Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 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_inline.h> |
| 11 | #include <linux/mmu_notifier.h> |
| 12 | #include <linux/oom.h> |
| 13 | #include <linux/pagewalk.h> |
| 14 | #include <linux/rmap.h> |
| 15 | #include <linux/swapops.h> |
| 16 | #include <asm/tlbflush.h> |
| 17 | #include "internal.h" |
| 18 | |
| 19 | static int migrate_vma_collect_skip(unsigned long start, |
| 20 | unsigned long end, |
| 21 | struct mm_walk *walk) |
| 22 | { |
| 23 | struct migrate_vma *migrate = walk->private; |
| 24 | unsigned long addr; |
| 25 | |
| 26 | for (addr = start; addr < end; addr += PAGE_SIZE) { |
| 27 | migrate->dst[migrate->npages] = 0; |
| 28 | migrate->src[migrate->npages++] = 0; |
| 29 | } |
| 30 | |
| 31 | return 0; |
| 32 | } |
| 33 | |
| 34 | static int migrate_vma_collect_hole(unsigned long start, |
| 35 | unsigned long end, |
| 36 | __always_unused int depth, |
| 37 | struct mm_walk *walk) |
| 38 | { |
| 39 | struct migrate_vma *migrate = walk->private; |
| 40 | unsigned long addr; |
| 41 | |
| 42 | /* Only allow populating anonymous memory. */ |
| 43 | if (!vma_is_anonymous(walk->vma)) |
| 44 | return migrate_vma_collect_skip(start, end, walk); |
| 45 | |
| 46 | for (addr = start; addr < end; addr += PAGE_SIZE) { |
| 47 | migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE; |
| 48 | migrate->dst[migrate->npages] = 0; |
| 49 | migrate->npages++; |
| 50 | migrate->cpages++; |
| 51 | } |
| 52 | |
| 53 | return 0; |
| 54 | } |
| 55 | |
| 56 | static int migrate_vma_collect_pmd(pmd_t *pmdp, |
| 57 | unsigned long start, |
| 58 | unsigned long end, |
| 59 | struct mm_walk *walk) |
| 60 | { |
| 61 | struct migrate_vma *migrate = walk->private; |
| 62 | struct vm_area_struct *vma = walk->vma; |
| 63 | struct mm_struct *mm = vma->vm_mm; |
| 64 | unsigned long addr = start, unmapped = 0; |
| 65 | spinlock_t *ptl; |
| 66 | pte_t *ptep; |
| 67 | |
| 68 | again: |
| 69 | if (pmd_none(*pmdp)) |
| 70 | return migrate_vma_collect_hole(start, end, -1, walk); |
| 71 | |
| 72 | if (pmd_trans_huge(*pmdp)) { |
| 73 | struct page *page; |
| 74 | |
| 75 | ptl = pmd_lock(mm, pmdp); |
| 76 | if (unlikely(!pmd_trans_huge(*pmdp))) { |
| 77 | spin_unlock(ptl); |
| 78 | goto again; |
| 79 | } |
| 80 | |
| 81 | page = pmd_page(*pmdp); |
| 82 | if (is_huge_zero_page(page)) { |
| 83 | spin_unlock(ptl); |
| 84 | split_huge_pmd(vma, pmdp, addr); |
| 85 | if (pmd_trans_unstable(pmdp)) |
| 86 | return migrate_vma_collect_skip(start, end, |
| 87 | walk); |
| 88 | } else { |
| 89 | int ret; |
| 90 | |
| 91 | get_page(page); |
| 92 | spin_unlock(ptl); |
| 93 | if (unlikely(!trylock_page(page))) |
| 94 | return migrate_vma_collect_skip(start, end, |
| 95 | walk); |
| 96 | ret = split_huge_page(page); |
| 97 | unlock_page(page); |
| 98 | put_page(page); |
| 99 | if (ret) |
| 100 | return migrate_vma_collect_skip(start, end, |
| 101 | walk); |
| 102 | if (pmd_none(*pmdp)) |
| 103 | return migrate_vma_collect_hole(start, end, -1, |
| 104 | walk); |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | if (unlikely(pmd_bad(*pmdp))) |
| 109 | return migrate_vma_collect_skip(start, end, walk); |
| 110 | |
| 111 | ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); |
| 112 | arch_enter_lazy_mmu_mode(); |
| 113 | |
| 114 | for (; addr < end; addr += PAGE_SIZE, ptep++) { |
| 115 | unsigned long mpfn = 0, pfn; |
| 116 | struct page *page; |
| 117 | swp_entry_t entry; |
| 118 | pte_t pte; |
| 119 | |
| 120 | pte = *ptep; |
| 121 | |
| 122 | if (pte_none(pte)) { |
| 123 | if (vma_is_anonymous(vma)) { |
| 124 | mpfn = MIGRATE_PFN_MIGRATE; |
| 125 | migrate->cpages++; |
| 126 | } |
| 127 | goto next; |
| 128 | } |
| 129 | |
| 130 | if (!pte_present(pte)) { |
| 131 | /* |
| 132 | * Only care about unaddressable device page special |
| 133 | * page table entry. Other special swap entries are not |
| 134 | * migratable, and we ignore regular swapped page. |
| 135 | */ |
| 136 | entry = pte_to_swp_entry(pte); |
| 137 | if (!is_device_private_entry(entry)) |
| 138 | goto next; |
| 139 | |
| 140 | page = pfn_swap_entry_to_page(entry); |
| 141 | if (!(migrate->flags & |
| 142 | MIGRATE_VMA_SELECT_DEVICE_PRIVATE) || |
| 143 | page->pgmap->owner != migrate->pgmap_owner) |
| 144 | goto next; |
| 145 | |
| 146 | mpfn = migrate_pfn(page_to_pfn(page)) | |
| 147 | MIGRATE_PFN_MIGRATE; |
| 148 | if (is_writable_device_private_entry(entry)) |
| 149 | mpfn |= MIGRATE_PFN_WRITE; |
| 150 | } else { |
| 151 | if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) |
| 152 | goto next; |
| 153 | pfn = pte_pfn(pte); |
| 154 | if (is_zero_pfn(pfn)) { |
| 155 | mpfn = MIGRATE_PFN_MIGRATE; |
| 156 | migrate->cpages++; |
| 157 | goto next; |
| 158 | } |
| 159 | page = vm_normal_page(migrate->vma, addr, pte); |
| 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 | /* |
| 182 | * Optimize for the common case where page is only mapped once |
| 183 | * in one process. If we can lock the page, then we can safely |
| 184 | * set up a special migration page table entry now. |
| 185 | */ |
| 186 | if (trylock_page(page)) { |
| 187 | pte_t swp_pte; |
| 188 | |
| 189 | migrate->cpages++; |
| 190 | ptep_get_and_clear(mm, addr, ptep); |
| 191 | |
| 192 | /* Setup special migration page table entry */ |
| 193 | if (mpfn & MIGRATE_PFN_WRITE) |
| 194 | entry = make_writable_migration_entry( |
| 195 | page_to_pfn(page)); |
| 196 | else |
| 197 | entry = make_readable_migration_entry( |
| 198 | page_to_pfn(page)); |
| 199 | swp_pte = swp_entry_to_pte(entry); |
| 200 | if (pte_present(pte)) { |
| 201 | if (pte_soft_dirty(pte)) |
| 202 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| 203 | if (pte_uffd_wp(pte)) |
| 204 | swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| 205 | } else { |
| 206 | if (pte_swp_soft_dirty(pte)) |
| 207 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| 208 | if (pte_swp_uffd_wp(pte)) |
| 209 | swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| 210 | } |
| 211 | set_pte_at(mm, addr, ptep, swp_pte); |
| 212 | |
| 213 | /* |
| 214 | * This is like regular unmap: we remove the rmap and |
| 215 | * drop page refcount. Page won't be freed, as we took |
| 216 | * a reference just above. |
| 217 | */ |
| 218 | page_remove_rmap(page, vma, false); |
| 219 | put_page(page); |
| 220 | |
| 221 | if (pte_present(pte)) |
| 222 | unmapped++; |
| 223 | } else { |
| 224 | put_page(page); |
| 225 | mpfn = 0; |
| 226 | } |
| 227 | |
| 228 | next: |
| 229 | migrate->dst[migrate->npages] = 0; |
| 230 | migrate->src[migrate->npages++] = mpfn; |
| 231 | } |
| 232 | arch_leave_lazy_mmu_mode(); |
| 233 | pte_unmap_unlock(ptep - 1, ptl); |
| 234 | |
| 235 | /* Only flush the TLB if we actually modified any entries */ |
| 236 | if (unmapped) |
| 237 | flush_tlb_range(walk->vma, start, end); |
| 238 | |
| 239 | return 0; |
| 240 | } |
| 241 | |
| 242 | static const struct mm_walk_ops migrate_vma_walk_ops = { |
| 243 | .pmd_entry = migrate_vma_collect_pmd, |
| 244 | .pte_hole = migrate_vma_collect_hole, |
| 245 | }; |
| 246 | |
| 247 | /* |
| 248 | * migrate_vma_collect() - collect pages over a range of virtual addresses |
| 249 | * @migrate: migrate struct containing all migration information |
| 250 | * |
| 251 | * This will walk the CPU page table. For each virtual address backed by a |
| 252 | * valid page, it updates the src array and takes a reference on the page, in |
| 253 | * order to pin the page until we lock it and unmap it. |
| 254 | */ |
| 255 | static void migrate_vma_collect(struct migrate_vma *migrate) |
| 256 | { |
| 257 | struct mmu_notifier_range range; |
| 258 | |
| 259 | /* |
| 260 | * Note that the pgmap_owner is passed to the mmu notifier callback so |
| 261 | * that the registered device driver can skip invalidating device |
| 262 | * private page mappings that won't be migrated. |
| 263 | */ |
| 264 | mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0, |
| 265 | migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end, |
| 266 | migrate->pgmap_owner); |
| 267 | mmu_notifier_invalidate_range_start(&range); |
| 268 | |
| 269 | walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end, |
| 270 | &migrate_vma_walk_ops, migrate); |
| 271 | |
| 272 | mmu_notifier_invalidate_range_end(&range); |
| 273 | migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT); |
| 274 | } |
| 275 | |
| 276 | /* |
| 277 | * migrate_vma_check_page() - check if page is pinned or not |
| 278 | * @page: struct page to check |
| 279 | * |
| 280 | * Pinned pages cannot be migrated. This is the same test as in |
| 281 | * folio_migrate_mapping(), except that here we allow migration of a |
| 282 | * ZONE_DEVICE page. |
| 283 | */ |
| 284 | static bool migrate_vma_check_page(struct page *page) |
| 285 | { |
| 286 | /* |
| 287 | * One extra ref because caller holds an extra reference, either from |
| 288 | * isolate_lru_page() for a regular page, or migrate_vma_collect() for |
| 289 | * a device page. |
| 290 | */ |
| 291 | int extra = 1; |
| 292 | |
| 293 | /* |
| 294 | * FIXME support THP (transparent huge page), it is bit more complex to |
| 295 | * check them than regular pages, because they can be mapped with a pmd |
| 296 | * or with a pte (split pte mapping). |
| 297 | */ |
| 298 | if (PageCompound(page)) |
| 299 | return false; |
| 300 | |
| 301 | /* Page from ZONE_DEVICE have one extra reference */ |
| 302 | if (is_zone_device_page(page)) |
| 303 | extra++; |
| 304 | |
| 305 | /* For file back page */ |
| 306 | if (page_mapping(page)) |
| 307 | extra += 1 + page_has_private(page); |
| 308 | |
| 309 | if ((page_count(page) - extra) > page_mapcount(page)) |
| 310 | return false; |
| 311 | |
| 312 | return true; |
| 313 | } |
| 314 | |
| 315 | /* |
| 316 | * migrate_vma_unmap() - replace page mapping with special migration pte entry |
| 317 | * @migrate: migrate struct containing all migration information |
| 318 | * |
| 319 | * Isolate pages from the LRU and replace mappings (CPU page table pte) with a |
| 320 | * special migration pte entry and check if it has been pinned. Pinned pages are |
| 321 | * restored because we cannot migrate them. |
| 322 | * |
| 323 | * This is the last step before we call the device driver callback to allocate |
| 324 | * destination memory and copy contents of original page over to new page. |
| 325 | */ |
| 326 | static void migrate_vma_unmap(struct migrate_vma *migrate) |
| 327 | { |
| 328 | const unsigned long npages = migrate->npages; |
| 329 | unsigned long i, restore = 0; |
| 330 | bool allow_drain = true; |
| 331 | |
| 332 | lru_add_drain(); |
| 333 | |
| 334 | for (i = 0; i < npages; i++) { |
| 335 | struct page *page = migrate_pfn_to_page(migrate->src[i]); |
Matthew Wilcox (Oracle) | 4b8554c | 2022-01-28 14:29:43 -0500 | [diff] [blame] | 336 | struct folio *folio; |
Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 337 | |
| 338 | if (!page) |
| 339 | continue; |
| 340 | |
| 341 | /* ZONE_DEVICE pages are not on LRU */ |
| 342 | if (!is_zone_device_page(page)) { |
| 343 | if (!PageLRU(page) && allow_drain) { |
| 344 | /* Drain CPU's pagevec */ |
| 345 | lru_add_drain_all(); |
| 346 | allow_drain = false; |
| 347 | } |
| 348 | |
| 349 | if (isolate_lru_page(page)) { |
| 350 | migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| 351 | migrate->cpages--; |
| 352 | restore++; |
| 353 | continue; |
| 354 | } |
| 355 | |
| 356 | /* Drop the reference we took in collect */ |
| 357 | put_page(page); |
| 358 | } |
| 359 | |
Matthew Wilcox (Oracle) | 4b8554c | 2022-01-28 14:29:43 -0500 | [diff] [blame] | 360 | folio = page_folio(page); |
| 361 | if (folio_mapped(folio)) |
| 362 | try_to_migrate(folio, 0); |
Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 363 | |
| 364 | if (page_mapped(page) || !migrate_vma_check_page(page)) { |
| 365 | if (!is_zone_device_page(page)) { |
| 366 | get_page(page); |
| 367 | putback_lru_page(page); |
| 368 | } |
| 369 | |
| 370 | migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| 371 | migrate->cpages--; |
| 372 | restore++; |
| 373 | continue; |
| 374 | } |
| 375 | } |
| 376 | |
| 377 | for (i = 0; i < npages && restore; i++) { |
| 378 | struct page *page = migrate_pfn_to_page(migrate->src[i]); |
Matthew Wilcox (Oracle) | 4eecb8b | 2022-01-28 23:32:59 -0500 | [diff] [blame] | 379 | struct folio *folio; |
Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 380 | |
| 381 | if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE)) |
| 382 | continue; |
| 383 | |
Matthew Wilcox (Oracle) | 4eecb8b | 2022-01-28 23:32:59 -0500 | [diff] [blame] | 384 | folio = page_folio(page); |
| 385 | remove_migration_ptes(folio, folio, false); |
Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 386 | |
| 387 | migrate->src[i] = 0; |
Matthew Wilcox (Oracle) | 4eecb8b | 2022-01-28 23:32:59 -0500 | [diff] [blame] | 388 | folio_unlock(folio); |
| 389 | folio_put(folio); |
Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 390 | restore--; |
| 391 | } |
| 392 | } |
| 393 | |
| 394 | /** |
| 395 | * migrate_vma_setup() - prepare to migrate a range of memory |
| 396 | * @args: contains the vma, start, and pfns arrays for the migration |
| 397 | * |
| 398 | * Returns: negative errno on failures, 0 when 0 or more pages were migrated |
| 399 | * without an error. |
| 400 | * |
| 401 | * Prepare to migrate a range of memory virtual address range by collecting all |
| 402 | * the pages backing each virtual address in the range, saving them inside the |
| 403 | * src array. Then lock those pages and unmap them. Once the pages are locked |
| 404 | * and unmapped, check whether each page is pinned or not. Pages that aren't |
| 405 | * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the |
| 406 | * corresponding src array entry. Then restores any pages that are pinned, by |
| 407 | * remapping and unlocking those pages. |
| 408 | * |
| 409 | * The caller should then allocate destination memory and copy source memory to |
| 410 | * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE |
| 411 | * flag set). Once these are allocated and copied, the caller must update each |
| 412 | * corresponding entry in the dst array with the pfn value of the destination |
| 413 | * page and with MIGRATE_PFN_VALID. Destination pages must be locked via |
| 414 | * lock_page(). |
| 415 | * |
| 416 | * Note that the caller does not have to migrate all the pages that are marked |
| 417 | * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from |
| 418 | * device memory to system memory. If the caller cannot migrate a device page |
| 419 | * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe |
| 420 | * consequences for the userspace process, so it must be avoided if at all |
| 421 | * possible. |
| 422 | * |
| 423 | * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we |
| 424 | * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus |
| 425 | * allowing the caller to allocate device memory for those unbacked virtual |
| 426 | * addresses. For this the caller simply has to allocate device memory and |
| 427 | * properly set the destination entry like for regular migration. Note that |
| 428 | * this can still fail, and thus inside the device driver you must check if the |
| 429 | * migration was successful for those entries after calling migrate_vma_pages(), |
| 430 | * just like for regular migration. |
| 431 | * |
| 432 | * After that, the callers must call migrate_vma_pages() to go over each entry |
| 433 | * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag |
| 434 | * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set, |
| 435 | * then migrate_vma_pages() to migrate struct page information from the source |
| 436 | * struct page to the destination struct page. If it fails to migrate the |
| 437 | * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the |
| 438 | * src array. |
| 439 | * |
| 440 | * At this point all successfully migrated pages have an entry in the src |
| 441 | * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst |
| 442 | * array entry with MIGRATE_PFN_VALID flag set. |
| 443 | * |
| 444 | * Once migrate_vma_pages() returns the caller may inspect which pages were |
| 445 | * successfully migrated, and which were not. Successfully migrated pages will |
| 446 | * have the MIGRATE_PFN_MIGRATE flag set for their src array entry. |
| 447 | * |
| 448 | * It is safe to update device page table after migrate_vma_pages() because |
| 449 | * both destination and source page are still locked, and the mmap_lock is held |
| 450 | * in read mode (hence no one can unmap the range being migrated). |
| 451 | * |
| 452 | * Once the caller is done cleaning up things and updating its page table (if it |
| 453 | * chose to do so, this is not an obligation) it finally calls |
| 454 | * migrate_vma_finalize() to update the CPU page table to point to new pages |
| 455 | * for successfully migrated pages or otherwise restore the CPU page table to |
| 456 | * point to the original source pages. |
| 457 | */ |
| 458 | int migrate_vma_setup(struct migrate_vma *args) |
| 459 | { |
| 460 | long nr_pages = (args->end - args->start) >> PAGE_SHIFT; |
| 461 | |
| 462 | args->start &= PAGE_MASK; |
| 463 | args->end &= PAGE_MASK; |
| 464 | if (!args->vma || is_vm_hugetlb_page(args->vma) || |
| 465 | (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma)) |
| 466 | return -EINVAL; |
| 467 | if (nr_pages <= 0) |
| 468 | return -EINVAL; |
| 469 | if (args->start < args->vma->vm_start || |
| 470 | args->start >= args->vma->vm_end) |
| 471 | return -EINVAL; |
| 472 | if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end) |
| 473 | return -EINVAL; |
| 474 | if (!args->src || !args->dst) |
| 475 | return -EINVAL; |
| 476 | |
| 477 | memset(args->src, 0, sizeof(*args->src) * nr_pages); |
| 478 | args->cpages = 0; |
| 479 | args->npages = 0; |
| 480 | |
| 481 | migrate_vma_collect(args); |
| 482 | |
| 483 | if (args->cpages) |
| 484 | migrate_vma_unmap(args); |
| 485 | |
| 486 | /* |
| 487 | * At this point pages are locked and unmapped, and thus they have |
| 488 | * stable content and can safely be copied to destination memory that |
| 489 | * is allocated by the drivers. |
| 490 | */ |
| 491 | return 0; |
| 492 | |
| 493 | } |
| 494 | EXPORT_SYMBOL(migrate_vma_setup); |
| 495 | |
| 496 | /* |
| 497 | * This code closely matches the code in: |
| 498 | * __handle_mm_fault() |
| 499 | * handle_pte_fault() |
| 500 | * do_anonymous_page() |
| 501 | * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE |
| 502 | * private page. |
| 503 | */ |
| 504 | static void migrate_vma_insert_page(struct migrate_vma *migrate, |
| 505 | unsigned long addr, |
| 506 | struct page *page, |
| 507 | unsigned long *src) |
| 508 | { |
| 509 | struct vm_area_struct *vma = migrate->vma; |
| 510 | struct mm_struct *mm = vma->vm_mm; |
| 511 | bool flush = false; |
| 512 | spinlock_t *ptl; |
| 513 | pte_t entry; |
| 514 | pgd_t *pgdp; |
| 515 | p4d_t *p4dp; |
| 516 | pud_t *pudp; |
| 517 | pmd_t *pmdp; |
| 518 | pte_t *ptep; |
| 519 | |
| 520 | /* Only allow populating anonymous memory */ |
| 521 | if (!vma_is_anonymous(vma)) |
| 522 | goto abort; |
| 523 | |
| 524 | pgdp = pgd_offset(mm, addr); |
| 525 | p4dp = p4d_alloc(mm, pgdp, addr); |
| 526 | if (!p4dp) |
| 527 | goto abort; |
| 528 | pudp = pud_alloc(mm, p4dp, addr); |
| 529 | if (!pudp) |
| 530 | goto abort; |
| 531 | pmdp = pmd_alloc(mm, pudp, addr); |
| 532 | if (!pmdp) |
| 533 | goto abort; |
| 534 | |
| 535 | if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp)) |
| 536 | goto abort; |
| 537 | |
| 538 | /* |
| 539 | * Use pte_alloc() instead of pte_alloc_map(). We can't run |
| 540 | * pte_offset_map() on pmds where a huge pmd might be created |
| 541 | * from a different thread. |
| 542 | * |
| 543 | * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when |
| 544 | * parallel threads are excluded by other means. |
| 545 | * |
| 546 | * Here we only have mmap_read_lock(mm). |
| 547 | */ |
| 548 | if (pte_alloc(mm, pmdp)) |
| 549 | goto abort; |
| 550 | |
| 551 | /* See the comment in pte_alloc_one_map() */ |
| 552 | if (unlikely(pmd_trans_unstable(pmdp))) |
| 553 | goto abort; |
| 554 | |
| 555 | if (unlikely(anon_vma_prepare(vma))) |
| 556 | goto abort; |
| 557 | if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL)) |
| 558 | goto abort; |
| 559 | |
| 560 | /* |
| 561 | * The memory barrier inside __SetPageUptodate makes sure that |
| 562 | * preceding stores to the page contents become visible before |
| 563 | * the set_pte_at() write. |
| 564 | */ |
| 565 | __SetPageUptodate(page); |
| 566 | |
| 567 | if (is_device_private_page(page)) { |
| 568 | swp_entry_t swp_entry; |
| 569 | |
| 570 | if (vma->vm_flags & VM_WRITE) |
| 571 | swp_entry = make_writable_device_private_entry( |
| 572 | page_to_pfn(page)); |
| 573 | else |
| 574 | swp_entry = make_readable_device_private_entry( |
| 575 | page_to_pfn(page)); |
| 576 | entry = swp_entry_to_pte(swp_entry); |
| 577 | } else { |
| 578 | /* |
| 579 | * For now we only support migrating to un-addressable device |
| 580 | * memory. |
| 581 | */ |
| 582 | if (is_zone_device_page(page)) { |
| 583 | pr_warn_once("Unsupported ZONE_DEVICE page type.\n"); |
| 584 | goto abort; |
| 585 | } |
| 586 | entry = mk_pte(page, vma->vm_page_prot); |
| 587 | if (vma->vm_flags & VM_WRITE) |
| 588 | entry = pte_mkwrite(pte_mkdirty(entry)); |
| 589 | } |
| 590 | |
| 591 | ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); |
| 592 | |
| 593 | if (check_stable_address_space(mm)) |
| 594 | goto unlock_abort; |
| 595 | |
| 596 | if (pte_present(*ptep)) { |
| 597 | unsigned long pfn = pte_pfn(*ptep); |
| 598 | |
| 599 | if (!is_zero_pfn(pfn)) |
| 600 | goto unlock_abort; |
| 601 | flush = true; |
| 602 | } else if (!pte_none(*ptep)) |
| 603 | goto unlock_abort; |
| 604 | |
| 605 | /* |
| 606 | * Check for userfaultfd but do not deliver the fault. Instead, |
| 607 | * just back off. |
| 608 | */ |
| 609 | if (userfaultfd_missing(vma)) |
| 610 | goto unlock_abort; |
| 611 | |
| 612 | inc_mm_counter(mm, MM_ANONPAGES); |
| 613 | page_add_new_anon_rmap(page, vma, addr, false); |
| 614 | if (!is_zone_device_page(page)) |
| 615 | lru_cache_add_inactive_or_unevictable(page, vma); |
| 616 | get_page(page); |
| 617 | |
| 618 | if (flush) { |
| 619 | flush_cache_page(vma, addr, pte_pfn(*ptep)); |
| 620 | ptep_clear_flush_notify(vma, addr, ptep); |
| 621 | set_pte_at_notify(mm, addr, ptep, entry); |
| 622 | update_mmu_cache(vma, addr, ptep); |
| 623 | } else { |
| 624 | /* No need to invalidate - it was non-present before */ |
| 625 | set_pte_at(mm, addr, ptep, entry); |
| 626 | update_mmu_cache(vma, addr, ptep); |
| 627 | } |
| 628 | |
| 629 | pte_unmap_unlock(ptep, ptl); |
| 630 | *src = MIGRATE_PFN_MIGRATE; |
| 631 | return; |
| 632 | |
| 633 | unlock_abort: |
| 634 | pte_unmap_unlock(ptep, ptl); |
| 635 | abort: |
| 636 | *src &= ~MIGRATE_PFN_MIGRATE; |
| 637 | } |
| 638 | |
| 639 | /** |
| 640 | * migrate_vma_pages() - migrate meta-data from src page to dst page |
| 641 | * @migrate: migrate struct containing all migration information |
| 642 | * |
| 643 | * This migrates struct page meta-data from source struct page to destination |
| 644 | * struct page. This effectively finishes the migration from source page to the |
| 645 | * destination page. |
| 646 | */ |
| 647 | void migrate_vma_pages(struct migrate_vma *migrate) |
| 648 | { |
| 649 | const unsigned long npages = migrate->npages; |
| 650 | const unsigned long start = migrate->start; |
| 651 | struct mmu_notifier_range range; |
| 652 | unsigned long addr, i; |
| 653 | bool notified = false; |
| 654 | |
| 655 | for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) { |
| 656 | struct page *newpage = migrate_pfn_to_page(migrate->dst[i]); |
| 657 | struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| 658 | struct address_space *mapping; |
| 659 | int r; |
| 660 | |
| 661 | if (!newpage) { |
| 662 | migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| 663 | continue; |
| 664 | } |
| 665 | |
| 666 | if (!page) { |
| 667 | if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) |
| 668 | continue; |
| 669 | if (!notified) { |
| 670 | notified = true; |
| 671 | |
| 672 | mmu_notifier_range_init_owner(&range, |
| 673 | MMU_NOTIFY_MIGRATE, 0, migrate->vma, |
| 674 | migrate->vma->vm_mm, addr, migrate->end, |
| 675 | migrate->pgmap_owner); |
| 676 | mmu_notifier_invalidate_range_start(&range); |
| 677 | } |
| 678 | migrate_vma_insert_page(migrate, addr, newpage, |
| 679 | &migrate->src[i]); |
| 680 | continue; |
| 681 | } |
| 682 | |
| 683 | mapping = page_mapping(page); |
| 684 | |
| 685 | if (is_device_private_page(newpage)) { |
| 686 | /* |
| 687 | * For now only support private anonymous when migrating |
| 688 | * to un-addressable device memory. |
| 689 | */ |
| 690 | if (mapping) { |
| 691 | migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| 692 | continue; |
| 693 | } |
| 694 | } else if (is_zone_device_page(newpage)) { |
| 695 | /* |
| 696 | * Other types of ZONE_DEVICE page are not supported. |
| 697 | */ |
| 698 | migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| 699 | continue; |
| 700 | } |
| 701 | |
| 702 | r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY); |
| 703 | if (r != MIGRATEPAGE_SUCCESS) |
| 704 | migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; |
| 705 | } |
| 706 | |
| 707 | /* |
| 708 | * No need to double call mmu_notifier->invalidate_range() callback as |
| 709 | * the above ptep_clear_flush_notify() inside migrate_vma_insert_page() |
| 710 | * did already call it. |
| 711 | */ |
| 712 | if (notified) |
| 713 | mmu_notifier_invalidate_range_only_end(&range); |
| 714 | } |
| 715 | EXPORT_SYMBOL(migrate_vma_pages); |
| 716 | |
| 717 | /** |
| 718 | * migrate_vma_finalize() - restore CPU page table entry |
| 719 | * @migrate: migrate struct containing all migration information |
| 720 | * |
| 721 | * This replaces the special migration pte entry with either a mapping to the |
| 722 | * new page if migration was successful for that page, or to the original page |
| 723 | * otherwise. |
| 724 | * |
| 725 | * This also unlocks the pages and puts them back on the lru, or drops the extra |
| 726 | * refcount, for device pages. |
| 727 | */ |
| 728 | void migrate_vma_finalize(struct migrate_vma *migrate) |
| 729 | { |
| 730 | const unsigned long npages = migrate->npages; |
| 731 | unsigned long i; |
| 732 | |
| 733 | for (i = 0; i < npages; i++) { |
Matthew Wilcox (Oracle) | 4eecb8b | 2022-01-28 23:32:59 -0500 | [diff] [blame] | 734 | struct folio *dst, *src; |
Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 735 | struct page *newpage = migrate_pfn_to_page(migrate->dst[i]); |
| 736 | struct page *page = migrate_pfn_to_page(migrate->src[i]); |
| 737 | |
| 738 | if (!page) { |
| 739 | if (newpage) { |
| 740 | unlock_page(newpage); |
| 741 | put_page(newpage); |
| 742 | } |
| 743 | continue; |
| 744 | } |
| 745 | |
| 746 | if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) { |
| 747 | if (newpage) { |
| 748 | unlock_page(newpage); |
| 749 | put_page(newpage); |
| 750 | } |
| 751 | newpage = page; |
| 752 | } |
| 753 | |
Matthew Wilcox (Oracle) | 4eecb8b | 2022-01-28 23:32:59 -0500 | [diff] [blame] | 754 | src = page_folio(page); |
| 755 | dst = page_folio(newpage); |
| 756 | remove_migration_ptes(src, dst, false); |
| 757 | folio_unlock(src); |
Christoph Hellwig | 76cbbea | 2022-02-16 15:31:38 +1100 | [diff] [blame] | 758 | |
| 759 | if (is_zone_device_page(page)) |
| 760 | put_page(page); |
| 761 | else |
| 762 | putback_lru_page(page); |
| 763 | |
| 764 | if (newpage != page) { |
| 765 | unlock_page(newpage); |
| 766 | if (is_zone_device_page(newpage)) |
| 767 | put_page(newpage); |
| 768 | else |
| 769 | putback_lru_page(newpage); |
| 770 | } |
| 771 | } |
| 772 | } |
| 773 | EXPORT_SYMBOL(migrate_vma_finalize); |