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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Device Memory Migration functionality.
4 *
5 * Originally written by Jérôme Glisse.
6 */
7#include <linux/export.h>
8#include <linux/memremap.h>
9#include <linux/migrate.h>
10#include <linux/mm.h>
11#include <linux/mm_inline.h>
12#include <linux/mmu_notifier.h>
13#include <linux/oom.h>
14#include <linux/pagewalk.h>
15#include <linux/rmap.h>
16#include <linux/swapops.h>
17#include <asm/tlbflush.h>
18#include "internal.h"
19
20static int migrate_vma_collect_skip(unsigned long start,
21 unsigned long end,
22 struct mm_walk *walk)
23{
24 struct migrate_vma *migrate = walk->private;
25 unsigned long addr;
26
27 for (addr = start; addr < end; addr += PAGE_SIZE) {
28 migrate->dst[migrate->npages] = 0;
29 migrate->src[migrate->npages++] = 0;
30 }
31
32 return 0;
33}
34
35static int migrate_vma_collect_hole(unsigned long start,
36 unsigned long end,
37 __always_unused int depth,
38 struct mm_walk *walk)
39{
40 struct migrate_vma *migrate = walk->private;
41 unsigned long addr;
42
43 /* Only allow populating anonymous memory. */
44 if (!vma_is_anonymous(walk->vma))
45 return migrate_vma_collect_skip(start, end, walk);
46
47 for (addr = start; addr < end; addr += PAGE_SIZE) {
48 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
49 migrate->dst[migrate->npages] = 0;
50 migrate->npages++;
51 migrate->cpages++;
52 }
53
54 return 0;
55}
56
57static int migrate_vma_collect_pmd(pmd_t *pmdp,
58 unsigned long start,
59 unsigned long end,
60 struct mm_walk *walk)
61{
62 struct migrate_vma *migrate = walk->private;
63 struct vm_area_struct *vma = walk->vma;
64 struct mm_struct *mm = vma->vm_mm;
65 unsigned long addr = start, unmapped = 0;
66 spinlock_t *ptl;
67 pte_t *ptep;
68
69again:
70 if (pmd_none(*pmdp))
71 return migrate_vma_collect_hole(start, end, -1, walk);
72
73 if (pmd_trans_huge(*pmdp)) {
74 struct page *page;
75
76 ptl = pmd_lock(mm, pmdp);
77 if (unlikely(!pmd_trans_huge(*pmdp))) {
78 spin_unlock(ptl);
79 goto again;
80 }
81
82 page = pmd_page(*pmdp);
83 if (is_huge_zero_page(page)) {
84 spin_unlock(ptl);
85 split_huge_pmd(vma, pmdp, addr);
86 if (pmd_trans_unstable(pmdp))
87 return migrate_vma_collect_skip(start, end,
88 walk);
89 } else {
90 int ret;
91
92 get_page(page);
93 spin_unlock(ptl);
94 if (unlikely(!trylock_page(page)))
95 return migrate_vma_collect_skip(start, end,
96 walk);
97 ret = split_huge_page(page);
98 unlock_page(page);
99 put_page(page);
100 if (ret)
101 return migrate_vma_collect_skip(start, end,
102 walk);
103 if (pmd_none(*pmdp))
104 return migrate_vma_collect_hole(start, end, -1,
105 walk);
106 }
107 }
108
109 if (unlikely(pmd_bad(*pmdp)))
110 return migrate_vma_collect_skip(start, end, walk);
111
112 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
113 arch_enter_lazy_mmu_mode();
114
115 for (; addr < end; addr += PAGE_SIZE, ptep++) {
116 unsigned long mpfn = 0, pfn;
117 struct page *page;
118 swp_entry_t entry;
119 pte_t pte;
120
121 pte = *ptep;
122
123 if (pte_none(pte)) {
124 if (vma_is_anonymous(vma)) {
125 mpfn = MIGRATE_PFN_MIGRATE;
126 migrate->cpages++;
127 }
128 goto next;
129 }
130
131 if (!pte_present(pte)) {
132 /*
133 * Only care about unaddressable device page special
134 * page table entry. Other special swap entries are not
135 * migratable, and we ignore regular swapped page.
136 */
137 entry = pte_to_swp_entry(pte);
138 if (!is_device_private_entry(entry))
139 goto next;
140
141 page = pfn_swap_entry_to_page(entry);
142 if (!(migrate->flags &
143 MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
144 page->pgmap->owner != migrate->pgmap_owner)
145 goto next;
146
147 mpfn = migrate_pfn(page_to_pfn(page)) |
148 MIGRATE_PFN_MIGRATE;
149 if (is_writable_device_private_entry(entry))
150 mpfn |= MIGRATE_PFN_WRITE;
151 } else {
152 pfn = pte_pfn(pte);
153 if (is_zero_pfn(pfn) &&
154 (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) {
155 mpfn = MIGRATE_PFN_MIGRATE;
156 migrate->cpages++;
157 goto next;
158 }
159 page = vm_normal_page(migrate->vma, addr, pte);
160 if (page && !is_zone_device_page(page) &&
161 !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
162 goto next;
163 else if (page && is_device_coherent_page(page) &&
164 (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
165 page->pgmap->owner != migrate->pgmap_owner))
166 goto next;
167 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
168 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
169 }
170
171 /* FIXME support THP */
172 if (!page || !page->mapping || PageTransCompound(page)) {
173 mpfn = 0;
174 goto next;
175 }
176
177 /*
178 * By getting a reference on the page we pin it and that blocks
179 * any kind of migration. Side effect is that it "freezes" the
180 * pte.
181 *
182 * We drop this reference after isolating the page from the lru
183 * for non device page (device page are not on the lru and thus
184 * can't be dropped from it).
185 */
186 get_page(page);
187
188 /*
189 * We rely on trylock_page() to avoid deadlock between
190 * concurrent migrations where each is waiting on the others
191 * page lock. If we can't immediately lock the page we fail this
192 * migration as it is only best effort anyway.
193 *
194 * If we can lock the page it's safe to set up a migration entry
195 * now. In the common case where the page is mapped once in a
196 * single process setting up the migration entry now is an
197 * optimisation to avoid walking the rmap later with
198 * try_to_migrate().
199 */
200 if (trylock_page(page)) {
201 bool anon_exclusive;
202 pte_t swp_pte;
203
204 flush_cache_page(vma, addr, pte_pfn(*ptep));
205 anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
206 if (anon_exclusive) {
207 pte = ptep_clear_flush(vma, addr, ptep);
208
209 if (page_try_share_anon_rmap(page)) {
210 set_pte_at(mm, addr, ptep, pte);
211 unlock_page(page);
212 put_page(page);
213 mpfn = 0;
214 goto next;
215 }
216 } else {
217 pte = ptep_get_and_clear(mm, addr, ptep);
218 }
219
220 migrate->cpages++;
221
222 /* Set the dirty flag on the folio now the pte is gone. */
223 if (pte_dirty(pte))
224 folio_mark_dirty(page_folio(page));
225
226 /* Setup special migration page table entry */
227 if (mpfn & MIGRATE_PFN_WRITE)
228 entry = make_writable_migration_entry(
229 page_to_pfn(page));
230 else if (anon_exclusive)
231 entry = make_readable_exclusive_migration_entry(
232 page_to_pfn(page));
233 else
234 entry = make_readable_migration_entry(
235 page_to_pfn(page));
236 if (pte_present(pte)) {
237 if (pte_young(pte))
238 entry = make_migration_entry_young(entry);
239 if (pte_dirty(pte))
240 entry = make_migration_entry_dirty(entry);
241 }
242 swp_pte = swp_entry_to_pte(entry);
243 if (pte_present(pte)) {
244 if (pte_soft_dirty(pte))
245 swp_pte = pte_swp_mksoft_dirty(swp_pte);
246 if (pte_uffd_wp(pte))
247 swp_pte = pte_swp_mkuffd_wp(swp_pte);
248 } else {
249 if (pte_swp_soft_dirty(pte))
250 swp_pte = pte_swp_mksoft_dirty(swp_pte);
251 if (pte_swp_uffd_wp(pte))
252 swp_pte = pte_swp_mkuffd_wp(swp_pte);
253 }
254 set_pte_at(mm, addr, ptep, swp_pte);
255
256 /*
257 * This is like regular unmap: we remove the rmap and
258 * drop page refcount. Page won't be freed, as we took
259 * a reference just above.
260 */
261 page_remove_rmap(page, vma, false);
262 put_page(page);
263
264 if (pte_present(pte))
265 unmapped++;
266 } else {
267 put_page(page);
268 mpfn = 0;
269 }
270
271next:
272 migrate->dst[migrate->npages] = 0;
273 migrate->src[migrate->npages++] = mpfn;
274 }
275
276 /* Only flush the TLB if we actually modified any entries */
277 if (unmapped)
278 flush_tlb_range(walk->vma, start, end);
279
280 arch_leave_lazy_mmu_mode();
281 pte_unmap_unlock(ptep - 1, ptl);
282
283 return 0;
284}
285
286static const struct mm_walk_ops migrate_vma_walk_ops = {
287 .pmd_entry = migrate_vma_collect_pmd,
288 .pte_hole = migrate_vma_collect_hole,
289};
290
291/*
292 * migrate_vma_collect() - collect pages over a range of virtual addresses
293 * @migrate: migrate struct containing all migration information
294 *
295 * This will walk the CPU page table. For each virtual address backed by a
296 * valid page, it updates the src array and takes a reference on the page, in
297 * order to pin the page until we lock it and unmap it.
298 */
299static void migrate_vma_collect(struct migrate_vma *migrate)
300{
301 struct mmu_notifier_range range;
302
303 /*
304 * Note that the pgmap_owner is passed to the mmu notifier callback so
305 * that the registered device driver can skip invalidating device
306 * private page mappings that won't be migrated.
307 */
308 mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
309 migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end,
310 migrate->pgmap_owner);
311 mmu_notifier_invalidate_range_start(&range);
312
313 walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
314 &migrate_vma_walk_ops, migrate);
315
316 mmu_notifier_invalidate_range_end(&range);
317 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
318}
319
320/*
321 * migrate_vma_check_page() - check if page is pinned or not
322 * @page: struct page to check
323 *
324 * Pinned pages cannot be migrated. This is the same test as in
325 * folio_migrate_mapping(), except that here we allow migration of a
326 * ZONE_DEVICE page.
327 */
328static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
329{
330 /*
331 * One extra ref because caller holds an extra reference, either from
332 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
333 * a device page.
334 */
335 int extra = 1 + (page == fault_page);
336
337 /*
338 * FIXME support THP (transparent huge page), it is bit more complex to
339 * check them than regular pages, because they can be mapped with a pmd
340 * or with a pte (split pte mapping).
341 */
342 if (PageCompound(page))
343 return false;
344
345 /* Page from ZONE_DEVICE have one extra reference */
346 if (is_zone_device_page(page))
347 extra++;
348
349 /* For file back page */
350 if (page_mapping(page))
351 extra += 1 + page_has_private(page);
352
353 if ((page_count(page) - extra) > page_mapcount(page))
354 return false;
355
356 return true;
357}
358
359/*
360 * Unmaps pages for migration. Returns number of source pfns marked as
361 * migrating.
362 */
363static unsigned long migrate_device_unmap(unsigned long *src_pfns,
364 unsigned long npages,
365 struct page *fault_page)
366{
367 unsigned long i, restore = 0;
368 bool allow_drain = true;
369 unsigned long unmapped = 0;
370
371 lru_add_drain();
372
373 for (i = 0; i < npages; i++) {
374 struct page *page = migrate_pfn_to_page(src_pfns[i]);
375 struct folio *folio;
376
377 if (!page) {
378 if (src_pfns[i] & MIGRATE_PFN_MIGRATE)
379 unmapped++;
380 continue;
381 }
382
383 /* ZONE_DEVICE pages are not on LRU */
384 if (!is_zone_device_page(page)) {
385 if (!PageLRU(page) && allow_drain) {
386 /* Drain CPU's pagevec */
387 lru_add_drain_all();
388 allow_drain = false;
389 }
390
391 if (isolate_lru_page(page)) {
392 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
393 restore++;
394 continue;
395 }
396
397 /* Drop the reference we took in collect */
398 put_page(page);
399 }
400
401 folio = page_folio(page);
402 if (folio_mapped(folio))
403 try_to_migrate(folio, 0);
404
405 if (page_mapped(page) ||
406 !migrate_vma_check_page(page, fault_page)) {
407 if (!is_zone_device_page(page)) {
408 get_page(page);
409 putback_lru_page(page);
410 }
411
412 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
413 restore++;
414 continue;
415 }
416
417 unmapped++;
418 }
419
420 for (i = 0; i < npages && restore; i++) {
421 struct page *page = migrate_pfn_to_page(src_pfns[i]);
422 struct folio *folio;
423
424 if (!page || (src_pfns[i] & MIGRATE_PFN_MIGRATE))
425 continue;
426
427 folio = page_folio(page);
428 remove_migration_ptes(folio, folio, false);
429
430 src_pfns[i] = 0;
431 folio_unlock(folio);
432 folio_put(folio);
433 restore--;
434 }
435
436 return unmapped;
437}
438
439/*
440 * migrate_vma_unmap() - replace page mapping with special migration pte entry
441 * @migrate: migrate struct containing all migration information
442 *
443 * Isolate pages from the LRU and replace mappings (CPU page table pte) with a
444 * special migration pte entry and check if it has been pinned. Pinned pages are
445 * restored because we cannot migrate them.
446 *
447 * This is the last step before we call the device driver callback to allocate
448 * destination memory and copy contents of original page over to new page.
449 */
450static void migrate_vma_unmap(struct migrate_vma *migrate)
451{
452 migrate->cpages = migrate_device_unmap(migrate->src, migrate->npages,
453 migrate->fault_page);
454}
455
456/**
457 * migrate_vma_setup() - prepare to migrate a range of memory
458 * @args: contains the vma, start, and pfns arrays for the migration
459 *
460 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
461 * without an error.
462 *
463 * Prepare to migrate a range of memory virtual address range by collecting all
464 * the pages backing each virtual address in the range, saving them inside the
465 * src array. Then lock those pages and unmap them. Once the pages are locked
466 * and unmapped, check whether each page is pinned or not. Pages that aren't
467 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
468 * corresponding src array entry. Then restores any pages that are pinned, by
469 * remapping and unlocking those pages.
470 *
471 * The caller should then allocate destination memory and copy source memory to
472 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
473 * flag set). Once these are allocated and copied, the caller must update each
474 * corresponding entry in the dst array with the pfn value of the destination
475 * page and with MIGRATE_PFN_VALID. Destination pages must be locked via
476 * lock_page().
477 *
478 * Note that the caller does not have to migrate all the pages that are marked
479 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
480 * device memory to system memory. If the caller cannot migrate a device page
481 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
482 * consequences for the userspace process, so it must be avoided if at all
483 * possible.
484 *
485 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
486 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
487 * allowing the caller to allocate device memory for those unbacked virtual
488 * addresses. For this the caller simply has to allocate device memory and
489 * properly set the destination entry like for regular migration. Note that
490 * this can still fail, and thus inside the device driver you must check if the
491 * migration was successful for those entries after calling migrate_vma_pages(),
492 * just like for regular migration.
493 *
494 * After that, the callers must call migrate_vma_pages() to go over each entry
495 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
496 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
497 * then migrate_vma_pages() to migrate struct page information from the source
498 * struct page to the destination struct page. If it fails to migrate the
499 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
500 * src array.
501 *
502 * At this point all successfully migrated pages have an entry in the src
503 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
504 * array entry with MIGRATE_PFN_VALID flag set.
505 *
506 * Once migrate_vma_pages() returns the caller may inspect which pages were
507 * successfully migrated, and which were not. Successfully migrated pages will
508 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
509 *
510 * It is safe to update device page table after migrate_vma_pages() because
511 * both destination and source page are still locked, and the mmap_lock is held
512 * in read mode (hence no one can unmap the range being migrated).
513 *
514 * Once the caller is done cleaning up things and updating its page table (if it
515 * chose to do so, this is not an obligation) it finally calls
516 * migrate_vma_finalize() to update the CPU page table to point to new pages
517 * for successfully migrated pages or otherwise restore the CPU page table to
518 * point to the original source pages.
519 */
520int migrate_vma_setup(struct migrate_vma *args)
521{
522 long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
523
524 args->start &= PAGE_MASK;
525 args->end &= PAGE_MASK;
526 if (!args->vma || is_vm_hugetlb_page(args->vma) ||
527 (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
528 return -EINVAL;
529 if (nr_pages <= 0)
530 return -EINVAL;
531 if (args->start < args->vma->vm_start ||
532 args->start >= args->vma->vm_end)
533 return -EINVAL;
534 if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
535 return -EINVAL;
536 if (!args->src || !args->dst)
537 return -EINVAL;
538 if (args->fault_page && !is_device_private_page(args->fault_page))
539 return -EINVAL;
540
541 memset(args->src, 0, sizeof(*args->src) * nr_pages);
542 args->cpages = 0;
543 args->npages = 0;
544
545 migrate_vma_collect(args);
546
547 if (args->cpages)
548 migrate_vma_unmap(args);
549
550 /*
551 * At this point pages are locked and unmapped, and thus they have
552 * stable content and can safely be copied to destination memory that
553 * is allocated by the drivers.
554 */
555 return 0;
556
557}
558EXPORT_SYMBOL(migrate_vma_setup);
559
560/*
561 * This code closely matches the code in:
562 * __handle_mm_fault()
563 * handle_pte_fault()
564 * do_anonymous_page()
565 * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
566 * private or coherent page.
567 */
568static void migrate_vma_insert_page(struct migrate_vma *migrate,
569 unsigned long addr,
570 struct page *page,
571 unsigned long *src)
572{
573 struct vm_area_struct *vma = migrate->vma;
574 struct mm_struct *mm = vma->vm_mm;
575 bool flush = false;
576 spinlock_t *ptl;
577 pte_t entry;
578 pgd_t *pgdp;
579 p4d_t *p4dp;
580 pud_t *pudp;
581 pmd_t *pmdp;
582 pte_t *ptep;
583
584 /* Only allow populating anonymous memory */
585 if (!vma_is_anonymous(vma))
586 goto abort;
587
588 pgdp = pgd_offset(mm, addr);
589 p4dp = p4d_alloc(mm, pgdp, addr);
590 if (!p4dp)
591 goto abort;
592 pudp = pud_alloc(mm, p4dp, addr);
593 if (!pudp)
594 goto abort;
595 pmdp = pmd_alloc(mm, pudp, addr);
596 if (!pmdp)
597 goto abort;
598
599 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
600 goto abort;
601
602 /*
603 * Use pte_alloc() instead of pte_alloc_map(). We can't run
604 * pte_offset_map() on pmds where a huge pmd might be created
605 * from a different thread.
606 *
607 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
608 * parallel threads are excluded by other means.
609 *
610 * Here we only have mmap_read_lock(mm).
611 */
612 if (pte_alloc(mm, pmdp))
613 goto abort;
614
615 /* See the comment in pte_alloc_one_map() */
616 if (unlikely(pmd_trans_unstable(pmdp)))
617 goto abort;
618
619 if (unlikely(anon_vma_prepare(vma)))
620 goto abort;
621 if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
622 goto abort;
623
624 /*
625 * The memory barrier inside __SetPageUptodate makes sure that
626 * preceding stores to the page contents become visible before
627 * the set_pte_at() write.
628 */
629 __SetPageUptodate(page);
630
631 if (is_device_private_page(page)) {
632 swp_entry_t swp_entry;
633
634 if (vma->vm_flags & VM_WRITE)
635 swp_entry = make_writable_device_private_entry(
636 page_to_pfn(page));
637 else
638 swp_entry = make_readable_device_private_entry(
639 page_to_pfn(page));
640 entry = swp_entry_to_pte(swp_entry);
641 } else {
642 if (is_zone_device_page(page) &&
643 !is_device_coherent_page(page)) {
644 pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
645 goto abort;
646 }
647 entry = mk_pte(page, vma->vm_page_prot);
648 if (vma->vm_flags & VM_WRITE)
649 entry = pte_mkwrite(pte_mkdirty(entry));
650 }
651
652 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
653
654 if (check_stable_address_space(mm))
655 goto unlock_abort;
656
657 if (pte_present(*ptep)) {
658 unsigned long pfn = pte_pfn(*ptep);
659
660 if (!is_zero_pfn(pfn))
661 goto unlock_abort;
662 flush = true;
663 } else if (!pte_none(*ptep))
664 goto unlock_abort;
665
666 /*
667 * Check for userfaultfd but do not deliver the fault. Instead,
668 * just back off.
669 */
670 if (userfaultfd_missing(vma))
671 goto unlock_abort;
672
673 inc_mm_counter(mm, MM_ANONPAGES);
674 page_add_new_anon_rmap(page, vma, addr);
675 if (!is_zone_device_page(page))
676 lru_cache_add_inactive_or_unevictable(page, vma);
677 get_page(page);
678
679 if (flush) {
680 flush_cache_page(vma, addr, pte_pfn(*ptep));
681 ptep_clear_flush_notify(vma, addr, ptep);
682 set_pte_at_notify(mm, addr, ptep, entry);
683 update_mmu_cache(vma, addr, ptep);
684 } else {
685 /* No need to invalidate - it was non-present before */
686 set_pte_at(mm, addr, ptep, entry);
687 update_mmu_cache(vma, addr, ptep);
688 }
689
690 pte_unmap_unlock(ptep, ptl);
691 *src = MIGRATE_PFN_MIGRATE;
692 return;
693
694unlock_abort:
695 pte_unmap_unlock(ptep, ptl);
696abort:
697 *src &= ~MIGRATE_PFN_MIGRATE;
698}
699
700static void __migrate_device_pages(unsigned long *src_pfns,
701 unsigned long *dst_pfns, unsigned long npages,
702 struct migrate_vma *migrate)
703{
704 struct mmu_notifier_range range;
705 unsigned long i;
706 bool notified = false;
707
708 for (i = 0; i < npages; i++) {
709 struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
710 struct page *page = migrate_pfn_to_page(src_pfns[i]);
711 struct address_space *mapping;
712 int r;
713
714 if (!newpage) {
715 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
716 continue;
717 }
718
719 if (!page) {
720 unsigned long addr;
721
722 if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE))
723 continue;
724
725 /*
726 * The only time there is no vma is when called from
727 * migrate_device_coherent_page(). However this isn't
728 * called if the page could not be unmapped.
729 */
730 VM_BUG_ON(!migrate);
731 addr = migrate->start + i*PAGE_SIZE;
732 if (!notified) {
733 notified = true;
734
735 mmu_notifier_range_init_owner(&range,
736 MMU_NOTIFY_MIGRATE, 0, migrate->vma,
737 migrate->vma->vm_mm, addr, migrate->end,
738 migrate->pgmap_owner);
739 mmu_notifier_invalidate_range_start(&range);
740 }
741 migrate_vma_insert_page(migrate, addr, newpage,
742 &src_pfns[i]);
743 continue;
744 }
745
746 mapping = page_mapping(page);
747
748 if (is_device_private_page(newpage) ||
749 is_device_coherent_page(newpage)) {
750 /*
751 * For now only support anonymous memory migrating to
752 * device private or coherent memory.
753 */
754 if (mapping) {
755 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
756 continue;
757 }
758 } else if (is_zone_device_page(newpage)) {
759 /*
760 * Other types of ZONE_DEVICE page are not supported.
761 */
762 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
763 continue;
764 }
765
766 if (migrate && migrate->fault_page == page)
767 r = migrate_folio_extra(mapping, page_folio(newpage),
768 page_folio(page),
769 MIGRATE_SYNC_NO_COPY, 1);
770 else
771 r = migrate_folio(mapping, page_folio(newpage),
772 page_folio(page), MIGRATE_SYNC_NO_COPY);
773 if (r != MIGRATEPAGE_SUCCESS)
774 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
775 }
776
777 /*
778 * No need to double call mmu_notifier->invalidate_range() callback as
779 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
780 * did already call it.
781 */
782 if (notified)
783 mmu_notifier_invalidate_range_only_end(&range);
784}
785
786/**
787 * migrate_device_pages() - migrate meta-data from src page to dst page
788 * @src_pfns: src_pfns returned from migrate_device_range()
789 * @dst_pfns: array of pfns allocated by the driver to migrate memory to
790 * @npages: number of pages in the range
791 *
792 * Equivalent to migrate_vma_pages(). This is called to migrate struct page
793 * meta-data from source struct page to destination.
794 */
795void migrate_device_pages(unsigned long *src_pfns, unsigned long *dst_pfns,
796 unsigned long npages)
797{
798 __migrate_device_pages(src_pfns, dst_pfns, npages, NULL);
799}
800EXPORT_SYMBOL(migrate_device_pages);
801
802/**
803 * migrate_vma_pages() - migrate meta-data from src page to dst page
804 * @migrate: migrate struct containing all migration information
805 *
806 * This migrates struct page meta-data from source struct page to destination
807 * struct page. This effectively finishes the migration from source page to the
808 * destination page.
809 */
810void migrate_vma_pages(struct migrate_vma *migrate)
811{
812 __migrate_device_pages(migrate->src, migrate->dst, migrate->npages, migrate);
813}
814EXPORT_SYMBOL(migrate_vma_pages);
815
816/*
817 * migrate_device_finalize() - complete page migration
818 * @src_pfns: src_pfns returned from migrate_device_range()
819 * @dst_pfns: array of pfns allocated by the driver to migrate memory to
820 * @npages: number of pages in the range
821 *
822 * Completes migration of the page by removing special migration entries.
823 * Drivers must ensure copying of page data is complete and visible to the CPU
824 * before calling this.
825 */
826void migrate_device_finalize(unsigned long *src_pfns,
827 unsigned long *dst_pfns, unsigned long npages)
828{
829 unsigned long i;
830
831 for (i = 0; i < npages; i++) {
832 struct folio *dst, *src;
833 struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
834 struct page *page = migrate_pfn_to_page(src_pfns[i]);
835
836 if (!page) {
837 if (newpage) {
838 unlock_page(newpage);
839 put_page(newpage);
840 }
841 continue;
842 }
843
844 if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
845 if (newpage) {
846 unlock_page(newpage);
847 put_page(newpage);
848 }
849 newpage = page;
850 }
851
852 src = page_folio(page);
853 dst = page_folio(newpage);
854 remove_migration_ptes(src, dst, false);
855 folio_unlock(src);
856
857 if (is_zone_device_page(page))
858 put_page(page);
859 else
860 putback_lru_page(page);
861
862 if (newpage != page) {
863 unlock_page(newpage);
864 if (is_zone_device_page(newpage))
865 put_page(newpage);
866 else
867 putback_lru_page(newpage);
868 }
869 }
870}
871EXPORT_SYMBOL(migrate_device_finalize);
872
873/**
874 * migrate_vma_finalize() - restore CPU page table entry
875 * @migrate: migrate struct containing all migration information
876 *
877 * This replaces the special migration pte entry with either a mapping to the
878 * new page if migration was successful for that page, or to the original page
879 * otherwise.
880 *
881 * This also unlocks the pages and puts them back on the lru, or drops the extra
882 * refcount, for device pages.
883 */
884void migrate_vma_finalize(struct migrate_vma *migrate)
885{
886 migrate_device_finalize(migrate->src, migrate->dst, migrate->npages);
887}
888EXPORT_SYMBOL(migrate_vma_finalize);
889
890/**
891 * migrate_device_range() - migrate device private pfns to normal memory.
892 * @src_pfns: array large enough to hold migrating source device private pfns.
893 * @start: starting pfn in the range to migrate.
894 * @npages: number of pages to migrate.
895 *
896 * migrate_vma_setup() is similar in concept to migrate_vma_setup() except that
897 * instead of looking up pages based on virtual address mappings a range of
898 * device pfns that should be migrated to system memory is used instead.
899 *
900 * This is useful when a driver needs to free device memory but doesn't know the
901 * virtual mappings of every page that may be in device memory. For example this
902 * is often the case when a driver is being unloaded or unbound from a device.
903 *
904 * Like migrate_vma_setup() this function will take a reference and lock any
905 * migrating pages that aren't free before unmapping them. Drivers may then
906 * allocate destination pages and start copying data from the device to CPU
907 * memory before calling migrate_device_pages().
908 */
909int migrate_device_range(unsigned long *src_pfns, unsigned long start,
910 unsigned long npages)
911{
912 unsigned long i, pfn;
913
914 for (pfn = start, i = 0; i < npages; pfn++, i++) {
915 struct page *page = pfn_to_page(pfn);
916
917 if (!get_page_unless_zero(page)) {
918 src_pfns[i] = 0;
919 continue;
920 }
921
922 if (!trylock_page(page)) {
923 src_pfns[i] = 0;
924 put_page(page);
925 continue;
926 }
927
928 src_pfns[i] = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
929 }
930
931 migrate_device_unmap(src_pfns, npages, NULL);
932
933 return 0;
934}
935EXPORT_SYMBOL(migrate_device_range);
936
937/*
938 * Migrate a device coherent page back to normal memory. The caller should have
939 * a reference on page which will be copied to the new page if migration is
940 * successful or dropped on failure.
941 */
942int migrate_device_coherent_page(struct page *page)
943{
944 unsigned long src_pfn, dst_pfn = 0;
945 struct page *dpage;
946
947 WARN_ON_ONCE(PageCompound(page));
948
949 lock_page(page);
950 src_pfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE;
951
952 /*
953 * We don't have a VMA and don't need to walk the page tables to find
954 * the source page. So call migrate_vma_unmap() directly to unmap the
955 * page as migrate_vma_setup() will fail if args.vma == NULL.
956 */
957 migrate_device_unmap(&src_pfn, 1, NULL);
958 if (!(src_pfn & MIGRATE_PFN_MIGRATE))
959 return -EBUSY;
960
961 dpage = alloc_page(GFP_USER | __GFP_NOWARN);
962 if (dpage) {
963 lock_page(dpage);
964 dst_pfn = migrate_pfn(page_to_pfn(dpage));
965 }
966
967 migrate_device_pages(&src_pfn, &dst_pfn, 1);
968 if (src_pfn & MIGRATE_PFN_MIGRATE)
969 copy_highpage(dpage, page);
970 migrate_device_finalize(&src_pfn, &dst_pfn, 1);
971
972 if (src_pfn & MIGRATE_PFN_MIGRATE)
973 return 0;
974 return -EBUSY;
975}