mm/hmm.c

   1 /*
   2  * Copyright 2013 Red Hat Inc.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * Authors: JÃ©rÃ´me Glisse <jglisse@redhat.com>
  15  */
  16 /*
  17  * Refer to include/linux/hmm.h for information about heterogeneous memory
  18  * management or HMM for short.
  19  */
  20 #include <linux/mm.h>
  21 #include <linux/hmm.h>
  22 #include <linux/init.h>
  23 #include <linux/rmap.h>
  24 #include <linux/swap.h>
  25 #include <linux/slab.h>
  26 #include <linux/sched.h>
  27 #include <linux/mmzone.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/swapops.h>
  30 #include <linux/hugetlb.h>
  31 #include <linux/memremap.h>
  32 #include <linux/jump_label.h>
  33 #include <linux/mmu_notifier.h>
  34 #include <linux/memory_hotplug.h>
  35
  36 #define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
  37
  38 #if IS_ENABLED(CONFIG_HMM_MIRROR)
  39 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
  40
  41 /*
  42  * struct hmm - HMM per mm struct
  43  *
  44  * @mm: mm struct this HMM struct is bound to
  45  * @lock: lock protecting ranges list
  46  * @sequence: we track updates to the CPU page table with a sequence number
  47  * @ranges: list of range being snapshotted
  48  * @mirrors: list of mirrors for this mm
  49  * @mmu_notifier: mmu notifier to track updates to CPU page table
  50  * @mirrors_sem: read/write semaphore protecting the mirrors list
  51  */
  52 struct hmm {
  53         struct mm_struct        *mm;
  54         spinlock_t              lock;
  55         atomic_t                sequence;
  56         struct list_head        ranges;
  57         struct list_head        mirrors;
  58         struct mmu_notifier     mmu_notifier;
  59         struct rw_semaphore     mirrors_sem;
  60 };
  61
  62 /*
  63  * hmm_register - register HMM against an mm (HMM internal)
  64  *
  65  * @mm: mm struct to attach to
  66  *
  67  * This is not intended to be used directly by device drivers. It allocates an
  68  * HMM struct if mm does not have one, and initializes it.
  69  */
  70 static struct hmm *hmm_register(struct mm_struct *mm)
  71 {
  72         struct hmm *hmm = READ_ONCE(mm->hmm);
  73         bool cleanup = false;
  74
  75         /*
  76          * The hmm struct can only be freed once the mm_struct goes away,
  77          * hence we should always have pre-allocated an new hmm struct
  78          * above.
  79          */
  80         if (hmm)
  81                 return hmm;
  82
  83         hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
  84         if (!hmm)
  85                 return NULL;
  86         INIT_LIST_HEAD(&hmm->mirrors);
  87         init_rwsem(&hmm->mirrors_sem);
  88         atomic_set(&hmm->sequence, 0);
  89         hmm->mmu_notifier.ops = NULL;
  90         INIT_LIST_HEAD(&hmm->ranges);
  91         spin_lock_init(&hmm->lock);
  92         hmm->mm = mm;
  93
  94         spin_lock(&mm->page_table_lock);
  95         if (!mm->hmm)
  96                 mm->hmm = hmm;
  97         else
  98                 cleanup = true;
  99         spin_unlock(&mm->page_table_lock);
 100
 101         if (cleanup)
 102                 goto error;
 103
 104         /*
 105          * We should only get here if hold the mmap_sem in write mode ie on
 106          * registration of first mirror through hmm_mirror_register()
 107          */
 108         hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
 109         if (__mmu_notifier_register(&hmm->mmu_notifier, mm))
 110                 goto error_mm;
 111
 112         return mm->hmm;
 113
 114 error_mm:
 115         spin_lock(&mm->page_table_lock);
 116         if (mm->hmm == hmm)
 117                 mm->hmm = NULL;
 118         spin_unlock(&mm->page_table_lock);
 119 error:
 120         kfree(hmm);
 121         return NULL;
 122 }
 123
 124 void hmm_mm_destroy(struct mm_struct *mm)
 125 {
 126         kfree(mm->hmm);
 127 }
 128
 129 static void hmm_invalidate_range(struct hmm *hmm,
 130                                  enum hmm_update_type action,
 131                                  unsigned long start,
 132                                  unsigned long end)
 133 {
 134         struct hmm_mirror *mirror;
 135         struct hmm_range *range;
 136
 137         spin_lock(&hmm->lock);
 138         list_for_each_entry(range, &hmm->ranges, list) {
 139                 unsigned long addr, idx, npages;
 140
 141                 if (end < range->start || start >= range->end)
 142                         continue;
 143
 144                 range->valid = false;
 145                 addr = max(start, range->start);
 146                 idx = (addr - range->start) >> PAGE_SHIFT;
 147                 npages = (min(range->end, end) - addr) >> PAGE_SHIFT;
 148                 memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
 149         }
 150         spin_unlock(&hmm->lock);
 151
 152         down_read(&hmm->mirrors_sem);
 153         list_for_each_entry(mirror, &hmm->mirrors, list)
 154                 mirror->ops->sync_cpu_device_pagetables(mirror, action,
 155                                                         start, end);
 156         up_read(&hmm->mirrors_sem);
 157 }
 158
 159 static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 160 {
 161         struct hmm_mirror *mirror;
 162         struct hmm *hmm = mm->hmm;
 163
 164         down_write(&hmm->mirrors_sem);
 165         mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
 166                                           list);
 167         while (mirror) {
 168                 list_del_init(&mirror->list);
 169                 if (mirror->ops->release) {
 170                         /*
 171                          * Drop mirrors_sem so callback can wait on any pending
 172                          * work that might itself trigger mmu_notifier callback
 173                          * and thus would deadlock with us.
 174                          */
 175                         up_write(&hmm->mirrors_sem);
 176                         mirror->ops->release(mirror);
 177                         down_write(&hmm->mirrors_sem);
 178                 }
 179                 mirror = list_first_entry_or_null(&hmm->mirrors,
 180                                                   struct hmm_mirror, list);
 181         }
 182         up_write(&hmm->mirrors_sem);
 183 }
 184
 185 static int hmm_invalidate_range_start(struct mmu_notifier *mn,
 186                                        struct mm_struct *mm,
 187                                        unsigned long start,
 188                                        unsigned long end,
 189                                        bool blockable)
 190 {
 191         struct hmm *hmm = mm->hmm;
 192
 193         VM_BUG_ON(!hmm);
 194
 195         atomic_inc(&hmm->sequence);
 196
 197         return 0;
 198 }
 199
 200 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
 201                                      struct mm_struct *mm,
 202                                      unsigned long start,
 203                                      unsigned long end)
 204 {
 205         struct hmm *hmm = mm->hmm;
 206
 207         VM_BUG_ON(!hmm);
 208
 209         hmm_invalidate_range(mm->hmm, HMM_UPDATE_INVALIDATE, start, end);
 210 }
 211
 212 static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
 213         .release                = hmm_release,
 214         .invalidate_range_start = hmm_invalidate_range_start,
 215         .invalidate_range_end   = hmm_invalidate_range_end,
 216 };
 217
 218 /*
 219  * hmm_mirror_register() - register a mirror against an mm
 220  *
 221  * @mirror: new mirror struct to register
 222  * @mm: mm to register against
 223  *
 224  * To start mirroring a process address space, the device driver must register
 225  * an HMM mirror struct.
 226  *
 227  * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
 228  */
 229 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
 230 {
 231         /* Sanity check */
 232         if (!mm || !mirror || !mirror->ops)
 233                 return -EINVAL;
 234
 235 again:
 236         mirror->hmm = hmm_register(mm);
 237         if (!mirror->hmm)
 238                 return -ENOMEM;
 239
 240         down_write(&mirror->hmm->mirrors_sem);
 241         if (mirror->hmm->mm == NULL) {
 242                 /*
 243                  * A racing hmm_mirror_unregister() is about to destroy the hmm
 244                  * struct. Try again to allocate a new one.
 245                  */
 246                 up_write(&mirror->hmm->mirrors_sem);
 247                 mirror->hmm = NULL;
 248                 goto again;
 249         } else {
 250                 list_add(&mirror->list, &mirror->hmm->mirrors);
 251                 up_write(&mirror->hmm->mirrors_sem);
 252         }
 253
 254         return 0;
 255 }
 256 EXPORT_SYMBOL(hmm_mirror_register);
 257
 258 /*
 259  * hmm_mirror_unregister() - unregister a mirror
 260  *
 261  * @mirror: new mirror struct to register
 262  *
 263  * Stop mirroring a process address space, and cleanup.
 264  */
 265 void hmm_mirror_unregister(struct hmm_mirror *mirror)
 266 {
 267         bool should_unregister = false;
 268         struct mm_struct *mm;
 269         struct hmm *hmm;
 270
 271         if (mirror->hmm == NULL)
 272                 return;
 273
 274         hmm = mirror->hmm;
 275         down_write(&hmm->mirrors_sem);
 276         list_del_init(&mirror->list);
 277         should_unregister = list_empty(&hmm->mirrors);
 278         mirror->hmm = NULL;
 279         mm = hmm->mm;
 280         hmm->mm = NULL;
 281         up_write(&hmm->mirrors_sem);
 282
 283         if (!should_unregister || mm == NULL)
 284                 return;
 285
 286         mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
 287
 288         spin_lock(&mm->page_table_lock);
 289         if (mm->hmm == hmm)
 290                 mm->hmm = NULL;
 291         spin_unlock(&mm->page_table_lock);
 292
 293         kfree(hmm);
 294 }
 295 EXPORT_SYMBOL(hmm_mirror_unregister);
 296
 297 struct hmm_vma_walk {
 298         struct hmm_range        *range;
 299         unsigned long           last;
 300         bool                    fault;
 301         bool                    block;
 302 };
 303
 304 static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
 305                             bool write_fault, uint64_t *pfn)
 306 {
 307         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
 308         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 309         struct hmm_range *range = hmm_vma_walk->range;
 310         struct vm_area_struct *vma = walk->vma;
 311         vm_fault_t ret;
 312
 313         flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
 314         flags |= write_fault ? FAULT_FLAG_WRITE : 0;
 315         ret = handle_mm_fault(vma, addr, flags);
 316         if (ret & VM_FAULT_RETRY)
 317                 return -EBUSY;
 318         if (ret & VM_FAULT_ERROR) {
 319                 *pfn = range->values[HMM_PFN_ERROR];
 320                 return -EFAULT;
 321         }
 322
 323         return -EAGAIN;
 324 }
 325
 326 static int hmm_pfns_bad(unsigned long addr,
 327                         unsigned long end,
 328                         struct mm_walk *walk)
 329 {
 330         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 331         struct hmm_range *range = hmm_vma_walk->range;
 332         uint64_t *pfns = range->pfns;
 333         unsigned long i;
 334
 335         i = (addr - range->start) >> PAGE_SHIFT;
 336         for (; addr < end; addr += PAGE_SIZE, i++)
 337                 pfns[i] = range->values[HMM_PFN_ERROR];
 338
 339         return 0;
 340 }
 341
 342 /*
 343  * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
 344  * @start: range virtual start address (inclusive)
 345  * @end: range virtual end address (exclusive)
 346  * @fault: should we fault or not ?
 347  * @write_fault: write fault ?
 348  * @walk: mm_walk structure
 349  * Returns: 0 on success, -EAGAIN after page fault, or page fault error
 350  *
 351  * This function will be called whenever pmd_none() or pte_none() returns true,
 352  * or whenever there is no page directory covering the virtual address range.
 353  */
 354 static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
 355                               bool fault, bool write_fault,
 356                               struct mm_walk *walk)
 357 {
 358         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 359         struct hmm_range *range = hmm_vma_walk->range;
 360         uint64_t *pfns = range->pfns;
 361         unsigned long i;
 362
 363         hmm_vma_walk->last = addr;
 364         i = (addr - range->start) >> PAGE_SHIFT;
 365         for (; addr < end; addr += PAGE_SIZE, i++) {
 366                 pfns[i] = range->values[HMM_PFN_NONE];
 367                 if (fault || write_fault) {
 368                         int ret;
 369
 370                         ret = hmm_vma_do_fault(walk, addr, write_fault,
 371                                                &pfns[i]);
 372                         if (ret != -EAGAIN)
 373                                 return ret;
 374                 }
 375         }
 376
 377         return (fault || write_fault) ? -EAGAIN : 0;
 378 }
 379
 380 static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 381                                       uint64_t pfns, uint64_t cpu_flags,
 382                                       bool *fault, bool *write_fault)
 383 {
 384         struct hmm_range *range = hmm_vma_walk->range;
 385
 386         *fault = *write_fault = false;
 387         if (!hmm_vma_walk->fault)
 388                 return;
 389
 390         /* We aren't ask to do anything ... */
 391         if (!(pfns & range->flags[HMM_PFN_VALID]))
 392                 return;
 393         /* If this is device memory than only fault if explicitly requested */
 394         if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
 395                 /* Do we fault on device memory ? */
 396                 if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
 397                         *write_fault = pfns & range->flags[HMM_PFN_WRITE];
 398                         *fault = true;
 399                 }
 400                 return;
 401         }
 402
 403         /* If CPU page table is not valid then we need to fault */
 404         *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
 405         /* Need to write fault ? */
 406         if ((pfns & range->flags[HMM_PFN_WRITE]) &&
 407             !(cpu_flags & range->flags[HMM_PFN_WRITE])) {
 408                 *write_fault = true;
 409                 *fault = true;
 410         }
 411 }
 412
 413 static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 414                                  const uint64_t *pfns, unsigned long npages,
 415                                  uint64_t cpu_flags, bool *fault,
 416                                  bool *write_fault)
 417 {
 418         unsigned long i;
 419
 420         if (!hmm_vma_walk->fault) {
 421                 *fault = *write_fault = false;
 422                 return;
 423         }
 424
 425         for (i = 0; i < npages; ++i) {
 426                 hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
 427                                    fault, write_fault);
 428                 if ((*fault) || (*write_fault))
 429                         return;
 430         }
 431 }
 432
 433 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
 434                              struct mm_walk *walk)
 435 {
 436         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 437         struct hmm_range *range = hmm_vma_walk->range;
 438         bool fault, write_fault;
 439         unsigned long i, npages;
 440         uint64_t *pfns;
 441
 442         i = (addr - range->start) >> PAGE_SHIFT;
 443         npages = (end - addr) >> PAGE_SHIFT;
 444         pfns = &range->pfns[i];
 445         hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 446                              0, &fault, &write_fault);
 447         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 448 }
 449
 450 static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
 451 {
 452         if (pmd_protnone(pmd))
 453                 return 0;
 454         return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
 455                                 range->flags[HMM_PFN_WRITE] :
 456                                 range->flags[HMM_PFN_VALID];
 457 }
 458
 459 static int hmm_vma_handle_pmd(struct mm_walk *walk,
 460                               unsigned long addr,
 461                               unsigned long end,
 462                               uint64_t *pfns,
 463                               pmd_t pmd)
 464 {
 465         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 466         struct hmm_range *range = hmm_vma_walk->range;
 467         unsigned long pfn, npages, i;
 468         bool fault, write_fault;
 469         uint64_t cpu_flags;
 470
 471         npages = (end - addr) >> PAGE_SHIFT;
 472         cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
 473         hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
 474                              &fault, &write_fault);
 475
 476         if (pmd_protnone(pmd) || fault || write_fault)
 477                 return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 478
 479         pfn = pmd_pfn(pmd) + pte_index(addr);
 480         for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
 481                 pfns[i] = hmm_pfn_from_pfn(range, pfn) | cpu_flags;
 482         hmm_vma_walk->last = end;
 483         return 0;
 484 }
 485
 486 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
 487 {
 488         if (pte_none(pte) || !pte_present(pte))
 489                 return 0;
 490         return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
 491                                 range->flags[HMM_PFN_WRITE] :
 492                                 range->flags[HMM_PFN_VALID];
 493 }
 494
 495 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 496                               unsigned long end, pmd_t *pmdp, pte_t *ptep,
 497                               uint64_t *pfn)
 498 {
 499         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 500         struct hmm_range *range = hmm_vma_walk->range;
 501         struct vm_area_struct *vma = walk->vma;
 502         bool fault, write_fault;
 503         uint64_t cpu_flags;
 504         pte_t pte = *ptep;
 505         uint64_t orig_pfn = *pfn;
 506
 507         *pfn = range->values[HMM_PFN_NONE];
 508         cpu_flags = pte_to_hmm_pfn_flags(range, pte);
 509         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 510                            &fault, &write_fault);
 511
 512         if (pte_none(pte)) {
 513                 if (fault || write_fault)
 514                         goto fault;
 515                 return 0;
 516         }
 517
 518         if (!pte_present(pte)) {
 519                 swp_entry_t entry = pte_to_swp_entry(pte);
 520
 521                 if (!non_swap_entry(entry)) {
 522                         if (fault || write_fault)
 523                                 goto fault;
 524                         return 0;
 525                 }
 526
 527                 /*
 528                  * This is a special swap entry, ignore migration, use
 529                  * device and report anything else as error.
 530                  */
 531                 if (is_device_private_entry(entry)) {
 532                         cpu_flags = range->flags[HMM_PFN_VALID] |
 533                                 range->flags[HMM_PFN_DEVICE_PRIVATE];
 534                         cpu_flags |= is_write_device_private_entry(entry) ?
 535                                 range->flags[HMM_PFN_WRITE] : 0;
 536                         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 537                                            &fault, &write_fault);
 538                         if (fault || write_fault)
 539                                 goto fault;
 540                         *pfn = hmm_pfn_from_pfn(range, swp_offset(entry));
 541                         *pfn |= cpu_flags;
 542                         return 0;
 543                 }
 544
 545                 if (is_migration_entry(entry)) {
 546                         if (fault || write_fault) {
 547                                 pte_unmap(ptep);
 548                                 hmm_vma_walk->last = addr;
 549                                 migration_entry_wait(vma->vm_mm,
 550                                                      pmdp, addr);
 551                                 return -EAGAIN;
 552                         }
 553                         return 0;
 554                 }
 555
 556                 /* Report error for everything else */
 557                 *pfn = range->values[HMM_PFN_ERROR];
 558                 return -EFAULT;
 559         }
 560
 561         if (fault || write_fault)
 562                 goto fault;
 563
 564         *pfn = hmm_pfn_from_pfn(range, pte_pfn(pte)) | cpu_flags;
 565         return 0;
 566
 567 fault:
 568         pte_unmap(ptep);
 569         /* Fault any virtual address we were asked to fault */
 570         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 571 }
 572
 573 static int hmm_vma_walk_pmd(pmd_t *pmdp,
 574                             unsigned long start,
 575                             unsigned long end,
 576                             struct mm_walk *walk)
 577 {
 578         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 579         struct hmm_range *range = hmm_vma_walk->range;
 580         uint64_t *pfns = range->pfns;
 581         unsigned long addr = start, i;
 582         pte_t *ptep;
 583
 584         i = (addr - range->start) >> PAGE_SHIFT;
 585
 586 again:
 587         if (pmd_none(*pmdp))
 588                 return hmm_vma_walk_hole(start, end, walk);
 589
 590         if (pmd_huge(*pmdp) && (range->vma->vm_flags & VM_HUGETLB))
 591                 return hmm_pfns_bad(start, end, walk);
 592
 593         if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
 594                 pmd_t pmd;
 595
 596                 /*
 597                  * No need to take pmd_lock here, even if some other threads
 598                  * is splitting the huge pmd we will get that event through
 599                  * mmu_notifier callback.
 600                  *
 601                  * So just read pmd value and check again its a transparent
 602                  * huge or device mapping one and compute corresponding pfn
 603                  * values.
 604                  */
 605                 pmd = pmd_read_atomic(pmdp);
 606                 barrier();
 607                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
 608                         goto again;
 609
 610                 return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
 611         }
 612
 613         if (pmd_bad(*pmdp))
 614                 return hmm_pfns_bad(start, end, walk);
 615
 616         ptep = pte_offset_map(pmdp, addr);
 617         for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
 618                 int r;
 619
 620                 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
 621                 if (r) {
 622                         /* hmm_vma_handle_pte() did unmap pte directory */
 623                         hmm_vma_walk->last = addr;
 624                         return r;
 625                 }
 626         }
 627         pte_unmap(ptep - 1);
 628
 629         hmm_vma_walk->last = addr;
 630         return 0;
 631 }
 632
 633 static void hmm_pfns_clear(struct hmm_range *range,
 634                            uint64_t *pfns,
 635                            unsigned long addr,
 636                            unsigned long end)
 637 {
 638         for (; addr < end; addr += PAGE_SIZE, pfns++)
 639                 *pfns = range->values[HMM_PFN_NONE];
 640 }
 641
 642 static void hmm_pfns_special(struct hmm_range *range)
 643 {
 644         unsigned long addr = range->start, i = 0;
 645
 646         for (; addr < range->end; addr += PAGE_SIZE, i++)
 647                 range->pfns[i] = range->values[HMM_PFN_SPECIAL];
 648 }
 649
 650 /*
 651  * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
 652  * @range: range being snapshotted
 653  * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
 654  *          vma permission, 0 success
 655  *
 656  * This snapshots the CPU page table for a range of virtual addresses. Snapshot
 657  * validity is tracked by range struct. See hmm_vma_range_done() for further
 658  * information.
 659  *
 660  * The range struct is initialized here. It tracks the CPU page table, but only
 661  * if the function returns success (0), in which case the caller must then call
 662  * hmm_vma_range_done() to stop CPU page table update tracking on this range.
 663  *
 664  * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
 665  * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
 666  */
 667 int hmm_vma_get_pfns(struct hmm_range *range)
 668 {
 669         struct vm_area_struct *vma = range->vma;
 670         struct hmm_vma_walk hmm_vma_walk;
 671         struct mm_walk mm_walk;
 672         struct hmm *hmm;
 673
 674         /* Sanity check, this really should not happen ! */
 675         if (range->start < vma->vm_start || range->start >= vma->vm_end)
 676                 return -EINVAL;
 677         if (range->end < vma->vm_start || range->end > vma->vm_end)
 678                 return -EINVAL;
 679
 680         hmm = hmm_register(vma->vm_mm);
 681         if (!hmm)
 682                 return -ENOMEM;
 683         /* Caller must have registered a mirror, via hmm_mirror_register() ! */
 684         if (!hmm->mmu_notifier.ops)
 685                 return -EINVAL;
 686
 687         /* FIXME support hugetlb fs */
 688         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
 689                         vma_is_dax(vma)) {
 690                 hmm_pfns_special(range);
 691                 return -EINVAL;
 692         }
 693
 694         if (!(vma->vm_flags & VM_READ)) {
 695                 /*
 696                  * If vma do not allow read access, then assume that it does
 697                  * not allow write access, either. Architecture that allow
 698                  * write without read access are not supported by HMM, because
 699                  * operations such has atomic access would not work.
 700                  */
 701                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
 702                 return -EPERM;
 703         }
 704
 705         /* Initialize range to track CPU page table update */
 706         spin_lock(&hmm->lock);
 707         range->valid = true;
 708         list_add_rcu(&range->list, &hmm->ranges);
 709         spin_unlock(&hmm->lock);
 710
 711         hmm_vma_walk.fault = false;
 712         hmm_vma_walk.range = range;
 713         mm_walk.private = &hmm_vma_walk;
 714
 715         mm_walk.vma = vma;
 716         mm_walk.mm = vma->vm_mm;
 717         mm_walk.pte_entry = NULL;
 718         mm_walk.test_walk = NULL;
 719         mm_walk.hugetlb_entry = NULL;
 720         mm_walk.pmd_entry = hmm_vma_walk_pmd;
 721         mm_walk.pte_hole = hmm_vma_walk_hole;
 722
 723         walk_page_range(range->start, range->end, &mm_walk);
 724         return 0;
 725 }
 726 EXPORT_SYMBOL(hmm_vma_get_pfns);
 727
 728 /*
 729  * hmm_vma_range_done() - stop tracking change to CPU page table over a range
 730  * @range: range being tracked
 731  * Returns: false if range data has been invalidated, true otherwise
 732  *
 733  * Range struct is used to track updates to the CPU page table after a call to
 734  * either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done
 735  * using the data,  or wants to lock updates to the data it got from those
 736  * functions, it must call the hmm_vma_range_done() function, which will then
 737  * stop tracking CPU page table updates.
 738  *
 739  * Note that device driver must still implement general CPU page table update
 740  * tracking either by using hmm_mirror (see hmm_mirror_register()) or by using
 741  * the mmu_notifier API directly.
 742  *
 743  * CPU page table update tracking done through hmm_range is only temporary and
 744  * to be used while trying to duplicate CPU page table contents for a range of
 745  * virtual addresses.
 746  *
 747  * There are two ways to use this :
 748  * again:
 749  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
 750  *   trans = device_build_page_table_update_transaction(pfns);
 751  *   device_page_table_lock();
 752  *   if (!hmm_vma_range_done(range)) {
 753  *     device_page_table_unlock();
 754  *     goto again;
 755  *   }
 756  *   device_commit_transaction(trans);
 757  *   device_page_table_unlock();
 758  *
 759  * Or:
 760  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
 761  *   device_page_table_lock();
 762  *   hmm_vma_range_done(range);
 763  *   device_update_page_table(range->pfns);
 764  *   device_page_table_unlock();
 765  */
 766 bool hmm_vma_range_done(struct hmm_range *range)
 767 {
 768         unsigned long npages = (range->end - range->start) >> PAGE_SHIFT;
 769         struct hmm *hmm;
 770
 771         if (range->end <= range->start) {
 772                 BUG();
 773                 return false;
 774         }
 775
 776         hmm = hmm_register(range->vma->vm_mm);
 777         if (!hmm) {
 778                 memset(range->pfns, 0, sizeof(*range->pfns) * npages);
 779                 return false;
 780         }
 781
 782         spin_lock(&hmm->lock);
 783         list_del_rcu(&range->list);
 784         spin_unlock(&hmm->lock);
 785
 786         return range->valid;
 787 }
 788 EXPORT_SYMBOL(hmm_vma_range_done);
 789
 790 /*
 791  * hmm_vma_fault() - try to fault some address in a virtual address range
 792  * @range: range being faulted
 793  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
 794  * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
 795  *
 796  * This is similar to a regular CPU page fault except that it will not trigger
 797  * any memory migration if the memory being faulted is not accessible by CPUs.
 798  *
 799  * On error, for one virtual address in the range, the function will mark the
 800  * corresponding HMM pfn entry with an error flag.
 801  *
 802  * Expected use pattern:
 803  * retry:
 804  *   down_read(&mm->mmap_sem);
 805  *   // Find vma and address device wants to fault, initialize hmm_pfn_t
 806  *   // array accordingly
 807  *   ret = hmm_vma_fault(range, write, block);
 808  *   switch (ret) {
 809  *   case -EAGAIN:
 810  *     hmm_vma_range_done(range);
 811  *     // You might want to rate limit or yield to play nicely, you may
 812  *     // also commit any valid pfn in the array assuming that you are
 813  *     // getting true from hmm_vma_range_monitor_end()
 814  *     goto retry;
 815  *   case 0:
 816  *     break;
 817  *   case -ENOMEM:
 818  *   case -EINVAL:
 819  *   case -EPERM:
 820  *   default:
 821  *     // Handle error !
 822  *     up_read(&mm->mmap_sem)
 823  *     return;
 824  *   }
 825  *   // Take device driver lock that serialize device page table update
 826  *   driver_lock_device_page_table_update();
 827  *   hmm_vma_range_done(range);
 828  *   // Commit pfns we got from hmm_vma_fault()
 829  *   driver_unlock_device_page_table_update();
 830  *   up_read(&mm->mmap_sem)
 831  *
 832  * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
 833  * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
 834  *
 835  * YOU HAVE BEEN WARNED !
 836  */
 837 int hmm_vma_fault(struct hmm_range *range, bool block)
 838 {
 839         struct vm_area_struct *vma = range->vma;
 840         unsigned long start = range->start;
 841         struct hmm_vma_walk hmm_vma_walk;
 842         struct mm_walk mm_walk;
 843         struct hmm *hmm;
 844         int ret;
 845
 846         /* Sanity check, this really should not happen ! */
 847         if (range->start < vma->vm_start || range->start >= vma->vm_end)
 848                 return -EINVAL;
 849         if (range->end < vma->vm_start || range->end > vma->vm_end)
 850                 return -EINVAL;
 851
 852         hmm = hmm_register(vma->vm_mm);
 853         if (!hmm) {
 854                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
 855                 return -ENOMEM;
 856         }
 857         /* Caller must have registered a mirror using hmm_mirror_register() */
 858         if (!hmm->mmu_notifier.ops)
 859                 return -EINVAL;
 860
 861         /* FIXME support hugetlb fs */
 862         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
 863                         vma_is_dax(vma)) {
 864                 hmm_pfns_special(range);
 865                 return -EINVAL;
 866         }
 867
 868         if (!(vma->vm_flags & VM_READ)) {
 869                 /*
 870                  * If vma do not allow read access, then assume that it does
 871                  * not allow write access, either. Architecture that allow
 872                  * write without read access are not supported by HMM, because
 873                  * operations such has atomic access would not work.
 874                  */
 875                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
 876                 return -EPERM;
 877         }
 878
 879         /* Initialize range to track CPU page table update */
 880         spin_lock(&hmm->lock);
 881         range->valid = true;
 882         list_add_rcu(&range->list, &hmm->ranges);
 883         spin_unlock(&hmm->lock);
 884
 885         hmm_vma_walk.fault = true;
 886         hmm_vma_walk.block = block;
 887         hmm_vma_walk.range = range;
 888         mm_walk.private = &hmm_vma_walk;
 889         hmm_vma_walk.last = range->start;
 890
 891         mm_walk.vma = vma;
 892         mm_walk.mm = vma->vm_mm;
 893         mm_walk.pte_entry = NULL;
 894         mm_walk.test_walk = NULL;
 895         mm_walk.hugetlb_entry = NULL;
 896         mm_walk.pmd_entry = hmm_vma_walk_pmd;
 897         mm_walk.pte_hole = hmm_vma_walk_hole;
 898
 899         do {
 900                 ret = walk_page_range(start, range->end, &mm_walk);
 901                 start = hmm_vma_walk.last;
 902         } while (ret == -EAGAIN);
 903
 904         if (ret) {
 905                 unsigned long i;
 906
 907                 i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
 908                 hmm_pfns_clear(range, &range->pfns[i], hmm_vma_walk.last,
 909                                range->end);
 910                 hmm_vma_range_done(range);
 911         }
 912         return ret;
 913 }
 914 EXPORT_SYMBOL(hmm_vma_fault);
 915 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
 916
 917
 918 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
 919 struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
 920                                        unsigned long addr)
 921 {
 922         struct page *page;
 923
 924         page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
 925         if (!page)
 926                 return NULL;
 927         lock_page(page);
 928         return page;
 929 }
 930 EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
 931
 932
 933 static void hmm_devmem_ref_release(struct percpu_ref *ref)
 934 {
 935         struct hmm_devmem *devmem;
 936
 937         devmem = container_of(ref, struct hmm_devmem, ref);
 938         complete(&devmem->completion);
 939 }
 940
 941 static void hmm_devmem_ref_exit(void *data)
 942 {
 943         struct percpu_ref *ref = data;
 944         struct hmm_devmem *devmem;
 945
 946         devmem = container_of(ref, struct hmm_devmem, ref);
 947         percpu_ref_exit(ref);
 948 }
 949
 950 static void hmm_devmem_ref_kill(void *data)
 951 {
 952         struct percpu_ref *ref = data;
 953         struct hmm_devmem *devmem;
 954
 955         devmem = container_of(ref, struct hmm_devmem, ref);
 956         percpu_ref_kill(ref);
 957         wait_for_completion(&devmem->completion);
 958 }
 959
 960 static int hmm_devmem_fault(struct vm_area_struct *vma,
 961                             unsigned long addr,
 962                             const struct page *page,
 963                             unsigned int flags,
 964                             pmd_t *pmdp)
 965 {
 966         struct hmm_devmem *devmem = page->pgmap->data;
 967
 968         return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
 969 }
 970
 971 static void hmm_devmem_free(struct page *page, void *data)
 972 {
 973         struct hmm_devmem *devmem = data;
 974
 975         page->mapping = NULL;
 976
 977         devmem->ops->free(devmem, page);
 978 }
 979
 980 static DEFINE_MUTEX(hmm_devmem_lock);
 981 static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
 982
 983 static void hmm_devmem_radix_release(struct resource *resource)
 984 {
 985         resource_size_t key;
 986
 987         mutex_lock(&hmm_devmem_lock);
 988         for (key = resource->start;
 989              key <= resource->end;
 990              key += PA_SECTION_SIZE)
 991                 radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
 992         mutex_unlock(&hmm_devmem_lock);
 993 }
 994
 995 static void hmm_devmem_release(void *data)
 996 {
 997         struct hmm_devmem *devmem = data;
 998         struct resource *resource = devmem->resource;
 999         unsigned long start_pfn, npages;
1000         struct page *page;
1001         int nid;
1002
1003         /* pages are dead and unused, undo the arch mapping */
1004         start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
1005         npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
1006
1007         page = pfn_to_page(start_pfn);
1008         nid = page_to_nid(page);
1009
1010         mem_hotplug_begin();
1011         if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
1012                 __remove_pages(start_pfn, npages, NULL);
1013         else
1014                 arch_remove_memory(nid, start_pfn << PAGE_SHIFT,
1015                                    npages << PAGE_SHIFT, NULL);
1016         mem_hotplug_done();
1017
1018         hmm_devmem_radix_release(resource);
1019 }
1020
1021 static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
1022 {
1023         resource_size_t key, align_start, align_size, align_end;
1024         struct device *device = devmem->device;
1025         int ret, nid, is_ram;
1026         unsigned long pfn;
1027
1028         align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
1029         align_size = ALIGN(devmem->resource->start +
1030                            resource_size(devmem->resource),
1031                            PA_SECTION_SIZE) - align_start;
1032
1033         is_ram = region_intersects(align_start, align_size,
1034                                    IORESOURCE_SYSTEM_RAM,
1035                                    IORES_DESC_NONE);
1036         if (is_ram == REGION_MIXED) {
1037                 WARN_ONCE(1, "%s attempted on mixed region %pr\n",
1038                                 __func__, devmem->resource);
1039                 return -ENXIO;
1040         }
1041         if (is_ram == REGION_INTERSECTS)
1042                 return -ENXIO;
1043
1044         if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
1045                 devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
1046         else
1047                 devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
1048
1049         devmem->pagemap.res = *devmem->resource;
1050         devmem->pagemap.page_fault = hmm_devmem_fault;
1051         devmem->pagemap.page_free = hmm_devmem_free;
1052         devmem->pagemap.dev = devmem->device;
1053         devmem->pagemap.ref = &devmem->ref;
1054         devmem->pagemap.data = devmem;
1055
1056         mutex_lock(&hmm_devmem_lock);
1057         align_end = align_start + align_size - 1;
1058         for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
1059                 struct hmm_devmem *dup;
1060
1061                 dup = radix_tree_lookup(&hmm_devmem_radix,
1062                                         key >> PA_SECTION_SHIFT);
1063                 if (dup) {
1064                         dev_err(device, "%s: collides with mapping for %s\n",
1065                                 __func__, dev_name(dup->device));
1066                         mutex_unlock(&hmm_devmem_lock);
1067                         ret = -EBUSY;
1068                         goto error;
1069                 }
1070                 ret = radix_tree_insert(&hmm_devmem_radix,
1071                                         key >> PA_SECTION_SHIFT,
1072                                         devmem);
1073                 if (ret) {
1074                         dev_err(device, "%s: failed: %d\n", __func__, ret);
1075                         mutex_unlock(&hmm_devmem_lock);
1076                         goto error_radix;
1077                 }
1078         }
1079         mutex_unlock(&hmm_devmem_lock);
1080
1081         nid = dev_to_node(device);
1082         if (nid < 0)
1083                 nid = numa_mem_id();
1084
1085         mem_hotplug_begin();
1086         /*
1087          * For device private memory we call add_pages() as we only need to
1088          * allocate and initialize struct page for the device memory. More-
1089          * over the device memory is un-accessible thus we do not want to
1090          * create a linear mapping for the memory like arch_add_memory()
1091          * would do.
1092          *
1093          * For device public memory, which is accesible by the CPU, we do
1094          * want the linear mapping and thus use arch_add_memory().
1095          */
1096         if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
1097                 ret = arch_add_memory(nid, align_start, align_size, NULL,
1098                                 false);
1099         else
1100                 ret = add_pages(nid, align_start >> PAGE_SHIFT,
1101                                 align_size >> PAGE_SHIFT, NULL, false);
1102         if (ret) {
1103                 mem_hotplug_done();
1104                 goto error_add_memory;
1105         }
1106         move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
1107                                 align_start >> PAGE_SHIFT,
1108                                 align_size >> PAGE_SHIFT, NULL);
1109         mem_hotplug_done();
1110
1111         for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
1112                 struct page *page = pfn_to_page(pfn);
1113
1114                 page->pgmap = &devmem->pagemap;
1115         }
1116         return 0;
1117
1118 error_add_memory:
1119         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
1120 error_radix:
1121         hmm_devmem_radix_release(devmem->resource);
1122 error:
1123         return ret;
1124 }
1125
1126 /*
1127  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
1128  *
1129  * @ops: memory event device driver callback (see struct hmm_devmem_ops)
1130  * @device: device struct to bind the resource too
1131  * @size: size in bytes of the device memory to add
1132  * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
1133  *
1134  * This function first finds an empty range of physical address big enough to
1135  * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
1136  * in turn allocates struct pages. It does not do anything beyond that; all
1137  * events affecting the memory will go through the various callbacks provided
1138  * by hmm_devmem_ops struct.
1139  *
1140  * Device driver should call this function during device initialization and
1141  * is then responsible of memory management. HMM only provides helpers.
1142  */
1143 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
1144                                   struct device *device,
1145                                   unsigned long size)
1146 {
1147         struct hmm_devmem *devmem;
1148         resource_size_t addr;
1149         int ret;
1150
1151         dev_pagemap_get_ops();
1152
1153         devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
1154         if (!devmem)
1155                 return ERR_PTR(-ENOMEM);
1156
1157         init_completion(&devmem->completion);
1158         devmem->pfn_first = -1UL;
1159         devmem->pfn_last = -1UL;
1160         devmem->resource = NULL;
1161         devmem->device = device;
1162         devmem->ops = ops;
1163
1164         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1165                               0, GFP_KERNEL);
1166         if (ret)
1167                 return ERR_PTR(ret);
1168
1169         ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, &devmem->ref);
1170         if (ret)
1171                 return ERR_PTR(ret);
1172
1173         size = ALIGN(size, PA_SECTION_SIZE);
1174         addr = min((unsigned long)iomem_resource.end,
1175                    (1UL << MAX_PHYSMEM_BITS) - 1);
1176         addr = addr - size + 1UL;
1177
1178         /*
1179          * FIXME add a new helper to quickly walk resource tree and find free
1180          * range
1181          *
1182          * FIXME what about ioport_resource resource ?
1183          */
1184         for (; addr > size && addr >= iomem_resource.start; addr -= size) {
1185                 ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
1186                 if (ret != REGION_DISJOINT)
1187                         continue;
1188
1189                 devmem->resource = devm_request_mem_region(device, addr, size,
1190                                                            dev_name(device));
1191                 if (!devmem->resource)
1192                         return ERR_PTR(-ENOMEM);
1193                 break;
1194         }
1195         if (!devmem->resource)
1196                 return ERR_PTR(-ERANGE);
1197
1198         devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
1199         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1200         devmem->pfn_last = devmem->pfn_first +
1201                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1202
1203         ret = hmm_devmem_pages_create(devmem);
1204         if (ret)
1205                 return ERR_PTR(ret);
1206
1207         ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
1208         if (ret)
1209                 return ERR_PTR(ret);
1210
1211         return devmem;
1212 }
1213 EXPORT_SYMBOL_GPL(hmm_devmem_add);
1214
1215 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
1216                                            struct device *device,
1217                                            struct resource *res)
1218 {
1219         struct hmm_devmem *devmem;
1220         int ret;
1221
1222         if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
1223                 return ERR_PTR(-EINVAL);
1224
1225         dev_pagemap_get_ops();
1226
1227         devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
1228         if (!devmem)
1229                 return ERR_PTR(-ENOMEM);
1230
1231         init_completion(&devmem->completion);
1232         devmem->pfn_first = -1UL;
1233         devmem->pfn_last = -1UL;
1234         devmem->resource = res;
1235         devmem->device = device;
1236         devmem->ops = ops;
1237
1238         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1239                               0, GFP_KERNEL);
1240         if (ret)
1241                 return ERR_PTR(ret);
1242
1243         ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit,
1244                         &devmem->ref);
1245         if (ret)
1246                 return ERR_PTR(ret);
1247
1248         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1249         devmem->pfn_last = devmem->pfn_first +
1250                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1251
1252         ret = hmm_devmem_pages_create(devmem);
1253         if (ret)
1254                 return ERR_PTR(ret);
1255
1256         ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
1257         if (ret)
1258                 return ERR_PTR(ret);
1259
1260         ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill,
1261                         &devmem->ref);
1262         if (ret)
1263                 return ERR_PTR(ret);
1264
1265         return devmem;
1266 }
1267 EXPORT_SYMBOL_GPL(hmm_devmem_add_resource);
1268
1269 /*
1270  * A device driver that wants to handle multiple devices memory through a
1271  * single fake device can use hmm_device to do so. This is purely a helper
1272  * and it is not needed to make use of any HMM functionality.
1273  */
1274 #define HMM_DEVICE_MAX 256
1275
1276 static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
1277 static DEFINE_SPINLOCK(hmm_device_lock);
1278 static struct class *hmm_device_class;
1279 static dev_t hmm_device_devt;
1280
1281 static void hmm_device_release(struct device *device)
1282 {
1283         struct hmm_device *hmm_device;
1284
1285         hmm_device = container_of(device, struct hmm_device, device);
1286         spin_lock(&hmm_device_lock);
1287         clear_bit(hmm_device->minor, hmm_device_mask);
1288         spin_unlock(&hmm_device_lock);
1289
1290         kfree(hmm_device);
1291 }
1292
1293 struct hmm_device *hmm_device_new(void *drvdata)
1294 {
1295         struct hmm_device *hmm_device;
1296
1297         hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
1298         if (!hmm_device)
1299                 return ERR_PTR(-ENOMEM);
1300
1301         spin_lock(&hmm_device_lock);
1302         hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
1303         if (hmm_device->minor >= HMM_DEVICE_MAX) {
1304                 spin_unlock(&hmm_device_lock);
1305                 kfree(hmm_device);
1306                 return ERR_PTR(-EBUSY);
1307         }
1308         set_bit(hmm_device->minor, hmm_device_mask);
1309         spin_unlock(&hmm_device_lock);
1310
1311         dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
1312         hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
1313                                         hmm_device->minor);
1314         hmm_device->device.release = hmm_device_release;
1315         dev_set_drvdata(&hmm_device->device, drvdata);
1316         hmm_device->device.class = hmm_device_class;
1317         device_initialize(&hmm_device->device);
1318
1319         return hmm_device;
1320 }
1321 EXPORT_SYMBOL(hmm_device_new);
1322
1323 void hmm_device_put(struct hmm_device *hmm_device)
1324 {
1325         put_device(&hmm_device->device);
1326 }
1327 EXPORT_SYMBOL(hmm_device_put);
1328
1329 static int __init hmm_init(void)
1330 {
1331         int ret;
1332
1333         ret = alloc_chrdev_region(&hmm_device_devt, 0,
1334                                   HMM_DEVICE_MAX,
1335                                   "hmm_device");
1336         if (ret)
1337                 return ret;
1338
1339         hmm_device_class = class_create(THIS_MODULE, "hmm_device");
1340         if (IS_ERR(hmm_device_class)) {
1341                 unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
1342                 return PTR_ERR(hmm_device_class);
1343         }
1344         return 0;
1345 }
1346
1347 device_initcall(hmm_init);
1348 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */