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         /*
  95          * We should only get here if hold the mmap_sem in write mode ie on
  96          * registration of first mirror through hmm_mirror_register()
  97          */
  98         hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
  99         if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) {
 100                 kfree(hmm);
 101                 return NULL;
 102         }
 103
 104         spin_lock(&mm->page_table_lock);
 105         if (!mm->hmm)
 106                 mm->hmm = hmm;
 107         else
 108                 cleanup = true;
 109         spin_unlock(&mm->page_table_lock);
 110
 111         if (cleanup) {
 112                 mmu_notifier_unregister(&hmm->mmu_notifier, mm);
 113                 kfree(hmm);
 114         }
 115
 116         return mm->hmm;
 117 }
 118
 119 void hmm_mm_destroy(struct mm_struct *mm)
 120 {
 121         kfree(mm->hmm);
 122 }
 123
 124 static void hmm_invalidate_range(struct hmm *hmm,
 125                                  enum hmm_update_type action,
 126                                  unsigned long start,
 127                                  unsigned long end)
 128 {
 129         struct hmm_mirror *mirror;
 130         struct hmm_range *range;
 131
 132         spin_lock(&hmm->lock);
 133         list_for_each_entry(range, &hmm->ranges, list) {
 134                 unsigned long addr, idx, npages;
 135
 136                 if (end < range->start || start >= range->end)
 137                         continue;
 138
 139                 range->valid = false;
 140                 addr = max(start, range->start);
 141                 idx = (addr - range->start) >> PAGE_SHIFT;
 142                 npages = (min(range->end, end) - addr) >> PAGE_SHIFT;
 143                 memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
 144         }
 145         spin_unlock(&hmm->lock);
 146
 147         down_read(&hmm->mirrors_sem);
 148         list_for_each_entry(mirror, &hmm->mirrors, list)
 149                 mirror->ops->sync_cpu_device_pagetables(mirror, action,
 150                                                         start, end);
 151         up_read(&hmm->mirrors_sem);
 152 }
 153
 154 static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 155 {
 156         struct hmm_mirror *mirror;
 157         struct hmm *hmm = mm->hmm;
 158
 159         down_write(&hmm->mirrors_sem);
 160         mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
 161                                           list);
 162         while (mirror) {
 163                 list_del_init(&mirror->list);
 164                 if (mirror->ops->release) {
 165                         /*
 166                          * Drop mirrors_sem so callback can wait on any pending
 167                          * work that might itself trigger mmu_notifier callback
 168                          * and thus would deadlock with us.
 169                          */
 170                         up_write(&hmm->mirrors_sem);
 171                         mirror->ops->release(mirror);
 172                         down_write(&hmm->mirrors_sem);
 173                 }
 174                 mirror = list_first_entry_or_null(&hmm->mirrors,
 175                                                   struct hmm_mirror, list);
 176         }
 177         up_write(&hmm->mirrors_sem);
 178 }
 179
 180 static int hmm_invalidate_range_start(struct mmu_notifier *mn,
 181                                        struct mm_struct *mm,
 182                                        unsigned long start,
 183                                        unsigned long end,
 184                                        bool blockable)
 185 {
 186         struct hmm *hmm = mm->hmm;
 187
 188         VM_BUG_ON(!hmm);
 189
 190         atomic_inc(&hmm->sequence);
 191
 192         return 0;
 193 }
 194
 195 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
 196                                      struct mm_struct *mm,
 197                                      unsigned long start,
 198                                      unsigned long end)
 199 {
 200         struct hmm *hmm = mm->hmm;
 201
 202         VM_BUG_ON(!hmm);
 203
 204         hmm_invalidate_range(mm->hmm, HMM_UPDATE_INVALIDATE, start, end);
 205 }
 206
 207 static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
 208         .release                = hmm_release,
 209         .invalidate_range_start = hmm_invalidate_range_start,
 210         .invalidate_range_end   = hmm_invalidate_range_end,
 211 };
 212
 213 /*
 214  * hmm_mirror_register() - register a mirror against an mm
 215  *
 216  * @mirror: new mirror struct to register
 217  * @mm: mm to register against
 218  *
 219  * To start mirroring a process address space, the device driver must register
 220  * an HMM mirror struct.
 221  *
 222  * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
 223  */
 224 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
 225 {
 226         /* Sanity check */
 227         if (!mm || !mirror || !mirror->ops)
 228                 return -EINVAL;
 229
 230 again:
 231         mirror->hmm = hmm_register(mm);
 232         if (!mirror->hmm)
 233                 return -ENOMEM;
 234
 235         down_write(&mirror->hmm->mirrors_sem);
 236         if (mirror->hmm->mm == NULL) {
 237                 /*
 238                  * A racing hmm_mirror_unregister() is about to destroy the hmm
 239                  * struct. Try again to allocate a new one.
 240                  */
 241                 up_write(&mirror->hmm->mirrors_sem);
 242                 mirror->hmm = NULL;
 243                 goto again;
 244         } else {
 245                 list_add(&mirror->list, &mirror->hmm->mirrors);
 246                 up_write(&mirror->hmm->mirrors_sem);
 247         }
 248
 249         return 0;
 250 }
 251 EXPORT_SYMBOL(hmm_mirror_register);
 252
 253 /*
 254  * hmm_mirror_unregister() - unregister a mirror
 255  *
 256  * @mirror: new mirror struct to register
 257  *
 258  * Stop mirroring a process address space, and cleanup.
 259  */
 260 void hmm_mirror_unregister(struct hmm_mirror *mirror)
 261 {
 262         bool should_unregister = false;
 263         struct mm_struct *mm;
 264         struct hmm *hmm;
 265
 266         if (mirror->hmm == NULL)
 267                 return;
 268
 269         hmm = mirror->hmm;
 270         down_write(&hmm->mirrors_sem);
 271         list_del_init(&mirror->list);
 272         should_unregister = list_empty(&hmm->mirrors);
 273         mirror->hmm = NULL;
 274         mm = hmm->mm;
 275         hmm->mm = NULL;
 276         up_write(&hmm->mirrors_sem);
 277
 278         if (!should_unregister || mm == NULL)
 279                 return;
 280
 281         spin_lock(&mm->page_table_lock);
 282         if (mm->hmm == hmm)
 283                 mm->hmm = NULL;
 284         spin_unlock(&mm->page_table_lock);
 285
 286         mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
 287         kfree(hmm);
 288 }
 289 EXPORT_SYMBOL(hmm_mirror_unregister);
 290
 291 struct hmm_vma_walk {
 292         struct hmm_range        *range;
 293         unsigned long           last;
 294         bool                    fault;
 295         bool                    block;
 296 };
 297
 298 static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
 299                             bool write_fault, uint64_t *pfn)
 300 {
 301         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
 302         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 303         struct hmm_range *range = hmm_vma_walk->range;
 304         struct vm_area_struct *vma = walk->vma;
 305         vm_fault_t ret;
 306
 307         flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
 308         flags |= write_fault ? FAULT_FLAG_WRITE : 0;
 309         ret = handle_mm_fault(vma, addr, flags);
 310         if (ret & VM_FAULT_RETRY)
 311                 return -EBUSY;
 312         if (ret & VM_FAULT_ERROR) {
 313                 *pfn = range->values[HMM_PFN_ERROR];
 314                 return -EFAULT;
 315         }
 316
 317         return -EAGAIN;
 318 }
 319
 320 static int hmm_pfns_bad(unsigned long addr,
 321                         unsigned long end,
 322                         struct mm_walk *walk)
 323 {
 324         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 325         struct hmm_range *range = hmm_vma_walk->range;
 326         uint64_t *pfns = range->pfns;
 327         unsigned long i;
 328
 329         i = (addr - range->start) >> PAGE_SHIFT;
 330         for (; addr < end; addr += PAGE_SIZE, i++)
 331                 pfns[i] = range->values[HMM_PFN_ERROR];
 332
 333         return 0;
 334 }
 335
 336 /*
 337  * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
 338  * @start: range virtual start address (inclusive)
 339  * @end: range virtual end address (exclusive)
 340  * @fault: should we fault or not ?
 341  * @write_fault: write fault ?
 342  * @walk: mm_walk structure
 343  * Returns: 0 on success, -EAGAIN after page fault, or page fault error
 344  *
 345  * This function will be called whenever pmd_none() or pte_none() returns true,
 346  * or whenever there is no page directory covering the virtual address range.
 347  */
 348 static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
 349                               bool fault, bool write_fault,
 350                               struct mm_walk *walk)
 351 {
 352         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 353         struct hmm_range *range = hmm_vma_walk->range;
 354         uint64_t *pfns = range->pfns;
 355         unsigned long i;
 356
 357         hmm_vma_walk->last = addr;
 358         i = (addr - range->start) >> PAGE_SHIFT;
 359         for (; addr < end; addr += PAGE_SIZE, i++) {
 360                 pfns[i] = range->values[HMM_PFN_NONE];
 361                 if (fault || write_fault) {
 362                         int ret;
 363
 364                         ret = hmm_vma_do_fault(walk, addr, write_fault,
 365                                                &pfns[i]);
 366                         if (ret != -EAGAIN)
 367                                 return ret;
 368                 }
 369         }
 370
 371         return (fault || write_fault) ? -EAGAIN : 0;
 372 }
 373
 374 static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 375                                       uint64_t pfns, uint64_t cpu_flags,
 376                                       bool *fault, bool *write_fault)
 377 {
 378         struct hmm_range *range = hmm_vma_walk->range;
 379
 380         *fault = *write_fault = false;
 381         if (!hmm_vma_walk->fault)
 382                 return;
 383
 384         /* We aren't ask to do anything ... */
 385         if (!(pfns & range->flags[HMM_PFN_VALID]))
 386                 return;
 387         /* If this is device memory than only fault if explicitly requested */
 388         if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
 389                 /* Do we fault on device memory ? */
 390                 if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
 391                         *write_fault = pfns & range->flags[HMM_PFN_WRITE];
 392                         *fault = true;
 393                 }
 394                 return;
 395         }
 396
 397         /* If CPU page table is not valid then we need to fault */
 398         *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
 399         /* Need to write fault ? */
 400         if ((pfns & range->flags[HMM_PFN_WRITE]) &&
 401             !(cpu_flags & range->flags[HMM_PFN_WRITE])) {
 402                 *write_fault = true;
 403                 *fault = true;
 404         }
 405 }
 406
 407 static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 408                                  const uint64_t *pfns, unsigned long npages,
 409                                  uint64_t cpu_flags, bool *fault,
 410                                  bool *write_fault)
 411 {
 412         unsigned long i;
 413
 414         if (!hmm_vma_walk->fault) {
 415                 *fault = *write_fault = false;
 416                 return;
 417         }
 418
 419         for (i = 0; i < npages; ++i) {
 420                 hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
 421                                    fault, write_fault);
 422                 if ((*fault) || (*write_fault))
 423                         return;
 424         }
 425 }
 426
 427 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
 428                              struct mm_walk *walk)
 429 {
 430         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 431         struct hmm_range *range = hmm_vma_walk->range;
 432         bool fault, write_fault;
 433         unsigned long i, npages;
 434         uint64_t *pfns;
 435
 436         i = (addr - range->start) >> PAGE_SHIFT;
 437         npages = (end - addr) >> PAGE_SHIFT;
 438         pfns = &range->pfns[i];
 439         hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 440                              0, &fault, &write_fault);
 441         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 442 }
 443
 444 static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
 445 {
 446         if (pmd_protnone(pmd))
 447                 return 0;
 448         return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
 449                                 range->flags[HMM_PFN_WRITE] :
 450                                 range->flags[HMM_PFN_VALID];
 451 }
 452
 453 static int hmm_vma_handle_pmd(struct mm_walk *walk,
 454                               unsigned long addr,
 455                               unsigned long end,
 456                               uint64_t *pfns,
 457                               pmd_t pmd)
 458 {
 459         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 460         struct hmm_range *range = hmm_vma_walk->range;
 461         unsigned long pfn, npages, i;
 462         bool fault, write_fault;
 463         uint64_t cpu_flags;
 464
 465         npages = (end - addr) >> PAGE_SHIFT;
 466         cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
 467         hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
 468                              &fault, &write_fault);
 469
 470         if (pmd_protnone(pmd) || fault || write_fault)
 471                 return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 472
 473         pfn = pmd_pfn(pmd) + pte_index(addr);
 474         for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
 475                 pfns[i] = hmm_pfn_from_pfn(range, pfn) | cpu_flags;
 476         hmm_vma_walk->last = end;
 477         return 0;
 478 }
 479
 480 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
 481 {
 482         if (pte_none(pte) || !pte_present(pte))
 483                 return 0;
 484         return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
 485                                 range->flags[HMM_PFN_WRITE] :
 486                                 range->flags[HMM_PFN_VALID];
 487 }
 488
 489 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 490                               unsigned long end, pmd_t *pmdp, pte_t *ptep,
 491                               uint64_t *pfn)
 492 {
 493         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 494         struct hmm_range *range = hmm_vma_walk->range;
 495         struct vm_area_struct *vma = walk->vma;
 496         bool fault, write_fault;
 497         uint64_t cpu_flags;
 498         pte_t pte = *ptep;
 499         uint64_t orig_pfn = *pfn;
 500
 501         *pfn = range->values[HMM_PFN_NONE];
 502         cpu_flags = pte_to_hmm_pfn_flags(range, pte);
 503         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 504                            &fault, &write_fault);
 505
 506         if (pte_none(pte)) {
 507                 if (fault || write_fault)
 508                         goto fault;
 509                 return 0;
 510         }
 511
 512         if (!pte_present(pte)) {
 513                 swp_entry_t entry = pte_to_swp_entry(pte);
 514
 515                 if (!non_swap_entry(entry)) {
 516                         if (fault || write_fault)
 517                                 goto fault;
 518                         return 0;
 519                 }
 520
 521                 /*
 522                  * This is a special swap entry, ignore migration, use
 523                  * device and report anything else as error.
 524                  */
 525                 if (is_device_private_entry(entry)) {
 526                         cpu_flags = range->flags[HMM_PFN_VALID] |
 527                                 range->flags[HMM_PFN_DEVICE_PRIVATE];
 528                         cpu_flags |= is_write_device_private_entry(entry) ?
 529                                 range->flags[HMM_PFN_WRITE] : 0;
 530                         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 531                                            &fault, &write_fault);
 532                         if (fault || write_fault)
 533                                 goto fault;
 534                         *pfn = hmm_pfn_from_pfn(range, swp_offset(entry));
 535                         *pfn |= cpu_flags;
 536                         return 0;
 537                 }
 538
 539                 if (is_migration_entry(entry)) {
 540                         if (fault || write_fault) {
 541                                 pte_unmap(ptep);
 542                                 hmm_vma_walk->last = addr;
 543                                 migration_entry_wait(vma->vm_mm,
 544                                                      pmdp, addr);
 545                                 return -EAGAIN;
 546                         }
 547                         return 0;
 548                 }
 549
 550                 /* Report error for everything else */
 551                 *pfn = range->values[HMM_PFN_ERROR];
 552                 return -EFAULT;
 553         }
 554
 555         if (fault || write_fault)
 556                 goto fault;
 557
 558         *pfn = hmm_pfn_from_pfn(range, pte_pfn(pte)) | cpu_flags;
 559         return 0;
 560
 561 fault:
 562         pte_unmap(ptep);
 563         /* Fault any virtual address we were asked to fault */
 564         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 565 }
 566
 567 static int hmm_vma_walk_pmd(pmd_t *pmdp,
 568                             unsigned long start,
 569                             unsigned long end,
 570                             struct mm_walk *walk)
 571 {
 572         struct hmm_vma_walk *hmm_vma_walk = walk->private;
 573         struct hmm_range *range = hmm_vma_walk->range;
 574         uint64_t *pfns = range->pfns;
 575         unsigned long addr = start, i;
 576         pte_t *ptep;
 577
 578         i = (addr - range->start) >> PAGE_SHIFT;
 579
 580 again:
 581         if (pmd_none(*pmdp))
 582                 return hmm_vma_walk_hole(start, end, walk);
 583
 584         if (pmd_huge(*pmdp) && (range->vma->vm_flags & VM_HUGETLB))
 585                 return hmm_pfns_bad(start, end, walk);
 586
 587         if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
 588                 pmd_t pmd;
 589
 590                 /*
 591                  * No need to take pmd_lock here, even if some other threads
 592                  * is splitting the huge pmd we will get that event through
 593                  * mmu_notifier callback.
 594                  *
 595                  * So just read pmd value and check again its a transparent
 596                  * huge or device mapping one and compute corresponding pfn
 597                  * values.
 598                  */
 599                 pmd = pmd_read_atomic(pmdp);
 600                 barrier();
 601                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
 602                         goto again;
 603
 604                 return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
 605         }
 606
 607         if (pmd_bad(*pmdp))
 608                 return hmm_pfns_bad(start, end, walk);
 609
 610         ptep = pte_offset_map(pmdp, addr);
 611         for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
 612                 int r;
 613
 614                 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
 615                 if (r) {
 616                         /* hmm_vma_handle_pte() did unmap pte directory */
 617                         hmm_vma_walk->last = addr;
 618                         return r;
 619                 }
 620         }
 621         pte_unmap(ptep - 1);
 622
 623         hmm_vma_walk->last = addr;
 624         return 0;
 625 }
 626
 627 static void hmm_pfns_clear(struct hmm_range *range,
 628                            uint64_t *pfns,
 629                            unsigned long addr,
 630                            unsigned long end)
 631 {
 632         for (; addr < end; addr += PAGE_SIZE, pfns++)
 633                 *pfns = range->values[HMM_PFN_NONE];
 634 }
 635
 636 static void hmm_pfns_special(struct hmm_range *range)
 637 {
 638         unsigned long addr = range->start, i = 0;
 639
 640         for (; addr < range->end; addr += PAGE_SIZE, i++)
 641                 range->pfns[i] = range->values[HMM_PFN_SPECIAL];
 642 }
 643
 644 /*
 645  * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
 646  * @range: range being snapshotted
 647  * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
 648  *          vma permission, 0 success
 649  *
 650  * This snapshots the CPU page table for a range of virtual addresses. Snapshot
 651  * validity is tracked by range struct. See hmm_vma_range_done() for further
 652  * information.
 653  *
 654  * The range struct is initialized here. It tracks the CPU page table, but only
 655  * if the function returns success (0), in which case the caller must then call
 656  * hmm_vma_range_done() to stop CPU page table update tracking on this range.
 657  *
 658  * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
 659  * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
 660  */
 661 int hmm_vma_get_pfns(struct hmm_range *range)
 662 {
 663         struct vm_area_struct *vma = range->vma;
 664         struct hmm_vma_walk hmm_vma_walk;
 665         struct mm_walk mm_walk;
 666         struct hmm *hmm;
 667
 668         /* Sanity check, this really should not happen ! */
 669         if (range->start < vma->vm_start || range->start >= vma->vm_end)
 670                 return -EINVAL;
 671         if (range->end < vma->vm_start || range->end > vma->vm_end)
 672                 return -EINVAL;
 673
 674         hmm = hmm_register(vma->vm_mm);
 675         if (!hmm)
 676                 return -ENOMEM;
 677         /* Caller must have registered a mirror, via hmm_mirror_register() ! */
 678         if (!hmm->mmu_notifier.ops)
 679                 return -EINVAL;
 680
 681         /* FIXME support hugetlb fs */
 682         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
 683                         vma_is_dax(vma)) {
 684                 hmm_pfns_special(range);
 685                 return -EINVAL;
 686         }
 687
 688         if (!(vma->vm_flags & VM_READ)) {
 689                 /*
 690                  * If vma do not allow read access, then assume that it does
 691                  * not allow write access, either. Architecture that allow
 692                  * write without read access are not supported by HMM, because
 693                  * operations such has atomic access would not work.
 694                  */
 695                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
 696                 return -EPERM;
 697         }
 698
 699         /* Initialize range to track CPU page table update */
 700         spin_lock(&hmm->lock);
 701         range->valid = true;
 702         list_add_rcu(&range->list, &hmm->ranges);
 703         spin_unlock(&hmm->lock);
 704
 705         hmm_vma_walk.fault = false;
 706         hmm_vma_walk.range = range;
 707         mm_walk.private = &hmm_vma_walk;
 708
 709         mm_walk.vma = vma;
 710         mm_walk.mm = vma->vm_mm;
 711         mm_walk.pte_entry = NULL;
 712         mm_walk.test_walk = NULL;
 713         mm_walk.hugetlb_entry = NULL;
 714         mm_walk.pmd_entry = hmm_vma_walk_pmd;
 715         mm_walk.pte_hole = hmm_vma_walk_hole;
 716
 717         walk_page_range(range->start, range->end, &mm_walk);
 718         return 0;
 719 }
 720 EXPORT_SYMBOL(hmm_vma_get_pfns);
 721
 722 /*
 723  * hmm_vma_range_done() - stop tracking change to CPU page table over a range
 724  * @range: range being tracked
 725  * Returns: false if range data has been invalidated, true otherwise
 726  *
 727  * Range struct is used to track updates to the CPU page table after a call to
 728  * either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done
 729  * using the data,  or wants to lock updates to the data it got from those
 730  * functions, it must call the hmm_vma_range_done() function, which will then
 731  * stop tracking CPU page table updates.
 732  *
 733  * Note that device driver must still implement general CPU page table update
 734  * tracking either by using hmm_mirror (see hmm_mirror_register()) or by using
 735  * the mmu_notifier API directly.
 736  *
 737  * CPU page table update tracking done through hmm_range is only temporary and
 738  * to be used while trying to duplicate CPU page table contents for a range of
 739  * virtual addresses.
 740  *
 741  * There are two ways to use this :
 742  * again:
 743  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
 744  *   trans = device_build_page_table_update_transaction(pfns);
 745  *   device_page_table_lock();
 746  *   if (!hmm_vma_range_done(range)) {
 747  *     device_page_table_unlock();
 748  *     goto again;
 749  *   }
 750  *   device_commit_transaction(trans);
 751  *   device_page_table_unlock();
 752  *
 753  * Or:
 754  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
 755  *   device_page_table_lock();
 756  *   hmm_vma_range_done(range);
 757  *   device_update_page_table(range->pfns);
 758  *   device_page_table_unlock();
 759  */
 760 bool hmm_vma_range_done(struct hmm_range *range)
 761 {
 762         unsigned long npages = (range->end - range->start) >> PAGE_SHIFT;
 763         struct hmm *hmm;
 764
 765         if (range->end <= range->start) {
 766                 BUG();
 767                 return false;
 768         }
 769
 770         hmm = hmm_register(range->vma->vm_mm);
 771         if (!hmm) {
 772                 memset(range->pfns, 0, sizeof(*range->pfns) * npages);
 773                 return false;
 774         }
 775
 776         spin_lock(&hmm->lock);
 777         list_del_rcu(&range->list);
 778         spin_unlock(&hmm->lock);
 779
 780         return range->valid;
 781 }
 782 EXPORT_SYMBOL(hmm_vma_range_done);
 783
 784 /*
 785  * hmm_vma_fault() - try to fault some address in a virtual address range
 786  * @range: range being faulted
 787  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
 788  * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
 789  *
 790  * This is similar to a regular CPU page fault except that it will not trigger
 791  * any memory migration if the memory being faulted is not accessible by CPUs.
 792  *
 793  * On error, for one virtual address in the range, the function will mark the
 794  * corresponding HMM pfn entry with an error flag.
 795  *
 796  * Expected use pattern:
 797  * retry:
 798  *   down_read(&mm->mmap_sem);
 799  *   // Find vma and address device wants to fault, initialize hmm_pfn_t
 800  *   // array accordingly
 801  *   ret = hmm_vma_fault(range, write, block);
 802  *   switch (ret) {
 803  *   case -EAGAIN:
 804  *     hmm_vma_range_done(range);
 805  *     // You might want to rate limit or yield to play nicely, you may
 806  *     // also commit any valid pfn in the array assuming that you are
 807  *     // getting true from hmm_vma_range_monitor_end()
 808  *     goto retry;
 809  *   case 0:
 810  *     break;
 811  *   case -ENOMEM:
 812  *   case -EINVAL:
 813  *   case -EPERM:
 814  *   default:
 815  *     // Handle error !
 816  *     up_read(&mm->mmap_sem)
 817  *     return;
 818  *   }
 819  *   // Take device driver lock that serialize device page table update
 820  *   driver_lock_device_page_table_update();
 821  *   hmm_vma_range_done(range);
 822  *   // Commit pfns we got from hmm_vma_fault()
 823  *   driver_unlock_device_page_table_update();
 824  *   up_read(&mm->mmap_sem)
 825  *
 826  * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
 827  * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
 828  *
 829  * YOU HAVE BEEN WARNED !
 830  */
 831 int hmm_vma_fault(struct hmm_range *range, bool block)
 832 {
 833         struct vm_area_struct *vma = range->vma;
 834         unsigned long start = range->start;
 835         struct hmm_vma_walk hmm_vma_walk;
 836         struct mm_walk mm_walk;
 837         struct hmm *hmm;
 838         int ret;
 839
 840         /* Sanity check, this really should not happen ! */
 841         if (range->start < vma->vm_start || range->start >= vma->vm_end)
 842                 return -EINVAL;
 843         if (range->end < vma->vm_start || range->end > vma->vm_end)
 844                 return -EINVAL;
 845
 846         hmm = hmm_register(vma->vm_mm);
 847         if (!hmm) {
 848                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
 849                 return -ENOMEM;
 850         }
 851         /* Caller must have registered a mirror using hmm_mirror_register() */
 852         if (!hmm->mmu_notifier.ops)
 853                 return -EINVAL;
 854
 855         /* FIXME support hugetlb fs */
 856         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
 857                         vma_is_dax(vma)) {
 858                 hmm_pfns_special(range);
 859                 return -EINVAL;
 860         }
 861
 862         if (!(vma->vm_flags & VM_READ)) {
 863                 /*
 864                  * If vma do not allow read access, then assume that it does
 865                  * not allow write access, either. Architecture that allow
 866                  * write without read access are not supported by HMM, because
 867                  * operations such has atomic access would not work.
 868                  */
 869                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
 870                 return -EPERM;
 871         }
 872
 873         /* Initialize range to track CPU page table update */
 874         spin_lock(&hmm->lock);
 875         range->valid = true;
 876         list_add_rcu(&range->list, &hmm->ranges);
 877         spin_unlock(&hmm->lock);
 878
 879         hmm_vma_walk.fault = true;
 880         hmm_vma_walk.block = block;
 881         hmm_vma_walk.range = range;
 882         mm_walk.private = &hmm_vma_walk;
 883         hmm_vma_walk.last = range->start;
 884
 885         mm_walk.vma = vma;
 886         mm_walk.mm = vma->vm_mm;
 887         mm_walk.pte_entry = NULL;
 888         mm_walk.test_walk = NULL;
 889         mm_walk.hugetlb_entry = NULL;
 890         mm_walk.pmd_entry = hmm_vma_walk_pmd;
 891         mm_walk.pte_hole = hmm_vma_walk_hole;
 892
 893         do {
 894                 ret = walk_page_range(start, range->end, &mm_walk);
 895                 start = hmm_vma_walk.last;
 896         } while (ret == -EAGAIN);
 897
 898         if (ret) {
 899                 unsigned long i;
 900
 901                 i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
 902                 hmm_pfns_clear(range, &range->pfns[i], hmm_vma_walk.last,
 903                                range->end);
 904                 hmm_vma_range_done(range);
 905         }
 906         return ret;
 907 }
 908 EXPORT_SYMBOL(hmm_vma_fault);
 909 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
 910
 911
 912 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
 913 struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
 914                                        unsigned long addr)
 915 {
 916         struct page *page;
 917
 918         page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
 919         if (!page)
 920                 return NULL;
 921         lock_page(page);
 922         return page;
 923 }
 924 EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
 925
 926
 927 static void hmm_devmem_ref_release(struct percpu_ref *ref)
 928 {
 929         struct hmm_devmem *devmem;
 930
 931         devmem = container_of(ref, struct hmm_devmem, ref);
 932         complete(&devmem->completion);
 933 }
 934
 935 static void hmm_devmem_ref_exit(void *data)
 936 {
 937         struct percpu_ref *ref = data;
 938         struct hmm_devmem *devmem;
 939
 940         devmem = container_of(ref, struct hmm_devmem, ref);
 941         percpu_ref_exit(ref);
 942         devm_remove_action(devmem->device, &hmm_devmem_ref_exit, data);
 943 }
 944
 945 static void hmm_devmem_ref_kill(void *data)
 946 {
 947         struct percpu_ref *ref = data;
 948         struct hmm_devmem *devmem;
 949
 950         devmem = container_of(ref, struct hmm_devmem, ref);
 951         percpu_ref_kill(ref);
 952         wait_for_completion(&devmem->completion);
 953         devm_remove_action(devmem->device, &hmm_devmem_ref_kill, data);
 954 }
 955
 956 static int hmm_devmem_fault(struct vm_area_struct *vma,
 957                             unsigned long addr,
 958                             const struct page *page,
 959                             unsigned int flags,
 960                             pmd_t *pmdp)
 961 {
 962         struct hmm_devmem *devmem = page->pgmap->data;
 963
 964         return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
 965 }
 966
 967 static void hmm_devmem_free(struct page *page, void *data)
 968 {
 969         struct hmm_devmem *devmem = data;
 970
 971         page->mapping = NULL;
 972
 973         devmem->ops->free(devmem, page);
 974 }
 975
 976 static DEFINE_MUTEX(hmm_devmem_lock);
 977 static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
 978
 979 static void hmm_devmem_radix_release(struct resource *resource)
 980 {
 981         resource_size_t key;
 982
 983         mutex_lock(&hmm_devmem_lock);
 984         for (key = resource->start;
 985              key <= resource->end;
 986              key += PA_SECTION_SIZE)
 987                 radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
 988         mutex_unlock(&hmm_devmem_lock);
 989 }
 990
 991 static void hmm_devmem_release(struct device *dev, void *data)
 992 {
 993         struct hmm_devmem *devmem = data;
 994         struct resource *resource = devmem->resource;
 995         unsigned long start_pfn, npages;
 996         struct zone *zone;
 997         struct page *page;
 998
 999         if (percpu_ref_tryget_live(&devmem->ref)) {
1000                 dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
1001                 percpu_ref_put(&devmem->ref);
1002         }
1003
1004         /* pages are dead and unused, undo the arch mapping */
1005         start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
1006         npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
1007
1008         page = pfn_to_page(start_pfn);
1009         zone = page_zone(page);
1010
1011         mem_hotplug_begin();
1012         if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
1013                 __remove_pages(zone, start_pfn, npages, NULL);
1014         else
1015                 arch_remove_memory(start_pfn << PAGE_SHIFT,
1016                                    npages << PAGE_SHIFT, NULL);
1017         mem_hotplug_done();
1018
1019         hmm_devmem_radix_release(resource);
1020 }
1021
1022 static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
1023 {
1024         resource_size_t key, align_start, align_size, align_end;
1025         struct device *device = devmem->device;
1026         int ret, nid, is_ram;
1027         unsigned long pfn;
1028
1029         align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
1030         align_size = ALIGN(devmem->resource->start +
1031                            resource_size(devmem->resource),
1032                            PA_SECTION_SIZE) - align_start;
1033
1034         is_ram = region_intersects(align_start, align_size,
1035                                    IORESOURCE_SYSTEM_RAM,
1036                                    IORES_DESC_NONE);
1037         if (is_ram == REGION_MIXED) {
1038                 WARN_ONCE(1, "%s attempted on mixed region %pr\n",
1039                                 __func__, devmem->resource);
1040                 return -ENXIO;
1041         }
1042         if (is_ram == REGION_INTERSECTS)
1043                 return -ENXIO;
1044
1045         if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
1046                 devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
1047         else
1048                 devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
1049
1050         devmem->pagemap.res = *devmem->resource;
1051         devmem->pagemap.page_fault = hmm_devmem_fault;
1052         devmem->pagemap.page_free = hmm_devmem_free;
1053         devmem->pagemap.dev = devmem->device;
1054         devmem->pagemap.ref = &devmem->ref;
1055         devmem->pagemap.data = devmem;
1056
1057         mutex_lock(&hmm_devmem_lock);
1058         align_end = align_start + align_size - 1;
1059         for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
1060                 struct hmm_devmem *dup;
1061
1062                 dup = radix_tree_lookup(&hmm_devmem_radix,
1063                                         key >> PA_SECTION_SHIFT);
1064                 if (dup) {
1065                         dev_err(device, "%s: collides with mapping for %s\n",
1066                                 __func__, dev_name(dup->device));
1067                         mutex_unlock(&hmm_devmem_lock);
1068                         ret = -EBUSY;
1069                         goto error;
1070                 }
1071                 ret = radix_tree_insert(&hmm_devmem_radix,
1072                                         key >> PA_SECTION_SHIFT,
1073                                         devmem);
1074                 if (ret) {
1075                         dev_err(device, "%s: failed: %d\n", __func__, ret);
1076                         mutex_unlock(&hmm_devmem_lock);
1077                         goto error_radix;
1078                 }
1079         }
1080         mutex_unlock(&hmm_devmem_lock);
1081
1082         nid = dev_to_node(device);
1083         if (nid < 0)
1084                 nid = numa_mem_id();
1085
1086         mem_hotplug_begin();
1087         /*
1088          * For device private memory we call add_pages() as we only need to
1089          * allocate and initialize struct page for the device memory. More-
1090          * over the device memory is un-accessible thus we do not want to
1091          * create a linear mapping for the memory like arch_add_memory()
1092          * would do.
1093          *
1094          * For device public memory, which is accesible by the CPU, we do
1095          * want the linear mapping and thus use arch_add_memory().
1096          */
1097         if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
1098                 ret = arch_add_memory(nid, align_start, align_size, NULL,
1099                                 false);
1100         else
1101                 ret = add_pages(nid, align_start >> PAGE_SHIFT,
1102                                 align_size >> PAGE_SHIFT, NULL, false);
1103         if (ret) {
1104                 mem_hotplug_done();
1105                 goto error_add_memory;
1106         }
1107         move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
1108                                 align_start >> PAGE_SHIFT,
1109                                 align_size >> PAGE_SHIFT, NULL);
1110         mem_hotplug_done();
1111
1112         for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
1113                 struct page *page = pfn_to_page(pfn);
1114
1115                 page->pgmap = &devmem->pagemap;
1116         }
1117         return 0;
1118
1119 error_add_memory:
1120         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
1121 error_radix:
1122         hmm_devmem_radix_release(devmem->resource);
1123 error:
1124         return ret;
1125 }
1126
1127 static int hmm_devmem_match(struct device *dev, void *data, void *match_data)
1128 {
1129         struct hmm_devmem *devmem = data;
1130
1131         return devmem->resource == match_data;
1132 }
1133
1134 static void hmm_devmem_pages_remove(struct hmm_devmem *devmem)
1135 {
1136         devres_release(devmem->device, &hmm_devmem_release,
1137                        &hmm_devmem_match, devmem->resource);
1138 }
1139
1140 /*
1141  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
1142  *
1143  * @ops: memory event device driver callback (see struct hmm_devmem_ops)
1144  * @device: device struct to bind the resource too
1145  * @size: size in bytes of the device memory to add
1146  * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
1147  *
1148  * This function first finds an empty range of physical address big enough to
1149  * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
1150  * in turn allocates struct pages. It does not do anything beyond that; all
1151  * events affecting the memory will go through the various callbacks provided
1152  * by hmm_devmem_ops struct.
1153  *
1154  * Device driver should call this function during device initialization and
1155  * is then responsible of memory management. HMM only provides helpers.
1156  */
1157 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
1158                                   struct device *device,
1159                                   unsigned long size)
1160 {
1161         struct hmm_devmem *devmem;
1162         resource_size_t addr;
1163         int ret;
1164
1165         dev_pagemap_get_ops();
1166
1167         devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
1168                                    GFP_KERNEL, dev_to_node(device));
1169         if (!devmem)
1170                 return ERR_PTR(-ENOMEM);
1171
1172         init_completion(&devmem->completion);
1173         devmem->pfn_first = -1UL;
1174         devmem->pfn_last = -1UL;
1175         devmem->resource = NULL;
1176         devmem->device = device;
1177         devmem->ops = ops;
1178
1179         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1180                               0, GFP_KERNEL);
1181         if (ret)
1182                 goto error_percpu_ref;
1183
1184         ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
1185         if (ret)
1186                 goto error_devm_add_action;
1187
1188         size = ALIGN(size, PA_SECTION_SIZE);
1189         addr = min((unsigned long)iomem_resource.end,
1190                    (1UL << MAX_PHYSMEM_BITS) - 1);
1191         addr = addr - size + 1UL;
1192
1193         /*
1194          * FIXME add a new helper to quickly walk resource tree and find free
1195          * range
1196          *
1197          * FIXME what about ioport_resource resource ?
1198          */
1199         for (; addr > size && addr >= iomem_resource.start; addr -= size) {
1200                 ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
1201                 if (ret != REGION_DISJOINT)
1202                         continue;
1203
1204                 devmem->resource = devm_request_mem_region(device, addr, size,
1205                                                            dev_name(device));
1206                 if (!devmem->resource) {
1207                         ret = -ENOMEM;
1208                         goto error_no_resource;
1209                 }
1210                 break;
1211         }
1212         if (!devmem->resource) {
1213                 ret = -ERANGE;
1214                 goto error_no_resource;
1215         }
1216
1217         devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
1218         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1219         devmem->pfn_last = devmem->pfn_first +
1220                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1221
1222         ret = hmm_devmem_pages_create(devmem);
1223         if (ret)
1224                 goto error_pages;
1225
1226         devres_add(device, devmem);
1227
1228         ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
1229         if (ret) {
1230                 hmm_devmem_remove(devmem);
1231                 return ERR_PTR(ret);
1232         }
1233
1234         return devmem;
1235
1236 error_pages:
1237         devm_release_mem_region(device, devmem->resource->start,
1238                                 resource_size(devmem->resource));
1239 error_no_resource:
1240 error_devm_add_action:
1241         hmm_devmem_ref_kill(&devmem->ref);
1242         hmm_devmem_ref_exit(&devmem->ref);
1243 error_percpu_ref:
1244         devres_free(devmem);
1245         return ERR_PTR(ret);
1246 }
1247 EXPORT_SYMBOL(hmm_devmem_add);
1248
1249 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
1250                                            struct device *device,
1251                                            struct resource *res)
1252 {
1253         struct hmm_devmem *devmem;
1254         int ret;
1255
1256         if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
1257                 return ERR_PTR(-EINVAL);
1258
1259         dev_pagemap_get_ops();
1260
1261         devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
1262                                    GFP_KERNEL, dev_to_node(device));
1263         if (!devmem)
1264                 return ERR_PTR(-ENOMEM);
1265
1266         init_completion(&devmem->completion);
1267         devmem->pfn_first = -1UL;
1268         devmem->pfn_last = -1UL;
1269         devmem->resource = res;
1270         devmem->device = device;
1271         devmem->ops = ops;
1272
1273         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1274                               0, GFP_KERNEL);
1275         if (ret)
1276                 goto error_percpu_ref;
1277
1278         ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
1279         if (ret)
1280                 goto error_devm_add_action;
1281
1282
1283         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1284         devmem->pfn_last = devmem->pfn_first +
1285                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1286
1287         ret = hmm_devmem_pages_create(devmem);
1288         if (ret)
1289                 goto error_devm_add_action;
1290
1291         devres_add(device, devmem);
1292
1293         ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
1294         if (ret) {
1295                 hmm_devmem_remove(devmem);
1296                 return ERR_PTR(ret);
1297         }
1298
1299         return devmem;
1300
1301 error_devm_add_action:
1302         hmm_devmem_ref_kill(&devmem->ref);
1303         hmm_devmem_ref_exit(&devmem->ref);
1304 error_percpu_ref:
1305         devres_free(devmem);
1306         return ERR_PTR(ret);
1307 }
1308 EXPORT_SYMBOL(hmm_devmem_add_resource);
1309
1310 /*
1311  * hmm_devmem_remove() - remove device memory (kill and free ZONE_DEVICE)
1312  *
1313  * @devmem: hmm_devmem struct use to track and manage the ZONE_DEVICE memory
1314  *
1315  * This will hot-unplug memory that was hotplugged by hmm_devmem_add on behalf
1316  * of the device driver. It will free struct page and remove the resource that
1317  * reserved the physical address range for this device memory.
1318  */
1319 void hmm_devmem_remove(struct hmm_devmem *devmem)
1320 {
1321         resource_size_t start, size;
1322         struct device *device;
1323         bool cdm = false;
1324
1325         if (!devmem)
1326                 return;
1327
1328         device = devmem->device;
1329         start = devmem->resource->start;
1330         size = resource_size(devmem->resource);
1331
1332         cdm = devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY;
1333         hmm_devmem_ref_kill(&devmem->ref);
1334         hmm_devmem_ref_exit(&devmem->ref);
1335         hmm_devmem_pages_remove(devmem);
1336
1337         if (!cdm)
1338                 devm_release_mem_region(device, start, size);
1339 }
1340 EXPORT_SYMBOL(hmm_devmem_remove);
1341
1342 /*
1343  * A device driver that wants to handle multiple devices memory through a
1344  * single fake device can use hmm_device to do so. This is purely a helper
1345  * and it is not needed to make use of any HMM functionality.
1346  */
1347 #define HMM_DEVICE_MAX 256
1348
1349 static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
1350 static DEFINE_SPINLOCK(hmm_device_lock);
1351 static struct class *hmm_device_class;
1352 static dev_t hmm_device_devt;
1353
1354 static void hmm_device_release(struct device *device)
1355 {
1356         struct hmm_device *hmm_device;
1357
1358         hmm_device = container_of(device, struct hmm_device, device);
1359         spin_lock(&hmm_device_lock);
1360         clear_bit(hmm_device->minor, hmm_device_mask);
1361         spin_unlock(&hmm_device_lock);
1362
1363         kfree(hmm_device);
1364 }
1365
1366 struct hmm_device *hmm_device_new(void *drvdata)
1367 {
1368         struct hmm_device *hmm_device;
1369
1370         hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
1371         if (!hmm_device)
1372                 return ERR_PTR(-ENOMEM);
1373
1374         spin_lock(&hmm_device_lock);
1375         hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
1376         if (hmm_device->minor >= HMM_DEVICE_MAX) {
1377                 spin_unlock(&hmm_device_lock);
1378                 kfree(hmm_device);
1379                 return ERR_PTR(-EBUSY);
1380         }
1381         set_bit(hmm_device->minor, hmm_device_mask);
1382         spin_unlock(&hmm_device_lock);
1383
1384         dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
1385         hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
1386                                         hmm_device->minor);
1387         hmm_device->device.release = hmm_device_release;
1388         dev_set_drvdata(&hmm_device->device, drvdata);
1389         hmm_device->device.class = hmm_device_class;
1390         device_initialize(&hmm_device->device);
1391
1392         return hmm_device;
1393 }
1394 EXPORT_SYMBOL(hmm_device_new);
1395
1396 void hmm_device_put(struct hmm_device *hmm_device)
1397 {
1398         put_device(&hmm_device->device);
1399 }
1400 EXPORT_SYMBOL(hmm_device_put);
1401
1402 static int __init hmm_init(void)
1403 {
1404         int ret;
1405
1406         ret = alloc_chrdev_region(&hmm_device_devt, 0,
1407                                   HMM_DEVICE_MAX,
1408                                   "hmm_device");
1409         if (ret)
1410                 return ret;
1411
1412         hmm_device_class = class_create(THIS_MODULE, "hmm_device");
1413         if (IS_ERR(hmm_device_class)) {
1414                 unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
1415                 return PTR_ERR(hmm_device_class);
1416         }
1417         return 0;
1418 }
1419
1420 device_initcall(hmm_init);
1421 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */