1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Virtual Memory Map support 4 * 5 * (C) 2007 sgi. Christoph Lameter. 6 * 7 * Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn, 8 * virt_to_page, page_address() to be implemented as a base offset 9 * calculation without memory access. 10 * 11 * However, virtual mappings need a page table and TLBs. Many Linux 12 * architectures already map their physical space using 1-1 mappings 13 * via TLBs. For those arches the virtual memory map is essentially 14 * for free if we use the same page size as the 1-1 mappings. In that 15 * case the overhead consists of a few additional pages that are 16 * allocated to create a view of memory for vmemmap. 17 * 18 * The architecture is expected to provide a vmemmap_populate() function 19 * to instantiate the mapping. 20 */ 21 #include <linux/mm.h> 22 #include <linux/mmzone.h> 23 #include <linux/memblock.h> 24 #include <linux/memremap.h> 25 #include <linux/highmem.h> 26 #include <linux/slab.h> 27 #include <linux/spinlock.h> 28 #include <linux/vmalloc.h> 29 #include <linux/sched.h> 30 #include <linux/pgtable.h> 31 #include <linux/bootmem_info.h> 32 33 #include <asm/dma.h> 34 #include <asm/pgalloc.h> 35 #include <asm/tlbflush.h> 36 37 #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP 38 /** 39 * struct vmemmap_remap_walk - walk vmemmap page table 40 * 41 * @remap_pte: called for each lowest-level entry (PTE). 42 * @nr_walked: the number of walked pte. 43 * @reuse_page: the page which is reused for the tail vmemmap pages. 44 * @reuse_addr: the virtual address of the @reuse_page page. 45 * @vmemmap_pages: the list head of the vmemmap pages that can be freed 46 * or is mapped from. 47 */ 48 struct vmemmap_remap_walk { 49 void (*remap_pte)(pte_t *pte, unsigned long addr, 50 struct vmemmap_remap_walk *walk); 51 unsigned long nr_walked; 52 struct page *reuse_page; 53 unsigned long reuse_addr; 54 struct list_head *vmemmap_pages; 55 }; 56 57 static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start) 58 { 59 pmd_t __pmd; 60 int i; 61 unsigned long addr = start; 62 struct page *page = pmd_page(*pmd); 63 pte_t *pgtable = pte_alloc_one_kernel(&init_mm); 64 65 if (!pgtable) 66 return -ENOMEM; 67 68 pmd_populate_kernel(&init_mm, &__pmd, pgtable); 69 70 for (i = 0; i < PMD_SIZE / PAGE_SIZE; i++, addr += PAGE_SIZE) { 71 pte_t entry, *pte; 72 pgprot_t pgprot = PAGE_KERNEL; 73 74 entry = mk_pte(page + i, pgprot); 75 pte = pte_offset_kernel(&__pmd, addr); 76 set_pte_at(&init_mm, addr, pte, entry); 77 } 78 79 spin_lock(&init_mm.page_table_lock); 80 if (likely(pmd_leaf(*pmd))) { 81 /* 82 * Higher order allocations from buddy allocator must be able to 83 * be treated as indepdenent small pages (as they can be freed 84 * individually). 85 */ 86 if (!PageReserved(page)) 87 split_page(page, get_order(PMD_SIZE)); 88 89 /* Make pte visible before pmd. See comment in pmd_install(). */ 90 smp_wmb(); 91 pmd_populate_kernel(&init_mm, pmd, pgtable); 92 flush_tlb_kernel_range(start, start + PMD_SIZE); 93 } else { 94 pte_free_kernel(&init_mm, pgtable); 95 } 96 spin_unlock(&init_mm.page_table_lock); 97 98 return 0; 99 } 100 101 static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start) 102 { 103 int leaf; 104 105 spin_lock(&init_mm.page_table_lock); 106 leaf = pmd_leaf(*pmd); 107 spin_unlock(&init_mm.page_table_lock); 108 109 if (!leaf) 110 return 0; 111 112 return __split_vmemmap_huge_pmd(pmd, start); 113 } 114 115 static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr, 116 unsigned long end, 117 struct vmemmap_remap_walk *walk) 118 { 119 pte_t *pte = pte_offset_kernel(pmd, addr); 120 121 /* 122 * The reuse_page is found 'first' in table walk before we start 123 * remapping (which is calling @walk->remap_pte). 124 */ 125 if (!walk->reuse_page) { 126 walk->reuse_page = pte_page(*pte); 127 /* 128 * Because the reuse address is part of the range that we are 129 * walking, skip the reuse address range. 130 */ 131 addr += PAGE_SIZE; 132 pte++; 133 walk->nr_walked++; 134 } 135 136 for (; addr != end; addr += PAGE_SIZE, pte++) { 137 walk->remap_pte(pte, addr, walk); 138 walk->nr_walked++; 139 } 140 } 141 142 static int vmemmap_pmd_range(pud_t *pud, unsigned long addr, 143 unsigned long end, 144 struct vmemmap_remap_walk *walk) 145 { 146 pmd_t *pmd; 147 unsigned long next; 148 149 pmd = pmd_offset(pud, addr); 150 do { 151 int ret; 152 153 ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK); 154 if (ret) 155 return ret; 156 157 next = pmd_addr_end(addr, end); 158 vmemmap_pte_range(pmd, addr, next, walk); 159 } while (pmd++, addr = next, addr != end); 160 161 return 0; 162 } 163 164 static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr, 165 unsigned long end, 166 struct vmemmap_remap_walk *walk) 167 { 168 pud_t *pud; 169 unsigned long next; 170 171 pud = pud_offset(p4d, addr); 172 do { 173 int ret; 174 175 next = pud_addr_end(addr, end); 176 ret = vmemmap_pmd_range(pud, addr, next, walk); 177 if (ret) 178 return ret; 179 } while (pud++, addr = next, addr != end); 180 181 return 0; 182 } 183 184 static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr, 185 unsigned long end, 186 struct vmemmap_remap_walk *walk) 187 { 188 p4d_t *p4d; 189 unsigned long next; 190 191 p4d = p4d_offset(pgd, addr); 192 do { 193 int ret; 194 195 next = p4d_addr_end(addr, end); 196 ret = vmemmap_pud_range(p4d, addr, next, walk); 197 if (ret) 198 return ret; 199 } while (p4d++, addr = next, addr != end); 200 201 return 0; 202 } 203 204 static int vmemmap_remap_range(unsigned long start, unsigned long end, 205 struct vmemmap_remap_walk *walk) 206 { 207 unsigned long addr = start; 208 unsigned long next; 209 pgd_t *pgd; 210 211 VM_BUG_ON(!PAGE_ALIGNED(start)); 212 VM_BUG_ON(!PAGE_ALIGNED(end)); 213 214 pgd = pgd_offset_k(addr); 215 do { 216 int ret; 217 218 next = pgd_addr_end(addr, end); 219 ret = vmemmap_p4d_range(pgd, addr, next, walk); 220 if (ret) 221 return ret; 222 } while (pgd++, addr = next, addr != end); 223 224 /* 225 * We only change the mapping of the vmemmap virtual address range 226 * [@start + PAGE_SIZE, end), so we only need to flush the TLB which 227 * belongs to the range. 228 */ 229 flush_tlb_kernel_range(start + PAGE_SIZE, end); 230 231 return 0; 232 } 233 234 /* 235 * Free a vmemmap page. A vmemmap page can be allocated from the memblock 236 * allocator or buddy allocator. If the PG_reserved flag is set, it means 237 * that it allocated from the memblock allocator, just free it via the 238 * free_bootmem_page(). Otherwise, use __free_page(). 239 */ 240 static inline void free_vmemmap_page(struct page *page) 241 { 242 if (PageReserved(page)) 243 free_bootmem_page(page); 244 else 245 __free_page(page); 246 } 247 248 /* Free a list of the vmemmap pages */ 249 static void free_vmemmap_page_list(struct list_head *list) 250 { 251 struct page *page, *next; 252 253 list_for_each_entry_safe(page, next, list, lru) { 254 list_del(&page->lru); 255 free_vmemmap_page(page); 256 } 257 } 258 259 static void vmemmap_remap_pte(pte_t *pte, unsigned long addr, 260 struct vmemmap_remap_walk *walk) 261 { 262 /* 263 * Remap the tail pages as read-only to catch illegal write operation 264 * to the tail pages. 265 */ 266 pgprot_t pgprot = PAGE_KERNEL_RO; 267 pte_t entry = mk_pte(walk->reuse_page, pgprot); 268 struct page *page = pte_page(*pte); 269 270 list_add_tail(&page->lru, walk->vmemmap_pages); 271 set_pte_at(&init_mm, addr, pte, entry); 272 } 273 274 /* 275 * How many struct page structs need to be reset. When we reuse the head 276 * struct page, the special metadata (e.g. page->flags or page->mapping) 277 * cannot copy to the tail struct page structs. The invalid value will be 278 * checked in the free_tail_pages_check(). In order to avoid the message 279 * of "corrupted mapping in tail page". We need to reset at least 3 (one 280 * head struct page struct and two tail struct page structs) struct page 281 * structs. 282 */ 283 #define NR_RESET_STRUCT_PAGE 3 284 285 static inline void reset_struct_pages(struct page *start) 286 { 287 int i; 288 struct page *from = start + NR_RESET_STRUCT_PAGE; 289 290 for (i = 0; i < NR_RESET_STRUCT_PAGE; i++) 291 memcpy(start + i, from, sizeof(*from)); 292 } 293 294 static void vmemmap_restore_pte(pte_t *pte, unsigned long addr, 295 struct vmemmap_remap_walk *walk) 296 { 297 pgprot_t pgprot = PAGE_KERNEL; 298 struct page *page; 299 void *to; 300 301 BUG_ON(pte_page(*pte) != walk->reuse_page); 302 303 page = list_first_entry(walk->vmemmap_pages, struct page, lru); 304 list_del(&page->lru); 305 to = page_to_virt(page); 306 copy_page(to, (void *)walk->reuse_addr); 307 reset_struct_pages(to); 308 309 set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot)); 310 } 311 312 /** 313 * vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end) 314 * to the page which @reuse is mapped to, then free vmemmap 315 * which the range are mapped to. 316 * @start: start address of the vmemmap virtual address range that we want 317 * to remap. 318 * @end: end address of the vmemmap virtual address range that we want to 319 * remap. 320 * @reuse: reuse address. 321 * 322 * Return: %0 on success, negative error code otherwise. 323 */ 324 int vmemmap_remap_free(unsigned long start, unsigned long end, 325 unsigned long reuse) 326 { 327 int ret; 328 LIST_HEAD(vmemmap_pages); 329 struct vmemmap_remap_walk walk = { 330 .remap_pte = vmemmap_remap_pte, 331 .reuse_addr = reuse, 332 .vmemmap_pages = &vmemmap_pages, 333 }; 334 335 /* 336 * In order to make remapping routine most efficient for the huge pages, 337 * the routine of vmemmap page table walking has the following rules 338 * (see more details from the vmemmap_pte_range()): 339 * 340 * - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE) 341 * should be continuous. 342 * - The @reuse address is part of the range [@reuse, @end) that we are 343 * walking which is passed to vmemmap_remap_range(). 344 * - The @reuse address is the first in the complete range. 345 * 346 * So we need to make sure that @start and @reuse meet the above rules. 347 */ 348 BUG_ON(start - reuse != PAGE_SIZE); 349 350 mmap_read_lock(&init_mm); 351 ret = vmemmap_remap_range(reuse, end, &walk); 352 if (ret && walk.nr_walked) { 353 end = reuse + walk.nr_walked * PAGE_SIZE; 354 /* 355 * vmemmap_pages contains pages from the previous 356 * vmemmap_remap_range call which failed. These 357 * are pages which were removed from the vmemmap. 358 * They will be restored in the following call. 359 */ 360 walk = (struct vmemmap_remap_walk) { 361 .remap_pte = vmemmap_restore_pte, 362 .reuse_addr = reuse, 363 .vmemmap_pages = &vmemmap_pages, 364 }; 365 366 vmemmap_remap_range(reuse, end, &walk); 367 } 368 mmap_read_unlock(&init_mm); 369 370 free_vmemmap_page_list(&vmemmap_pages); 371 372 return ret; 373 } 374 375 static int alloc_vmemmap_page_list(unsigned long start, unsigned long end, 376 gfp_t gfp_mask, struct list_head *list) 377 { 378 unsigned long nr_pages = (end - start) >> PAGE_SHIFT; 379 int nid = page_to_nid((struct page *)start); 380 struct page *page, *next; 381 382 while (nr_pages--) { 383 page = alloc_pages_node(nid, gfp_mask, 0); 384 if (!page) 385 goto out; 386 list_add_tail(&page->lru, list); 387 } 388 389 return 0; 390 out: 391 list_for_each_entry_safe(page, next, list, lru) 392 __free_pages(page, 0); 393 return -ENOMEM; 394 } 395 396 /** 397 * vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end) 398 * to the page which is from the @vmemmap_pages 399 * respectively. 400 * @start: start address of the vmemmap virtual address range that we want 401 * to remap. 402 * @end: end address of the vmemmap virtual address range that we want to 403 * remap. 404 * @reuse: reuse address. 405 * @gfp_mask: GFP flag for allocating vmemmap pages. 406 * 407 * Return: %0 on success, negative error code otherwise. 408 */ 409 int vmemmap_remap_alloc(unsigned long start, unsigned long end, 410 unsigned long reuse, gfp_t gfp_mask) 411 { 412 LIST_HEAD(vmemmap_pages); 413 struct vmemmap_remap_walk walk = { 414 .remap_pte = vmemmap_restore_pte, 415 .reuse_addr = reuse, 416 .vmemmap_pages = &vmemmap_pages, 417 }; 418 419 /* See the comment in the vmemmap_remap_free(). */ 420 BUG_ON(start - reuse != PAGE_SIZE); 421 422 if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages)) 423 return -ENOMEM; 424 425 mmap_read_lock(&init_mm); 426 vmemmap_remap_range(reuse, end, &walk); 427 mmap_read_unlock(&init_mm); 428 429 return 0; 430 } 431 #endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */ 432 433 /* 434 * Allocate a block of memory to be used to back the virtual memory map 435 * or to back the page tables that are used to create the mapping. 436 * Uses the main allocators if they are available, else bootmem. 437 */ 438 439 static void * __ref __earlyonly_bootmem_alloc(int node, 440 unsigned long size, 441 unsigned long align, 442 unsigned long goal) 443 { 444 return memblock_alloc_try_nid_raw(size, align, goal, 445 MEMBLOCK_ALLOC_ACCESSIBLE, node); 446 } 447 448 void * __meminit vmemmap_alloc_block(unsigned long size, int node) 449 { 450 /* If the main allocator is up use that, fallback to bootmem. */ 451 if (slab_is_available()) { 452 gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN; 453 int order = get_order(size); 454 static bool warned; 455 struct page *page; 456 457 page = alloc_pages_node(node, gfp_mask, order); 458 if (page) 459 return page_address(page); 460 461 if (!warned) { 462 warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL, 463 "vmemmap alloc failure: order:%u", order); 464 warned = true; 465 } 466 return NULL; 467 } else 468 return __earlyonly_bootmem_alloc(node, size, size, 469 __pa(MAX_DMA_ADDRESS)); 470 } 471 472 static void * __meminit altmap_alloc_block_buf(unsigned long size, 473 struct vmem_altmap *altmap); 474 475 /* need to make sure size is all the same during early stage */ 476 void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node, 477 struct vmem_altmap *altmap) 478 { 479 void *ptr; 480 481 if (altmap) 482 return altmap_alloc_block_buf(size, altmap); 483 484 ptr = sparse_buffer_alloc(size); 485 if (!ptr) 486 ptr = vmemmap_alloc_block(size, node); 487 return ptr; 488 } 489 490 static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap) 491 { 492 return altmap->base_pfn + altmap->reserve + altmap->alloc 493 + altmap->align; 494 } 495 496 static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap) 497 { 498 unsigned long allocated = altmap->alloc + altmap->align; 499 500 if (altmap->free > allocated) 501 return altmap->free - allocated; 502 return 0; 503 } 504 505 static void * __meminit altmap_alloc_block_buf(unsigned long size, 506 struct vmem_altmap *altmap) 507 { 508 unsigned long pfn, nr_pfns, nr_align; 509 510 if (size & ~PAGE_MASK) { 511 pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)\n", 512 __func__, size); 513 return NULL; 514 } 515 516 pfn = vmem_altmap_next_pfn(altmap); 517 nr_pfns = size >> PAGE_SHIFT; 518 nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG); 519 nr_align = ALIGN(pfn, nr_align) - pfn; 520 if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap)) 521 return NULL; 522 523 altmap->alloc += nr_pfns; 524 altmap->align += nr_align; 525 pfn += nr_align; 526 527 pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx\n", 528 __func__, pfn, altmap->alloc, altmap->align, nr_pfns); 529 return __va(__pfn_to_phys(pfn)); 530 } 531 532 void __meminit vmemmap_verify(pte_t *pte, int node, 533 unsigned long start, unsigned long end) 534 { 535 unsigned long pfn = pte_pfn(*pte); 536 int actual_node = early_pfn_to_nid(pfn); 537 538 if (node_distance(actual_node, node) > LOCAL_DISTANCE) 539 pr_warn_once("[%lx-%lx] potential offnode page_structs\n", 540 start, end - 1); 541 } 542 543 pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node, 544 struct vmem_altmap *altmap, 545 struct page *reuse) 546 { 547 pte_t *pte = pte_offset_kernel(pmd, addr); 548 if (pte_none(*pte)) { 549 pte_t entry; 550 void *p; 551 552 if (!reuse) { 553 p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); 554 if (!p) 555 return NULL; 556 } else { 557 /* 558 * When a PTE/PMD entry is freed from the init_mm 559 * there's a free_pages() call to this page allocated 560 * above. Thus this get_page() is paired with the 561 * put_page_testzero() on the freeing path. 562 * This can only called by certain ZONE_DEVICE path, 563 * and through vmemmap_populate_compound_pages() when 564 * slab is available. 565 */ 566 get_page(reuse); 567 p = page_to_virt(reuse); 568 } 569 entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL); 570 set_pte_at(&init_mm, addr, pte, entry); 571 } 572 return pte; 573 } 574 575 static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node) 576 { 577 void *p = vmemmap_alloc_block(size, node); 578 579 if (!p) 580 return NULL; 581 memset(p, 0, size); 582 583 return p; 584 } 585 586 pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node) 587 { 588 pmd_t *pmd = pmd_offset(pud, addr); 589 if (pmd_none(*pmd)) { 590 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); 591 if (!p) 592 return NULL; 593 pmd_populate_kernel(&init_mm, pmd, p); 594 } 595 return pmd; 596 } 597 598 pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node) 599 { 600 pud_t *pud = pud_offset(p4d, addr); 601 if (pud_none(*pud)) { 602 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); 603 if (!p) 604 return NULL; 605 pud_populate(&init_mm, pud, p); 606 } 607 return pud; 608 } 609 610 p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node) 611 { 612 p4d_t *p4d = p4d_offset(pgd, addr); 613 if (p4d_none(*p4d)) { 614 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); 615 if (!p) 616 return NULL; 617 p4d_populate(&init_mm, p4d, p); 618 } 619 return p4d; 620 } 621 622 pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node) 623 { 624 pgd_t *pgd = pgd_offset_k(addr); 625 if (pgd_none(*pgd)) { 626 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); 627 if (!p) 628 return NULL; 629 pgd_populate(&init_mm, pgd, p); 630 } 631 return pgd; 632 } 633 634 static pte_t * __meminit vmemmap_populate_address(unsigned long addr, int node, 635 struct vmem_altmap *altmap, 636 struct page *reuse) 637 { 638 pgd_t *pgd; 639 p4d_t *p4d; 640 pud_t *pud; 641 pmd_t *pmd; 642 pte_t *pte; 643 644 pgd = vmemmap_pgd_populate(addr, node); 645 if (!pgd) 646 return NULL; 647 p4d = vmemmap_p4d_populate(pgd, addr, node); 648 if (!p4d) 649 return NULL; 650 pud = vmemmap_pud_populate(p4d, addr, node); 651 if (!pud) 652 return NULL; 653 pmd = vmemmap_pmd_populate(pud, addr, node); 654 if (!pmd) 655 return NULL; 656 pte = vmemmap_pte_populate(pmd, addr, node, altmap, reuse); 657 if (!pte) 658 return NULL; 659 vmemmap_verify(pte, node, addr, addr + PAGE_SIZE); 660 661 return pte; 662 } 663 664 static int __meminit vmemmap_populate_range(unsigned long start, 665 unsigned long end, int node, 666 struct vmem_altmap *altmap, 667 struct page *reuse) 668 { 669 unsigned long addr = start; 670 pte_t *pte; 671 672 for (; addr < end; addr += PAGE_SIZE) { 673 pte = vmemmap_populate_address(addr, node, altmap, reuse); 674 if (!pte) 675 return -ENOMEM; 676 } 677 678 return 0; 679 } 680 681 int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end, 682 int node, struct vmem_altmap *altmap) 683 { 684 return vmemmap_populate_range(start, end, node, altmap, NULL); 685 } 686 687 /* 688 * For compound pages bigger than section size (e.g. x86 1G compound 689 * pages with 2M subsection size) fill the rest of sections as tail 690 * pages. 691 * 692 * Note that memremap_pages() resets @nr_range value and will increment 693 * it after each range successful onlining. Thus the value or @nr_range 694 * at section memmap populate corresponds to the in-progress range 695 * being onlined here. 696 */ 697 static bool __meminit reuse_compound_section(unsigned long start_pfn, 698 struct dev_pagemap *pgmap) 699 { 700 unsigned long nr_pages = pgmap_vmemmap_nr(pgmap); 701 unsigned long offset = start_pfn - 702 PHYS_PFN(pgmap->ranges[pgmap->nr_range].start); 703 704 return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION; 705 } 706 707 static pte_t * __meminit compound_section_tail_page(unsigned long addr) 708 { 709 pte_t *pte; 710 711 addr -= PAGE_SIZE; 712 713 /* 714 * Assuming sections are populated sequentially, the previous section's 715 * page data can be reused. 716 */ 717 pte = pte_offset_kernel(pmd_off_k(addr), addr); 718 if (!pte) 719 return NULL; 720 721 return pte; 722 } 723 724 static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, 725 unsigned long start, 726 unsigned long end, int node, 727 struct dev_pagemap *pgmap) 728 { 729 unsigned long size, addr; 730 pte_t *pte; 731 int rc; 732 733 if (reuse_compound_section(start_pfn, pgmap)) { 734 pte = compound_section_tail_page(start); 735 if (!pte) 736 return -ENOMEM; 737 738 /* 739 * Reuse the page that was populated in the prior iteration 740 * with just tail struct pages. 741 */ 742 return vmemmap_populate_range(start, end, node, NULL, 743 pte_page(*pte)); 744 } 745 746 size = min(end - start, pgmap_vmemmap_nr(pgmap) * sizeof(struct page)); 747 for (addr = start; addr < end; addr += size) { 748 unsigned long next, last = addr + size; 749 750 /* Populate the head page vmemmap page */ 751 pte = vmemmap_populate_address(addr, node, NULL, NULL); 752 if (!pte) 753 return -ENOMEM; 754 755 /* Populate the tail pages vmemmap page */ 756 next = addr + PAGE_SIZE; 757 pte = vmemmap_populate_address(next, node, NULL, NULL); 758 if (!pte) 759 return -ENOMEM; 760 761 /* 762 * Reuse the previous page for the rest of tail pages 763 * See layout diagram in Documentation/mm/vmemmap_dedup.rst 764 */ 765 next += PAGE_SIZE; 766 rc = vmemmap_populate_range(next, last, node, NULL, 767 pte_page(*pte)); 768 if (rc) 769 return -ENOMEM; 770 } 771 772 return 0; 773 } 774 775 struct page * __meminit __populate_section_memmap(unsigned long pfn, 776 unsigned long nr_pages, int nid, struct vmem_altmap *altmap, 777 struct dev_pagemap *pgmap) 778 { 779 unsigned long start = (unsigned long) pfn_to_page(pfn); 780 unsigned long end = start + nr_pages * sizeof(struct page); 781 int r; 782 783 if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) || 784 !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION))) 785 return NULL; 786 787 if (is_power_of_2(sizeof(struct page)) && 788 pgmap && pgmap_vmemmap_nr(pgmap) > 1 && !altmap) 789 r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap); 790 else 791 r = vmemmap_populate(start, end, nid, altmap); 792 793 if (r < 0) 794 return NULL; 795 796 return pfn_to_page(pfn); 797 } 798