_none() returns true,
 378  * or whenever there is no page directory covering the virtual address range.
 379  */
 380 static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
 381                               bool fault, bool write_fault,
 382                               struct mm_walk *walk)
 383 {
 384         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 385         struct hmm_range *range = hmm_vma_walk->range;
 386         uint64_t *pfns = range->pfns;
 387         unsigned long i, page_size;
 388
 389         hmm_vma_walk->last = addr;
 390         page_size = hmm_range_page_size(range);
 391         i = (addr - range->start) >> range->page_shift;
 392
 393         for (; addr < end; addr += page_size, i++) {
 394                 pfns[i] = range->values[HMM_PFN_NONE];
 395                 if (fault || write_fault) {
 396                         int ret;
 397
 398                         ret = hmm_vma_do_fault(walk, addr, write_fault,
 399                                                &pfns[i]);
 400                         if (ret != -EBUSY)
 401                                 return ret;
 402                 }
 403         }
 404
 405         return (fault || write_fault) ? -EBUSY : 0;
 406 }
 407
 408 static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 409                                       uint64_t pfns, uint64_t cpu_flags,
 410                                       bool *fault, bool *write_fault)
 411 {
 412         struct hmm_range *range = hmm_vma_walk->range;
 413
 414         if (!hmm_vma_walk->fault)
 415                 return;
 416
 417         /*
 418          * So we not only consider the individual per page request we also
 419          * consider the default flags requested for the range. The API can
 420          * be use in 2 fashions. The first one where the HMM user coalesce
 421          * multiple page fault into one request and set flags per pfns for
 422          * of those faults. The second one where the HMM user want to pre-
 423          * fault a range with specific flags. For the latter one it is a
 424          * waste to have the user pre-fill the pfn arrays with a default
 425          * flags value.
 426          */
 427         pfns = (pfns & range->pfn_flags_mask) | range->default_flags;
 428
 429         /* We aren't ask to do anything ... */
 430         if (!(pfns & range->flags[HMM_PFN_VALID]))
 431                 return;
 432         /* If this is device memory than only fault if explicitly requested */
 433         if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
 434                 /* Do we fault on device memory ? */
 435                 if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
 436                         *write_fault = pfns & range->flags[HMM_PFN_WRITE];
 437                         *fault = true;
 438                 }
 439                 return;
 440         }
 441
 442         /* If CPU page table is not valid then we need to fault */
 443         *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
 444         /* Need to write fault ? */
 445         if ((pfns & range->flags[HMM_PFN_WRITE]) &&
 446             !(cpu_flags & range->flags[HMM_PFN_WRITE])) {
 447                 *write_fault = true;
 448                 *fault = true;
 449         }
 450 }
 451
 452 static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 453                                  const uint64_t *pfns, unsigned long npages,
 454                                  uint64_t cpu_flags, bool *fault,
 455                                  bool *write_fault)
 456 {
 457         unsigned long i;
 458
 459         if (!hmm_vma_walk->fault) {
 460                 *fault = *write_fault = false;
 461                 return;
 462         }
 463
 464         *fault = *write_fault = false;
 465         for (i = 0; i < npages; ++i) {
 466                 hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
 467                                    fault, write_fault);
 468                 if ((*write_fault))
 469                         return;
 470         }
 471 }
 472
 473 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
 474                              struct mm_walk *walk)
 475 {
 476         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 477         struct hmm_range *range = hmm_vma_walk->range;
 478         bool fault, write_fault;
 479         unsigned long i, npages;
 480         uint64_t *pfns;
 481
 482         i = (addr - range->start) >> PAGE_SHIFT;
 483         npages = (end - addr) >> PAGE_SHIFT;
 484         pfns = &range->pfns[i];
 485         hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 486                              0, &fault, &write_fault);
 487         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 488 }
 489
 490 static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
 491 {
 492         if (pmd_protnone(pmd))
 493                 return 0;
 494         return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
 495                                 range->flags[HMM_PFN_WRITE] :
 496                                 range->flags[HMM_PFN_VALID];
 497 }
 498
 499 static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud)
 500 {
 501         if (!pud_present(pud))
 502                 return 0;
 503         return pud_write(pud) ? range->flags[HMM_PFN_VALID] |
 504                                 range->flags[HMM_PFN_WRITE] :
 505                                 range->flags[HMM_PFN_VALID];
 506 }
 507
 508 static int hmm_vma_handle_pmd(struct mm_walk *walk,
 509                               unsigned long addr,
 510                               unsigned long end,
 511                               uint64_t *pfns,
 512                               pmd_t pmd)
 513 {
 514 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 515         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 516         struct hmm_range *range = hmm_vma_walk->range;
 517         unsigned long pfn, npages, i;
 518         bool fault, write_fault;
 519         uint64_t cpu_flags;
 520
 521         npages = (end - addr) >> PAGE_SHIFT;
 522         cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
 523         hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
 524                              &fault, &write_fault);
 525
 526         if (pmd_protnone(pmd) || fault || write_fault)
 527                 return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 528
 529         pfn = pmd_pfn(pmd) + pte_index(addr);
 530         for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
 531                 if (pmd_devmap(pmd)) {
 532                         hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
 533                                               hmm_vma_walk->pgmap);
 534                         if (unlikely(!hmm_vma_walk->pgmap))
 535                                 return -EBUSY;
 536                 }
 537                 pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags;
 538         }
 539         if (hmm_vma_walk->pgmap) {
 540                 put_dev_pagemap(hmm_vma_walk->pgmap);
 541                 hmm_vma_walk->pgmap = NULL;
 542         }
 543         hmm_vma_walk->last = end;
 544         return 0;
 545 #else
 546         /* If THP is not enabled then we should never reach that code ! */
 547         return -EINVAL;
 548 #endif
 549 }
 550
 551 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
 552 {
 553         if (pte_none(pte) || !pte_present(pte))
 554                 return 0;
 555         return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
 556                                 range->flags[HMM_PFN_WRITE] :
 557                                 range->flags[HMM_PFN_VALID];
 558 }
 559
 560 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 561                               unsigned long end, pmd_t *pmdp, pte_t *ptep,
 562                               uint64_t *pfn)
 563 {
 564         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 565         struct hmm_range *range = hmm_vma_walk->range;
 566         struct vm_area_struct *vma = walk->vma;
 567         bool fault, write_fault;
 568         uint64_t cpu_flags;
 569         pte_t pte = *ptep;
 570         uint64_t orig_pfn = *pfn;
 571
 572         *pfn = range->values[HMM_PFN_NONE];
 573         fault = write_fault = false;
 574
 575         if (pte_none(pte)) {
 576                 hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0,
 577                                    &fault, &write_fault);
 578                 if (fault || write_fault)
 579                         goto fault;
 580                 return 0;
 581         }
 582
 583         if (!pte_present(pte)) {
 584                 swp_entry_t entry = pte_to_swp_entry(pte);
 585
 586                 if (!non_swap_entry(entry)) {
 587                         if (fault || write_fault)
 588                                 goto fault;
 589                         return 0;
 590                 }
 591
 592                 /*
 593                  * This is a special swap entry, ignore migration, use
 594                  * device and report anything else as error.
 595                  */
 596                 if (is_device_private_entry(entry)) {
 597                         cpu_flags = range->flags[HMM_PFN_VALID] |
 598                                 range->flags[HMM_PFN_DEVICE_PRIVATE];
 599                         cpu_flags |= is_write_device_private_entry(entry) ?
 600                                 range->flags[HMM_PFN_WRITE] : 0;
 601                         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 602                                            &fault, &write_fault);
 603                         if (fault || write_fault)
 604                                 goto fault;
 605                         *pfn = hmm_device_entry_from_pfn(range,
 606                                             swp_offset(entry));
 607                         *pfn |= cpu_flags;
 608                         return 0;
 609                 }
 610
 611                 if (is_migration_entry(entry)) {
 612                         if (fault || write_fault) {
 613                                 pte_unmap(ptep);
 614                                 hmm_vma_walk->last = addr;
 615                                 migration_entry_wait(vma->vm_mm,
 616                                                      pmdp, addr);
 617                                 return -EBUSY;
 618                         }
 619                         return 0;
 620                 }
 621
 622                 /* Report error for everything else */
 623                 *pfn = range->values[HMM_PFN_ERROR];
 624                 return -EFAULT;
 625         } else {
 626                 cpu_flags = pte_to_hmm_pfn_flags(range, pte);
 627                 hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 628                                    &fault, &write_fault);
 629         }
 630
 631         if (fault || write_fault)
 632                 goto fault;
 633
 634         if (pte_devmap(pte)) {
 635                 hmm_vma_walk->pgmap = get_dev_pagemap(pte_pfn(pte),
 636                                               hmm_vma_walk->pgmap);
 637                 if (unlikely(!hmm_vma_walk->pgmap))
 638                         return -EBUSY;
 639         } else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
 640                 *pfn = range->values[HMM_PFN_SPECIAL];
 641                 return -EFAULT;
 642         }
 643
 644         *pfn = hmm_device_entry_from_pfn(range, pte_pfn(pte)) | cpu_flags;
 645         return 0;
 646
 647 fault:
 648         if (hmm_vma_walk->pgmap) {
 649                 put_dev_pagemap(hmm_vma_walk->pgmap);
 650                 hmm_vma_walk->pgmap = NULL;
 651         }
 652         pte_unmap(ptep);
 653         /* Fault any virtual address we were asked to fault */
 654         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 655 }
 656
 657 static int hmm_vma_walk_pmd(pmd_t *pmdp,
 658                             unsigned long start,
 659                             unsigned long end,
 660                             struct mm_walk *walk)
 661 {
 662         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 663         struct hmm_range *range = hmm_vma_walk->range;
 664         struct vm_area_struct *vma = walk->vma;
 665         uint64_t *pfns = range->pfns;
 666         unsigned long addr = start, i;
 667         pte_t *ptep;
 668         pmd_t pmd;
 669
 670
 671 again:
 672         pmd = READ_ONCE(*pmdp);
 673         if (pmd_none(pmd))
 674                 return hmm_vma_walk_hole(start, end, walk);
 675
 676         if (pmd_huge(pmd) && (range->vma->vm_flags & VM_HUGETLB))
 677                 return hmm_pfns_bad(start, end, walk);
 678
 679         if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
 680                 bool fault, write_fault;
 681                 unsigned long npages;
 682                 uint64_t *pfns;
 683
 684                 i = (addr - range->start) >> PAGE_SHIFT;
 685                 npages = (end - addr) >> PAGE_SHIFT;
 686                 pfns = &range->pfns[i];
 687
 688                 hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 689                                      0, &fault, &write_fault);
 690                 if (fault || write_fault) {
 691                         hmm_vma_walk->last = addr;
 692                         pmd_migration_entry_wait(vma->vm_mm, pmdp);
 693                         return -EBUSY;
 694                 }
 695                 return 0;
 696         } else if (!pmd_present(pmd))
 697                 return hmm_pfns_bad(start, end, walk);
 698
 699         if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
 700                 /*
 701                  * No need to take pmd_lock here, even if some other threads
 702                  * is splitting the huge pmd we will get that event through
 703                  * mmu_notifier callback.
 704                  *
 705                  * So just read pmd value and check again its a transparent
 706                  * huge or device mapping one and compute corresponding pfn
 707                  * values.
 708                  */
 709                 pmd = pmd_read_atomic(pmdp);
 710                 barrier();
 711                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
 712                         goto again;
 713
 714                 i = (addr - range->start) >> PAGE_SHIFT;
 715                 return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
 716         }
 717
 718         /*
 719          * We have handled all the valid case above ie either none, migration,
 720          * huge or transparent huge. At this point either it is a valid pmd
 721          * entry pointing to pte directory or it is a bad pmd that will not
 722          * recover.
 723          */
 724         if (pmd_bad(pmd))
 725                 return hmm_pfns_bad(start, end, walk);
 726
 727         ptep = pte_offset_map(pmdp, addr);
 728         i = (addr - range->start) >> PAGE_SHIFT;
 729         for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
 730                 int r;
 731
 732                 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
 733                 if (r) {
 734                         /* hmm_vma_handle_pte() did unmap pte directory */
 735                         hmm_vma_walk->last = addr;
 736                         return r;
 737                 }
 738         }
 739         if (hmm_vma_walk->pgmap) {
 740                 /*
 741                  * We do put_dev_pagemap() here and not in hmm_vma_handle_pte()
 742                  * so that we can leverage get_dev_pagemap() optimization which
 743                  * will not re-take a reference on a pgmap if we already have
 744                  * one.
 745                  */
 746                 put_dev_pagemap(hmm_vma_walk->pgmap);
 747                 hmm_vma_walk->pgmap = NULL;
 748         }
 749         pte_unmap(ptep - 1);
 750
 751         hmm_vma_walk->last = addr;
 752         return 0;
 753 }
 754
 755 static int hmm_vma_walk_pud(pud_t *pudp,
 756                             unsigned long start,
 757                             unsigned long end,
 758                             struct mm_walk *walk)
 759 {
 760         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 761         struct hmm_range *range = hmm_vma_walk->range;
 762         unsigned long addr = start, next;
 763         pmd_t *pmdp;
 764         pud_t pud;
 765         int ret;
 766
 767 again:
 768         pud = READ_ONCE(*pudp);
 769         if (pud_none(pud))
 770                 return hmm_vma_walk_hole(start, end, walk);
 771
 772         if (pud_huge(pud) && pud_devmap(pud)) {
 773                 unsigned long i, npages, pfn;
 774                 uint64_t *pfns, cpu_flags;
 775                 bool fault, write_fault;
 776
 777                 if (!pud_present(pud))
 778                         return hmm_vma_walk_hole(start, end, walk);
 779
 780                 i = (addr - range->start) >> PAGE_SHIFT;
 781                 npages = (end - addr) >> PAGE_SHIFT;
 782                 pfns = &range->pfns[i];
 783
 784                 cpu_flags = pud_to_hmm_pfn_flags(range, pud);
 785                 hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 786                                      cpu_flags, &fault, &write_fault);
 787                 if (fault || write_fault)
 788                         return hmm_vma_walk_hole_(addr, end, fault,
 789                                                 write_fault, walk);
 790
 791 #ifdef CONFIG_HUGETLB_PAGE
 792                 pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 793                 for (i = 0; i < npages; ++i, ++pfn) {
 794                         hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
 795                                               hmm_vma_walk->pgmap);
 796                         if (unlikely(!hmm_vma_walk->pgmap))
 797                                 return -EBUSY;
 798                         pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 799                                   cpu_flags;
 800                 }
 801                 if (hmm_vma_walk->pgmap) {
 802                         put_dev_pagemap(hmm_vma_walk->pgmap);
 803                         hmm_vma_walk->pgmap = NULL;
 804                 }
 805                 hmm_vma_walk->last = end;
 806                 return 0;
 807 #else
 808                 return -EINVAL;
 809 #endif
 810         }
 811
 812         split_huge_pud(walk->vma, pudp, addr);
 813         if (pud_none(*pudp))
 814                 goto again;
 815
 816         pmdp = pmd_offset(pudp, addr);
 817         do {
 818                 next = pmd_addr_end(addr, end);
 819                 ret = hmm_vma_walk_pmd(pmdp, addr, next, walk);
 820                 if (ret)
 821                         return ret;
 822         } while (pmdp++, addr = next, addr != end);
 823
 824         return 0;
 825 }
 826
 827 static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 828                                       unsigned long start, unsigned long end,
 829                                       struct mm_walk *walk)
 830 {
 831 #ifdef CONFIG_HUGETLB_PAGE
 832         unsigned long addr = start, i, pfn, mask, size, pfn_inc;
 833         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 834         struct hmm_range *range = hmm_vma_walk->range;
 835         struct vm_area_struct *vma = walk->vma;
 836         struct hstate *h = hstate_vma(vma);
 837         uint64_t orig_pfn, cpu_flags;
 838         bool fault, write_fault;
 839         spinlock_t *ptl;
 840         pte_t entry;
 841         int ret = 0;
 842
 843         size = 1UL << huge_page_shift(h);
 844         mask = size - 1;
 845         if (range->page_shift != PAGE_SHIFT) {
 846                 /* Make sure we are looking at full page. */
 847                 if (start & mask)
 848                         return -EINVAL;
 849                 if (end < (start + size))
 850                         return -EINVAL;
 851                 pfn_inc = size >> PAGE_SHIFT;
 852         } else {
 853                 pfn_inc = 1;
 854                 size = PAGE_SIZE;
 855         }
 856
 857
 858         ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
 859         entry = huge_ptep_get(pte);
 860
 861         i = (start - range->start) >> range->page_shift;
 862         orig_pfn = range->pfns[i];
 863         range->pfns[i] = range->values[HMM_PFN_NONE];
 864         cpu_flags = pte_to_hmm_pfn_flags(range, entry);
 865         fault = write_fault = false;
 866         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 867                            &fault, &write_fault);
 868         if (fault || write_fault) {
 869                 ret = -ENOENT;
 870                 goto unlock;
 871         }
 872
 873         pfn = pte_pfn(entry) + ((start & mask) >> range->page_shift);
 874         for (; addr < end; addr += size, i++, pfn += pfn_inc)
 875                 range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 876                                  cpu_flags;
 877         hmm_vma_walk->last = end;
 878
 879 unlock:
 880         spin_unlock(ptl);
 881
 882         if (ret == -ENOENT)
 883                 return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 884
 885         return ret;
 886 #else /* CONFIG_HUGETLB_PAGE */
 887         return -EINVAL;
 888 #endif
 889 }
 890
 891 static void hmm_pfns_clear(struct hmm_range *range,
 892                            uint64_t *pfns,
 893                            unsigned long addr,
 894                            unsigned long end)
 895 {
 896         for (; addr < end; addr += PAGE_SIZE, pfns++)
 897                 *pfns = range->values[HMM_PFN_NONE];
 898 }
 899
 900 /*
 901  * hmm_range_register() - start tracking change to CPU page table over a range
 902  * @range: range
 903  * @mm: the mm struct for the range of virtual address
 904  * @start: start virtual address (inclusive)
 905  * @end: end virtual address (exclusive)
 906  * @page_shift: expect page shift for the range
 907  * Returns 0 on success, -EFAULT if the address space is no longer valid
 908  *
 909  * Track updates to the CPU page table see include/linux/hmm.h
 910  */
 911 int hmm_range_register(struct hmm_range *range,
 912                        struct mm_struct *mm,
 913                        unsigned long start,
 914                        unsigned long end,
 915                        unsigned page_shift)
 916 {
 917         unsigned long mask = ((1UL << page_shift) - 1UL);
 918
 919         range->valid = false;
 920         range->hmm = NULL;
 921
 922         if ((start & mask) || (end & mask))
 923                 return -EINVAL;
 924         if (start >= end)
 925                 return -EINVAL;
 926
 927         range->page_shift = page_shift;
 928         range->start = start;
 929         range->end = end;
 930
 931         range->hmm = hmm_get_or_create(mm);
 932         if (!range->hmm)
 933                 return -EFAULT;
 934
 935         /* Check if hmm_mm_destroy() was call. */
 936         if (range->hmm->mm == NULL || range->hmm->dead) {
 937                 hmm_put(range->hmm);
 938                 return -EFAULT;
 939         }
 940
 941         /* Initialize range to track CPU page table update */
 942         mutex_lock(&range->hmm->lock);
 943
 944         list_add_rcu(&range->list, &range->hmm->ranges);
 945
 946         /*
 947          * If there are any concurrent notifiers we have to wait for them for
 948          * the range to be valid (see hmm_range_wait_until_valid()).
 949          */
 950         if (!range->hmm->notifiers)
 951                 range->valid = true;
 952         mutex_unlock(&range->hmm->lock);
 953
 954         return 0;
 955 }
 956 EXPORT_SYMBOL(hmm_range_register);
 957
 958 /*
 959  * hmm_range_unregister() - stop tracking change to CPU page table over a range
 960  * @range: range
 961  *
 962  * Range struct is used to track updates to the CPU page table after a call to
 963  * hmm_range_register(). See include/linux/hmm.h for how to use it.
 964  */
 965 void hmm_range_unregister(struct hmm_range *range)
 966 {
 967         /* Sanity check this really should not happen. */
 968         if (range->hmm == NULL || range->end <= range->start)
 969                 return;
 970
 971         mutex_lock(&range->hmm->lock);
 972         list_del_rcu(&range->list);
 973         mutex_unlock(&range->hmm->lock);
 974
 975         /* Drop reference taken by hmm_range_register() */
 976         range->valid = false;
 977         hmm_put(range->hmm);
 978         range->hmm = NULL;
 979 }
 980 EXPORT_SYMBOL(hmm_range_unregister);
 981
 982 /*
 983  * hmm_range_snapshot() - snapshot CPU page table for a range
 984  * @range: range
 985  * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
 986  *          permission (for instance asking for write and range is read only),
 987  *          -EAGAIN if you need to retry, -EFAULT invalid (ie either no valid
 988  *          vma or it is illegal to access that range), number of valid pages
 989  *          in range->pfns[] (from range start address).
 990  *
 991  * This snapshots the CPU page table for a range of virtual addresses. Snapshot
 992  * validity is tracked by range struct. See in include/linux/hmm.h for example
 993  * on how to use.
 994  */
 995 long hmm_range_snapshot(struct hmm_range *range)
 996 {
 997         const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
 998         unsigned long start = range->start, end;
 999         struct hmm_vma_walk hmm_vma_walk;
1000         struct hmm *hmm = range->hmm;
1001         struct vm_area_struct *vma;
1002         struct mm_walk mm_walk;
1003
1004         /* Check if hmm_mm_destroy() was call. */
1005         if (hmm->mm == NULL || hmm->dead)
1006                 return -EFAULT;
1007
1008         do {
1009                 /* If range is no longer valid force retry. */
1010                 if (!range->valid)
1011                         return -EAGAIN;
1012
1013                 vma = find_vma(hmm->mm, start);
1014                 if (vma == NULL || (vma->vm_flags & device_vma))
1015                         return -EFAULT;
1016
1017                 if (is_vm_hugetlb_page(vma)) {
1018                         struct hstate *h = hstate_vma(vma);
1019
1020                         if (huge_page_shift(h) != range->page_shift &&
1021                             range->page_shift != PAGE_SHIFT)
1022                                 return -EINVAL;
1023                 } else {
1024                         if (range->page_shift != PAGE_SHIFT)
1025                                 return -EINVAL;
1026                 }
1027
1028                 if (!(vma->vm_flags & VM_READ)) {
1029                         /*
1030                          * If vma do not allow read access, then assume that it
1031                          * does not allow write access, either. HMM does not
1032                          * support architecture that allow write without read.
1033                          */
1034                         hmm_pfns_clear(range, range->pfns,
1035                                 range->start, range->end);
1036                         return -EPERM;
1037                 }
1038
1039                 range->vma = vma;
1040                 hmm_vma_walk.pgmap = NULL;
1041                 hmm_vma_walk.last = start;
1042                 hmm_vma_walk.fault = false;
1043                 hmm_vma_walk.range = range;
1044                 mm_walk.private = &hmm_vma_walk;
1045                 end = min(range->end, vma->vm_end);
1046
1047                 mm_walk.vma = vma;
1048                 mm_walk.mm = vma->vm_mm;
1049                 mm_walk.pte_entry = NULL;
1050                 mm_walk.test_walk = NULL;
1051                 mm_walk.hugetlb_entry = NULL;
1052                 mm_walk.pud_entry = hmm_vma_walk_pud;
1053                 mm_walk.pmd_entry = hmm_vma_walk_pmd;
1054                 mm_walk.pte_hole = hmm_vma_walk_hole;
1055                 mm_walk.hugetlb_entry = hmm_vma_walk_hugetlb_entry;
1056
1057                 walk_page_range(start, end, &mm_walk);
1058                 start = end;
1059         } while (start < range->end);
1060
1061         return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
1062 }
1063 EXPORT_SYMBOL(hmm_range_snapshot);
1064
1065 /*
1066  * hmm_range_fault() - try to fault some address in a virtual address range
1067  * @range: range being faulted
1068  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
1069  * Returns: number of valid pages in range->pfns[] (from range start
1070  *          address). This may be zero. If the return value is negative,
1071  *          then one of the following values may be returned:
1072  *
1073  *           -EINVAL  invalid arguments or mm or virtual address are in an
1074  *                    invalid vma (for instance device file vma).
1075  *           -ENOMEM: Out of memory.
1076  *           -EPERM:  Invalid permission (for instance asking for write and
1077  *                    range is read only).
1078  *           -EAGAIN: If you need to retry and mmap_sem was drop. This can only
1079  *                    happens if block argument is false.
1080  *           -EBUSY:  If the the range is being invalidated and you should wait
1081  *                    for invalidation to finish.
1082  *           -EFAULT: Invalid (ie either no valid vma or it is illegal to access
1083  *                    that range), number of valid pages in range->pfns[] (from
1084  *                    range start address).
1085  *
1086  * This is similar to a regular CPU page fault except that it will not trigger
1087  * any memory migration if the memory being faulted is not accessible by CPUs
1088  * and caller does not ask for migration.
1089  *
1090  * On error, for one virtual address in the range, the function will mark the
1091  * corresponding HMM pfn entry with an error flag.
1092  */
1093 long hmm_range_fault(struct hmm_range *range, bool block)
1094 {
1095         const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
1096         unsigned long start = range->start, end;
1097         struct hmm_vma_walk hmm_vma_walk;
1098         struct hmm *hmm = range->hmm;
1099         struct vm_area_struct *vma;
1100         struct mm_walk mm_walk;
1101         int ret;
1102
1103         /* Check if hmm_mm_destroy() was call. */
1104         if (hmm->mm == NULL || hmm->dead)
1105                 return -EFAULT;
1106
1107         do {
1108                 /* If range is no longer valid force retry. */
1109                 if (!range->valid) {
1110                         up_read(&hmm->mm->mmap_sem);
1111                         return -EAGAIN;
1112                 }
1113
1114                 vma = find_vma(hmm->mm, start);
1115                 if (vma == NULL || (vma->vm_flags & device_vma))
1116                         return -EFAULT;
1117
1118                 if (is_vm_hugetlb_page(vma)) {
1119                         if (huge_page_shift(hstate_vma(vma)) !=
1120                             range->page_shift &&
1121                             range->page_shift != PAGE_SHIFT)
1122                                 return -EINVAL;
1123                 } else {
1124                         if (range->page_shift != PAGE_SHIFT)
1125                                 return -EINVAL;
1126                 }
1127
1128                 if (!(vma->vm_flags & VM_READ)) {
1129                         /*
1130                          * If vma do not allow read access, then assume that it
1131                          * does not allow write access, either. HMM does not
1132                          * support architecture that allow write without read.
1133                          */
1134                         hmm_pfns_clear(range, range->pfns,
1135                                 range->start, range->end);
1136                         return -EPERM;
1137                 }
1138
1139                 range->vma = vma;
1140                 hmm_vma_walk.pgmap = NULL;
1141                 hmm_vma_walk.last = start;
1142                 hmm_vma_walk.fault = true;
1143                 hmm_vma_walk.block = block;
1144                 hmm_vma_walk.range = range;
1145                 mm_walk.private = &hmm_vma_walk;
1146                 end = min(range->end, vma->vm_end);
1147
1148                 mm_walk.vma = vma;
1149                 mm_walk.mm = vma->vm_mm;
1150                 mm_walk.pte_entry = NULL;
1151                 mm_walk.test_walk = NULL;
1152                 mm_walk.hugetlb_entry = NULL;
1153                 mm_walk.pud_entry = hmm_vma_walk_pud;
1154                 mm_walk.pmd_entry = hmm_vma_walk_pmd;
1155                 mm_walk.pte_hole = hmm_vma_walk_hole;
1156                 mm_walk.hugetlb_entry = hmm_vma_walk_hugetlb_entry;
1157
1158                 do {
1159                         ret = walk_page_range(start, end, &mm_walk);
1160                         start = hmm_vma_walk.last;
1161
1162                         /* Keep trying while the range is valid. */
1163                 } while (ret == -EBUSY && range->valid);
1164
1165                 if (ret) {
1166                         unsigned long i;
1167
1168                         i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
1169                         hmm_pfns_clear(range, &range->pfns[i],
1170                                 hmm_vma_walk.last, range->end);
1171                         return ret;
1172                 }
1173                 start = end;
1174
1175         } while (start < range->end);
1176
1177         return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
1178 }
1179 EXPORT_SYMBOL(hmm_range_fault);
1180
1181 /**
1182  * hmm_range_dma_map() - hmm_range_fault() and dma map page all in one.
1183  * @range: range being faulted
1184  * @device: device against to dma map page to
1185  * @daddrs: dma address of mapped pages
1186  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
1187  * Returns: number of pages mapped on success, -EAGAIN if mmap_sem have been
1188  *          drop and you need to try again, some other error value otherwise
1189  *
1190  * Note same usage pattern as hmm_range_fault().
1191  */
1192 long hmm_range_dma_map(struct hmm_range *range,
1193                        struct device *device,
1194                        dma_addr_t *daddrs,
1195                        bool block)
1196 {
1197         unsigned long i, npages, mapped;
1198         long ret;
1199
1200         ret = hmm_range_fault(range, block);
1201         if (ret <= 0)
1202                 return ret ? ret : -EBUSY;
1203
1204         npages = (range->end - range->start) >> PAGE_SHIFT;
1205         for (i = 0, mapped = 0; i < npages; ++i) {
1206                 enum dma_data_direction dir = DMA_TO_DEVICE;
1207                 struct page *page;
1208
1209                 /*
1210                  * FIXME need to update DMA API to provide invalid DMA address
1211                  * value instead of a function to test dma address value. This
1212                  * would remove lot of dumb code duplicated accross many arch.
1213                  *
1214                  * For now setting it to 0 here is good enough as the pfns[]
1215                  * value is what is use to check what is valid and what isn't.
1216                  */
1217                 daddrs[i] = 0;
1218
1219                 page = hmm_device_entry_to_page(range, range->pfns[i]);
1220                 if (page == NULL)
1221                         continue;
1222
1223                 /* Check if range is being invalidated */
1224                 if (!range->valid) {
1225                         ret = -EBUSY;
1226                         goto unmap;
1227                 }
1228
1229                 /* If it is read and write than map bi-directional. */
1230                 if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
1231                         dir = DMA_BIDIRECTIONAL;
1232
1233                 daddrs[i] = dma_map_page(device, page, 0, PAGE_SIZE, dir);
1234                 if (dma_mapping_error(device, daddrs[i])) {
1235                         ret = -EFAULT;
1236                         goto unmap;
1237                 }
1238
1239                 mapped++;
1240         }
1241
1242         return mapped;
1243
1244 unmap:
1245         for (npages = i, i = 0; (i < npages) && mapped; ++i) {
1246                 enum dma_data_direction dir = DMA_TO_DEVICE;
1247                 struct page *page;
1248
1249                 page = hmm_device_entry_to_page(range, range->pfns[i]);
1250                 if (page == NULL)
1251                         continue;
1252
1253                 if (dma_mapping_error(device, daddrs[i]))
1254                         continue;
1255
1256                 /* If it is read and write than map bi-directional. */
1257                 if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
1258                         dir = DMA_BIDIRECTIONAL;
1259
1260                 dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
1261                 mapped--;
1262         }
1263
1264         return ret;
1265 }
1266 EXPORT_SYMBOL(hmm_range_dma_map);
1267
1268 /**
1269  * hmm_range_dma_unmap() - unmap range of that was map with hmm_range_dma_map()
1270  * @range: range being unmapped
1271  * @vma: the vma against which the range (optional)
1272  * @device: device against which dma map was done
1273  * @daddrs: dma address of mapped pages
1274  * @dirty: dirty page if it had the write flag set
1275  * Returns: number of page unmapped on success, -EINVAL otherwise
1276  *
1277  * Note that caller MUST abide by mmu notifier or use HMM mirror and abide
1278  * to the sync_cpu_device_pagetables() callback so that it is safe here to
1279  * call set_page_dirty(). Caller must also take appropriate locks to avoid
1280  * concurrent mmu notifier or sync_cpu_device_pagetables() to make progress.
1281  */
1282 long hmm_range_dma_unmap(struct hmm_range *range,
1283                          struct vm_area_struct *vma,
1284                          struct device *device,
1285                          dma_addr_t *daddrs,
1286                          bool dirty)
1287 {
1288         unsigned long i, npages;
1289         long cpages = 0;
1290
1291         /* Sanity check. */
1292         if (range->end <= range->start)
1293                 return -EINVAL;
1294         if (!daddrs)
1295                 return -EINVAL;
1296         if (!range->pfns)
1297                 return -EINVAL;
1298
1299         npages = (range->end - range->start) >> PAGE_SHIFT;
1300         for (i = 0; i < npages; ++i) {
1301                 enum dma_data_direction dir = DMA_TO_DEVICE;
1302                 struct page *page;
1303
1304                 page = hmm_device_entry_to_page(range, range->pfns[i]);
1305                 if (page == NULL)
1306                         continue;
1307
1308                 /* If it is read and write than map bi-directional. */
1309                 if (range->pfns[i] & range->flags[HMM_PFN_WRITE]) {
1310                         dir = DMA_BIDIRECTIONAL;
1311
1312                         /*
1313                          * See comments in function description on why it is
1314                          * safe here to call set_page_dirty()
1315                          */
1316                         if (dirty)
1317                                 set_page_dirty(page);
1318                 }
1319
1320                 /* Unmap and clear pfns/dma address */
1321                 dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
1322                 range->pfns[i] = range->values[HMM_PFN_NONE];
1323                 /* FIXME see comments in hmm_vma_dma_map() */
1324                 daddrs[i] = 0;
1325                 cpages++;
1326         }
1327
1328         return cpages;
1329 }
1330 EXPORT_SYMBOL(hmm_range_dma_unmap);
1331 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
1332
1333
1334 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
1335 struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
1336                                        unsigned long addr)
1337 {
1338         struct page *page;
1339
1340         page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
1341         if (!page)
1342                 return NULL;
1343         lock_page(page);
1344         return page;
1345 }
1346 EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
1347
1348
1349 static void hmm_devmem_ref_release(struct percpu_ref *ref)
1350 {
1351         struct hmm_devmem *devmem;
1352
1353         devmem = container_of(ref, struct hmm_devmem, ref);
1354         complete(&devmem->completion);
1355 }
1356
1357 static void hmm_devmem_ref_exit(struct percpu_ref *ref)
1358 {
1359         struct hmm_devmem *devmem;
1360
1361         devmem = container_of(ref, struct hmm_devmem, ref);
1362         wait_for_completion(&devmem->completion);
1363         percpu_ref_exit(ref);
1364 }
1365
1366 static void hmm_devmem_ref_kill(struct percpu_ref *ref)
1367 {
1368         percpu_ref_kill(ref);
1369 }
1370
1371 static vm_fault_t hmm_devmem_fault(struct vm_area_struct *vma,
1372                             unsigned long addr,
1373                             const struct page *page,
1374                             unsigned int flags,
1375                             pmd_t *pmdp)
1376 {
1377         struct hmm_devmem *devmem = page->pgmap->data;
1378
1379         return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
1380 }
1381
1382 static void hmm_devmem_free(struct page *page, void *data)
1383 {
1384         struct hmm_devmem *devmem = data;
1385
1386         page->mapping = NULL;
1387
1388         devmem->ops->free(devmem, page);
1389 }
1390
1391 /*
1392  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
1393  *
1394  * @ops: memory event device driver callback (see struct hmm_devmem_ops)
1395  * @device: device struct to bind the resource too
1396  * @size: size in bytes of the device memory to add
1397  * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
1398  *
1399  * This function first finds an empty range of physical address big enough to
1400  * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
1401  * in turn allocates struct pages. It does not do anything beyond that; all
1402  * events affecting the memory will go through the various callbacks provided
1403  * by hmm_devmem_ops struct.
1404  *
1405  * Device driver should call this function during device initialization and
1406  * is then responsible of memory management. HMM only provides helpers.
1407  */
1408 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
1409                                   struct device *device,
1410                                   unsigned long size)
1411 {
1412         struct hmm_devmem *devmem;
1413         resource_size_t addr;
1414         void *result;
1415         int ret;
1416
1417         dev_pagemap_get_ops();
1418
1419         devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
1420         if (!devmem)
1421                 return ERR_PTR(-ENOMEM);
1422
1423         init_completion(&devmem->completion);
1424         devmem->pfn_first = -1UL;
1425         devmem->pfn_last = -1UL;
1426         devmem->resource = NULL;
1427         devmem->device = device;
1428         devmem->ops = ops;
1429
1430         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1431                               0, GFP_KERNEL);
1432         if (ret)
1433                 return ERR_PTR(ret);
1434
1435         size = ALIGN(size, PA_SECTION_SIZE);
1436         addr = min((unsigned long)iomem_resource.end,
1437                    (1UL << MAX_PHYSMEM_BITS) - 1);
1438         addr = addr - size + 1UL;
1439
1440         /*
1441          * FIXME add a new helper to quickly walk resource tree and find free
1442          * range
1443          *
1444          * FIXME what about ioport_resource resource ?
1445          */
1446         for (; addr > size && addr >= iomem_resource.start; addr -= size) {
1447                 ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
1448                 if (ret != REGION_DISJOINT)
1449                         continue;
1450
1451                 devmem->resource = devm_request_mem_region(device, addr, size,
1452                                                            dev_name(device));
1453                 if (!devmem->resource)
1454                         return ERR_PTR(-ENOMEM);
1455                 break;
1456         }
1457         if (!devmem->resource)
1458                 return ERR_PTR(-ERANGE);
1459
1460         devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
1461         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1462         devmem->pfn_last = devmem->pfn_first +
1463                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1464         devmem->page_fault = hmm_devmem_fault;
1465
1466         devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
1467         devmem->pagemap.res = *devmem->resource;
1468         devmem->pagemap.page_free = hmm_devmem_free;
1469         devmem->pagemap.altmap_valid = false;
1470         devmem->pagemap.ref = &devmem->ref;
1471         devmem->pagemap.data = devmem;
1472         devmem->pagemap.kill = hmm_devmem_ref_kill;
1473         devmem->pagemap.cleanup = hmm_devmem_ref_exit;
1474
1475         result = devm_memremap_pages(devmem->device, &devmem->pagemap);
1476         if (IS_ERR(result))
1477                 return result;
1478         return devmem;
1479 }
1480 EXPORT_SYMBOL_GPL(hmm_devmem_add);
1481 #endif /* CONFIG_DEVICE_PRIVATE  */