arch/powerpc/mm/mem.c

   1 /*
   2  *  PowerPC version
   3  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   4  *
   5  *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
   6  *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
   7  *    Copyright (C) 1996 Paul Mackerras
   8  *  PPC44x/36-bit changes by Matt Porter (mporter@mvista.com)
   9  *
  10  *  Derived from "arch/i386/mm/init.c"
  11  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  12  *
  13  *  This program is free software; you can redistribute it and/or
  14  *  modify it under the terms of the GNU General Public License
  15  *  as published by the Free Software Foundation; either version
  16  *  2 of the License, or (at your option) any later version.
  17  *
  18  */
  19
  20 #include <linux/export.h>
  21 #include <linux/sched.h>
  22 #include <linux/kernel.h>
  23 #include <linux/errno.h>
  24 #include <linux/string.h>
  25 #include <linux/gfp.h>
  26 #include <linux/types.h>
  27 #include <linux/mm.h>
  28 #include <linux/stddef.h>
  29 #include <linux/init.h>
  30 #include <linux/bootmem.h>
  31 #include <linux/highmem.h>
  32 #include <linux/initrd.h>
  33 #include <linux/pagemap.h>
  34 #include <linux/suspend.h>
  35 #include <linux/memblock.h>
  36 #include <linux/hugetlb.h>
  37 #include <linux/slab.h>
  38
  39 #include <asm/pgalloc.h>
  40 #include <asm/prom.h>
  41 #include <asm/io.h>
  42 #include <asm/mmu_context.h>
  43 #include <asm/pgtable.h>
  44 #include <asm/mmu.h>
  45 #include <asm/smp.h>
  46 #include <asm/machdep.h>
  47 #include <asm/btext.h>
  48 #include <asm/tlb.h>
  49 #include <asm/sections.h>
  50 #include <asm/sparsemem.h>
  51 #include <asm/vdso.h>
  52 #include <asm/fixmap.h>
  53 #include <asm/swiotlb.h>
  54 #include <asm/rtas.h>
  55
  56 #include "mmu_decl.h"
  57
  58 #ifndef CPU_FTR_COHERENT_ICACHE
  59 #define CPU_FTR_COHERENT_ICACHE 0       /* XXX for now */
  60 #define CPU_FTR_NOEXECUTE       0
  61 #endif
  62
  63 int init_bootmem_done;
  64 int mem_init_done;
  65 unsigned long long memory_limit;
  66
  67 #ifdef CONFIG_HIGHMEM
  68 pte_t *kmap_pte;
  69 pgprot_t kmap_prot;
  70
  71 EXPORT_SYMBOL(kmap_prot);
  72 EXPORT_SYMBOL(kmap_pte);
  73
  74 static inline pte_t *virt_to_kpte(unsigned long vaddr)
  75 {
  76         return pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr),
  77                         vaddr), vaddr), vaddr);
  78 }
  79 #endif
  80
  81 int page_is_ram(unsigned long pfn)
  82 {
  83 #ifndef CONFIG_PPC64    /* XXX for now */
  84         return pfn < max_pfn;
  85 #else
  86         unsigned long paddr = (pfn << PAGE_SHIFT);
  87         struct memblock_region *reg;
  88
  89         for_each_memblock(memory, reg)
  90                 if (paddr >= reg->base && paddr < (reg->base + reg->size))
  91                         return 1;
  92         return 0;
  93 #endif
  94 }
  95
  96 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  97                               unsigned long size, pgprot_t vma_prot)
  98 {
  99         if (ppc_md.phys_mem_access_prot)
 100                 return ppc_md.phys_mem_access_prot(file, pfn, size, vma_prot);
 101
 102         if (!page_is_ram(pfn))
 103                 vma_prot = pgprot_noncached(vma_prot);
 104
 105         return vma_prot;
 106 }
 107 EXPORT_SYMBOL(phys_mem_access_prot);
 108
 109 #ifdef CONFIG_MEMORY_HOTPLUG
 110
 111 #ifdef CONFIG_NUMA
 112 int memory_add_physaddr_to_nid(u64 start)
 113 {
 114         return hot_add_scn_to_nid(start);
 115 }
 116 #endif
 117
 118 int arch_add_memory(int nid, u64 start, u64 size)
 119 {
 120         struct pglist_data *pgdata;
 121         struct zone *zone;
 122         unsigned long start_pfn = start >> PAGE_SHIFT;
 123         unsigned long nr_pages = size >> PAGE_SHIFT;
 124
 125         pgdata = NODE_DATA(nid);
 126
 127         start = (unsigned long)__va(start);
 128         if (create_section_mapping(start, start + size))
 129                 return -EINVAL;
 130
 131         /* this should work for most non-highmem platforms */
 132         zone = pgdata->node_zones;
 133
 134         return __add_pages(nid, zone, start_pfn, nr_pages);
 135 }
 136 #endif /* CONFIG_MEMORY_HOTPLUG */
 137
 138 /*
 139  * walk_memory_resource() needs to make sure there is no holes in a given
 140  * memory range.  PPC64 does not maintain the memory layout in /proc/iomem.
 141  * Instead it maintains it in memblock.memory structures.  Walk through the
 142  * memory regions, find holes and callback for contiguous regions.
 143  */
 144 int
 145 walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 146                 void *arg, int (*func)(unsigned long, unsigned long, void *))
 147 {
 148         struct memblock_region *reg;
 149         unsigned long end_pfn = start_pfn + nr_pages;
 150         unsigned long tstart, tend;
 151         int ret = -1;
 152
 153         for_each_memblock(memory, reg) {
 154                 tstart = max(start_pfn, memblock_region_memory_base_pfn(reg));
 155                 tend = min(end_pfn, memblock_region_memory_end_pfn(reg));
 156                 if (tstart >= tend)
 157                         continue;
 158                 ret = (*func)(tstart, tend - tstart, arg);
 159                 if (ret)
 160                         break;
 161         }
 162         return ret;
 163 }
 164 EXPORT_SYMBOL_GPL(walk_system_ram_range);
 165
 166 /*
 167  * Initialize the bootmem system and give it all the memory we
 168  * have available.  If we are using highmem, we only put the
 169  * lowmem into the bootmem system.
 170  */
 171 #ifndef CONFIG_NEED_MULTIPLE_NODES
 172 void __init do_init_bootmem(void)
 173 {
 174         unsigned long start, bootmap_pages;
 175         unsigned long total_pages;
 176         struct memblock_region *reg;
 177         int boot_mapsize;
 178
 179         max_low_pfn = max_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
 180         total_pages = (memblock_end_of_DRAM() - memstart_addr) >> PAGE_SHIFT;
 181 #ifdef CONFIG_HIGHMEM
 182         total_pages = total_lowmem >> PAGE_SHIFT;
 183         max_low_pfn = lowmem_end_addr >> PAGE_SHIFT;
 184 #endif
 185
 186         /*
 187          * Find an area to use for the bootmem bitmap.  Calculate the size of
 188          * bitmap required as (Total Memory) / PAGE_SIZE / BITS_PER_BYTE.
 189          * Add 1 additional page in case the address isn't page-aligned.
 190          */
 191         bootmap_pages = bootmem_bootmap_pages(total_pages);
 192
 193         start = memblock_alloc(bootmap_pages << PAGE_SHIFT, PAGE_SIZE);
 194
 195         min_low_pfn = MEMORY_START >> PAGE_SHIFT;
 196         boot_mapsize = init_bootmem_node(NODE_DATA(0), start >> PAGE_SHIFT, min_low_pfn, max_low_pfn);
 197
 198         /* Add active regions with valid PFNs */
 199         for_each_memblock(memory, reg) {
 200                 unsigned long start_pfn, end_pfn;
 201                 start_pfn = memblock_region_memory_base_pfn(reg);
 202                 end_pfn = memblock_region_memory_end_pfn(reg);
 203                 memblock_set_node(0, (phys_addr_t)ULLONG_MAX, 0);
 204         }
 205
 206         /* Add all physical memory to the bootmem map, mark each area
 207          * present.
 208          */
 209 #ifdef CONFIG_HIGHMEM
 210         free_bootmem_with_active_regions(0, lowmem_end_addr >> PAGE_SHIFT);
 211
 212         /* reserve the sections we're already using */
 213         for_each_memblock(reserved, reg) {
 214                 unsigned long top = reg->base + reg->size - 1;
 215                 if (top < lowmem_end_addr)
 216                         reserve_bootmem(reg->base, reg->size, BOOTMEM_DEFAULT);
 217                 else if (reg->base < lowmem_end_addr) {
 218                         unsigned long trunc_size = lowmem_end_addr - reg->base;
 219                         reserve_bootmem(reg->base, trunc_size, BOOTMEM_DEFAULT);
 220                 }
 221         }
 222 #else
 223         free_bootmem_with_active_regions(0, max_pfn);
 224
 225         /* reserve the sections we're already using */
 226         for_each_memblock(reserved, reg)
 227                 reserve_bootmem(reg->base, reg->size, BOOTMEM_DEFAULT);
 228 #endif
 229         /* XXX need to clip this if using highmem? */
 230         sparse_memory_present_with_active_regions(0);
 231
 232         init_bootmem_done = 1;
 233 }
 234
 235 /* mark pages that don't exist as nosave */
 236 static int __init mark_nonram_nosave(void)
 237 {
 238         struct memblock_region *reg, *prev = NULL;
 239
 240         for_each_memblock(memory, reg) {
 241                 if (prev &&
 242                     memblock_region_memory_end_pfn(prev) < memblock_region_memory_base_pfn(reg))
 243                         register_nosave_region(memblock_region_memory_end_pfn(prev),
 244                                                memblock_region_memory_base_pfn(reg));
 245                 prev = reg;
 246         }
 247         return 0;
 248 }
 249
 250 /*
 251  * paging_init() sets up the page tables - in fact we've already done this.
 252  */
 253 void __init paging_init(void)
 254 {
 255         unsigned long long total_ram = memblock_phys_mem_size();
 256         phys_addr_t top_of_ram = memblock_end_of_DRAM();
 257         unsigned long max_zone_pfns[MAX_NR_ZONES];
 258
 259 #ifdef CONFIG_PPC32
 260         unsigned long v = __fix_to_virt(__end_of_fixed_addresses - 1);
 261         unsigned long end = __fix_to_virt(FIX_HOLE);
 262
 263         for (; v < end; v += PAGE_SIZE)
 264                 map_page(v, 0, 0); /* XXX gross */
 265 #endif
 266
 267 #ifdef CONFIG_HIGHMEM
 268         map_page(PKMAP_BASE, 0, 0);     /* XXX gross */
 269         pkmap_page_table = virt_to_kpte(PKMAP_BASE);
 270
 271         kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 272         kmap_prot = PAGE_KERNEL;
 273 #endif /* CONFIG_HIGHMEM */
 274
 275         printk(KERN_DEBUG "Top of RAM: 0x%llx, Total RAM: 0x%llx\n",
 276                (unsigned long long)top_of_ram, total_ram);
 277         printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 278                (long int)((top_of_ram - total_ram) >> 20));
 279         memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 280 #ifdef CONFIG_HIGHMEM
 281         max_zone_pfns[ZONE_DMA] = lowmem_end_addr >> PAGE_SHIFT;
 282         max_zone_pfns[ZONE_HIGHMEM] = top_of_ram >> PAGE_SHIFT;
 283 #else
 284         max_zone_pfns[ZONE_DMA] = top_of_ram >> PAGE_SHIFT;
 285 #endif
 286         free_area_init_nodes(max_zone_pfns);
 287
 288         mark_nonram_nosave();
 289 }
 290 #endif /* ! CONFIG_NEED_MULTIPLE_NODES */
 291
 292 void __init mem_init(void)
 293 {
 294 #ifdef CONFIG_NEED_MULTIPLE_NODES
 295         int nid;
 296 #endif
 297         pg_data_t *pgdat;
 298         unsigned long i;
 299         struct page *page;
 300         unsigned long reservedpages = 0, codesize, initsize, datasize, bsssize;
 301
 302 #ifdef CONFIG_SWIOTLB
 303         swiotlb_init(0);
 304 #endif
 305
 306         num_physpages = memblock_phys_mem_size() >> PAGE_SHIFT;
 307         high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
 308
 309 #ifdef CONFIG_NEED_MULTIPLE_NODES
 310         for_each_online_node(nid) {
 311                 if (NODE_DATA(nid)->node_spanned_pages != 0) {
 312                         printk("freeing bootmem node %d\n", nid);
 313                         totalram_pages +=
 314                                 free_all_bootmem_node(NODE_DATA(nid));
 315                 }
 316         }
 317 #else
 318         max_mapnr = max_pfn;
 319         totalram_pages += free_all_bootmem();
 320 #endif
 321         for_each_online_pgdat(pgdat) {
 322                 for (i = 0; i < pgdat->node_spanned_pages; i++) {
 323                         if (!pfn_valid(pgdat->node_start_pfn + i))
 324                                 continue;
 325                         page = pgdat_page_nr(pgdat, i);
 326                         if (PageReserved(page))
 327                                 reservedpages++;
 328                 }
 329         }
 330
 331         codesize = (unsigned long)&_sdata - (unsigned long)&_stext;
 332         datasize = (unsigned long)&_edata - (unsigned long)&_sdata;
 333         initsize = (unsigned long)&__init_end - (unsigned long)&__init_begin;
 334         bsssize = (unsigned long)&__bss_stop - (unsigned long)&__bss_start;
 335
 336 #ifdef CONFIG_HIGHMEM
 337         {
 338                 unsigned long pfn, highmem_mapnr;
 339
 340                 highmem_mapnr = lowmem_end_addr >> PAGE_SHIFT;
 341                 for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
 342                         phys_addr_t paddr = (phys_addr_t)pfn << PAGE_SHIFT;
 343                         struct page *page = pfn_to_page(pfn);
 344                         if (memblock_is_reserved(paddr))
 345                                 continue;
 346                         ClearPageReserved(page);
 347                         init_page_count(page);
 348                         __free_page(page);
 349                         totalhigh_pages++;
 350                         reservedpages--;
 351                 }
 352                 totalram_pages += totalhigh_pages;
 353                 printk(KERN_DEBUG "High memory: %luk\n",
 354                        totalhigh_pages << (PAGE_SHIFT-10));
 355         }
 356 #endif /* CONFIG_HIGHMEM */
 357
 358 #if defined(CONFIG_PPC_FSL_BOOK3E) && !defined(CONFIG_SMP)
 359         /*
 360          * If smp is enabled, next_tlbcam_idx is initialized in the cpu up
 361          * functions.... do it here for the non-smp case.
 362          */
 363         per_cpu(next_tlbcam_idx, smp_processor_id()) =
 364                 (mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) - 1;
 365 #endif
 366
 367         printk(KERN_INFO "Memory: %luk/%luk available (%luk kernel code, "
 368                "%luk reserved, %luk data, %luk bss, %luk init)\n",
 369                 nr_free_pages() << (PAGE_SHIFT-10),
 370                 num_physpages << (PAGE_SHIFT-10),
 371                 codesize >> 10,
 372                 reservedpages << (PAGE_SHIFT-10),
 373                 datasize >> 10,
 374                 bsssize >> 10,
 375                 initsize >> 10);
 376
 377 #ifdef CONFIG_PPC32
 378         pr_info("Kernel virtual memory layout:\n");
 379         pr_info("  * 0x%08lx..0x%08lx  : fixmap\n", FIXADDR_START, FIXADDR_TOP);
 380 #ifdef CONFIG_HIGHMEM
 381         pr_info("  * 0x%08lx..0x%08lx  : highmem PTEs\n",
 382                 PKMAP_BASE, PKMAP_ADDR(LAST_PKMAP));
 383 #endif /* CONFIG_HIGHMEM */
 384 #ifdef CONFIG_NOT_COHERENT_CACHE
 385         pr_info("  * 0x%08lx..0x%08lx  : consistent mem\n",
 386                 IOREMAP_TOP, IOREMAP_TOP + CONFIG_CONSISTENT_SIZE);
 387 #endif /* CONFIG_NOT_COHERENT_CACHE */
 388         pr_info("  * 0x%08lx..0x%08lx  : early ioremap\n",
 389                 ioremap_bot, IOREMAP_TOP);
 390         pr_info("  * 0x%08lx..0x%08lx  : vmalloc & ioremap\n",
 391                 VMALLOC_START, VMALLOC_END);
 392 #endif /* CONFIG_PPC32 */
 393
 394         mem_init_done = 1;
 395 }
 396
 397 void free_initmem(void)
 398 {
 399         unsigned long addr;
 400
 401         ppc_md.progress = ppc_printk_progress;
 402
 403         addr = (unsigned long)__init_begin;
 404         for (; addr < (unsigned long)__init_end; addr += PAGE_SIZE) {
 405                 memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
 406                 ClearPageReserved(virt_to_page(addr));
 407                 init_page_count(virt_to_page(addr));
 408                 free_page(addr);
 409                 totalram_pages++;
 410         }
 411         pr_info("Freeing unused kernel memory: %luk freed\n",
 412                 ((unsigned long)__init_end -
 413                 (unsigned long)__init_begin) >> 10);
 414 }
 415
 416 #ifdef CONFIG_BLK_DEV_INITRD
 417 void __init free_initrd_mem(unsigned long start, unsigned long end)
 418 {
 419         if (start >= end)
 420                 return;
 421
 422         start = _ALIGN_DOWN(start, PAGE_SIZE);
 423         end = _ALIGN_UP(end, PAGE_SIZE);
 424         pr_info("Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
 425
 426         for (; start < end; start += PAGE_SIZE) {
 427                 ClearPageReserved(virt_to_page(start));
 428                 init_page_count(virt_to_page(start));
 429                 free_page(start);
 430                 totalram_pages++;
 431         }
 432 }
 433 #endif
 434
 435 /*
 436  * This is called when a page has been modified by the kernel.
 437  * It just marks the page as not i-cache clean.  We do the i-cache
 438  * flush later when the page is given to a user process, if necessary.
 439  */
 440 void flush_dcache_page(struct page *page)
 441 {
 442         if (cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 443                 return;
 444         /* avoid an atomic op if possible */
 445         if (test_bit(PG_arch_1, &page->flags))
 446                 clear_bit(PG_arch_1, &page->flags);
 447 }
 448 EXPORT_SYMBOL(flush_dcache_page);
 449
 450 void flush_dcache_icache_page(struct page *page)
 451 {
 452 #ifdef CONFIG_HUGETLB_PAGE
 453         if (PageCompound(page)) {
 454                 flush_dcache_icache_hugepage(page);
 455                 return;
 456         }
 457 #endif
 458 #ifdef CONFIG_BOOKE
 459         {
 460                 void *start = kmap_atomic(page);
 461                 __flush_dcache_icache(start);
 462                 kunmap_atomic(start);
 463         }
 464 #elif defined(CONFIG_8xx) || defined(CONFIG_PPC64)
 465         /* On 8xx there is no need to kmap since highmem is not supported */
 466         __flush_dcache_icache(page_address(page));
 467 #else
 468         __flush_dcache_icache_phys(page_to_pfn(page) << PAGE_SHIFT);
 469 #endif
 470 }
 471 EXPORT_SYMBOL(flush_dcache_icache_page);
 472
 473 void clear_user_page(void *page, unsigned long vaddr, struct page *pg)
 474 {
 475         clear_page(page);
 476
 477         /*
 478          * We shouldn't have to do this, but some versions of glibc
 479          * require it (ld.so assumes zero filled pages are icache clean)
 480          * - Anton
 481          */
 482         flush_dcache_page(pg);
 483 }
 484 EXPORT_SYMBOL(clear_user_page);
 485
 486 void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
 487                     struct page *pg)
 488 {
 489         copy_page(vto, vfrom);
 490
 491         /*
 492          * We should be able to use the following optimisation, however
 493          * there are two problems.
 494          * Firstly a bug in some versions of binutils meant PLT sections
 495          * were not marked executable.
 496          * Secondly the first word in the GOT section is blrl, used
 497          * to establish the GOT address. Until recently the GOT was
 498          * not marked executable.
 499          * - Anton
 500          */
 501 #if 0
 502         if (!vma->vm_file && ((vma->vm_flags & VM_EXEC) == 0))
 503                 return;
 504 #endif
 505
 506         flush_dcache_page(pg);
 507 }
 508
 509 void flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 510                              unsigned long addr, int len)
 511 {
 512         unsigned long maddr;
 513
 514         maddr = (unsigned long) kmap(page) + (addr & ~PAGE_MASK);
 515         flush_icache_range(maddr, maddr + len);
 516         kunmap(page);
 517 }
 518 EXPORT_SYMBOL(flush_icache_user_range);
 519
 520 /*
 521  * This is called at the end of handling a user page fault, when the
 522  * fault has been handled by updating a PTE in the linux page tables.
 523  * We use it to preload an HPTE into the hash table corresponding to
 524  * the updated linux PTE.
 525  *
 526  * This must always be called with the pte lock held.
 527  */
 528 void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
 529                       pte_t *ptep)
 530 {
 531 #ifdef CONFIG_PPC_STD_MMU
 532         unsigned long access = 0, trap;
 533
 534         /* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */
 535         if (!pte_young(*ptep) || address >= TASK_SIZE)
 536                 return;
 537
 538         /* We try to figure out if we are coming from an instruction
 539          * access fault and pass that down to __hash_page so we avoid
 540          * double-faulting on execution of fresh text. We have to test
 541          * for regs NULL since init will get here first thing at boot
 542          *
 543          * We also avoid filling the hash if not coming from a fault
 544          */
 545         if (current->thread.regs == NULL)
 546                 return;
 547         trap = TRAP(current->thread.regs);
 548         if (trap == 0x400)
 549                 access |= _PAGE_EXEC;
 550         else if (trap != 0x300)
 551                 return;
 552         hash_preload(vma->vm_mm, address, access, trap);
 553 #endif /* CONFIG_PPC_STD_MMU */
 554 #if (defined(CONFIG_PPC_BOOK3E_64) || defined(CONFIG_PPC_FSL_BOOK3E)) \
 555         && defined(CONFIG_HUGETLB_PAGE)
 556         if (is_vm_hugetlb_page(vma))
 557                 book3e_hugetlb_preload(vma, address, *ptep);
 558 #endif
 559 }
 560
 561 /*
 562  * System memory should not be in /proc/iomem but various tools expect it
 563  * (eg kdump).
 564  */
 565 static int add_system_ram_resources(void)
 566 {
 567         struct memblock_region *reg;
 568
 569         for_each_memblock(memory, reg) {
 570                 struct resource *res;
 571                 unsigned long base = reg->base;
 572                 unsigned long size = reg->size;
 573
 574                 res = kzalloc(sizeof(struct resource), GFP_KERNEL);
 575                 WARN_ON(!res);
 576
 577                 if (res) {
 578                         res->name = "System RAM";
 579                         res->start = base;
 580                         res->end = base + size - 1;
 581                         res->flags = IORESOURCE_MEM;
 582                         WARN_ON(request_resource(&iomem_resource, res) < 0);
 583                 }
 584         }
 585
 586         return 0;
 587 }
 588 subsys_initcall(add_system_ram_resources);
 589
 590 #ifdef CONFIG_STRICT_DEVMEM
 591 /*
 592  * devmem_is_allowed(): check to see if /dev/mem access to a certain address
 593  * is valid. The argument is a physical page number.
 594  *
 595  * Access has to be given to non-kernel-ram areas as well, these contain the
 596  * PCI mmio resources as well as potential bios/acpi data regions.
 597  */
 598 int devmem_is_allowed(unsigned long pfn)
 599 {
 600         if (iomem_is_exclusive(pfn << PAGE_SHIFT))
 601                 return 0;
 602         if (!page_is_ram(pfn))
 603                 return 1;
 604         if (page_is_rtas_user_buf(pfn))
 605                 return 1;
 606         return 0;
 607 }
 608 #endif /* CONFIG_STRICT_DEVMEM */