linux/arch/powerpc/mm/mem.c
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   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#include <linux/vmalloc.h>
  39
  40#include <asm/pgalloc.h>
  41#include <asm/prom.h>
  42#include <asm/io.h>
  43#include <asm/mmu_context.h>
  44#include <asm/pgtable.h>
  45#include <asm/mmu.h>
  46#include <asm/smp.h>
  47#include <asm/machdep.h>
  48#include <asm/btext.h>
  49#include <asm/tlb.h>
  50#include <asm/sections.h>
  51#include <asm/sparsemem.h>
  52#include <asm/vdso.h>
  53#include <asm/fixmap.h>
  54#include <asm/swiotlb.h>
  55#include <asm/rtas.h>
  56
  57#include "mmu_decl.h"
  58
  59#ifndef CPU_FTR_COHERENT_ICACHE
  60#define CPU_FTR_COHERENT_ICACHE 0       /* XXX for now */
  61#define CPU_FTR_NOEXECUTE       0
  62#endif
  63
  64int init_bootmem_done;
  65int mem_init_done;
  66unsigned long long memory_limit;
  67bool init_mem_is_free;
  68
  69#ifdef CONFIG_HIGHMEM
  70pte_t *kmap_pte;
  71EXPORT_SYMBOL(kmap_pte);
  72pgprot_t kmap_prot;
  73EXPORT_SYMBOL(kmap_prot);
  74
  75static inline pte_t *virt_to_kpte(unsigned long vaddr)
  76{
  77        return pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr),
  78                        vaddr), vaddr), vaddr);
  79}
  80#endif
  81
  82int page_is_ram(unsigned long pfn)
  83{
  84#ifndef CONFIG_PPC64    /* XXX for now */
  85        return pfn < max_pfn;
  86#else
  87        unsigned long paddr = (pfn << PAGE_SHIFT);
  88        struct memblock_region *reg;
  89
  90        for_each_memblock(memory, reg)
  91                if (paddr >= reg->base && paddr < (reg->base + reg->size))
  92                        return 1;
  93        return 0;
  94#endif
  95}
  96
  97pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  98                              unsigned long size, pgprot_t vma_prot)
  99{
 100        if (ppc_md.phys_mem_access_prot)
 101                return ppc_md.phys_mem_access_prot(file, pfn, size, vma_prot);
 102
 103        if (!page_is_ram(pfn))
 104                vma_prot = pgprot_noncached(vma_prot);
 105
 106        return vma_prot;
 107}
 108EXPORT_SYMBOL(phys_mem_access_prot);
 109
 110#ifdef CONFIG_MEMORY_HOTPLUG
 111
 112#ifdef CONFIG_NUMA
 113int memory_add_physaddr_to_nid(u64 start)
 114{
 115        return hot_add_scn_to_nid(start);
 116}
 117#endif
 118
 119int arch_add_memory(int nid, u64 start, u64 size, struct vmem_altmap *altmap,
 120                bool for_device)
 121{
 122        struct pglist_data *pgdata;
 123        struct zone *zone;
 124        unsigned long start_pfn = start >> PAGE_SHIFT;
 125        unsigned long nr_pages = size >> PAGE_SHIFT;
 126
 127        resize_hpt_for_hotplug(memblock_phys_mem_size());
 128
 129        pgdata = NODE_DATA(nid);
 130
 131        start = (unsigned long)__va(start);
 132        if (create_section_mapping(start, start + size))
 133                return -EINVAL;
 134
 135        /* this should work for most non-highmem platforms */
 136        zone = pgdata->node_zones +
 137                zone_for_memory(nid, start, size, 0, for_device);
 138
 139        return __add_pages(nid, zone, start_pfn, nr_pages, altmap);
 140}
 141
 142#ifdef CONFIG_MEMORY_HOTREMOVE
 143int arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
 144{
 145        unsigned long start_pfn = start >> PAGE_SHIFT;
 146        unsigned long nr_pages = size >> PAGE_SHIFT;
 147        struct zone *zone;
 148        int ret;
 149
 150        zone = page_zone(pfn_to_page(start_pfn));
 151        ret = __remove_pages(zone, start_pfn, nr_pages, altmap);
 152        if (ret)
 153                return ret;
 154
 155        /* Remove htab bolted mappings for this section of memory */
 156        start = (unsigned long)__va(start);
 157        ret = remove_section_mapping(start, start + size);
 158
 159        /* Ensure all vmalloc mappings are flushed in case they also
 160         * hit that section of memory
 161         */
 162        vm_unmap_aliases();
 163
 164        if (resize_hpt_for_hotplug(memblock_phys_mem_size()) == -ENOSPC)
 165                pr_warn("Hash collision while resizing HPT\n");
 166
 167        return ret;
 168}
 169#endif
 170#endif /* CONFIG_MEMORY_HOTPLUG */
 171
 172/*
 173 * walk_memory_resource() needs to make sure there is no holes in a given
 174 * memory range.  PPC64 does not maintain the memory layout in /proc/iomem.
 175 * Instead it maintains it in memblock.memory structures.  Walk through the
 176 * memory regions, find holes and callback for contiguous regions.
 177 */
 178int
 179walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 180                void *arg, int (*func)(unsigned long, unsigned long, void *))
 181{
 182        struct memblock_region *reg;
 183        unsigned long end_pfn = start_pfn + nr_pages;
 184        unsigned long tstart, tend;
 185        int ret = -1;
 186
 187        for_each_memblock(memory, reg) {
 188                tstart = max(start_pfn, memblock_region_memory_base_pfn(reg));
 189                tend = min(end_pfn, memblock_region_memory_end_pfn(reg));
 190                if (tstart >= tend)
 191                        continue;
 192                ret = (*func)(tstart, tend - tstart, arg);
 193                if (ret)
 194                        break;
 195        }
 196        return ret;
 197}
 198EXPORT_SYMBOL_GPL(walk_system_ram_range);
 199
 200/*
 201 * Initialize the bootmem system and give it all the memory we
 202 * have available.  If we are using highmem, we only put the
 203 * lowmem into the bootmem system.
 204 */
 205#ifndef CONFIG_NEED_MULTIPLE_NODES
 206void __init do_init_bootmem(void)
 207{
 208        unsigned long start, bootmap_pages;
 209        unsigned long total_pages;
 210        struct memblock_region *reg;
 211        int boot_mapsize;
 212
 213        max_low_pfn = max_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
 214        total_pages = (memblock_end_of_DRAM() - memstart_addr) >> PAGE_SHIFT;
 215#ifdef CONFIG_HIGHMEM
 216        total_pages = total_lowmem >> PAGE_SHIFT;
 217        max_low_pfn = lowmem_end_addr >> PAGE_SHIFT;
 218#endif
 219
 220        /*
 221         * Find an area to use for the bootmem bitmap.  Calculate the size of
 222         * bitmap required as (Total Memory) / PAGE_SIZE / BITS_PER_BYTE.
 223         * Add 1 additional page in case the address isn't page-aligned.
 224         */
 225        bootmap_pages = bootmem_bootmap_pages(total_pages);
 226
 227        start = memblock_alloc(bootmap_pages << PAGE_SHIFT, PAGE_SIZE);
 228
 229        min_low_pfn = MEMORY_START >> PAGE_SHIFT;
 230        boot_mapsize = init_bootmem_node(NODE_DATA(0), start >> PAGE_SHIFT, min_low_pfn, max_low_pfn);
 231
 232        /* Place all memblock_regions in the same node and merge contiguous
 233         * memblock_regions
 234         */
 235        memblock_set_node(0, (phys_addr_t)ULLONG_MAX, &memblock.memory, 0);
 236
 237        /* Add all physical memory to the bootmem map, mark each area
 238         * present.
 239         */
 240#ifdef CONFIG_HIGHMEM
 241        free_bootmem_with_active_regions(0, lowmem_end_addr >> PAGE_SHIFT);
 242
 243        /* reserve the sections we're already using */
 244        for_each_memblock(reserved, reg) {
 245                unsigned long top = reg->base + reg->size - 1;
 246                if (top < lowmem_end_addr)
 247                        reserve_bootmem(reg->base, reg->size, BOOTMEM_DEFAULT);
 248                else if (reg->base < lowmem_end_addr) {
 249                        unsigned long trunc_size = lowmem_end_addr - reg->base;
 250                        reserve_bootmem(reg->base, trunc_size, BOOTMEM_DEFAULT);
 251                }
 252        }
 253#else
 254        free_bootmem_with_active_regions(0, max_pfn);
 255
 256        /* reserve the sections we're already using */
 257        for_each_memblock(reserved, reg)
 258                reserve_bootmem(reg->base, reg->size, BOOTMEM_DEFAULT);
 259#endif
 260        /* XXX need to clip this if using highmem? */
 261        sparse_memory_present_with_active_regions(0);
 262
 263        init_bootmem_done = 1;
 264}
 265
 266/* mark pages that don't exist as nosave */
 267static int __init mark_nonram_nosave(void)
 268{
 269        struct memblock_region *reg, *prev = NULL;
 270
 271        for_each_memblock(memory, reg) {
 272                if (prev &&
 273                    memblock_region_memory_end_pfn(prev) < memblock_region_memory_base_pfn(reg))
 274                        register_nosave_region(memblock_region_memory_end_pfn(prev),
 275                                               memblock_region_memory_base_pfn(reg));
 276                prev = reg;
 277        }
 278        return 0;
 279}
 280
 281/*
 282 * paging_init() sets up the page tables - in fact we've already done this.
 283 */
 284void __init paging_init(void)
 285{
 286        unsigned long long total_ram = memblock_phys_mem_size();
 287        phys_addr_t top_of_ram = memblock_end_of_DRAM();
 288        unsigned long max_zone_pfns[MAX_NR_ZONES];
 289
 290#ifdef CONFIG_PPC32
 291        unsigned long v = __fix_to_virt(__end_of_fixed_addresses - 1);
 292        unsigned long end = __fix_to_virt(FIX_HOLE);
 293
 294        for (; v < end; v += PAGE_SIZE)
 295                map_page(v, 0, 0); /* XXX gross */
 296#endif
 297
 298#ifdef CONFIG_HIGHMEM
 299        map_page(PKMAP_BASE, 0, 0);     /* XXX gross */
 300        pkmap_page_table = virt_to_kpte(PKMAP_BASE);
 301
 302        kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 303        kmap_prot = PAGE_KERNEL;
 304#endif /* CONFIG_HIGHMEM */
 305
 306        printk(KERN_DEBUG "Top of RAM: 0x%llx, Total RAM: 0x%llx\n",
 307               (unsigned long long)top_of_ram, total_ram);
 308        printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 309               (long int)((top_of_ram - total_ram) >> 20));
 310        memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 311#ifdef CONFIG_HIGHMEM
 312        max_zone_pfns[ZONE_DMA] = lowmem_end_addr >> PAGE_SHIFT;
 313        max_zone_pfns[ZONE_HIGHMEM] = top_of_ram >> PAGE_SHIFT;
 314#else
 315        max_zone_pfns[ZONE_DMA] = top_of_ram >> PAGE_SHIFT;
 316#endif
 317        free_area_init_nodes(max_zone_pfns);
 318
 319        mark_nonram_nosave();
 320}
 321#endif /* ! CONFIG_NEED_MULTIPLE_NODES */
 322
 323static void __init register_page_bootmem_info(void)
 324{
 325        int i;
 326
 327        for_each_online_node(i)
 328                register_page_bootmem_info_node(NODE_DATA(i));
 329}
 330
 331void __init mem_init(void)
 332{
 333#ifdef CONFIG_NEED_MULTIPLE_NODES
 334        int nid;
 335#endif
 336        pg_data_t *pgdat;
 337        unsigned long i;
 338        struct page *page;
 339        unsigned long reservedpages = 0, codesize, initsize, datasize, bsssize;
 340
 341#ifdef CONFIG_SWIOTLB
 342        swiotlb_init(0);
 343#endif
 344
 345        register_page_bootmem_info();
 346        num_physpages = memblock_phys_mem_size() >> PAGE_SHIFT;
 347        high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
 348
 349#ifdef CONFIG_NEED_MULTIPLE_NODES
 350        for_each_online_node(nid) {
 351                if (NODE_DATA(nid)->node_spanned_pages != 0) {
 352                        printk("freeing bootmem node %d\n", nid);
 353                        totalram_pages +=
 354                                free_all_bootmem_node(NODE_DATA(nid));
 355                }
 356        }
 357#else
 358        max_mapnr = max_pfn;
 359        totalram_pages += free_all_bootmem();
 360#endif
 361        for_each_online_pgdat(pgdat) {
 362                for (i = 0; i < pgdat->node_spanned_pages; i++) {
 363                        if (!pfn_valid(pgdat->node_start_pfn + i))
 364                                continue;
 365                        page = pgdat_page_nr(pgdat, i);
 366                        if (PageReserved(page))
 367                                reservedpages++;
 368                }
 369        }
 370
 371        codesize = (unsigned long)&_sdata - (unsigned long)&_stext;
 372        datasize = (unsigned long)&_edata - (unsigned long)&_sdata;
 373        initsize = (unsigned long)&__init_end - (unsigned long)&__init_begin;
 374        bsssize = (unsigned long)&__bss_stop - (unsigned long)&__bss_start;
 375
 376#ifdef CONFIG_HIGHMEM
 377        {
 378                unsigned long pfn, highmem_mapnr;
 379
 380                highmem_mapnr = lowmem_end_addr >> PAGE_SHIFT;
 381                for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
 382                        phys_addr_t paddr = (phys_addr_t)pfn << PAGE_SHIFT;
 383                        struct page *page = pfn_to_page(pfn);
 384                        if (memblock_is_reserved(paddr))
 385                                continue;
 386                        free_highmem_page(page);
 387                        reservedpages--;
 388                }
 389                printk(KERN_DEBUG "High memory: %luk\n",
 390                       totalhigh_pages << (PAGE_SHIFT-10));
 391        }
 392#endif /* CONFIG_HIGHMEM */
 393
 394#if defined(CONFIG_PPC_FSL_BOOK3E) && !defined(CONFIG_SMP)
 395        /*
 396         * If smp is enabled, next_tlbcam_idx is initialized in the cpu up
 397         * functions.... do it here for the non-smp case.
 398         */
 399        per_cpu(next_tlbcam_idx, smp_processor_id()) =
 400                (mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) - 1;
 401#endif
 402
 403        printk(KERN_INFO "Memory: %luk/%luk available (%luk kernel code, "
 404               "%luk reserved, %luk data, %luk bss, %luk init)\n",
 405                nr_free_pages() << (PAGE_SHIFT-10),
 406                num_physpages << (PAGE_SHIFT-10),
 407                codesize >> 10,
 408                reservedpages << (PAGE_SHIFT-10),
 409                datasize >> 10,
 410                bsssize >> 10,
 411                initsize >> 10);
 412
 413#ifdef CONFIG_PPC32
 414        pr_info("Kernel virtual memory layout:\n");
 415        pr_info("  * 0x%08lx..0x%08lx  : fixmap\n", FIXADDR_START, FIXADDR_TOP);
 416#ifdef CONFIG_HIGHMEM
 417        pr_info("  * 0x%08lx..0x%08lx  : highmem PTEs\n",
 418                PKMAP_BASE, PKMAP_ADDR(LAST_PKMAP));
 419#endif /* CONFIG_HIGHMEM */
 420#ifdef CONFIG_NOT_COHERENT_CACHE
 421        pr_info("  * 0x%08lx..0x%08lx  : consistent mem\n",
 422                IOREMAP_TOP, IOREMAP_TOP + CONFIG_CONSISTENT_SIZE);
 423#endif /* CONFIG_NOT_COHERENT_CACHE */
 424        pr_info("  * 0x%08lx..0x%08lx  : early ioremap\n",
 425                ioremap_bot, IOREMAP_TOP);
 426        pr_info("  * 0x%08lx..0x%08lx  : vmalloc & ioremap\n",
 427                VMALLOC_START, VMALLOC_END);
 428#endif /* CONFIG_PPC32 */
 429
 430        mem_init_done = 1;
 431}
 432
 433void free_initmem(void)
 434{
 435        ppc_md.progress = ppc_printk_progress;
 436        init_mem_is_free = true;
 437        free_initmem_default(POISON_FREE_INITMEM);
 438}
 439
 440#ifdef CONFIG_BLK_DEV_INITRD
 441void __init free_initrd_mem(unsigned long start, unsigned long end)
 442{
 443        free_reserved_area(start, end, 0, "initrd");
 444}
 445#endif
 446
 447/*
 448 * This is called when a page has been modified by the kernel.
 449 * It just marks the page as not i-cache clean.  We do the i-cache
 450 * flush later when the page is given to a user process, if necessary.
 451 */
 452void flush_dcache_page(struct page *page)
 453{
 454        if (cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 455                return;
 456        /* avoid an atomic op if possible */
 457        if (test_bit(PG_arch_1, &page->flags))
 458                clear_bit(PG_arch_1, &page->flags);
 459}
 460EXPORT_SYMBOL(flush_dcache_page);
 461
 462void flush_dcache_icache_page(struct page *page)
 463{
 464#ifdef CONFIG_HUGETLB_PAGE
 465        if (PageCompound(page)) {
 466                flush_dcache_icache_hugepage(page);
 467                return;
 468        }
 469#endif
 470#ifdef CONFIG_BOOKE
 471        {
 472                void *start = kmap_atomic(page);
 473                __flush_dcache_icache(start);
 474                kunmap_atomic(start);
 475        }
 476#elif defined(CONFIG_8xx) || defined(CONFIG_PPC64)
 477        /* On 8xx there is no need to kmap since highmem is not supported */
 478        __flush_dcache_icache(page_address(page)); 
 479#else
 480        __flush_dcache_icache_phys(page_to_pfn(page) << PAGE_SHIFT);
 481#endif
 482}
 483EXPORT_SYMBOL(flush_dcache_icache_page);
 484
 485void clear_user_page(void *page, unsigned long vaddr, struct page *pg)
 486{
 487        clear_page(page);
 488
 489        /*
 490         * We shouldn't have to do this, but some versions of glibc
 491         * require it (ld.so assumes zero filled pages are icache clean)
 492         * - Anton
 493         */
 494        flush_dcache_page(pg);
 495}
 496EXPORT_SYMBOL(clear_user_page);
 497
 498void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
 499                    struct page *pg)
 500{
 501        copy_page(vto, vfrom);
 502
 503        /*
 504         * We should be able to use the following optimisation, however
 505         * there are two problems.
 506         * Firstly a bug in some versions of binutils meant PLT sections
 507         * were not marked executable.
 508         * Secondly the first word in the GOT section is blrl, used
 509         * to establish the GOT address. Until recently the GOT was
 510         * not marked executable.
 511         * - Anton
 512         */
 513#if 0
 514        if (!vma->vm_file && ((vma->vm_flags & VM_EXEC) == 0))
 515                return;
 516#endif
 517
 518        flush_dcache_page(pg);
 519}
 520
 521void flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 522                             unsigned long addr, int len)
 523{
 524        unsigned long maddr;
 525
 526        maddr = (unsigned long) kmap(page) + (addr & ~PAGE_MASK);
 527        flush_icache_range(maddr, maddr + len);
 528        kunmap(page);
 529}
 530EXPORT_SYMBOL(flush_icache_user_range);
 531
 532/*
 533 * This is called at the end of handling a user page fault, when the
 534 * fault has been handled by updating a PTE in the linux page tables.
 535 * We use it to preload an HPTE into the hash table corresponding to
 536 * the updated linux PTE.
 537 * 
 538 * This must always be called with the pte lock held.
 539 */
 540void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
 541                      pte_t *ptep)
 542{
 543#ifdef CONFIG_PPC_STD_MMU
 544        /*
 545         * We don't need to worry about _PAGE_PRESENT here because we are
 546         * called with either mm->page_table_lock held or ptl lock held
 547         */
 548        unsigned long access = 0, trap;
 549
 550        /* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */
 551        if (!pte_young(*ptep) || address >= TASK_SIZE)
 552                return;
 553
 554        /* We try to figure out if we are coming from an instruction
 555         * access fault and pass that down to __hash_page so we avoid
 556         * double-faulting on execution of fresh text. We have to test
 557         * for regs NULL since init will get here first thing at boot
 558         *
 559         * We also avoid filling the hash if not coming from a fault
 560         */
 561        if (current->thread.regs == NULL)
 562                return;
 563        trap = TRAP(current->thread.regs);
 564        if (trap == 0x400)
 565                access |= _PAGE_EXEC;
 566        else if (trap != 0x300)
 567                return;
 568        hash_preload(vma->vm_mm, address, access, trap);
 569#endif /* CONFIG_PPC_STD_MMU */
 570#if (defined(CONFIG_PPC_BOOK3E_64) || defined(CONFIG_PPC_FSL_BOOK3E)) \
 571        && defined(CONFIG_HUGETLB_PAGE)
 572        if (is_vm_hugetlb_page(vma))
 573                book3e_hugetlb_preload(vma, address, *ptep);
 574#endif
 575}
 576
 577/*
 578 * System memory should not be in /proc/iomem but various tools expect it
 579 * (eg kdump).
 580 */
 581static int __init add_system_ram_resources(void)
 582{
 583        struct memblock_region *reg;
 584
 585        for_each_memblock(memory, reg) {
 586                struct resource *res;
 587                unsigned long base = reg->base;
 588                unsigned long size = reg->size;
 589
 590                res = kzalloc(sizeof(struct resource), GFP_KERNEL);
 591                WARN_ON(!res);
 592
 593                if (res) {
 594                        res->name = "System RAM";
 595                        res->start = base;
 596                        res->end = base + size - 1;
 597                        res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 598                        WARN_ON(request_resource(&iomem_resource, res) < 0);
 599                }
 600        }
 601
 602        return 0;
 603}
 604subsys_initcall(add_system_ram_resources);
 605
 606#ifdef CONFIG_STRICT_DEVMEM
 607/*
 608 * devmem_is_allowed(): check to see if /dev/mem access to a certain address
 609 * is valid. The argument is a physical page number.
 610 *
 611 * Access has to be given to non-kernel-ram areas as well, these contain the
 612 * PCI mmio resources as well as potential bios/acpi data regions.
 613 */
 614int devmem_is_allowed(unsigned long pfn)
 615{
 616        if (iomem_is_exclusive(pfn << PAGE_SHIFT))
 617                return 0;
 618        if (!page_is_ram(pfn))
 619                return 1;
 620        if (page_is_rtas_user_buf(pfn))
 621                return 1;
 622        return 0;
 623}
 624#endif /* CONFIG_STRICT_DEVMEM */
 625