smaps: use vm_normal_page_pmd() instead of follow_trans_huge_pmd()
[linux-block.git] / mm / migrate_device.c
CommitLineData
76cbbead
CH
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>
fd35ca3d 10#include <linux/mm.h>
76cbbead
CH
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);
76cbbead
CH
86 } else {
87 int ret;
88
89 get_page(page);
90 spin_unlock(ptl);
91 if (unlikely(!trylock_page(page)))
92 return migrate_vma_collect_skip(start, end,
93 walk);
94 ret = split_huge_page(page);
95 unlock_page(page);
96 put_page(page);
97 if (ret)
98 return migrate_vma_collect_skip(start, end,
99 walk);
76cbbead
CH
100 }
101 }
102
76cbbead 103 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
4b56069c
HD
104 if (!ptep)
105 goto again;
76cbbead
CH
106 arch_enter_lazy_mmu_mode();
107
108 for (; addr < end; addr += PAGE_SIZE, ptep++) {
109 unsigned long mpfn = 0, pfn;
110 struct page *page;
111 swp_entry_t entry;
112 pte_t pte;
113
c33c7948 114 pte = ptep_get(ptep);
76cbbead
CH
115
116 if (pte_none(pte)) {
117 if (vma_is_anonymous(vma)) {
118 mpfn = MIGRATE_PFN_MIGRATE;
119 migrate->cpages++;
120 }
121 goto next;
122 }
123
124 if (!pte_present(pte)) {
125 /*
126 * Only care about unaddressable device page special
127 * page table entry. Other special swap entries are not
128 * migratable, and we ignore regular swapped page.
129 */
130 entry = pte_to_swp_entry(pte);
131 if (!is_device_private_entry(entry))
132 goto next;
133
134 page = pfn_swap_entry_to_page(entry);
135 if (!(migrate->flags &
136 MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
137 page->pgmap->owner != migrate->pgmap_owner)
138 goto next;
139
140 mpfn = migrate_pfn(page_to_pfn(page)) |
141 MIGRATE_PFN_MIGRATE;
142 if (is_writable_device_private_entry(entry))
143 mpfn |= MIGRATE_PFN_WRITE;
144 } else {
76cbbead 145 pfn = pte_pfn(pte);
dd19e6d8
AS
146 if (is_zero_pfn(pfn) &&
147 (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) {
76cbbead
CH
148 mpfn = MIGRATE_PFN_MIGRATE;
149 migrate->cpages++;
150 goto next;
151 }
152 page = vm_normal_page(migrate->vma, addr, pte);
dd19e6d8
AS
153 if (page && !is_zone_device_page(page) &&
154 !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
155 goto next;
156 else if (page && is_device_coherent_page(page) &&
157 (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
158 page->pgmap->owner != migrate->pgmap_owner))
159 goto next;
76cbbead
CH
160 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
161 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
162 }
163
164 /* FIXME support THP */
165 if (!page || !page->mapping || PageTransCompound(page)) {
166 mpfn = 0;
167 goto next;
168 }
169
170 /*
171 * By getting a reference on the page we pin it and that blocks
172 * any kind of migration. Side effect is that it "freezes" the
173 * pte.
174 *
175 * We drop this reference after isolating the page from the lru
176 * for non device page (device page are not on the lru and thus
177 * can't be dropped from it).
178 */
179 get_page(page);
180
181 /*
0742e490
AP
182 * We rely on trylock_page() to avoid deadlock between
183 * concurrent migrations where each is waiting on the others
184 * page lock. If we can't immediately lock the page we fail this
185 * migration as it is only best effort anyway.
186 *
187 * If we can lock the page it's safe to set up a migration entry
188 * now. In the common case where the page is mapped once in a
189 * single process setting up the migration entry now is an
190 * optimisation to avoid walking the rmap later with
191 * try_to_migrate().
76cbbead
CH
192 */
193 if (trylock_page(page)) {
6c287605 194 bool anon_exclusive;
76cbbead
CH
195 pte_t swp_pte;
196
c33c7948 197 flush_cache_page(vma, addr, pte_pfn(pte));
6c287605
DH
198 anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
199 if (anon_exclusive) {
fd35ca3d 200 pte = ptep_clear_flush(vma, addr, ptep);
6c287605
DH
201
202 if (page_try_share_anon_rmap(page)) {
203 set_pte_at(mm, addr, ptep, pte);
204 unlock_page(page);
205 put_page(page);
206 mpfn = 0;
207 goto next;
208 }
209 } else {
fd35ca3d 210 pte = ptep_get_and_clear(mm, addr, ptep);
6c287605
DH
211 }
212
76cbbead 213 migrate->cpages++;
76cbbead 214
fd35ca3d
AP
215 /* Set the dirty flag on the folio now the pte is gone. */
216 if (pte_dirty(pte))
217 folio_mark_dirty(page_folio(page));
218
76cbbead
CH
219 /* Setup special migration page table entry */
220 if (mpfn & MIGRATE_PFN_WRITE)
221 entry = make_writable_migration_entry(
222 page_to_pfn(page));
6c287605
DH
223 else if (anon_exclusive)
224 entry = make_readable_exclusive_migration_entry(
225 page_to_pfn(page));
76cbbead
CH
226 else
227 entry = make_readable_migration_entry(
228 page_to_pfn(page));
2e346877
PX
229 if (pte_present(pte)) {
230 if (pte_young(pte))
231 entry = make_migration_entry_young(entry);
232 if (pte_dirty(pte))
233 entry = make_migration_entry_dirty(entry);
234 }
76cbbead
CH
235 swp_pte = swp_entry_to_pte(entry);
236 if (pte_present(pte)) {
237 if (pte_soft_dirty(pte))
238 swp_pte = pte_swp_mksoft_dirty(swp_pte);
239 if (pte_uffd_wp(pte))
240 swp_pte = pte_swp_mkuffd_wp(swp_pte);
241 } else {
242 if (pte_swp_soft_dirty(pte))
243 swp_pte = pte_swp_mksoft_dirty(swp_pte);
244 if (pte_swp_uffd_wp(pte))
245 swp_pte = pte_swp_mkuffd_wp(swp_pte);
246 }
247 set_pte_at(mm, addr, ptep, swp_pte);
248
249 /*
250 * This is like regular unmap: we remove the rmap and
251 * drop page refcount. Page won't be freed, as we took
252 * a reference just above.
253 */
254 page_remove_rmap(page, vma, false);
255 put_page(page);
256
257 if (pte_present(pte))
258 unmapped++;
259 } else {
260 put_page(page);
261 mpfn = 0;
262 }
263
264next:
265 migrate->dst[migrate->npages] = 0;
266 migrate->src[migrate->npages++] = mpfn;
267 }
76cbbead
CH
268
269 /* Only flush the TLB if we actually modified any entries */
270 if (unmapped)
271 flush_tlb_range(walk->vma, start, end);
272
60bae737
AP
273 arch_leave_lazy_mmu_mode();
274 pte_unmap_unlock(ptep - 1, ptl);
275
76cbbead
CH
276 return 0;
277}
278
279static const struct mm_walk_ops migrate_vma_walk_ops = {
280 .pmd_entry = migrate_vma_collect_pmd,
281 .pte_hole = migrate_vma_collect_hole,
282};
283
284/*
285 * migrate_vma_collect() - collect pages over a range of virtual addresses
286 * @migrate: migrate struct containing all migration information
287 *
288 * This will walk the CPU page table. For each virtual address backed by a
289 * valid page, it updates the src array and takes a reference on the page, in
290 * order to pin the page until we lock it and unmap it.
291 */
292static void migrate_vma_collect(struct migrate_vma *migrate)
293{
294 struct mmu_notifier_range range;
295
296 /*
297 * Note that the pgmap_owner is passed to the mmu notifier callback so
298 * that the registered device driver can skip invalidating device
299 * private page mappings that won't be migrated.
300 */
301 mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
7d4a8be0 302 migrate->vma->vm_mm, migrate->start, migrate->end,
76cbbead
CH
303 migrate->pgmap_owner);
304 mmu_notifier_invalidate_range_start(&range);
305
306 walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
307 &migrate_vma_walk_ops, migrate);
308
309 mmu_notifier_invalidate_range_end(&range);
310 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
311}
312
313/*
314 * migrate_vma_check_page() - check if page is pinned or not
315 * @page: struct page to check
316 *
317 * Pinned pages cannot be migrated. This is the same test as in
318 * folio_migrate_mapping(), except that here we allow migration of a
319 * ZONE_DEVICE page.
320 */
16ce101d 321static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
76cbbead
CH
322{
323 /*
324 * One extra ref because caller holds an extra reference, either from
325 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
326 * a device page.
327 */
16ce101d 328 int extra = 1 + (page == fault_page);
76cbbead
CH
329
330 /*
331 * FIXME support THP (transparent huge page), it is bit more complex to
332 * check them than regular pages, because they can be mapped with a pmd
333 * or with a pte (split pte mapping).
334 */
335 if (PageCompound(page))
336 return false;
337
338 /* Page from ZONE_DEVICE have one extra reference */
339 if (is_zone_device_page(page))
340 extra++;
341
342 /* For file back page */
343 if (page_mapping(page))
344 extra += 1 + page_has_private(page);
345
346 if ((page_count(page) - extra) > page_mapcount(page))
347 return false;
348
349 return true;
350}
351
352/*
44af0b45
AP
353 * Unmaps pages for migration. Returns number of source pfns marked as
354 * migrating.
76cbbead 355 */
241f6885
AP
356static unsigned long migrate_device_unmap(unsigned long *src_pfns,
357 unsigned long npages,
358 struct page *fault_page)
76cbbead 359{
76cbbead
CH
360 unsigned long i, restore = 0;
361 bool allow_drain = true;
241f6885 362 unsigned long unmapped = 0;
76cbbead
CH
363
364 lru_add_drain();
365
366 for (i = 0; i < npages; i++) {
241f6885 367 struct page *page = migrate_pfn_to_page(src_pfns[i]);
4b8554c5 368 struct folio *folio;
76cbbead 369
44af0b45
AP
370 if (!page) {
371 if (src_pfns[i] & MIGRATE_PFN_MIGRATE)
372 unmapped++;
76cbbead 373 continue;
44af0b45 374 }
76cbbead
CH
375
376 /* ZONE_DEVICE pages are not on LRU */
377 if (!is_zone_device_page(page)) {
378 if (!PageLRU(page) && allow_drain) {
1fec6890 379 /* Drain CPU's lru cache */
76cbbead
CH
380 lru_add_drain_all();
381 allow_drain = false;
382 }
383
f7f9c00d 384 if (!isolate_lru_page(page)) {
241f6885 385 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
76cbbead
CH
386 restore++;
387 continue;
388 }
389
390 /* Drop the reference we took in collect */
391 put_page(page);
392 }
393
4b8554c5
MWO
394 folio = page_folio(page);
395 if (folio_mapped(folio))
396 try_to_migrate(folio, 0);
76cbbead 397
16ce101d 398 if (page_mapped(page) ||
241f6885 399 !migrate_vma_check_page(page, fault_page)) {
76cbbead
CH
400 if (!is_zone_device_page(page)) {
401 get_page(page);
402 putback_lru_page(page);
403 }
404
241f6885 405 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
76cbbead
CH
406 restore++;
407 continue;
408 }
241f6885
AP
409
410 unmapped++;
76cbbead
CH
411 }
412
413 for (i = 0; i < npages && restore; i++) {
241f6885 414 struct page *page = migrate_pfn_to_page(src_pfns[i]);
4eecb8b9 415 struct folio *folio;
76cbbead 416
241f6885 417 if (!page || (src_pfns[i] & MIGRATE_PFN_MIGRATE))
76cbbead
CH
418 continue;
419
4eecb8b9
MWO
420 folio = page_folio(page);
421 remove_migration_ptes(folio, folio, false);
76cbbead 422
241f6885 423 src_pfns[i] = 0;
4eecb8b9
MWO
424 folio_unlock(folio);
425 folio_put(folio);
76cbbead
CH
426 restore--;
427 }
241f6885
AP
428
429 return unmapped;
430}
431
432/*
433 * migrate_vma_unmap() - replace page mapping with special migration pte entry
434 * @migrate: migrate struct containing all migration information
435 *
436 * Isolate pages from the LRU and replace mappings (CPU page table pte) with a
437 * special migration pte entry and check if it has been pinned. Pinned pages are
438 * restored because we cannot migrate them.
439 *
440 * This is the last step before we call the device driver callback to allocate
441 * destination memory and copy contents of original page over to new page.
442 */
443static void migrate_vma_unmap(struct migrate_vma *migrate)
444{
445 migrate->cpages = migrate_device_unmap(migrate->src, migrate->npages,
446 migrate->fault_page);
76cbbead
CH
447}
448
449/**
450 * migrate_vma_setup() - prepare to migrate a range of memory
451 * @args: contains the vma, start, and pfns arrays for the migration
452 *
453 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
454 * without an error.
455 *
456 * Prepare to migrate a range of memory virtual address range by collecting all
457 * the pages backing each virtual address in the range, saving them inside the
458 * src array. Then lock those pages and unmap them. Once the pages are locked
459 * and unmapped, check whether each page is pinned or not. Pages that aren't
460 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
461 * corresponding src array entry. Then restores any pages that are pinned, by
462 * remapping and unlocking those pages.
463 *
464 * The caller should then allocate destination memory and copy source memory to
465 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
466 * flag set). Once these are allocated and copied, the caller must update each
467 * corresponding entry in the dst array with the pfn value of the destination
468 * page and with MIGRATE_PFN_VALID. Destination pages must be locked via
469 * lock_page().
470 *
471 * Note that the caller does not have to migrate all the pages that are marked
472 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
473 * device memory to system memory. If the caller cannot migrate a device page
474 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
475 * consequences for the userspace process, so it must be avoided if at all
476 * possible.
477 *
478 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
479 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
480 * allowing the caller to allocate device memory for those unbacked virtual
481 * addresses. For this the caller simply has to allocate device memory and
482 * properly set the destination entry like for regular migration. Note that
483 * this can still fail, and thus inside the device driver you must check if the
484 * migration was successful for those entries after calling migrate_vma_pages(),
485 * just like for regular migration.
486 *
487 * After that, the callers must call migrate_vma_pages() to go over each entry
488 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
489 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
490 * then migrate_vma_pages() to migrate struct page information from the source
491 * struct page to the destination struct page. If it fails to migrate the
492 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
493 * src array.
494 *
495 * At this point all successfully migrated pages have an entry in the src
496 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
497 * array entry with MIGRATE_PFN_VALID flag set.
498 *
499 * Once migrate_vma_pages() returns the caller may inspect which pages were
500 * successfully migrated, and which were not. Successfully migrated pages will
501 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
502 *
503 * It is safe to update device page table after migrate_vma_pages() because
504 * both destination and source page are still locked, and the mmap_lock is held
505 * in read mode (hence no one can unmap the range being migrated).
506 *
507 * Once the caller is done cleaning up things and updating its page table (if it
508 * chose to do so, this is not an obligation) it finally calls
509 * migrate_vma_finalize() to update the CPU page table to point to new pages
510 * for successfully migrated pages or otherwise restore the CPU page table to
511 * point to the original source pages.
512 */
513int migrate_vma_setup(struct migrate_vma *args)
514{
515 long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
516
517 args->start &= PAGE_MASK;
518 args->end &= PAGE_MASK;
519 if (!args->vma || is_vm_hugetlb_page(args->vma) ||
520 (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
521 return -EINVAL;
522 if (nr_pages <= 0)
523 return -EINVAL;
524 if (args->start < args->vma->vm_start ||
525 args->start >= args->vma->vm_end)
526 return -EINVAL;
527 if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
528 return -EINVAL;
529 if (!args->src || !args->dst)
530 return -EINVAL;
16ce101d
AP
531 if (args->fault_page && !is_device_private_page(args->fault_page))
532 return -EINVAL;
76cbbead
CH
533
534 memset(args->src, 0, sizeof(*args->src) * nr_pages);
535 args->cpages = 0;
536 args->npages = 0;
537
538 migrate_vma_collect(args);
539
540 if (args->cpages)
541 migrate_vma_unmap(args);
542
543 /*
544 * At this point pages are locked and unmapped, and thus they have
545 * stable content and can safely be copied to destination memory that
546 * is allocated by the drivers.
547 */
548 return 0;
549
550}
551EXPORT_SYMBOL(migrate_vma_setup);
552
553/*
554 * This code closely matches the code in:
555 * __handle_mm_fault()
556 * handle_pte_fault()
557 * do_anonymous_page()
558 * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
f25cbb7a 559 * private or coherent page.
76cbbead
CH
560 */
561static void migrate_vma_insert_page(struct migrate_vma *migrate,
562 unsigned long addr,
563 struct page *page,
564 unsigned long *src)
565{
566 struct vm_area_struct *vma = migrate->vma;
567 struct mm_struct *mm = vma->vm_mm;
568 bool flush = false;
569 spinlock_t *ptl;
570 pte_t entry;
571 pgd_t *pgdp;
572 p4d_t *p4dp;
573 pud_t *pudp;
574 pmd_t *pmdp;
575 pte_t *ptep;
c33c7948 576 pte_t orig_pte;
76cbbead
CH
577
578 /* Only allow populating anonymous memory */
579 if (!vma_is_anonymous(vma))
580 goto abort;
581
582 pgdp = pgd_offset(mm, addr);
583 p4dp = p4d_alloc(mm, pgdp, addr);
584 if (!p4dp)
585 goto abort;
586 pudp = pud_alloc(mm, p4dp, addr);
587 if (!pudp)
588 goto abort;
589 pmdp = pmd_alloc(mm, pudp, addr);
590 if (!pmdp)
591 goto abort;
76cbbead
CH
592 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
593 goto abort;
76cbbead
CH
594 if (pte_alloc(mm, pmdp))
595 goto abort;
76cbbead
CH
596 if (unlikely(anon_vma_prepare(vma)))
597 goto abort;
598 if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
599 goto abort;
600
601 /*
602 * The memory barrier inside __SetPageUptodate makes sure that
603 * preceding stores to the page contents become visible before
604 * the set_pte_at() write.
605 */
606 __SetPageUptodate(page);
607
608 if (is_device_private_page(page)) {
609 swp_entry_t swp_entry;
610
611 if (vma->vm_flags & VM_WRITE)
612 swp_entry = make_writable_device_private_entry(
613 page_to_pfn(page));
614 else
615 swp_entry = make_readable_device_private_entry(
616 page_to_pfn(page));
617 entry = swp_entry_to_pte(swp_entry);
618 } else {
f25cbb7a
AS
619 if (is_zone_device_page(page) &&
620 !is_device_coherent_page(page)) {
76cbbead
CH
621 pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
622 goto abort;
623 }
624 entry = mk_pte(page, vma->vm_page_prot);
625 if (vma->vm_flags & VM_WRITE)
626 entry = pte_mkwrite(pte_mkdirty(entry));
627 }
628
629 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
4b56069c
HD
630 if (!ptep)
631 goto abort;
c33c7948
RR
632 orig_pte = ptep_get(ptep);
633
76cbbead
CH
634 if (check_stable_address_space(mm))
635 goto unlock_abort;
636
c33c7948
RR
637 if (pte_present(orig_pte)) {
638 unsigned long pfn = pte_pfn(orig_pte);
76cbbead
CH
639
640 if (!is_zero_pfn(pfn))
641 goto unlock_abort;
642 flush = true;
c33c7948 643 } else if (!pte_none(orig_pte))
76cbbead
CH
644 goto unlock_abort;
645
646 /*
647 * Check for userfaultfd but do not deliver the fault. Instead,
648 * just back off.
649 */
650 if (userfaultfd_missing(vma))
651 goto unlock_abort;
652
653 inc_mm_counter(mm, MM_ANONPAGES);
40f2bbf7 654 page_add_new_anon_rmap(page, vma, addr);
76cbbead
CH
655 if (!is_zone_device_page(page))
656 lru_cache_add_inactive_or_unevictable(page, vma);
657 get_page(page);
658
659 if (flush) {
c33c7948 660 flush_cache_page(vma, addr, pte_pfn(orig_pte));
76cbbead
CH
661 ptep_clear_flush_notify(vma, addr, ptep);
662 set_pte_at_notify(mm, addr, ptep, entry);
663 update_mmu_cache(vma, addr, ptep);
664 } else {
665 /* No need to invalidate - it was non-present before */
666 set_pte_at(mm, addr, ptep, entry);
667 update_mmu_cache(vma, addr, ptep);
668 }
669
670 pte_unmap_unlock(ptep, ptl);
671 *src = MIGRATE_PFN_MIGRATE;
672 return;
673
674unlock_abort:
675 pte_unmap_unlock(ptep, ptl);
676abort:
677 *src &= ~MIGRATE_PFN_MIGRATE;
678}
679
e778406b 680static void __migrate_device_pages(unsigned long *src_pfns,
241f6885
AP
681 unsigned long *dst_pfns, unsigned long npages,
682 struct migrate_vma *migrate)
76cbbead 683{
76cbbead 684 struct mmu_notifier_range range;
241f6885 685 unsigned long i;
76cbbead
CH
686 bool notified = false;
687
241f6885
AP
688 for (i = 0; i < npages; i++) {
689 struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
690 struct page *page = migrate_pfn_to_page(src_pfns[i]);
76cbbead
CH
691 struct address_space *mapping;
692 int r;
693
694 if (!newpage) {
241f6885 695 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
76cbbead
CH
696 continue;
697 }
698
699 if (!page) {
241f6885
AP
700 unsigned long addr;
701
e778406b
AP
702 if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE))
703 continue;
704
b05a79d4
AP
705 /*
706 * The only time there is no vma is when called from
707 * migrate_device_coherent_page(). However this isn't
708 * called if the page could not be unmapped.
709 */
241f6885
AP
710 VM_BUG_ON(!migrate);
711 addr = migrate->start + i*PAGE_SIZE;
76cbbead
CH
712 if (!notified) {
713 notified = true;
714
715 mmu_notifier_range_init_owner(&range,
7d4a8be0 716 MMU_NOTIFY_MIGRATE, 0,
76cbbead
CH
717 migrate->vma->vm_mm, addr, migrate->end,
718 migrate->pgmap_owner);
719 mmu_notifier_invalidate_range_start(&range);
720 }
721 migrate_vma_insert_page(migrate, addr, newpage,
241f6885 722 &src_pfns[i]);
76cbbead
CH
723 continue;
724 }
725
726 mapping = page_mapping(page);
727
f25cbb7a
AS
728 if (is_device_private_page(newpage) ||
729 is_device_coherent_page(newpage)) {
76cbbead 730 /*
f25cbb7a
AS
731 * For now only support anonymous memory migrating to
732 * device private or coherent memory.
76cbbead
CH
733 */
734 if (mapping) {
241f6885 735 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
76cbbead
CH
736 continue;
737 }
738 } else if (is_zone_device_page(newpage)) {
739 /*
740 * Other types of ZONE_DEVICE page are not supported.
741 */
241f6885 742 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
76cbbead
CH
743 continue;
744 }
745
241f6885 746 if (migrate && migrate->fault_page == page)
16ce101d
AP
747 r = migrate_folio_extra(mapping, page_folio(newpage),
748 page_folio(page),
749 MIGRATE_SYNC_NO_COPY, 1);
750 else
751 r = migrate_folio(mapping, page_folio(newpage),
752 page_folio(page), MIGRATE_SYNC_NO_COPY);
76cbbead 753 if (r != MIGRATEPAGE_SUCCESS)
241f6885 754 src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
76cbbead
CH
755 }
756
757 /*
758 * No need to double call mmu_notifier->invalidate_range() callback as
759 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
760 * did already call it.
761 */
762 if (notified)
763 mmu_notifier_invalidate_range_only_end(&range);
764}
76cbbead 765
e778406b
AP
766/**
767 * migrate_device_pages() - migrate meta-data from src page to dst page
768 * @src_pfns: src_pfns returned from migrate_device_range()
769 * @dst_pfns: array of pfns allocated by the driver to migrate memory to
770 * @npages: number of pages in the range
771 *
772 * Equivalent to migrate_vma_pages(). This is called to migrate struct page
773 * meta-data from source struct page to destination.
774 */
775void migrate_device_pages(unsigned long *src_pfns, unsigned long *dst_pfns,
776 unsigned long npages)
777{
778 __migrate_device_pages(src_pfns, dst_pfns, npages, NULL);
779}
780EXPORT_SYMBOL(migrate_device_pages);
781
76cbbead 782/**
241f6885 783 * migrate_vma_pages() - migrate meta-data from src page to dst page
76cbbead
CH
784 * @migrate: migrate struct containing all migration information
785 *
241f6885
AP
786 * This migrates struct page meta-data from source struct page to destination
787 * struct page. This effectively finishes the migration from source page to the
788 * destination page.
76cbbead 789 */
241f6885
AP
790void migrate_vma_pages(struct migrate_vma *migrate)
791{
e778406b 792 __migrate_device_pages(migrate->src, migrate->dst, migrate->npages, migrate);
241f6885
AP
793}
794EXPORT_SYMBOL(migrate_vma_pages);
795
e778406b
AP
796/*
797 * migrate_device_finalize() - complete page migration
798 * @src_pfns: src_pfns returned from migrate_device_range()
799 * @dst_pfns: array of pfns allocated by the driver to migrate memory to
800 * @npages: number of pages in the range
801 *
802 * Completes migration of the page by removing special migration entries.
803 * Drivers must ensure copying of page data is complete and visible to the CPU
804 * before calling this.
805 */
806void migrate_device_finalize(unsigned long *src_pfns,
807 unsigned long *dst_pfns, unsigned long npages)
76cbbead 808{
76cbbead
CH
809 unsigned long i;
810
811 for (i = 0; i < npages; i++) {
4eecb8b9 812 struct folio *dst, *src;
241f6885
AP
813 struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
814 struct page *page = migrate_pfn_to_page(src_pfns[i]);
76cbbead
CH
815
816 if (!page) {
817 if (newpage) {
818 unlock_page(newpage);
819 put_page(newpage);
820 }
821 continue;
822 }
823
241f6885 824 if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
76cbbead
CH
825 if (newpage) {
826 unlock_page(newpage);
827 put_page(newpage);
828 }
829 newpage = page;
830 }
831
4eecb8b9
MWO
832 src = page_folio(page);
833 dst = page_folio(newpage);
834 remove_migration_ptes(src, dst, false);
835 folio_unlock(src);
76cbbead
CH
836
837 if (is_zone_device_page(page))
838 put_page(page);
839 else
840 putback_lru_page(page);
841
842 if (newpage != page) {
843 unlock_page(newpage);
844 if (is_zone_device_page(newpage))
845 put_page(newpage);
846 else
847 putback_lru_page(newpage);
848 }
849 }
850}
e778406b 851EXPORT_SYMBOL(migrate_device_finalize);
241f6885
AP
852
853/**
854 * migrate_vma_finalize() - restore CPU page table entry
855 * @migrate: migrate struct containing all migration information
856 *
857 * This replaces the special migration pte entry with either a mapping to the
858 * new page if migration was successful for that page, or to the original page
859 * otherwise.
860 *
861 * This also unlocks the pages and puts them back on the lru, or drops the extra
862 * refcount, for device pages.
863 */
864void migrate_vma_finalize(struct migrate_vma *migrate)
865{
866 migrate_device_finalize(migrate->src, migrate->dst, migrate->npages);
867}
76cbbead 868EXPORT_SYMBOL(migrate_vma_finalize);
b05a79d4 869
e778406b
AP
870/**
871 * migrate_device_range() - migrate device private pfns to normal memory.
872 * @src_pfns: array large enough to hold migrating source device private pfns.
873 * @start: starting pfn in the range to migrate.
874 * @npages: number of pages to migrate.
875 *
876 * migrate_vma_setup() is similar in concept to migrate_vma_setup() except that
877 * instead of looking up pages based on virtual address mappings a range of
878 * device pfns that should be migrated to system memory is used instead.
879 *
880 * This is useful when a driver needs to free device memory but doesn't know the
881 * virtual mappings of every page that may be in device memory. For example this
882 * is often the case when a driver is being unloaded or unbound from a device.
883 *
884 * Like migrate_vma_setup() this function will take a reference and lock any
885 * migrating pages that aren't free before unmapping them. Drivers may then
886 * allocate destination pages and start copying data from the device to CPU
887 * memory before calling migrate_device_pages().
888 */
889int migrate_device_range(unsigned long *src_pfns, unsigned long start,
890 unsigned long npages)
891{
892 unsigned long i, pfn;
893
894 for (pfn = start, i = 0; i < npages; pfn++, i++) {
895 struct page *page = pfn_to_page(pfn);
896
897 if (!get_page_unless_zero(page)) {
898 src_pfns[i] = 0;
899 continue;
900 }
901
902 if (!trylock_page(page)) {
903 src_pfns[i] = 0;
904 put_page(page);
905 continue;
906 }
907
908 src_pfns[i] = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
909 }
910
911 migrate_device_unmap(src_pfns, npages, NULL);
912
913 return 0;
914}
915EXPORT_SYMBOL(migrate_device_range);
916
b05a79d4
AP
917/*
918 * Migrate a device coherent page back to normal memory. The caller should have
919 * a reference on page which will be copied to the new page if migration is
920 * successful or dropped on failure.
921 */
922int migrate_device_coherent_page(struct page *page)
923{
924 unsigned long src_pfn, dst_pfn = 0;
b05a79d4
AP
925 struct page *dpage;
926
927 WARN_ON_ONCE(PageCompound(page));
928
929 lock_page(page);
930 src_pfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE;
b05a79d4
AP
931
932 /*
933 * We don't have a VMA and don't need to walk the page tables to find
934 * the source page. So call migrate_vma_unmap() directly to unmap the
935 * page as migrate_vma_setup() will fail if args.vma == NULL.
936 */
241f6885 937 migrate_device_unmap(&src_pfn, 1, NULL);
b05a79d4
AP
938 if (!(src_pfn & MIGRATE_PFN_MIGRATE))
939 return -EBUSY;
940
941 dpage = alloc_page(GFP_USER | __GFP_NOWARN);
942 if (dpage) {
943 lock_page(dpage);
944 dst_pfn = migrate_pfn(page_to_pfn(dpage));
945 }
946
e778406b 947 migrate_device_pages(&src_pfn, &dst_pfn, 1);
b05a79d4
AP
948 if (src_pfn & MIGRATE_PFN_MIGRATE)
949 copy_highpage(dpage, page);
241f6885 950 migrate_device_finalize(&src_pfn, &dst_pfn, 1);
b05a79d4
AP
951
952 if (src_pfn & MIGRATE_PFN_MIGRATE)
953 return 0;
954 return -EBUSY;
955}