mm/sparse-vmemmap.c

   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
  31 #include <asm/dma.h>
  32 #include <asm/pgalloc.h>
  33
  34 /*
  35  * Allocate a block of memory to be used to back the virtual memory map
  36  * or to back the page tables that are used to create the mapping.
  37  * Uses the main allocators if they are available, else bootmem.
  38  */
  39
  40 static void * __ref __earlyonly_bootmem_alloc(int node,
  41                                 unsigned long size,
  42                                 unsigned long align,
  43                                 unsigned long goal)
  44 {
  45         return memblock_alloc_try_nid_raw(size, align, goal,
  46                                                MEMBLOCK_ALLOC_ACCESSIBLE, node);
  47 }
  48
  49 void * __meminit vmemmap_alloc_block(unsigned long size, int node)
  50 {
  51         /* If the main allocator is up use that, fallback to bootmem. */
  52         if (slab_is_available()) {
  53                 gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN;
  54                 int order = get_order(size);
  55                 static bool warned;
  56                 struct page *page;
  57
  58                 page = alloc_pages_node(node, gfp_mask, order);
  59                 if (page)
  60                         return page_address(page);
  61
  62                 if (!warned) {
  63                         warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL,
  64                                    "vmemmap alloc failure: order:%u", order);
  65                         warned = true;
  66                 }
  67                 return NULL;
  68         } else
  69                 return __earlyonly_bootmem_alloc(node, size, size,
  70                                 __pa(MAX_DMA_ADDRESS));
  71 }
  72
  73 static void * __meminit altmap_alloc_block_buf(unsigned long size,
  74                                                struct vmem_altmap *altmap);
  75
  76 /* need to make sure size is all the same during early stage */
  77 void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node,
  78                                          struct vmem_altmap *altmap)
  79 {
  80         void *ptr;
  81
  82         if (altmap)
  83                 return altmap_alloc_block_buf(size, altmap);
  84
  85         ptr = sparse_buffer_alloc(size);
  86         if (!ptr)
  87                 ptr = vmemmap_alloc_block(size, node);
  88         return ptr;
  89 }
  90
  91 static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap)
  92 {
  93         return altmap->base_pfn + altmap->reserve + altmap->alloc
  94                 + altmap->align;
  95 }
  96
  97 static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap)
  98 {
  99         unsigned long allocated = altmap->alloc + altmap->align;
 100
 101         if (altmap->free > allocated)
 102                 return altmap->free - allocated;
 103         return 0;
 104 }
 105
 106 static void * __meminit altmap_alloc_block_buf(unsigned long size,
 107                                                struct vmem_altmap *altmap)
 108 {
 109         unsigned long pfn, nr_pfns, nr_align;
 110
 111         if (size & ~PAGE_MASK) {
 112                 pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)\n",
 113                                 __func__, size);
 114                 return NULL;
 115         }
 116
 117         pfn = vmem_altmap_next_pfn(altmap);
 118         nr_pfns = size >> PAGE_SHIFT;
 119         nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG);
 120         nr_align = ALIGN(pfn, nr_align) - pfn;
 121         if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap))
 122                 return NULL;
 123
 124         altmap->alloc += nr_pfns;
 125         altmap->align += nr_align;
 126         pfn += nr_align;
 127
 128         pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx\n",
 129                         __func__, pfn, altmap->alloc, altmap->align, nr_pfns);
 130         return __va(__pfn_to_phys(pfn));
 131 }
 132
 133 void __meminit vmemmap_verify(pte_t *pte, int node,
 134                                 unsigned long start, unsigned long end)
 135 {
 136         unsigned long pfn = pte_pfn(*pte);
 137         int actual_node = early_pfn_to_nid(pfn);
 138
 139         if (node_distance(actual_node, node) > LOCAL_DISTANCE)
 140                 pr_warn_once("[%lx-%lx] potential offnode page_structs\n",
 141                         start, end - 1);
 142 }
 143
 144 pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
 145                                        struct vmem_altmap *altmap,
 146                                        struct page *reuse)
 147 {
 148         pte_t *pte = pte_offset_kernel(pmd, addr);
 149         if (pte_none(*pte)) {
 150                 pte_t entry;
 151                 void *p;
 152
 153                 if (!reuse) {
 154                         p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap);
 155                         if (!p)
 156                                 return NULL;
 157                 } else {
 158                         /*
 159                          * When a PTE/PMD entry is freed from the init_mm
 160                          * there's a free_pages() call to this page allocated
 161                          * above. Thus this get_page() is paired with the
 162                          * put_page_testzero() on the freeing path.
 163                          * This can only called by certain ZONE_DEVICE path,
 164                          * and through vmemmap_populate_compound_pages() when
 165                          * slab is available.
 166                          */
 167                         get_page(reuse);
 168                         p = page_to_virt(reuse);
 169                 }
 170                 entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL);
 171                 set_pte_at(&init_mm, addr, pte, entry);
 172         }
 173         return pte;
 174 }
 175
 176 static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
 177 {
 178         void *p = vmemmap_alloc_block(size, node);
 179
 180         if (!p)
 181                 return NULL;
 182         memset(p, 0, size);
 183
 184         return p;
 185 }
 186
 187 pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
 188 {
 189         pmd_t *pmd = pmd_offset(pud, addr);
 190         if (pmd_none(*pmd)) {
 191                 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 192                 if (!p)
 193                         return NULL;
 194                 pmd_populate_kernel(&init_mm, pmd, p);
 195         }
 196         return pmd;
 197 }
 198
 199 pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node)
 200 {
 201         pud_t *pud = pud_offset(p4d, addr);
 202         if (pud_none(*pud)) {
 203                 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 204                 if (!p)
 205                         return NULL;
 206                 pud_populate(&init_mm, pud, p);
 207         }
 208         return pud;
 209 }
 210
 211 p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
 212 {
 213         p4d_t *p4d = p4d_offset(pgd, addr);
 214         if (p4d_none(*p4d)) {
 215                 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 216                 if (!p)
 217                         return NULL;
 218                 p4d_populate(&init_mm, p4d, p);
 219         }
 220         return p4d;
 221 }
 222
 223 pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
 224 {
 225         pgd_t *pgd = pgd_offset_k(addr);
 226         if (pgd_none(*pgd)) {
 227                 void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 228                 if (!p)
 229                         return NULL;
 230                 pgd_populate(&init_mm, pgd, p);
 231         }
 232         return pgd;
 233 }
 234
 235 static pte_t * __meminit vmemmap_populate_address(unsigned long addr, int node,
 236                                               struct vmem_altmap *altmap,
 237                                               struct page *reuse)
 238 {
 239         pgd_t *pgd;
 240         p4d_t *p4d;
 241         pud_t *pud;
 242         pmd_t *pmd;
 243         pte_t *pte;
 244
 245         pgd = vmemmap_pgd_populate(addr, node);
 246         if (!pgd)
 247                 return NULL;
 248         p4d = vmemmap_p4d_populate(pgd, addr, node);
 249         if (!p4d)
 250                 return NULL;
 251         pud = vmemmap_pud_populate(p4d, addr, node);
 252         if (!pud)
 253                 return NULL;
 254         pmd = vmemmap_pmd_populate(pud, addr, node);
 255         if (!pmd)
 256                 return NULL;
 257         pte = vmemmap_pte_populate(pmd, addr, node, altmap, reuse);
 258         if (!pte)
 259                 return NULL;
 260         vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);
 261
 262         return pte;
 263 }
 264
 265 static int __meminit vmemmap_populate_range(unsigned long start,
 266                                             unsigned long end, int node,
 267                                             struct vmem_altmap *altmap,
 268                                             struct page *reuse)
 269 {
 270         unsigned long addr = start;
 271         pte_t *pte;
 272
 273         for (; addr < end; addr += PAGE_SIZE) {
 274                 pte = vmemmap_populate_address(addr, node, altmap, reuse);
 275                 if (!pte)
 276                         return -ENOMEM;
 277         }
 278
 279         return 0;
 280 }
 281
 282 int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
 283                                          int node, struct vmem_altmap *altmap)
 284 {
 285         return vmemmap_populate_range(start, end, node, altmap, NULL);
 286 }
 287
 288 /*
 289  * For compound pages bigger than section size (e.g. x86 1G compound
 290  * pages with 2M subsection size) fill the rest of sections as tail
 291  * pages.
 292  *
 293  * Note that memremap_pages() resets @nr_range value and will increment
 294  * it after each range successful onlining. Thus the value or @nr_range
 295  * at section memmap populate corresponds to the in-progress range
 296  * being onlined here.
 297  */
 298 static bool __meminit reuse_compound_section(unsigned long start_pfn,
 299                                              struct dev_pagemap *pgmap)
 300 {
 301         unsigned long nr_pages = pgmap_vmemmap_nr(pgmap);
 302         unsigned long offset = start_pfn -
 303                 PHYS_PFN(pgmap->ranges[pgmap->nr_range].start);
 304
 305         return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION;
 306 }
 307
 308 static pte_t * __meminit compound_section_tail_page(unsigned long addr)
 309 {
 310         pte_t *pte;
 311
 312         addr -= PAGE_SIZE;
 313
 314         /*
 315          * Assuming sections are populated sequentially, the previous section's
 316          * page data can be reused.
 317          */
 318         pte = pte_offset_kernel(pmd_off_k(addr), addr);
 319         if (!pte)
 320                 return NULL;
 321
 322         return pte;
 323 }
 324
 325 static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn,
 326                                                      unsigned long start,
 327                                                      unsigned long end, int node,
 328                                                      struct dev_pagemap *pgmap)
 329 {
 330         unsigned long size, addr;
 331         pte_t *pte;
 332         int rc;
 333
 334         if (reuse_compound_section(start_pfn, pgmap)) {
 335                 pte = compound_section_tail_page(start);
 336                 if (!pte)
 337                         return -ENOMEM;
 338
 339                 /*
 340                  * Reuse the page that was populated in the prior iteration
 341                  * with just tail struct pages.
 342                  */
 343                 return vmemmap_populate_range(start, end, node, NULL,
 344                                               pte_page(*pte));
 345         }
 346
 347         size = min(end - start, pgmap_vmemmap_nr(pgmap) * sizeof(struct page));
 348         for (addr = start; addr < end; addr += size) {
 349                 unsigned long next, last = addr + size;
 350
 351                 /* Populate the head page vmemmap page */
 352                 pte = vmemmap_populate_address(addr, node, NULL, NULL);
 353                 if (!pte)
 354                         return -ENOMEM;
 355
 356                 /* Populate the tail pages vmemmap page */
 357                 next = addr + PAGE_SIZE;
 358                 pte = vmemmap_populate_address(next, node, NULL, NULL);
 359                 if (!pte)
 360                         return -ENOMEM;
 361
 362                 /*
 363                  * Reuse the previous page for the rest of tail pages
 364                  * See layout diagram in Documentation/mm/vmemmap_dedup.rst
 365                  */
 366                 next += PAGE_SIZE;
 367                 rc = vmemmap_populate_range(next, last, node, NULL,
 368                                             pte_page(*pte));
 369                 if (rc)
 370                         return -ENOMEM;
 371         }
 372
 373         return 0;
 374 }
 375
 376 struct page * __meminit __populate_section_memmap(unsigned long pfn,
 377                 unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
 378                 struct dev_pagemap *pgmap)
 379 {
 380         unsigned long start = (unsigned long) pfn_to_page(pfn);
 381         unsigned long end = start + nr_pages * sizeof(struct page);
 382         int r;
 383
 384         if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) ||
 385                 !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
 386                 return NULL;
 387
 388         if (is_power_of_2(sizeof(struct page)) &&
 389             pgmap && pgmap_vmemmap_nr(pgmap) > 1 && !altmap)
 390                 r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap);
 391         else
 392                 r = vmemmap_populate(start, end, nid, altmap);
 393
 394         if (r < 0)
 395                 return NULL;
 396
 397         return pfn_to_page(pfn);
 398 }