linux/mm/hmm.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright 2013 Red Hat Inc.
   4 *
   5 * Authors: Jérôme Glisse <jglisse@redhat.com>
   6 */
   7/*
   8 * Refer to include/linux/hmm.h for information about heterogeneous memory
   9 * management or HMM for short.
  10 */
  11#include <linux/pagewalk.h>
  12#include <linux/hmm.h>
  13#include <linux/init.h>
  14#include <linux/rmap.h>
  15#include <linux/swap.h>
  16#include <linux/slab.h>
  17#include <linux/sched.h>
  18#include <linux/mmzone.h>
  19#include <linux/pagemap.h>
  20#include <linux/swapops.h>
  21#include <linux/hugetlb.h>
  22#include <linux/memremap.h>
  23#include <linux/sched/mm.h>
  24#include <linux/jump_label.h>
  25#include <linux/dma-mapping.h>
  26#include <linux/mmu_notifier.h>
  27#include <linux/memory_hotplug.h>
  28
  29static struct mmu_notifier *hmm_alloc_notifier(struct mm_struct *mm)
  30{
  31        struct hmm *hmm;
  32
  33        hmm = kzalloc(sizeof(*hmm), GFP_KERNEL);
  34        if (!hmm)
  35                return ERR_PTR(-ENOMEM);
  36
  37        init_waitqueue_head(&hmm->wq);
  38        INIT_LIST_HEAD(&hmm->mirrors);
  39        init_rwsem(&hmm->mirrors_sem);
  40        INIT_LIST_HEAD(&hmm->ranges);
  41        spin_lock_init(&hmm->ranges_lock);
  42        hmm->notifiers = 0;
  43        return &hmm->mmu_notifier;
  44}
  45
  46static void hmm_free_notifier(struct mmu_notifier *mn)
  47{
  48        struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
  49
  50        WARN_ON(!list_empty(&hmm->ranges));
  51        WARN_ON(!list_empty(&hmm->mirrors));
  52        kfree(hmm);
  53}
  54
  55static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
  56{
  57        struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
  58        struct hmm_mirror *mirror;
  59
  60        /*
  61         * Since hmm_range_register() holds the mmget() lock hmm_release() is
  62         * prevented as long as a range exists.
  63         */
  64        WARN_ON(!list_empty_careful(&hmm->ranges));
  65
  66        down_read(&hmm->mirrors_sem);
  67        list_for_each_entry(mirror, &hmm->mirrors, list) {
  68                /*
  69                 * Note: The driver is not allowed to trigger
  70                 * hmm_mirror_unregister() from this thread.
  71                 */
  72                if (mirror->ops->release)
  73                        mirror->ops->release(mirror);
  74        }
  75        up_read(&hmm->mirrors_sem);
  76}
  77
  78static void notifiers_decrement(struct hmm *hmm)
  79{
  80        unsigned long flags;
  81
  82        spin_lock_irqsave(&hmm->ranges_lock, flags);
  83        hmm->notifiers--;
  84        if (!hmm->notifiers) {
  85                struct hmm_range *range;
  86
  87                list_for_each_entry(range, &hmm->ranges, list) {
  88                        if (range->valid)
  89                                continue;
  90                        range->valid = true;
  91                }
  92                wake_up_all(&hmm->wq);
  93        }
  94        spin_unlock_irqrestore(&hmm->ranges_lock, flags);
  95}
  96
  97static int hmm_invalidate_range_start(struct mmu_notifier *mn,
  98                        const struct mmu_notifier_range *nrange)
  99{
 100        struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
 101        struct hmm_mirror *mirror;
 102        struct hmm_range *range;
 103        unsigned long flags;
 104        int ret = 0;
 105
 106        spin_lock_irqsave(&hmm->ranges_lock, flags);
 107        hmm->notifiers++;
 108        list_for_each_entry(range, &hmm->ranges, list) {
 109                if (nrange->end < range->start || nrange->start >= range->end)
 110                        continue;
 111
 112                range->valid = false;
 113        }
 114        spin_unlock_irqrestore(&hmm->ranges_lock, flags);
 115
 116        if (mmu_notifier_range_blockable(nrange))
 117                down_read(&hmm->mirrors_sem);
 118        else if (!down_read_trylock(&hmm->mirrors_sem)) {
 119                ret = -EAGAIN;
 120                goto out;
 121        }
 122
 123        list_for_each_entry(mirror, &hmm->mirrors, list) {
 124                int rc;
 125
 126                rc = mirror->ops->sync_cpu_device_pagetables(mirror, nrange);
 127                if (rc) {
 128                        if (WARN_ON(mmu_notifier_range_blockable(nrange) ||
 129                            rc != -EAGAIN))
 130                                continue;
 131                        ret = -EAGAIN;
 132                        break;
 133                }
 134        }
 135        up_read(&hmm->mirrors_sem);
 136
 137out:
 138        if (ret)
 139                notifiers_decrement(hmm);
 140        return ret;
 141}
 142
 143static void hmm_invalidate_range_end(struct mmu_notifier *mn,
 144                        const struct mmu_notifier_range *nrange)
 145{
 146        struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
 147
 148        notifiers_decrement(hmm);
 149}
 150
 151static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
 152        .release                = hmm_release,
 153        .invalidate_range_start = hmm_invalidate_range_start,
 154        .invalidate_range_end   = hmm_invalidate_range_end,
 155        .alloc_notifier         = hmm_alloc_notifier,
 156        .free_notifier          = hmm_free_notifier,
 157};
 158
 159/*
 160 * hmm_mirror_register() - register a mirror against an mm
 161 *
 162 * @mirror: new mirror struct to register
 163 * @mm: mm to register against
 164 * Return: 0 on success, -ENOMEM if no memory, -EINVAL if invalid arguments
 165 *
 166 * To start mirroring a process address space, the device driver must register
 167 * an HMM mirror struct.
 168 *
 169 * The caller cannot unregister the hmm_mirror while any ranges are
 170 * registered.
 171 *
 172 * Callers using this function must put a call to mmu_notifier_synchronize()
 173 * in their module exit functions.
 174 */
 175int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
 176{
 177        struct mmu_notifier *mn;
 178
 179        lockdep_assert_held_write(&mm->mmap_sem);
 180
 181        /* Sanity check */
 182        if (!mm || !mirror || !mirror->ops)
 183                return -EINVAL;
 184
 185        mn = mmu_notifier_get_locked(&hmm_mmu_notifier_ops, mm);
 186        if (IS_ERR(mn))
 187                return PTR_ERR(mn);
 188        mirror->hmm = container_of(mn, struct hmm, mmu_notifier);
 189
 190        down_write(&mirror->hmm->mirrors_sem);
 191        list_add(&mirror->list, &mirror->hmm->mirrors);
 192        up_write(&mirror->hmm->mirrors_sem);
 193
 194        return 0;
 195}
 196EXPORT_SYMBOL(hmm_mirror_register);
 197
 198/*
 199 * hmm_mirror_unregister() - unregister a mirror
 200 *
 201 * @mirror: mirror struct to unregister
 202 *
 203 * Stop mirroring a process address space, and cleanup.
 204 */
 205void hmm_mirror_unregister(struct hmm_mirror *mirror)
 206{
 207        struct hmm *hmm = mirror->hmm;
 208
 209        down_write(&hmm->mirrors_sem);
 210        list_del(&mirror->list);
 211        up_write(&hmm->mirrors_sem);
 212        mmu_notifier_put(&hmm->mmu_notifier);
 213}
 214EXPORT_SYMBOL(hmm_mirror_unregister);
 215
 216struct hmm_vma_walk {
 217        struct hmm_range        *range;
 218        struct dev_pagemap      *pgmap;
 219        unsigned long           last;
 220        unsigned int            flags;
 221};
 222
 223static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
 224                            bool write_fault, uint64_t *pfn)
 225{
 226        unsigned int flags = FAULT_FLAG_REMOTE;
 227        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 228        struct hmm_range *range = hmm_vma_walk->range;
 229        struct vm_area_struct *vma = walk->vma;
 230        vm_fault_t ret;
 231
 232        if (!vma)
 233                goto err;
 234
 235        if (hmm_vma_walk->flags & HMM_FAULT_ALLOW_RETRY)
 236                flags |= FAULT_FLAG_ALLOW_RETRY;
 237        if (write_fault)
 238                flags |= FAULT_FLAG_WRITE;
 239
 240        ret = handle_mm_fault(vma, addr, flags);
 241        if (ret & VM_FAULT_RETRY) {
 242                /* Note, handle_mm_fault did up_read(&mm->mmap_sem)) */
 243                return -EAGAIN;
 244        }
 245        if (ret & VM_FAULT_ERROR)
 246                goto err;
 247
 248        return -EBUSY;
 249
 250err:
 251        *pfn = range->values[HMM_PFN_ERROR];
 252        return -EFAULT;
 253}
 254
 255static int hmm_pfns_bad(unsigned long addr,
 256                        unsigned long end,
 257                        struct mm_walk *walk)
 258{
 259        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 260        struct hmm_range *range = hmm_vma_walk->range;
 261        uint64_t *pfns = range->pfns;
 262        unsigned long i;
 263
 264        i = (addr - range->start) >> PAGE_SHIFT;
 265        for (; addr < end; addr += PAGE_SIZE, i++)
 266                pfns[i] = range->values[HMM_PFN_ERROR];
 267
 268        return 0;
 269}
 270
 271/*
 272 * hmm_vma_walk_hole_() - handle a range lacking valid pmd or pte(s)
 273 * @addr: range virtual start address (inclusive)
 274 * @end: range virtual end address (exclusive)
 275 * @fault: should we fault or not ?
 276 * @write_fault: write fault ?
 277 * @walk: mm_walk structure
 278 * Return: 0 on success, -EBUSY after page fault, or page fault error
 279 *
 280 * This function will be called whenever pmd_none() or pte_none() returns true,
 281 * or whenever there is no page directory covering the virtual address range.
 282 */
 283static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
 284                              bool fault, bool write_fault,
 285                              struct mm_walk *walk)
 286{
 287        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 288        struct hmm_range *range = hmm_vma_walk->range;
 289        uint64_t *pfns = range->pfns;
 290        unsigned long i;
 291
 292        hmm_vma_walk->last = addr;
 293        i = (addr - range->start) >> PAGE_SHIFT;
 294
 295        if (write_fault && walk->vma && !(walk->vma->vm_flags & VM_WRITE))
 296                return -EPERM;
 297
 298        for (; addr < end; addr += PAGE_SIZE, i++) {
 299                pfns[i] = range->values[HMM_PFN_NONE];
 300                if (fault || write_fault) {
 301                        int ret;
 302
 303                        ret = hmm_vma_do_fault(walk, addr, write_fault,
 304                                               &pfns[i]);
 305                        if (ret != -EBUSY)
 306                                return ret;
 307                }
 308        }
 309
 310        return (fault || write_fault) ? -EBUSY : 0;
 311}
 312
 313static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 314                                      uint64_t pfns, uint64_t cpu_flags,
 315                                      bool *fault, bool *write_fault)
 316{
 317        struct hmm_range *range = hmm_vma_walk->range;
 318
 319        if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT)
 320                return;
 321
 322        /*
 323         * So we not only consider the individual per page request we also
 324         * consider the default flags requested for the range. The API can
 325         * be used 2 ways. The first one where the HMM user coalesces
 326         * multiple page faults into one request and sets flags per pfn for
 327         * those faults. The second one where the HMM user wants to pre-
 328         * fault a range with specific flags. For the latter one it is a
 329         * waste to have the user pre-fill the pfn arrays with a default
 330         * flags value.
 331         */
 332        pfns = (pfns & range->pfn_flags_mask) | range->default_flags;
 333
 334        /* We aren't ask to do anything ... */
 335        if (!(pfns & range->flags[HMM_PFN_VALID]))
 336                return;
 337        /* If this is device memory then only fault if explicitly requested */
 338        if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
 339                /* Do we fault on device memory ? */
 340                if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
 341                        *write_fault = pfns & range->flags[HMM_PFN_WRITE];
 342                        *fault = true;
 343                }
 344                return;
 345        }
 346
 347        /* If CPU page table is not valid then we need to fault */
 348        *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
 349        /* Need to write fault ? */
 350        if ((pfns & range->flags[HMM_PFN_WRITE]) &&
 351            !(cpu_flags & range->flags[HMM_PFN_WRITE])) {
 352                *write_fault = true;
 353                *fault = true;
 354        }
 355}
 356
 357static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 358                                 const uint64_t *pfns, unsigned long npages,
 359                                 uint64_t cpu_flags, bool *fault,
 360                                 bool *write_fault)
 361{
 362        unsigned long i;
 363
 364        if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) {
 365                *fault = *write_fault = false;
 366                return;
 367        }
 368
 369        *fault = *write_fault = false;
 370        for (i = 0; i < npages; ++i) {
 371                hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
 372                                   fault, write_fault);
 373                if ((*write_fault))
 374                        return;
 375        }
 376}
 377
 378static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
 379                             struct mm_walk *walk)
 380{
 381        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 382        struct hmm_range *range = hmm_vma_walk->range;
 383        bool fault, write_fault;
 384        unsigned long i, npages;
 385        uint64_t *pfns;
 386
 387        i = (addr - range->start) >> PAGE_SHIFT;
 388        npages = (end - addr) >> PAGE_SHIFT;
 389        pfns = &range->pfns[i];
 390        hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 391                             0, &fault, &write_fault);
 392        return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 393}
 394
 395static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
 396{
 397        if (pmd_protnone(pmd))
 398                return 0;
 399        return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
 400                                range->flags[HMM_PFN_WRITE] :
 401                                range->flags[HMM_PFN_VALID];
 402}
 403
 404#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 405static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
 406                unsigned long end, uint64_t *pfns, pmd_t pmd)
 407{
 408        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 409        struct hmm_range *range = hmm_vma_walk->range;
 410        unsigned long pfn, npages, i;
 411        bool fault, write_fault;
 412        uint64_t cpu_flags;
 413
 414        npages = (end - addr) >> PAGE_SHIFT;
 415        cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
 416        hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
 417                             &fault, &write_fault);
 418
 419        if (pmd_protnone(pmd) || fault || write_fault)
 420                return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 421
 422        pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 423        for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
 424                if (pmd_devmap(pmd)) {
 425                        hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
 426                                              hmm_vma_walk->pgmap);
 427                        if (unlikely(!hmm_vma_walk->pgmap))
 428                                return -EBUSY;
 429                }
 430                pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags;
 431        }
 432        if (hmm_vma_walk->pgmap) {
 433                put_dev_pagemap(hmm_vma_walk->pgmap);
 434                hmm_vma_walk->pgmap = NULL;
 435        }
 436        hmm_vma_walk->last = end;
 437        return 0;
 438}
 439#else /* CONFIG_TRANSPARENT_HUGEPAGE */
 440/* stub to allow the code below to compile */
 441int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
 442                unsigned long end, uint64_t *pfns, pmd_t pmd);
 443#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 444
 445static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
 446{
 447        if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
 448                return 0;
 449        return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
 450                                range->flags[HMM_PFN_WRITE] :
 451                                range->flags[HMM_PFN_VALID];
 452}
 453
 454static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 455                              unsigned long end, pmd_t *pmdp, pte_t *ptep,
 456                              uint64_t *pfn)
 457{
 458        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 459        struct hmm_range *range = hmm_vma_walk->range;
 460        bool fault, write_fault;
 461        uint64_t cpu_flags;
 462        pte_t pte = *ptep;
 463        uint64_t orig_pfn = *pfn;
 464
 465        *pfn = range->values[HMM_PFN_NONE];
 466        fault = write_fault = false;
 467
 468        if (pte_none(pte)) {
 469                hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0,
 470                                   &fault, &write_fault);
 471                if (fault || write_fault)
 472                        goto fault;
 473                return 0;
 474        }
 475
 476        if (!pte_present(pte)) {
 477                swp_entry_t entry = pte_to_swp_entry(pte);
 478
 479                if (!non_swap_entry(entry)) {
 480                        cpu_flags = pte_to_hmm_pfn_flags(range, pte);
 481                        hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 482                                           &fault, &write_fault);
 483                        if (fault || write_fault)
 484                                goto fault;
 485                        return 0;
 486                }
 487
 488                /*
 489                 * This is a special swap entry, ignore migration, use
 490                 * device and report anything else as error.
 491                 */
 492                if (is_device_private_entry(entry)) {
 493                        cpu_flags = range->flags[HMM_PFN_VALID] |
 494                                range->flags[HMM_PFN_DEVICE_PRIVATE];
 495                        cpu_flags |= is_write_device_private_entry(entry) ?
 496                                range->flags[HMM_PFN_WRITE] : 0;
 497                        hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 498                                           &fault, &write_fault);
 499                        if (fault || write_fault)
 500                                goto fault;
 501                        *pfn = hmm_device_entry_from_pfn(range,
 502                                            swp_offset(entry));
 503                        *pfn |= cpu_flags;
 504                        return 0;
 505                }
 506
 507                if (is_migration_entry(entry)) {
 508                        if (fault || write_fault) {
 509                                pte_unmap(ptep);
 510                                hmm_vma_walk->last = addr;
 511                                migration_entry_wait(walk->mm, pmdp, addr);
 512                                return -EBUSY;
 513                        }
 514                        return 0;
 515                }
 516
 517                /* Report error for everything else */
 518                *pfn = range->values[HMM_PFN_ERROR];
 519                return -EFAULT;
 520        } else {
 521                cpu_flags = pte_to_hmm_pfn_flags(range, pte);
 522                hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 523                                   &fault, &write_fault);
 524        }
 525
 526        if (fault || write_fault)
 527                goto fault;
 528
 529        if (pte_devmap(pte)) {
 530                hmm_vma_walk->pgmap = get_dev_pagemap(pte_pfn(pte),
 531                                              hmm_vma_walk->pgmap);
 532                if (unlikely(!hmm_vma_walk->pgmap))
 533                        return -EBUSY;
 534        } else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
 535                *pfn = range->values[HMM_PFN_SPECIAL];
 536                return -EFAULT;
 537        }
 538
 539        *pfn = hmm_device_entry_from_pfn(range, pte_pfn(pte)) | cpu_flags;
 540        return 0;
 541
 542fault:
 543        if (hmm_vma_walk->pgmap) {
 544                put_dev_pagemap(hmm_vma_walk->pgmap);
 545                hmm_vma_walk->pgmap = NULL;
 546        }
 547        pte_unmap(ptep);
 548        /* Fault any virtual address we were asked to fault */
 549        return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 550}
 551
 552static int hmm_vma_walk_pmd(pmd_t *pmdp,
 553                            unsigned long start,
 554                            unsigned long end,
 555                            struct mm_walk *walk)
 556{
 557        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 558        struct hmm_range *range = hmm_vma_walk->range;
 559        uint64_t *pfns = range->pfns;
 560        unsigned long addr = start, i;
 561        pte_t *ptep;
 562        pmd_t pmd;
 563
 564again:
 565        pmd = READ_ONCE(*pmdp);
 566        if (pmd_none(pmd))
 567                return hmm_vma_walk_hole(start, end, walk);
 568
 569        if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
 570                bool fault, write_fault;
 571                unsigned long npages;
 572                uint64_t *pfns;
 573
 574                i = (addr - range->start) >> PAGE_SHIFT;
 575                npages = (end - addr) >> PAGE_SHIFT;
 576                pfns = &range->pfns[i];
 577
 578                hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 579                                     0, &fault, &write_fault);
 580                if (fault || write_fault) {
 581                        hmm_vma_walk->last = addr;
 582                        pmd_migration_entry_wait(walk->mm, pmdp);
 583                        return -EBUSY;
 584                }
 585                return 0;
 586        } else if (!pmd_present(pmd))
 587                return hmm_pfns_bad(start, end, walk);
 588
 589        if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
 590                /*
 591                 * No need to take pmd_lock here, even if some other thread
 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 it's 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                i = (addr - range->start) >> PAGE_SHIFT;
 605                return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
 606        }
 607
 608        /*
 609         * We have handled all the valid cases above ie either none, migration,
 610         * huge or transparent huge. At this point either it is a valid pmd
 611         * entry pointing to pte directory or it is a bad pmd that will not
 612         * recover.
 613         */
 614        if (pmd_bad(pmd))
 615                return hmm_pfns_bad(start, end, walk);
 616
 617        ptep = pte_offset_map(pmdp, addr);
 618        i = (addr - range->start) >> PAGE_SHIFT;
 619        for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
 620                int r;
 621
 622                r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
 623                if (r) {
 624                        /* hmm_vma_handle_pte() did unmap pte directory */
 625                        hmm_vma_walk->last = addr;
 626                        return r;
 627                }
 628        }
 629        if (hmm_vma_walk->pgmap) {
 630                /*
 631                 * We do put_dev_pagemap() here and not in hmm_vma_handle_pte()
 632                 * so that we can leverage get_dev_pagemap() optimization which
 633                 * will not re-take a reference on a pgmap if we already have
 634                 * one.
 635                 */
 636                put_dev_pagemap(hmm_vma_walk->pgmap);
 637                hmm_vma_walk->pgmap = NULL;
 638        }
 639        pte_unmap(ptep - 1);
 640
 641        hmm_vma_walk->last = addr;
 642        return 0;
 643}
 644
 645#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
 646    defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
 647static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud)
 648{
 649        if (!pud_present(pud))
 650                return 0;
 651        return pud_write(pud) ? range->flags[HMM_PFN_VALID] |
 652                                range->flags[HMM_PFN_WRITE] :
 653                                range->flags[HMM_PFN_VALID];
 654}
 655
 656static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 657                struct mm_walk *walk)
 658{
 659        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 660        struct hmm_range *range = hmm_vma_walk->range;
 661        unsigned long addr = start, next;
 662        pmd_t *pmdp;
 663        pud_t pud;
 664        int ret;
 665
 666again:
 667        pud = READ_ONCE(*pudp);
 668        if (pud_none(pud))
 669                return hmm_vma_walk_hole(start, end, walk);
 670
 671        if (pud_huge(pud) && pud_devmap(pud)) {
 672                unsigned long i, npages, pfn;
 673                uint64_t *pfns, cpu_flags;
 674                bool fault, write_fault;
 675
 676                if (!pud_present(pud))
 677                        return hmm_vma_walk_hole(start, end, walk);
 678
 679                i = (addr - range->start) >> PAGE_SHIFT;
 680                npages = (end - addr) >> PAGE_SHIFT;
 681                pfns = &range->pfns[i];
 682
 683                cpu_flags = pud_to_hmm_pfn_flags(range, pud);
 684                hmm_range_need_fault(hmm_vma_walk, pfns, npages,
 685                                     cpu_flags, &fault, &write_fault);
 686                if (fault || write_fault)
 687                        return hmm_vma_walk_hole_(addr, end, fault,
 688                                                write_fault, walk);
 689
 690                pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 691                for (i = 0; i < npages; ++i, ++pfn) {
 692                        hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
 693                                              hmm_vma_walk->pgmap);
 694                        if (unlikely(!hmm_vma_walk->pgmap))
 695                                return -EBUSY;
 696                        pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 697                                  cpu_flags;
 698                }
 699                if (hmm_vma_walk->pgmap) {
 700                        put_dev_pagemap(hmm_vma_walk->pgmap);
 701                        hmm_vma_walk->pgmap = NULL;
 702                }
 703                hmm_vma_walk->last = end;
 704                return 0;
 705        }
 706
 707        split_huge_pud(walk->vma, pudp, addr);
 708        if (pud_none(*pudp))
 709                goto again;
 710
 711        pmdp = pmd_offset(pudp, addr);
 712        do {
 713                next = pmd_addr_end(addr, end);
 714                ret = hmm_vma_walk_pmd(pmdp, addr, next, walk);
 715                if (ret)
 716                        return ret;
 717        } while (pmdp++, addr = next, addr != end);
 718
 719        return 0;
 720}
 721#else
 722#define hmm_vma_walk_pud        NULL
 723#endif
 724
 725#ifdef CONFIG_HUGETLB_PAGE
 726static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 727                                      unsigned long start, unsigned long end,
 728                                      struct mm_walk *walk)
 729{
 730        unsigned long addr = start, i, pfn;
 731        struct hmm_vma_walk *hmm_vma_walk = walk->private;
 732        struct hmm_range *range = hmm_vma_walk->range;
 733        struct vm_area_struct *vma = walk->vma;
 734        uint64_t orig_pfn, cpu_flags;
 735        bool fault, write_fault;
 736        spinlock_t *ptl;
 737        pte_t entry;
 738        int ret = 0;
 739
 740        ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
 741        entry = huge_ptep_get(pte);
 742
 743        i = (start - range->start) >> PAGE_SHIFT;
 744        orig_pfn = range->pfns[i];
 745        range->pfns[i] = range->values[HMM_PFN_NONE];
 746        cpu_flags = pte_to_hmm_pfn_flags(range, entry);
 747        fault = write_fault = false;
 748        hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
 749                           &fault, &write_fault);
 750        if (fault || write_fault) {
 751                ret = -ENOENT;
 752                goto unlock;
 753        }
 754
 755        pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
 756        for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
 757                range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 758                                 cpu_flags;
 759        hmm_vma_walk->last = end;
 760
 761unlock:
 762        spin_unlock(ptl);
 763
 764        if (ret == -ENOENT)
 765                return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 766
 767        return ret;
 768}
 769#else
 770#define hmm_vma_walk_hugetlb_entry NULL
 771#endif /* CONFIG_HUGETLB_PAGE */
 772
 773static void hmm_pfns_clear(struct hmm_range *range,
 774                           uint64_t *pfns,
 775                           unsigned long addr,
 776                           unsigned long end)
 777{
 778        for (; addr < end; addr += PAGE_SIZE, pfns++)
 779                *pfns = range->values[HMM_PFN_NONE];
 780}
 781
 782/*
 783 * hmm_range_register() - start tracking change to CPU page table over a range
 784 * @range: range
 785 * @mm: the mm struct for the range of virtual address
 786 *
 787 * Return: 0 on success, -EFAULT if the address space is no longer valid
 788 *
 789 * Track updates to the CPU page table see include/linux/hmm.h
 790 */
 791int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror)
 792{
 793        struct hmm *hmm = mirror->hmm;
 794        unsigned long flags;
 795
 796        range->valid = false;
 797        range->hmm = NULL;
 798
 799        if ((range->start & (PAGE_SIZE - 1)) || (range->end & (PAGE_SIZE - 1)))
 800                return -EINVAL;
 801        if (range->start >= range->end)
 802                return -EINVAL;
 803
 804        /* Prevent hmm_release() from running while the range is valid */
 805        if (!mmget_not_zero(hmm->mmu_notifier.mm))
 806                return -EFAULT;
 807
 808        /* Initialize range to track CPU page table updates. */
 809        spin_lock_irqsave(&hmm->ranges_lock, flags);
 810
 811        range->hmm = hmm;
 812        list_add(&range->list, &hmm->ranges);
 813
 814        /*
 815         * If there are any concurrent notifiers we have to wait for them for
 816         * the range to be valid (see hmm_range_wait_until_valid()).
 817         */
 818        if (!hmm->notifiers)
 819                range->valid = true;
 820        spin_unlock_irqrestore(&hmm->ranges_lock, flags);
 821
 822        return 0;
 823}
 824EXPORT_SYMBOL(hmm_range_register);
 825
 826/*
 827 * hmm_range_unregister() - stop tracking change to CPU page table over a range
 828 * @range: range
 829 *
 830 * Range struct is used to track updates to the CPU page table after a call to
 831 * hmm_range_register(). See include/linux/hmm.h for how to use it.
 832 */
 833void hmm_range_unregister(struct hmm_range *range)
 834{
 835        struct hmm *hmm = range->hmm;
 836        unsigned long flags;
 837
 838        spin_lock_irqsave(&hmm->ranges_lock, flags);
 839        list_del_init(&range->list);
 840        spin_unlock_irqrestore(&hmm->ranges_lock, flags);
 841
 842        /* Drop reference taken by hmm_range_register() */
 843        mmput(hmm->mmu_notifier.mm);
 844
 845        /*
 846         * The range is now invalid and the ref on the hmm is dropped, so
 847         * poison the pointer.  Leave other fields in place, for the caller's
 848         * use.
 849         */
 850        range->valid = false;
 851        memset(&range->hmm, POISON_INUSE, sizeof(range->hmm));
 852}
 853EXPORT_SYMBOL(hmm_range_unregister);
 854
 855static const struct mm_walk_ops hmm_walk_ops = {
 856        .pud_entry      = hmm_vma_walk_pud,
 857        .pmd_entry      = hmm_vma_walk_pmd,
 858        .pte_hole       = hmm_vma_walk_hole,
 859        .hugetlb_entry  = hmm_vma_walk_hugetlb_entry,
 860};
 861
 862/**
 863 * hmm_range_fault - try to fault some address in a virtual address range
 864 * @range:      range being faulted
 865 * @flags:      HMM_FAULT_* flags
 866 *
 867 * Return: the number of valid pages in range->pfns[] (from range start
 868 * address), which may be zero.  On error one of the following status codes
 869 * can be returned:
 870 *
 871 * -EINVAL:     Invalid arguments or mm or virtual address is in an invalid vma
 872 *              (e.g., device file vma).
 873 * -ENOMEM:     Out of memory.
 874 * -EPERM:      Invalid permission (e.g., asking for write and range is read
 875 *              only).
 876 * -EAGAIN:     A page fault needs to be retried and mmap_sem was dropped.
 877 * -EBUSY:      The range has been invalidated and the caller needs to wait for
 878 *              the invalidation to finish.
 879 * -EFAULT:     Invalid (i.e., either no valid vma or it is illegal to access
 880 *              that range) number of valid pages in range->pfns[] (from
 881 *              range start address).
 882 *
 883 * This is similar to a regular CPU page fault except that it will not trigger
 884 * any memory migration if the memory being faulted is not accessible by CPUs
 885 * and caller does not ask for migration.
 886 *
 887 * On error, for one virtual address in the range, the function will mark the
 888 * corresponding HMM pfn entry with an error flag.
 889 */
 890long hmm_range_fault(struct hmm_range *range, unsigned int flags)
 891{
 892        const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
 893        unsigned long start = range->start, end;
 894        struct hmm_vma_walk hmm_vma_walk;
 895        struct hmm *hmm = range->hmm;
 896        struct vm_area_struct *vma;
 897        int ret;
 898
 899        lockdep_assert_held(&hmm->mmu_notifier.mm->mmap_sem);
 900
 901        do {
 902                /* If range is no longer valid force retry. */
 903                if (!range->valid)
 904                        return -EBUSY;
 905
 906                vma = find_vma(hmm->mmu_notifier.mm, start);
 907                if (vma == NULL || (vma->vm_flags & device_vma))
 908                        return -EFAULT;
 909
 910                if (!(vma->vm_flags & VM_READ)) {
 911                        /*
 912                         * If vma do not allow read access, then assume that it
 913                         * does not allow write access, either. HMM does not
 914                         * support architecture that allow write without read.
 915                         */
 916                        hmm_pfns_clear(range, range->pfns,
 917                                range->start, range->end);
 918                        return -EPERM;
 919                }
 920
 921                hmm_vma_walk.pgmap = NULL;
 922                hmm_vma_walk.last = start;
 923                hmm_vma_walk.flags = flags;
 924                hmm_vma_walk.range = range;
 925                end = min(range->end, vma->vm_end);
 926
 927                walk_page_range(vma->vm_mm, start, end, &hmm_walk_ops,
 928                                &hmm_vma_walk);
 929
 930                do {
 931                        ret = walk_page_range(vma->vm_mm, start, end,
 932                                        &hmm_walk_ops, &hmm_vma_walk);
 933                        start = hmm_vma_walk.last;
 934
 935                        /* Keep trying while the range is valid. */
 936                } while (ret == -EBUSY && range->valid);
 937
 938                if (ret) {
 939                        unsigned long i;
 940
 941                        i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
 942                        hmm_pfns_clear(range, &range->pfns[i],
 943                                hmm_vma_walk.last, range->end);
 944                        return ret;
 945                }
 946                start = end;
 947
 948        } while (start < range->end);
 949
 950        return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
 951}
 952EXPORT_SYMBOL(hmm_range_fault);
 953
 954/**
 955 * hmm_range_dma_map - hmm_range_fault() and dma map page all in one.
 956 * @range:      range being faulted
 957 * @device:     device to map page to
 958 * @daddrs:     array of dma addresses for the mapped pages
 959 * @flags:      HMM_FAULT_*
 960 *
 961 * Return: the number of pages mapped on success (including zero), or any
 962 * status return from hmm_range_fault() otherwise.
 963 */
 964long hmm_range_dma_map(struct hmm_range *range, struct device *device,
 965                dma_addr_t *daddrs, unsigned int flags)
 966{
 967        unsigned long i, npages, mapped;
 968        long ret;
 969
 970        ret = hmm_range_fault(range, flags);
 971        if (ret <= 0)
 972                return ret ? ret : -EBUSY;
 973
 974        npages = (range->end - range->start) >> PAGE_SHIFT;
 975        for (i = 0, mapped = 0; i < npages; ++i) {
 976                enum dma_data_direction dir = DMA_TO_DEVICE;
 977                struct page *page;
 978
 979                /*
 980                 * FIXME need to update DMA API to provide invalid DMA address
 981                 * value instead of a function to test dma address value. This
 982                 * would remove lot of dumb code duplicated accross many arch.
 983                 *
 984                 * For now setting it to 0 here is good enough as the pfns[]
 985                 * value is what is use to check what is valid and what isn't.
 986                 */
 987                daddrs[i] = 0;
 988
 989                page = hmm_device_entry_to_page(range, range->pfns[i]);
 990                if (page == NULL)
 991                        continue;
 992
 993                /* Check if range is being invalidated */
 994                if (!range->valid) {
 995                        ret = -EBUSY;
 996                        goto unmap;
 997                }
 998
 999                /* If it is read and write than map bi-directional. */
1000                if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
1001                        dir = DMA_BIDIRECTIONAL;
1002
1003                daddrs[i] = dma_map_page(device, page, 0, PAGE_SIZE, dir);
1004                if (dma_mapping_error(device, daddrs[i])) {
1005                        ret = -EFAULT;
1006                        goto unmap;
1007                }
1008
1009                mapped++;
1010        }
1011
1012        return mapped;
1013
1014unmap:
1015        for (npages = i, i = 0; (i < npages) && mapped; ++i) {
1016                enum dma_data_direction dir = DMA_TO_DEVICE;
1017                struct page *page;
1018
1019                page = hmm_device_entry_to_page(range, range->pfns[i]);
1020                if (page == NULL)
1021                        continue;
1022
1023                if (dma_mapping_error(device, daddrs[i]))
1024                        continue;
1025
1026                /* If it is read and write than map bi-directional. */
1027                if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
1028                        dir = DMA_BIDIRECTIONAL;
1029
1030                dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
1031                mapped--;
1032        }
1033
1034        return ret;
1035}
1036EXPORT_SYMBOL(hmm_range_dma_map);
1037
1038/**
1039 * hmm_range_dma_unmap() - unmap range of that was map with hmm_range_dma_map()
1040 * @range: range being unmapped
1041 * @device: device against which dma map was done
1042 * @daddrs: dma address of mapped pages
1043 * @dirty: dirty page if it had the write flag set
1044 * Return: number of page unmapped on success, -EINVAL otherwise
1045 *
1046 * Note that caller MUST abide by mmu notifier or use HMM mirror and abide
1047 * to the sync_cpu_device_pagetables() callback so that it is safe here to
1048 * call set_page_dirty(). Caller must also take appropriate locks to avoid
1049 * concurrent mmu notifier or sync_cpu_device_pagetables() to make progress.
1050 */
1051long hmm_range_dma_unmap(struct hmm_range *range,
1052                         struct device *device,
1053                         dma_addr_t *daddrs,
1054                         bool dirty)
1055{
1056        unsigned long i, npages;
1057        long cpages = 0;
1058
1059        /* Sanity check. */
1060        if (range->end <= range->start)
1061                return -EINVAL;
1062        if (!daddrs)
1063                return -EINVAL;
1064        if (!range->pfns)
1065                return -EINVAL;
1066
1067        npages = (range->end - range->start) >> PAGE_SHIFT;
1068        for (i = 0; i < npages; ++i) {
1069                enum dma_data_direction dir = DMA_TO_DEVICE;
1070                struct page *page;
1071
1072                page = hmm_device_entry_to_page(range, range->pfns[i]);
1073                if (page == NULL)
1074                        continue;
1075
1076                /* If it is read and write than map bi-directional. */
1077                if (range->pfns[i] & range->flags[HMM_PFN_WRITE]) {
1078                        dir = DMA_BIDIRECTIONAL;
1079
1080                        /*
1081                         * See comments in function description on why it is
1082                         * safe here to call set_page_dirty()
1083                         */
1084                        if (dirty)
1085                                set_page_dirty(page);
1086                }
1087
1088                /* Unmap and clear pfns/dma address */
1089                dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
1090                range->pfns[i] = range->values[HMM_PFN_NONE];
1091                /* FIXME see comments in hmm_vma_dma_map() */
1092                daddrs[i] = 0;
1093                cpages++;
1094        }
1095
1096        return cpages;
1097}
1098EXPORT_SYMBOL(hmm_range_dma_unmap);
1099