arch/ppc/mm/init.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  *  Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
   9  *  PPC44x/36-bit changes by Matt Porter (mporter@mvista.com)
  10  *
  11  *  Derived from "arch/i386/mm/init.c"
  12  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  13  *
  14  *  This program is free software; you can redistribute it and/or
  15  *  modify it under the terms of the GNU General Public License
  16  *  as published by the Free Software Foundation; either version
  17  *  2 of the License, or (at your option) any later version.
  18  *
  19  */
  20
  21 #include <linux/config.h>
  22 #include <linux/module.h>
  23 #include <linux/sched.h>
  24 #include <linux/kernel.h>
  25 #include <linux/errno.h>
  26 #include <linux/string.h>
  27 #include <linux/types.h>
  28 #include <linux/mm.h>
  29 #include <linux/stddef.h>
  30 #include <linux/init.h>
  31 #include <linux/bootmem.h>
  32 #include <linux/highmem.h>
  33 #include <linux/initrd.h>
  34 #include <linux/pagemap.h>
  35
  36 #include <asm/pgalloc.h>
  37 #include <asm/prom.h>
  38 #include <asm/io.h>
  39 #include <asm/mmu_context.h>
  40 #include <asm/pgtable.h>
  41 #include <asm/mmu.h>
  42 #include <asm/smp.h>
  43 #include <asm/machdep.h>
  44 #include <asm/btext.h>
  45 #include <asm/tlb.h>
  46 #include <asm/bootinfo.h>
  47
  48 #include "mem_pieces.h"
  49 #include "mmu_decl.h"
  50
  51 #if defined(CONFIG_KERNEL_START_BOOL) || defined(CONFIG_LOWMEM_SIZE_BOOL)
  52 /* The ammount of lowmem must be within 0xF0000000 - KERNELBASE. */
  53 #if (CONFIG_LOWMEM_SIZE > (0xF0000000 - KERNELBASE))
  54 #error "You must adjust CONFIG_LOWMEM_SIZE or CONFIG_START_KERNEL"
  55 #endif
  56 #endif
  57 #define MAX_LOW_MEM     CONFIG_LOWMEM_SIZE
  58
  59 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
  60
  61 unsigned long total_memory;
  62 unsigned long total_lowmem;
  63
  64 unsigned long ppc_memstart;
  65 unsigned long ppc_memoffset = PAGE_OFFSET;
  66
  67 int mem_init_done;
  68 int init_bootmem_done;
  69 int boot_mapsize;
  70 #ifdef CONFIG_PPC_PMAC
  71 unsigned long agp_special_page;
  72 #endif
  73
  74 extern char _end[];
  75 extern char etext[], _stext[];
  76 extern char __init_begin, __init_end;
  77 extern char __prep_begin, __prep_end;
  78 extern char __chrp_begin, __chrp_end;
  79 extern char __pmac_begin, __pmac_end;
  80 extern char __openfirmware_begin, __openfirmware_end;
  81
  82 #ifdef CONFIG_HIGHMEM
  83 pte_t *kmap_pte;
  84 pgprot_t kmap_prot;
  85
  86 EXPORT_SYMBOL(kmap_prot);
  87 EXPORT_SYMBOL(kmap_pte);
  88 #endif
  89
  90 void MMU_init(void);
  91 void set_phys_avail(unsigned long total_ram);
  92
  93 /* XXX should be in current.h  -- paulus */
  94 extern struct task_struct *current_set[NR_CPUS];
  95
  96 char *klimit = _end;
  97 struct mem_pieces phys_avail;
  98
  99 /*
 100  * this tells the system to map all of ram with the segregs
 101  * (i.e. page tables) instead of the bats.
 102  * -- Cort
 103  */
 104 int __map_without_bats;
 105 int __map_without_ltlbs;
 106
 107 /* max amount of RAM to use */
 108 unsigned long __max_memory;
 109 /* max amount of low RAM to map in */
 110 unsigned long __max_low_memory = MAX_LOW_MEM;
 111
 112 void show_mem(void)
 113 {
 114         int i,free = 0,total = 0,reserved = 0;
 115         int shared = 0, cached = 0;
 116         int highmem = 0;
 117
 118         printk("Mem-info:\n");
 119         show_free_areas();
 120         printk("Free swap:       %6ldkB\n", nr_swap_pages<<(PAGE_SHIFT-10));
 121         i = max_mapnr;
 122         while (i-- > 0) {
 123                 total++;
 124                 if (PageHighMem(mem_map+i))
 125                         highmem++;
 126                 if (PageReserved(mem_map+i))
 127                         reserved++;
 128                 else if (PageSwapCache(mem_map+i))
 129                         cached++;
 130                 else if (!page_count(mem_map+i))
 131                         free++;
 132                 else
 133                         shared += page_count(mem_map+i) - 1;
 134         }
 135         printk("%d pages of RAM\n",total);
 136         printk("%d pages of HIGHMEM\n", highmem);
 137         printk("%d free pages\n",free);
 138         printk("%d reserved pages\n",reserved);
 139         printk("%d pages shared\n",shared);
 140         printk("%d pages swap cached\n",cached);
 141 }
 142
 143 /* Free up now-unused memory */
 144 static void free_sec(unsigned long start, unsigned long end, const char *name)
 145 {
 146         unsigned long cnt = 0;
 147
 148         while (start < end) {
 149                 ClearPageReserved(virt_to_page(start));
 150                 set_page_count(virt_to_page(start), 1);
 151                 free_page(start);
 152                 cnt++;
 153                 start += PAGE_SIZE;
 154         }
 155         if (cnt) {
 156                 printk(" %ldk %s", cnt << (PAGE_SHIFT - 10), name);
 157                 totalram_pages += cnt;
 158         }
 159 }
 160
 161 void free_initmem(void)
 162 {
 163 #define FREESEC(TYPE) \
 164         free_sec((unsigned long)(&__ ## TYPE ## _begin), \
 165                  (unsigned long)(&__ ## TYPE ## _end), \
 166                  #TYPE);
 167
 168         printk ("Freeing unused kernel memory:");
 169         FREESEC(init);
 170         if (_machine != _MACH_Pmac)
 171                 FREESEC(pmac);
 172         if (_machine != _MACH_chrp)
 173                 FREESEC(chrp);
 174         if (_machine != _MACH_prep)
 175                 FREESEC(prep);
 176         if (!have_of)
 177                 FREESEC(openfirmware);
 178         printk("\n");
 179         ppc_md.progress = NULL;
 180 #undef FREESEC
 181 }
 182
 183 #ifdef CONFIG_BLK_DEV_INITRD
 184 void free_initrd_mem(unsigned long start, unsigned long end)
 185 {
 186         printk ("Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
 187
 188         for (; start < end; start += PAGE_SIZE) {
 189                 ClearPageReserved(virt_to_page(start));
 190                 set_page_count(virt_to_page(start), 1);
 191                 free_page(start);
 192                 totalram_pages++;
 193         }
 194 }
 195 #endif
 196
 197 /*
 198  * Check for command-line options that affect what MMU_init will do.
 199  */
 200 void MMU_setup(void)
 201 {
 202         /* Check for nobats option (used in mapin_ram). */
 203         if (strstr(cmd_line, "nobats")) {
 204                 __map_without_bats = 1;
 205         }
 206
 207         if (strstr(cmd_line, "noltlbs")) {
 208                 __map_without_ltlbs = 1;
 209         }
 210
 211         /* Look for mem= option on command line */
 212         if (strstr(cmd_line, "mem=")) {
 213                 char *p, *q;
 214                 unsigned long maxmem = 0;
 215
 216                 for (q = cmd_line; (p = strstr(q, "mem=")) != 0; ) {
 217                         q = p + 4;
 218                         if (p > cmd_line && p[-1] != ' ')
 219                                 continue;
 220                         maxmem = simple_strtoul(q, &q, 0);
 221                         if (*q == 'k' || *q == 'K') {
 222                                 maxmem <<= 10;
 223                                 ++q;
 224                         } else if (*q == 'm' || *q == 'M') {
 225                                 maxmem <<= 20;
 226                                 ++q;
 227                         }
 228                 }
 229                 __max_memory = maxmem;
 230         }
 231 }
 232
 233 /*
 234  * MMU_init sets up the basic memory mappings for the kernel,
 235  * including both RAM and possibly some I/O regions,
 236  * and sets up the page tables and the MMU hardware ready to go.
 237  */
 238 void __init MMU_init(void)
 239 {
 240         if (ppc_md.progress)
 241                 ppc_md.progress("MMU:enter", 0x111);
 242
 243         /* parse args from command line */
 244         MMU_setup();
 245
 246         /*
 247          * Figure out how much memory we have, how much
 248          * is lowmem, and how much is highmem.  If we were
 249          * passed the total memory size from the bootloader,
 250          * just use it.
 251          */
 252         if (boot_mem_size)
 253                 total_memory = boot_mem_size;
 254         else
 255                 total_memory = ppc_md.find_end_of_memory();
 256
 257         if (__max_memory && total_memory > __max_memory)
 258                 total_memory = __max_memory;
 259         total_lowmem = total_memory;
 260 #ifdef CONFIG_FSL_BOOKE
 261         /* Freescale Book-E parts expect lowmem to be mapped by fixed TLB
 262          * entries, so we need to adjust lowmem to match the amount we can map
 263          * in the fixed entries */
 264         adjust_total_lowmem();
 265 #endif /* CONFIG_FSL_BOOKE */
 266         if (total_lowmem > __max_low_memory) {
 267                 total_lowmem = __max_low_memory;
 268 #ifndef CONFIG_HIGHMEM
 269                 total_memory = total_lowmem;
 270 #endif /* CONFIG_HIGHMEM */
 271         }
 272         set_phys_avail(total_lowmem);
 273
 274         /* Initialize the MMU hardware */
 275         if (ppc_md.progress)
 276                 ppc_md.progress("MMU:hw init", 0x300);
 277         MMU_init_hw();
 278
 279         /* Map in all of RAM starting at KERNELBASE */
 280         if (ppc_md.progress)
 281                 ppc_md.progress("MMU:mapin", 0x301);
 282         mapin_ram();
 283
 284 #ifdef CONFIG_HIGHMEM
 285         ioremap_base = PKMAP_BASE;
 286 #else
 287         ioremap_base = 0xfe000000UL;    /* for now, could be 0xfffff000 */
 288 #endif /* CONFIG_HIGHMEM */
 289         ioremap_bot = ioremap_base;
 290
 291         /* Map in I/O resources */
 292         if (ppc_md.progress)
 293                 ppc_md.progress("MMU:setio", 0x302);
 294         if (ppc_md.setup_io_mappings)
 295                 ppc_md.setup_io_mappings();
 296
 297         /* Initialize the context management stuff */
 298         mmu_context_init();
 299
 300         if (ppc_md.progress)
 301                 ppc_md.progress("MMU:exit", 0x211);
 302
 303 #ifdef CONFIG_BOOTX_TEXT
 304         /* By default, we are no longer mapped */
 305         boot_text_mapped = 0;
 306         /* Must be done last, or ppc_md.progress will die. */
 307         map_boot_text();
 308 #endif
 309 }
 310
 311 /* This is only called until mem_init is done. */
 312 void __init *early_get_page(void)
 313 {
 314         void *p;
 315
 316         if (init_bootmem_done) {
 317                 p = alloc_bootmem_pages(PAGE_SIZE);
 318         } else {
 319                 p = mem_pieces_find(PAGE_SIZE, PAGE_SIZE);
 320         }
 321         return p;
 322 }
 323
 324 /*
 325  * Initialize the bootmem system and give it all the memory we
 326  * have available.
 327  */
 328 void __init do_init_bootmem(void)
 329 {
 330         unsigned long start, size;
 331         int i;
 332
 333         /*
 334          * Find an area to use for the bootmem bitmap.
 335          * We look for the first area which is at least
 336          * 128kB in length (128kB is enough for a bitmap
 337          * for 4GB of memory, using 4kB pages), plus 1 page
 338          * (in case the address isn't page-aligned).
 339          */
 340         start = 0;
 341         size = 0;
 342         for (i = 0; i < phys_avail.n_regions; ++i) {
 343                 unsigned long a = phys_avail.regions[i].address;
 344                 unsigned long s = phys_avail.regions[i].size;
 345                 if (s <= size)
 346                         continue;
 347                 start = a;
 348                 size = s;
 349                 if (s >= 33 * PAGE_SIZE)
 350                         break;
 351         }
 352         start = PAGE_ALIGN(start);
 353
 354         min_low_pfn = start >> PAGE_SHIFT;
 355         max_low_pfn = (PPC_MEMSTART + total_lowmem) >> PAGE_SHIFT;
 356         max_pfn = (PPC_MEMSTART + total_memory) >> PAGE_SHIFT;
 357         boot_mapsize = init_bootmem_node(&contig_page_data, min_low_pfn,
 358                                          PPC_MEMSTART >> PAGE_SHIFT,
 359                                          max_low_pfn);
 360
 361         /* remove the bootmem bitmap from the available memory */
 362         mem_pieces_remove(&phys_avail, start, boot_mapsize, 1);
 363
 364         /* add everything in phys_avail into the bootmem map */
 365         for (i = 0; i < phys_avail.n_regions; ++i)
 366                 free_bootmem(phys_avail.regions[i].address,
 367                              phys_avail.regions[i].size);
 368
 369         init_bootmem_done = 1;
 370 }
 371
 372 /*
 373  * paging_init() sets up the page tables - in fact we've already done this.
 374  */
 375 void __init paging_init(void)
 376 {
 377         unsigned long zones_size[MAX_NR_ZONES], i;
 378
 379 #ifdef CONFIG_HIGHMEM
 380         map_page(PKMAP_BASE, 0, 0);     /* XXX gross */
 381         pkmap_page_table = pte_offset_kernel(pmd_offset(pgd_offset_k
 382                         (PKMAP_BASE), PKMAP_BASE), PKMAP_BASE);
 383         map_page(KMAP_FIX_BEGIN, 0, 0); /* XXX gross */
 384         kmap_pte = pte_offset_kernel(pmd_offset(pgd_offset_k
 385                         (KMAP_FIX_BEGIN), KMAP_FIX_BEGIN), KMAP_FIX_BEGIN);
 386         kmap_prot = PAGE_KERNEL;
 387 #endif /* CONFIG_HIGHMEM */
 388
 389         /*
 390          * All pages are DMA-able so we put them all in the DMA zone.
 391          */
 392         zones_size[ZONE_DMA] = total_lowmem >> PAGE_SHIFT;
 393         for (i = 1; i < MAX_NR_ZONES; i++)
 394                 zones_size[i] = 0;
 395
 396 #ifdef CONFIG_HIGHMEM
 397         zones_size[ZONE_HIGHMEM] = (total_memory - total_lowmem) >> PAGE_SHIFT;
 398 #endif /* CONFIG_HIGHMEM */
 399
 400         free_area_init(zones_size);
 401 }
 402
 403 void __init mem_init(void)
 404 {
 405         unsigned long addr;
 406         int codepages = 0;
 407         int datapages = 0;
 408         int initpages = 0;
 409 #ifdef CONFIG_HIGHMEM
 410         unsigned long highmem_mapnr;
 411
 412         highmem_mapnr = total_lowmem >> PAGE_SHIFT;
 413 #endif /* CONFIG_HIGHMEM */
 414         max_mapnr = total_memory >> PAGE_SHIFT;
 415
 416         high_memory = (void *) __va(PPC_MEMSTART + total_lowmem);
 417         num_physpages = max_mapnr;      /* RAM is assumed contiguous */
 418
 419         totalram_pages += free_all_bootmem();
 420
 421 #ifdef CONFIG_BLK_DEV_INITRD
 422         /* if we are booted from BootX with an initial ramdisk,
 423            make sure the ramdisk pages aren't reserved. */
 424         if (initrd_start) {
 425                 for (addr = initrd_start; addr < initrd_end; addr += PAGE_SIZE)
 426                         ClearPageReserved(virt_to_page(addr));
 427         }
 428 #endif /* CONFIG_BLK_DEV_INITRD */
 429
 430 #ifdef CONFIG_PPC_OF
 431         /* mark the RTAS pages as reserved */
 432         if ( rtas_data )
 433                 for (addr = (ulong)__va(rtas_data);
 434                      addr < PAGE_ALIGN((ulong)__va(rtas_data)+rtas_size) ;
 435                      addr += PAGE_SIZE)
 436                         SetPageReserved(virt_to_page(addr));
 437 #endif
 438 #ifdef CONFIG_PPC_PMAC
 439         if (agp_special_page)
 440                 SetPageReserved(virt_to_page(agp_special_page));
 441 #endif
 442         for (addr = PAGE_OFFSET; addr < (unsigned long)high_memory;
 443              addr += PAGE_SIZE) {
 444                 if (!PageReserved(virt_to_page(addr)))
 445                         continue;
 446                 if (addr < (ulong) etext)
 447                         codepages++;
 448                 else if (addr >= (unsigned long)&__init_begin
 449                          && addr < (unsigned long)&__init_end)
 450                         initpages++;
 451                 else if (addr < (ulong) klimit)
 452                         datapages++;
 453         }
 454
 455 #ifdef CONFIG_HIGHMEM
 456         {
 457                 unsigned long pfn;
 458
 459                 for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
 460                         struct page *page = mem_map + pfn;
 461
 462                         ClearPageReserved(page);
 463                         set_page_count(page, 1);
 464                         __free_page(page);
 465                         totalhigh_pages++;
 466                 }
 467                 totalram_pages += totalhigh_pages;
 468         }
 469 #endif /* CONFIG_HIGHMEM */
 470
 471         printk("Memory: %luk available (%dk kernel code, %dk data, %dk init, %ldk highmem)\n",
 472                (unsigned long)nr_free_pages()<< (PAGE_SHIFT-10),
 473                codepages<< (PAGE_SHIFT-10), datapages<< (PAGE_SHIFT-10),
 474                initpages<< (PAGE_SHIFT-10),
 475                (unsigned long) (totalhigh_pages << (PAGE_SHIFT-10)));
 476
 477 #ifdef CONFIG_PPC_PMAC
 478         if (agp_special_page)
 479                 printk(KERN_INFO "AGP special page: 0x%08lx\n", agp_special_page);
 480 #endif
 481
 482         mem_init_done = 1;
 483 }
 484
 485 /*
 486  * Set phys_avail to the amount of physical memory,
 487  * less the kernel text/data/bss.
 488  */
 489 void __init
 490 set_phys_avail(unsigned long total_memory)
 491 {
 492         unsigned long kstart, ksize;
 493
 494         /*
 495          * Initially, available physical memory is equivalent to all
 496          * physical memory.
 497          */
 498
 499         phys_avail.regions[0].address = PPC_MEMSTART;
 500         phys_avail.regions[0].size = total_memory;
 501         phys_avail.n_regions = 1;
 502
 503         /*
 504          * Map out the kernel text/data/bss from the available physical
 505          * memory.
 506          */
 507
 508         kstart = __pa(_stext);  /* should be 0 */
 509         ksize = PAGE_ALIGN(klimit - _stext);
 510
 511         mem_pieces_remove(&phys_avail, kstart, ksize, 0);
 512         mem_pieces_remove(&phys_avail, 0, 0x4000, 0);
 513
 514 #if defined(CONFIG_BLK_DEV_INITRD)
 515         /* Remove the init RAM disk from the available memory. */
 516         if (initrd_start) {
 517                 mem_pieces_remove(&phys_avail, __pa(initrd_start),
 518                                   initrd_end - initrd_start, 1);
 519         }
 520 #endif /* CONFIG_BLK_DEV_INITRD */
 521 #ifdef CONFIG_PPC_OF
 522         /* remove the RTAS pages from the available memory */
 523         if (rtas_data)
 524                 mem_pieces_remove(&phys_avail, rtas_data, rtas_size, 1);
 525 #endif
 526 #ifdef CONFIG_PPC_PMAC
 527         /* Because of some uninorth weirdness, we need a page of
 528          * memory as high as possible (it must be outside of the
 529          * bus address seen as the AGP aperture). It will be used
 530          * by the r128 DRM driver
 531          *
 532          * FIXME: We need to make sure that page doesn't overlap any of the\
 533          * above. This could be done by improving mem_pieces_find to be able
 534          * to do a backward search from the end of the list.
 535          */
 536         if (_machine == _MACH_Pmac && find_devices("uni-north-agp")) {
 537                 agp_special_page = (total_memory - PAGE_SIZE);
 538                 mem_pieces_remove(&phys_avail, agp_special_page, PAGE_SIZE, 0);
 539                 agp_special_page = (unsigned long)__va(agp_special_page);
 540         }
 541 #endif /* CONFIG_PPC_PMAC */
 542 }
 543
 544 /* Mark some memory as reserved by removing it from phys_avail. */
 545 void __init reserve_phys_mem(unsigned long start, unsigned long size)
 546 {
 547         mem_pieces_remove(&phys_avail, start, size, 1);
 548 }
 549
 550 /*
 551  * This is called when a page has been modified by the kernel.
 552  * It just marks the page as not i-cache clean.  We do the i-cache
 553  * flush later when the page is given to a user process, if necessary.
 554  */
 555 void flush_dcache_page(struct page *page)
 556 {
 557         clear_bit(PG_arch_1, &page->flags);
 558 }
 559
 560 void flush_dcache_icache_page(struct page *page)
 561 {
 562 #ifdef CONFIG_BOOKE
 563         __flush_dcache_icache(kmap(page));
 564         kunmap(page);
 565 #elif CONFIG_8xx
 566         /* On 8xx there is no need to kmap since highmem is not supported */
 567         __flush_dcache_icache(page_address(page));
 568 #else
 569         __flush_dcache_icache_phys(page_to_pfn(page) << PAGE_SHIFT);
 570 #endif
 571
 572 }
 573 void clear_user_page(void *page, unsigned long vaddr, struct page *pg)
 574 {
 575         clear_page(page);
 576         clear_bit(PG_arch_1, &pg->flags);
 577 }
 578
 579 void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
 580                     struct page *pg)
 581 {
 582         copy_page(vto, vfrom);
 583         clear_bit(PG_arch_1, &pg->flags);
 584 }
 585
 586 void flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 587                              unsigned long addr, int len)
 588 {
 589         unsigned long maddr;
 590
 591         maddr = (unsigned long) kmap(page) + (addr & ~PAGE_MASK);
 592         flush_icache_range(maddr, maddr + len);
 593         kunmap(page);
 594 }
 595
 596 /*
 597  * This is called at the end of handling a user page fault, when the
 598  * fault has been handled by updating a PTE in the linux page tables.
 599  * We use it to preload an HPTE into the hash table corresponding to
 600  * the updated linux PTE.
 601  */
 602 void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
 603                       pte_t pte)
 604 {
 605         /* handle i-cache coherency */
 606         unsigned long pfn = pte_pfn(pte);
 607
 608         if (pfn_valid(pfn)) {
 609                 struct page *page = pfn_to_page(pfn);
 610                 if (!PageReserved(page)
 611                     && !test_bit(PG_arch_1, &page->flags)) {
 612                         if (vma->vm_mm == current->active_mm) {
 613 #ifdef CONFIG_8xx
 614                         /* On 8xx, cache control instructions (particularly
 615                          * "dcbst" from flush_dcache_icache) fault as write
 616                          * operation if there is an unpopulated TLB entry
 617                          * for the address in question. To workaround that,
 618                          * we invalidate the TLB here, thus avoiding dcbst
 619                          * misbehaviour.
 620                          */
 621                                 _tlbie(address);
 622 #endif
 623                                 __flush_dcache_icache((void *) address);
 624                         } else
 625                                 flush_dcache_icache_page(page);
 626                         set_bit(PG_arch_1, &page->flags);
 627                 }
 628         }
 629
 630 #ifdef CONFIG_PPC_STD_MMU
 631         /* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */
 632         if (Hash != 0 && pte_young(pte)) {
 633                 struct mm_struct *mm;
 634                 pmd_t *pmd;
 635
 636                 mm = (address < TASK_SIZE)? vma->vm_mm: &init_mm;
 637                 pmd = pmd_offset(pgd_offset(mm, address), address);
 638                 if (!pmd_none(*pmd))
 639                         add_hash_page(mm->context, address, pmd_val(*pmd));
 640         }
 641 #endif
 642 }
 643
 644 /*
 645  * This is called by /dev/mem to know if a given address has to
 646  * be mapped non-cacheable or not
 647  */
 648 int page_is_ram(unsigned long pfn)
 649 {
 650         unsigned long paddr = (pfn << PAGE_SHIFT);
 651
 652         return paddr < __pa(high_memory);
 653 }
 654
 655 pgprot_t phys_mem_access_prot(struct file *file, unsigned long addr,
 656                               unsigned long size, pgprot_t vma_prot)
 657 {
 658         if (ppc_md.phys_mem_access_prot)
 659                 return ppc_md.phys_mem_access_prot(file, addr, size, vma_prot);
 660
 661         if (!page_is_ram(addr >> PAGE_SHIFT))
 662                 vma_prot = __pgprot(pgprot_val(vma_prot)
 663                                     | _PAGE_GUARDED | _PAGE_NO_CACHE);
 664         return vma_prot;
 665 }
 666 EXPORT_SYMBOL(phys_mem_access_prot);