arch/x86_64/kernel/e820.c

   1 /*
   2  * Handle the memory map.
   3  * The functions here do the job until bootmem takes over.
   4  *
   5  *  Getting sanitize_e820_map() in sync with i386 version by applying change:
   6  *  -  Provisions for empty E820 memory regions (reported by certain BIOSes).
   7  *     Alex Achenbach <xela@slit.de>, December 2002.
   8  *  Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
   9  *
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/types.h>
  13 #include <linux/init.h>
  14 #include <linux/bootmem.h>
  15 #include <linux/ioport.h>
  16 #include <linux/string.h>
  17 #include <linux/kexec.h>
  18 #include <linux/module.h>
  19
  20 #include <asm/pgtable.h>
  21 #include <asm/page.h>
  22 #include <asm/e820.h>
  23 #include <asm/proto.h>
  24 #include <asm/bootsetup.h>
  25 #include <asm/sections.h>
  26
  27 struct e820map e820 __initdata;
  28
  29 /*
  30  * PFN of last memory page.
  31  */
  32 unsigned long end_pfn;
  33 EXPORT_SYMBOL(end_pfn);
  34
  35 /*
  36  * end_pfn only includes RAM, while end_pfn_map includes all e820 entries.
  37  * The direct mapping extends to end_pfn_map, so that we can directly access
  38  * apertures, ACPI and other tables without having to play with fixmaps.
  39  */
  40 unsigned long end_pfn_map;
  41
  42 /*
  43  * Last pfn which the user wants to use.
  44  */
  45 static unsigned long __initdata end_user_pfn = MAXMEM>>PAGE_SHIFT;
  46
  47 extern struct resource code_resource, data_resource;
  48
  49 /* Check for some hardcoded bad areas that early boot is not allowed to touch */
  50 static inline int bad_addr(unsigned long *addrp, unsigned long size)
  51 {
  52         unsigned long addr = *addrp, last = addr + size;
  53
  54         /* various gunk below that needed for SMP startup */
  55         if (addr < 0x8000) {
  56                 *addrp = 0x8000;
  57                 return 1;
  58         }
  59
  60         /* direct mapping tables of the kernel */
  61         if (last >= table_start<<PAGE_SHIFT && addr < table_end<<PAGE_SHIFT) {
  62                 *addrp = table_end << PAGE_SHIFT;
  63                 return 1;
  64         }
  65
  66         /* initrd */
  67 #ifdef CONFIG_BLK_DEV_INITRD
  68         if (LOADER_TYPE && INITRD_START && last >= INITRD_START &&
  69             addr < INITRD_START+INITRD_SIZE) {
  70                 *addrp = INITRD_START + INITRD_SIZE;
  71                 return 1;
  72         }
  73 #endif
  74         /* kernel code + 640k memory hole (later should not be needed, but
  75            be paranoid for now) */
  76         if (last >= 640*1024 && addr < 1024*1024) {
  77                 *addrp = 1024*1024;
  78                 return 1;
  79         }
  80         if (last >= __pa_symbol(&_text) && last < __pa_symbol(&_end)) {
  81                 *addrp = __pa_symbol(&_end);
  82                 return 1;
  83         }
  84
  85         if (last >= ebda_addr && addr < ebda_addr + ebda_size) {
  86                 *addrp = ebda_addr + ebda_size;
  87                 return 1;
  88         }
  89
  90         /* XXX ramdisk image here? */
  91         return 0;
  92 }
  93
  94 /*
  95  * This function checks if any part of the range <start,end> is mapped
  96  * with type.
  97  */
  98 int __meminit
  99 e820_any_mapped(unsigned long start, unsigned long end, unsigned type)
 100 {
 101         int i;
 102         for (i = 0; i < e820.nr_map; i++) {
 103                 struct e820entry *ei = &e820.map[i];
 104                 if (type && ei->type != type)
 105                         continue;
 106                 if (ei->addr >= end || ei->addr + ei->size <= start)
 107                         continue;
 108                 return 1;
 109         }
 110         return 0;
 111 }
 112
 113 /*
 114  * This function checks if the entire range <start,end> is mapped with type.
 115  *
 116  * Note: this function only works correct if the e820 table is sorted and
 117  * not-overlapping, which is the case
 118  */
 119 int __init e820_all_mapped(unsigned long start, unsigned long end, unsigned type)
 120 {
 121         int i;
 122         for (i = 0; i < e820.nr_map; i++) {
 123                 struct e820entry *ei = &e820.map[i];
 124                 if (type && ei->type != type)
 125                         continue;
 126                 /* is the region (part) in overlap with the current region ?*/
 127                 if (ei->addr >= end || ei->addr + ei->size <= start)
 128                         continue;
 129
 130                 /* if the region is at the beginning of <start,end> we move
 131                  * start to the end of the region since it's ok until there
 132                  */
 133                 if (ei->addr <= start)
 134                         start = ei->addr + ei->size;
 135                 /* if start is now at or beyond end, we're done, full coverage */
 136                 if (start >= end)
 137                         return 1; /* we're done */
 138         }
 139         return 0;
 140 }
 141
 142 /*
 143  * Find a free area in a specific range.
 144  */
 145 unsigned long __init find_e820_area(unsigned long start, unsigned long end, unsigned size)
 146 {
 147         int i;
 148         for (i = 0; i < e820.nr_map; i++) {
 149                 struct e820entry *ei = &e820.map[i];
 150                 unsigned long addr = ei->addr, last;
 151                 if (ei->type != E820_RAM)
 152                         continue;
 153                 if (addr < start)
 154                         addr = start;
 155                 if (addr > ei->addr + ei->size)
 156                         continue;
 157                 while (bad_addr(&addr, size) && addr+size <= ei->addr+ei->size)
 158                         ;
 159                 last = addr + size;
 160                 if (last > ei->addr + ei->size)
 161                         continue;
 162                 if (last > end)
 163                         continue;
 164                 return addr;
 165         }
 166         return -1UL;
 167 }
 168
 169 /*
 170  * Free bootmem based on the e820 table for a node.
 171  */
 172 void __init e820_bootmem_free(pg_data_t *pgdat, unsigned long start,unsigned long end)
 173 {
 174         int i;
 175         for (i = 0; i < e820.nr_map; i++) {
 176                 struct e820entry *ei = &e820.map[i];
 177                 unsigned long last, addr;
 178
 179                 if (ei->type != E820_RAM ||
 180                     ei->addr+ei->size <= start ||
 181                     ei->addr >= end)
 182                         continue;
 183
 184                 addr = round_up(ei->addr, PAGE_SIZE);
 185                 if (addr < start)
 186                         addr = start;
 187
 188                 last = round_down(ei->addr + ei->size, PAGE_SIZE);
 189                 if (last >= end)
 190                         last = end;
 191
 192                 if (last > addr && last-addr >= PAGE_SIZE)
 193                         free_bootmem_node(pgdat, addr, last-addr);
 194         }
 195 }
 196
 197 /*
 198  * Find the highest page frame number we have available
 199  */
 200 unsigned long __init e820_end_of_ram(void)
 201 {
 202         int i;
 203         unsigned long end_pfn = 0;
 204
 205         for (i = 0; i < e820.nr_map; i++) {
 206                 struct e820entry *ei = &e820.map[i];
 207                 unsigned long start, end;
 208
 209                 start = round_up(ei->addr, PAGE_SIZE);
 210                 end = round_down(ei->addr + ei->size, PAGE_SIZE);
 211                 if (start >= end)
 212                         continue;
 213                 if (ei->type == E820_RAM) {
 214                 if (end > end_pfn<<PAGE_SHIFT)
 215                         end_pfn = end>>PAGE_SHIFT;
 216                 } else {
 217                         if (end > end_pfn_map<<PAGE_SHIFT)
 218                                 end_pfn_map = end>>PAGE_SHIFT;
 219                 }
 220         }
 221
 222         if (end_pfn > end_pfn_map)
 223                 end_pfn_map = end_pfn;
 224         if (end_pfn_map > MAXMEM>>PAGE_SHIFT)
 225                 end_pfn_map = MAXMEM>>PAGE_SHIFT;
 226         if (end_pfn > end_user_pfn)
 227                 end_pfn = end_user_pfn;
 228         if (end_pfn > end_pfn_map)
 229                 end_pfn = end_pfn_map;
 230
 231         return end_pfn;
 232 }
 233
 234 /*
 235  * Compute how much memory is missing in a range.
 236  * Unlike the other functions in this file the arguments are in page numbers.
 237  */
 238 unsigned long __init
 239 e820_hole_size(unsigned long start_pfn, unsigned long end_pfn)
 240 {
 241         unsigned long ram = 0;
 242         unsigned long start = start_pfn << PAGE_SHIFT;
 243         unsigned long end = end_pfn << PAGE_SHIFT;
 244         int i;
 245         for (i = 0; i < e820.nr_map; i++) {
 246                 struct e820entry *ei = &e820.map[i];
 247                 unsigned long last, addr;
 248
 249                 if (ei->type != E820_RAM ||
 250                     ei->addr+ei->size <= start ||
 251                     ei->addr >= end)
 252                         continue;
 253
 254                 addr = round_up(ei->addr, PAGE_SIZE);
 255                 if (addr < start)
 256                         addr = start;
 257
 258                 last = round_down(ei->addr + ei->size, PAGE_SIZE);
 259                 if (last >= end)
 260                         last = end;
 261
 262                 if (last > addr)
 263                         ram += last - addr;
 264         }
 265         return ((end - start) - ram) >> PAGE_SHIFT;
 266 }
 267
 268 /*
 269  * Mark e820 reserved areas as busy for the resource manager.
 270  */
 271 void __init e820_reserve_resources(void)
 272 {
 273         int i;
 274         for (i = 0; i < e820.nr_map; i++) {
 275                 struct resource *res;
 276                 res = alloc_bootmem_low(sizeof(struct resource));
 277                 switch (e820.map[i].type) {
 278                 case E820_RAM:  res->name = "System RAM"; break;
 279                 case E820_ACPI: res->name = "ACPI Tables"; break;
 280                 case E820_NVS:  res->name = "ACPI Non-volatile Storage"; break;
 281                 default:        res->name = "reserved";
 282                 }
 283                 res->start = e820.map[i].addr;
 284                 res->end = res->start + e820.map[i].size - 1;
 285                 res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 286                 request_resource(&iomem_resource, res);
 287                 if (e820.map[i].type == E820_RAM) {
 288                         /*
 289                          *  We don't know which RAM region contains kernel data,
 290                          *  so we try it repeatedly and let the resource manager
 291                          *  test it.
 292                          */
 293                         request_resource(res, &code_resource);
 294                         request_resource(res, &data_resource);
 295 #ifdef CONFIG_KEXEC
 296                         request_resource(res, &crashk_res);
 297 #endif
 298                 }
 299         }
 300 }
 301
 302 /*
 303  * Add a memory region to the kernel e820 map.
 304  */
 305 void __init add_memory_region(unsigned long start, unsigned long size, int type)
 306 {
 307         int x = e820.nr_map;
 308
 309         if (x == E820MAX) {
 310                 printk(KERN_ERR "Ooops! Too many entries in the memory map!\n");
 311                 return;
 312         }
 313
 314         e820.map[x].addr = start;
 315         e820.map[x].size = size;
 316         e820.map[x].type = type;
 317         e820.nr_map++;
 318 }
 319
 320 void __init e820_print_map(char *who)
 321 {
 322         int i;
 323
 324         for (i = 0; i < e820.nr_map; i++) {
 325                 printk(" %s: %016Lx - %016Lx ", who,
 326                         (unsigned long long) e820.map[i].addr,
 327                         (unsigned long long) (e820.map[i].addr + e820.map[i].size));
 328                 switch (e820.map[i].type) {
 329                 case E820_RAM:  printk("(usable)\n");
 330                                 break;
 331                 case E820_RESERVED:
 332                                 printk("(reserved)\n");
 333                                 break;
 334                 case E820_ACPI:
 335                                 printk("(ACPI data)\n");
 336                                 break;
 337                 case E820_NVS:
 338                                 printk("(ACPI NVS)\n");
 339                                 break;
 340                 default:        printk("type %u\n", e820.map[i].type);
 341                                 break;
 342                 }
 343         }
 344 }
 345
 346 /*
 347  * Sanitize the BIOS e820 map.
 348  *
 349  * Some e820 responses include overlapping entries.  The following
 350  * replaces the original e820 map with a new one, removing overlaps.
 351  *
 352  */
 353 static int __init sanitize_e820_map(struct e820entry * biosmap, char * pnr_map)
 354 {
 355         struct change_member {
 356                 struct e820entry *pbios; /* pointer to original bios entry */
 357                 unsigned long long addr; /* address for this change point */
 358         };
 359         static struct change_member change_point_list[2*E820MAX] __initdata;
 360         static struct change_member *change_point[2*E820MAX] __initdata;
 361         static struct e820entry *overlap_list[E820MAX] __initdata;
 362         static struct e820entry new_bios[E820MAX] __initdata;
 363         struct change_member *change_tmp;
 364         unsigned long current_type, last_type;
 365         unsigned long long last_addr;
 366         int chgidx, still_changing;
 367         int overlap_entries;
 368         int new_bios_entry;
 369         int old_nr, new_nr, chg_nr;
 370         int i;
 371
 372         /*
 373                 Visually we're performing the following (1,2,3,4 = memory types)...
 374
 375                 Sample memory map (w/overlaps):
 376                    ____22__________________
 377                    ______________________4_
 378                    ____1111________________
 379                    _44_____________________
 380                    11111111________________
 381                    ____________________33__
 382                    ___________44___________
 383                    __________33333_________
 384                    ______________22________
 385                    ___________________2222_
 386                    _________111111111______
 387                    _____________________11_
 388                    _________________4______
 389
 390                 Sanitized equivalent (no overlap):
 391                    1_______________________
 392                    _44_____________________
 393                    ___1____________________
 394                    ____22__________________
 395                    ______11________________
 396                    _________1______________
 397                    __________3_____________
 398                    ___________44___________
 399                    _____________33_________
 400                    _______________2________
 401                    ________________1_______
 402                    _________________4______
 403                    ___________________2____
 404                    ____________________33__
 405                    ______________________4_
 406         */
 407
 408         /* if there's only one memory region, don't bother */
 409         if (*pnr_map < 2)
 410                 return -1;
 411
 412         old_nr = *pnr_map;
 413
 414         /* bail out if we find any unreasonable addresses in bios map */
 415         for (i=0; i<old_nr; i++)
 416                 if (biosmap[i].addr + biosmap[i].size < biosmap[i].addr)
 417                         return -1;
 418
 419         /* create pointers for initial change-point information (for sorting) */
 420         for (i=0; i < 2*old_nr; i++)
 421                 change_point[i] = &change_point_list[i];
 422
 423         /* record all known change-points (starting and ending addresses),
 424            omitting those that are for empty memory regions */
 425         chgidx = 0;
 426         for (i=0; i < old_nr; i++)      {
 427                 if (biosmap[i].size != 0) {
 428                         change_point[chgidx]->addr = biosmap[i].addr;
 429                         change_point[chgidx++]->pbios = &biosmap[i];
 430                         change_point[chgidx]->addr = biosmap[i].addr + biosmap[i].size;
 431                         change_point[chgidx++]->pbios = &biosmap[i];
 432                 }
 433         }
 434         chg_nr = chgidx;
 435
 436         /* sort change-point list by memory addresses (low -> high) */
 437         still_changing = 1;
 438         while (still_changing)  {
 439                 still_changing = 0;
 440                 for (i=1; i < chg_nr; i++)  {
 441                         /* if <current_addr> > <last_addr>, swap */
 442                         /* or, if current=<start_addr> & last=<end_addr>, swap */
 443                         if ((change_point[i]->addr < change_point[i-1]->addr) ||
 444                                 ((change_point[i]->addr == change_point[i-1]->addr) &&
 445                                  (change_point[i]->addr == change_point[i]->pbios->addr) &&
 446                                  (change_point[i-1]->addr != change_point[i-1]->pbios->addr))
 447                            )
 448                         {
 449                                 change_tmp = change_point[i];
 450                                 change_point[i] = change_point[i-1];
 451                                 change_point[i-1] = change_tmp;
 452                                 still_changing=1;
 453                         }
 454                 }
 455         }
 456
 457         /* create a new bios memory map, removing overlaps */
 458         overlap_entries=0;       /* number of entries in the overlap table */
 459         new_bios_entry=0;        /* index for creating new bios map entries */
 460         last_type = 0;           /* start with undefined memory type */
 461         last_addr = 0;           /* start with 0 as last starting address */
 462         /* loop through change-points, determining affect on the new bios map */
 463         for (chgidx=0; chgidx < chg_nr; chgidx++)
 464         {
 465                 /* keep track of all overlapping bios entries */
 466                 if (change_point[chgidx]->addr == change_point[chgidx]->pbios->addr)
 467                 {
 468                         /* add map entry to overlap list (> 1 entry implies an overlap) */
 469                         overlap_list[overlap_entries++]=change_point[chgidx]->pbios;
 470                 }
 471                 else
 472                 {
 473                         /* remove entry from list (order independent, so swap with last) */
 474                         for (i=0; i<overlap_entries; i++)
 475                         {
 476                                 if (overlap_list[i] == change_point[chgidx]->pbios)
 477                                         overlap_list[i] = overlap_list[overlap_entries-1];
 478                         }
 479                         overlap_entries--;
 480                 }
 481                 /* if there are overlapping entries, decide which "type" to use */
 482                 /* (larger value takes precedence -- 1=usable, 2,3,4,4+=unusable) */
 483                 current_type = 0;
 484                 for (i=0; i<overlap_entries; i++)
 485                         if (overlap_list[i]->type > current_type)
 486                                 current_type = overlap_list[i]->type;
 487                 /* continue building up new bios map based on this information */
 488                 if (current_type != last_type)  {
 489                         if (last_type != 0)      {
 490                                 new_bios[new_bios_entry].size =
 491                                         change_point[chgidx]->addr - last_addr;
 492                                 /* move forward only if the new size was non-zero */
 493                                 if (new_bios[new_bios_entry].size != 0)
 494                                         if (++new_bios_entry >= E820MAX)
 495                                                 break;  /* no more space left for new bios entries */
 496                         }
 497                         if (current_type != 0)  {
 498                                 new_bios[new_bios_entry].addr = change_point[chgidx]->addr;
 499                                 new_bios[new_bios_entry].type = current_type;
 500                                 last_addr=change_point[chgidx]->addr;
 501                         }
 502                         last_type = current_type;
 503                 }
 504         }
 505         new_nr = new_bios_entry;   /* retain count for new bios entries */
 506
 507         /* copy new bios mapping into original location */
 508         memcpy(biosmap, new_bios, new_nr*sizeof(struct e820entry));
 509         *pnr_map = new_nr;
 510
 511         return 0;
 512 }
 513
 514 /*
 515  * Copy the BIOS e820 map into a safe place.
 516  *
 517  * Sanity-check it while we're at it..
 518  *
 519  * If we're lucky and live on a modern system, the setup code
 520  * will have given us a memory map that we can use to properly
 521  * set up memory.  If we aren't, we'll fake a memory map.
 522  *
 523  * We check to see that the memory map contains at least 2 elements
 524  * before we'll use it, because the detection code in setup.S may
 525  * not be perfect and most every PC known to man has two memory
 526  * regions: one from 0 to 640k, and one from 1mb up.  (The IBM
 527  * thinkpad 560x, for example, does not cooperate with the memory
 528  * detection code.)
 529  */
 530 static int __init copy_e820_map(struct e820entry * biosmap, int nr_map)
 531 {
 532         /* Only one memory region (or negative)? Ignore it */
 533         if (nr_map < 2)
 534                 return -1;
 535
 536         do {
 537                 unsigned long start = biosmap->addr;
 538                 unsigned long size = biosmap->size;
 539                 unsigned long end = start + size;
 540                 unsigned long type = biosmap->type;
 541
 542                 /* Overflow in 64 bits? Ignore the memory map. */
 543                 if (start > end)
 544                         return -1;
 545
 546                 /*
 547                  * Some BIOSes claim RAM in the 640k - 1M region.
 548                  * Not right. Fix it up.
 549                  *
 550                  * This should be removed on Hammer which is supposed to not
 551                  * have non e820 covered ISA mappings there, but I had some strange
 552                  * problems so it stays for now.  -AK
 553                  */
 554                 if (type == E820_RAM) {
 555                         if (start < 0x100000ULL && end > 0xA0000ULL) {
 556                                 if (start < 0xA0000ULL)
 557                                         add_memory_region(start, 0xA0000ULL-start, type);
 558                                 if (end <= 0x100000ULL)
 559                                         continue;
 560                                 start = 0x100000ULL;
 561                                 size = end - start;
 562                         }
 563                 }
 564
 565                 add_memory_region(start, size, type);
 566         } while (biosmap++,--nr_map);
 567         return 0;
 568 }
 569
 570 void __init setup_memory_region(void)
 571 {
 572         char *who = "BIOS-e820";
 573
 574         /*
 575          * Try to copy the BIOS-supplied E820-map.
 576          *
 577          * Otherwise fake a memory map; one section from 0k->640k,
 578          * the next section from 1mb->appropriate_mem_k
 579          */
 580         sanitize_e820_map(E820_MAP, &E820_MAP_NR);
 581         if (copy_e820_map(E820_MAP, E820_MAP_NR) < 0) {
 582                 unsigned long mem_size;
 583
 584                 /* compare results from other methods and take the greater */
 585                 if (ALT_MEM_K < EXT_MEM_K) {
 586                         mem_size = EXT_MEM_K;
 587                         who = "BIOS-88";
 588                 } else {
 589                         mem_size = ALT_MEM_K;
 590                         who = "BIOS-e801";
 591                 }
 592
 593                 e820.nr_map = 0;
 594                 add_memory_region(0, LOWMEMSIZE(), E820_RAM);
 595                 add_memory_region(HIGH_MEMORY, mem_size << 10, E820_RAM);
 596         }
 597         printk(KERN_INFO "BIOS-provided physical RAM map:\n");
 598         e820_print_map(who);
 599 }
 600
 601 static int __init parse_memopt(char *p)
 602 {
 603         if (!p)
 604                 return -EINVAL;
 605         end_user_pfn = memparse(p, &p);
 606         end_user_pfn >>= PAGE_SHIFT;
 607         return 0;
 608 }
 609 early_param("mem", parse_memopt);
 610
 611 static int userdef __initdata;
 612
 613 static int __init parse_memmap_opt(char *p)
 614 {
 615         char *oldp;
 616         unsigned long long start_at, mem_size;
 617
 618         if (!strcmp(p, "exactmap")) {
 619 #ifdef CONFIG_CRASH_DUMP
 620                 /* If we are doing a crash dump, we
 621                  * still need to know the real mem
 622                  * size before original memory map is
 623                  * reset.
 624                  */
 625                 saved_max_pfn = e820_end_of_ram();
 626 #endif
 627                 end_pfn_map = 0;
 628                 e820.nr_map = 0;
 629                 userdef = 1;
 630                 return 0;
 631         }
 632
 633         oldp = p;
 634         mem_size = memparse(p, &p);
 635         if (p == oldp)
 636                 return -EINVAL;
 637         if (*p == '@') {
 638                 start_at = memparse(p+1, &p);
 639                 add_memory_region(start_at, mem_size, E820_RAM);
 640         } else if (*p == '#') {
 641                 start_at = memparse(p+1, &p);
 642                 add_memory_region(start_at, mem_size, E820_ACPI);
 643         } else if (*p == '$') {
 644                 start_at = memparse(p+1, &p);
 645                 add_memory_region(start_at, mem_size, E820_RESERVED);
 646         } else {
 647                 end_user_pfn = (mem_size >> PAGE_SHIFT);
 648         }
 649         return *p == '\0' ? 0 : -EINVAL;
 650 }
 651 early_param("memmap", parse_memmap_opt);
 652
 653 void finish_e820_parsing(void)
 654 {
 655         if (userdef) {
 656                 printk(KERN_INFO "user-defined physical RAM map:\n");
 657                 e820_print_map("user");
 658         }
 659 }
 660
 661 unsigned long pci_mem_start = 0xaeedbabe;
 662 EXPORT_SYMBOL(pci_mem_start);
 663
 664 /*
 665  * Search for the biggest gap in the low 32 bits of the e820
 666  * memory space.  We pass this space to PCI to assign MMIO resources
 667  * for hotplug or unconfigured devices in.
 668  * Hopefully the BIOS let enough space left.
 669  */
 670 __init void e820_setup_gap(void)
 671 {
 672         unsigned long gapstart, gapsize, round;
 673         unsigned long last;
 674         int i;
 675         int found = 0;
 676
 677         last = 0x100000000ull;
 678         gapstart = 0x10000000;
 679         gapsize = 0x400000;
 680         i = e820.nr_map;
 681         while (--i >= 0) {
 682                 unsigned long long start = e820.map[i].addr;
 683                 unsigned long long end = start + e820.map[i].size;
 684
 685                 /*
 686                  * Since "last" is at most 4GB, we know we'll
 687                  * fit in 32 bits if this condition is true
 688                  */
 689                 if (last > end) {
 690                         unsigned long gap = last - end;
 691
 692                         if (gap > gapsize) {
 693                                 gapsize = gap;
 694                                 gapstart = end;
 695                                 found = 1;
 696                         }
 697                 }
 698                 if (start < last)
 699                         last = start;
 700         }
 701
 702         if (!found) {
 703                 gapstart = (end_pfn << PAGE_SHIFT) + 1024*1024;
 704                 printk(KERN_ERR "PCI: Warning: Cannot find a gap in the 32bit address range\n"
 705                        KERN_ERR "PCI: Unassigned devices with 32bit resource registers may break!\n");
 706         }
 707
 708         /*
 709          * See how much we want to round up: start off with
 710          * rounding to the next 1MB area.
 711          */
 712         round = 0x100000;
 713         while ((gapsize >> 4) > round)
 714                 round += round;
 715         /* Fun with two's complement */
 716         pci_mem_start = (gapstart + round) & -round;
 717
 718         printk(KERN_INFO "Allocating PCI resources starting at %lx (gap: %lx:%lx)\n",
 719                 pci_mem_start, gapstart, gapsize);
 720 }