x86 boot: longer comment explaining sanitize_e820_map routine

[deliverable/linux.git] / arch / x86 / kernel / e820.c

/*
 * Handle the memory map.
 * The functions here do the job until bootmem takes over.
 *
 *  Getting sanitize_e820_map() in sync with i386 version by applying change:
 *  -  Provisions for empty E820 memory regions (reported by certain BIOSes).
 *     Alex Achenbach <xela@slit.de>, December 2002.
 *  Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/ioport.h>
#include <linux/string.h>
#include <linux/kexec.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pfn.h>

#include <asm/pgtable.h>
#include <asm/page.h>
#include <asm/e820.h>
#include <asm/setup.h>

struct e820map e820;

/* For PCI or other memory-mapped resources */
unsigned long pci_mem_start = 0xaeedbabe;
#ifdef CONFIG_PCI
EXPORT_SYMBOL(pci_mem_start);
#endif

/*
 * This function checks if any part of the range <start,end> is mapped
 * with type.
 */
int
e820_any_mapped(u64 start, u64 end, unsigned type)
{
        int i;

        for (i = 0; i < e820.nr_map; i++) {
                struct e820entry *ei = &e820.map[i];

                if (type && ei->type != type)
                        continue;
                if (ei->addr >= end || ei->addr + ei->size <= start)
                        continue;
                return 1;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(e820_any_mapped);

/*
 * This function checks if the entire range <start,end> is mapped with type.
 *
 * Note: this function only works correct if the e820 table is sorted and
 * not-overlapping, which is the case
 */
int __init e820_all_mapped(u64 start, u64 end, unsigned type)
{
        int i;

        for (i = 0; i < e820.nr_map; i++) {
                struct e820entry *ei = &e820.map[i];

                if (type && ei->type != type)
                        continue;
                /* is the region (part) in overlap with the current region ?*/
                if (ei->addr >= end || ei->addr + ei->size <= start)
                        continue;

                /* if the region is at the beginning of <start,end> we move
                 * start to the end of the region since it's ok until there
                 */
                if (ei->addr <= start)
                        start = ei->addr + ei->size;
                /*
                 * if start is now at or beyond end, we're done, full
                 * coverage
                 */
                if (start >= end)
                        return 1;
        }
        return 0;
}

/*
 * Add a memory region to the kernel e820 map.
 */
void __init add_memory_region(u64 start, u64 size, int type)
{
        int x = e820.nr_map;

        if (x == ARRAY_SIZE(e820.map)) {
                printk(KERN_ERR "Ooops! Too many entries in the memory map!\n");
                return;
        }

        e820.map[x].addr = start;
        e820.map[x].size = size;
        e820.map[x].type = type;
        e820.nr_map++;
}

void __init e820_print_map(char *who)
{
        int i;

        for (i = 0; i < e820.nr_map; i++) {
                printk(KERN_INFO " %s: %016Lx - %016Lx ", who,
                       (unsigned long long) e820.map[i].addr,
                       (unsigned long long)
                       (e820.map[i].addr + e820.map[i].size));
                switch (e820.map[i].type) {
                case E820_RAM:
                        printk(KERN_CONT "(usable)\n");
                        break;
                case E820_RESERVED:
                        printk(KERN_CONT "(reserved)\n");
                        break;
                case E820_ACPI:
                        printk(KERN_CONT "(ACPI data)\n");
                        break;
                case E820_NVS:
                        printk(KERN_CONT "(ACPI NVS)\n");
                        break;
                default:
                        printk(KERN_CONT "type %u\n", e820.map[i].type);
                        break;
                }
        }
}

/*
 * Sanitize the BIOS e820 map.
 *
 * Some e820 responses include overlapping entries. The following
 * replaces the original e820 map with a new one, removing overlaps,
 * and resolving conflicting memory types in favor of highest
 * numbered type.
 *
 * The input parameter biosmap points to an array of 'struct
 * e820entry' which on entry has elements in the range [0, *pnr_map)
 * valid, and which has space for up to max_nr_map entries.
 * On return, the resulting sanitized e820 map entries will be in
 * overwritten in the same location, starting at biosmap.
 *
 * The integer pointed to by pnr_map must be valid on entry (the
 * current number of valid entries located at biosmap) and will
 * be updated on return, with the new number of valid entries
 * (something no more than max_nr_map.)
 *
 * The return value from sanitize_e820_map() is zero if it
 * successfully 'sanitized' the map entries passed in, and is -1
 * if it did nothing, which can happen if either of (1) it was
 * only passed one map entry, or (2) any of the input map entries
 * were invalid (start + size < start, meaning that the size was
 * so big the described memory range wrapped around through zero.)
 *
 *      Visually we're performing the following
 *      (1,2,3,4 = memory types)...
 *
 *      Sample memory map (w/overlaps):
 *         ____22__________________
 *         ______________________4_
 *         ____1111________________
 *         _44_____________________
 *         11111111________________
 *         ____________________33__
 *         ___________44___________
 *         __________33333_________
 *         ______________22________
 *         ___________________2222_
 *         _________111111111______
 *         _____________________11_
 *         _________________4______
 *
 *      Sanitized equivalent (no overlap):
 *         1_______________________
 *         _44_____________________
 *         ___1____________________
 *         ____22__________________
 *         ______11________________
 *         _________1______________
 *         __________3_____________
 *         ___________44___________
 *         _____________33_________
 *         _______________2________
 *         ________________1_______
 *         _________________4______
 *         ___________________2____
 *         ____________________33__
 *         ______________________4_
 */

int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
                                int *pnr_map)
{
        struct change_member {
                struct e820entry *pbios; /* pointer to original bios entry */
                unsigned long long addr; /* address for this change point */
        };
static struct change_member change_point_list[2*E820_X_MAX] __initdata;
static struct change_member *change_point[2*E820_X_MAX] __initdata;
static struct e820entry *overlap_list[E820_X_MAX] __initdata;
static struct e820entry new_bios[E820_X_MAX] __initdata;
        struct change_member *change_tmp;
        unsigned long current_type, last_type;
        unsigned long long last_addr;
        int chgidx, still_changing;
        int overlap_entries;
        int new_bios_entry;
        int old_nr, new_nr, chg_nr;
        int i;

        /* if there's only one memory region, don't bother */
        if (*pnr_map < 2)
                return -1;

        old_nr = *pnr_map;
        BUG_ON(old_nr > max_nr_map);

        /* bail out if we find any unreasonable addresses in bios map */
        for (i = 0; i < old_nr; i++)
                if (biosmap[i].addr + biosmap[i].size < biosmap[i].addr)
                        return -1;

        /* create pointers for initial change-point information (for sorting) */
        for (i = 0; i < 2 * old_nr; i++)
                change_point[i] = &change_point_list[i];

        /* record all known change-points (starting and ending addresses),
           omitting those that are for empty memory regions */
        chgidx = 0;
        for (i = 0; i < old_nr; i++)    {
                if (biosmap[i].size != 0) {
                        change_point[chgidx]->addr = biosmap[i].addr;
                        change_point[chgidx++]->pbios = &biosmap[i];
                        change_point[chgidx]->addr = biosmap[i].addr +
                                biosmap[i].size;
                        change_point[chgidx++]->pbios = &biosmap[i];
                }
        }
        chg_nr = chgidx;

        /* sort change-point list by memory addresses (low -> high) */
        still_changing = 1;
        while (still_changing)  {
                still_changing = 0;
                for (i = 1; i < chg_nr; i++)  {
                        unsigned long long curaddr, lastaddr;
                        unsigned long long curpbaddr, lastpbaddr;

                        curaddr = change_point[i]->addr;
                        lastaddr = change_point[i - 1]->addr;
                        curpbaddr = change_point[i]->pbios->addr;
                        lastpbaddr = change_point[i - 1]->pbios->addr;

                        /*
                         * swap entries, when:
                         *
                         * curaddr > lastaddr or
                         * curaddr == lastaddr and curaddr == curpbaddr and
                         * lastaddr != lastpbaddr
                         */
                        if (curaddr < lastaddr ||
                            (curaddr == lastaddr && curaddr == curpbaddr &&
                             lastaddr != lastpbaddr)) {
                                change_tmp = change_point[i];
                                change_point[i] = change_point[i-1];
                                change_point[i-1] = change_tmp;
                                still_changing = 1;
                        }
                }
        }

        /* create a new bios memory map, removing overlaps */
        overlap_entries = 0;     /* number of entries in the overlap table */
        new_bios_entry = 0;      /* index for creating new bios map entries */
        last_type = 0;           /* start with undefined memory type */
        last_addr = 0;           /* start with 0 as last starting address */

        /* loop through change-points, determining affect on the new bios map */
        for (chgidx = 0; chgidx < chg_nr; chgidx++) {
                /* keep track of all overlapping bios entries */
                if (change_point[chgidx]->addr ==
                    change_point[chgidx]->pbios->addr) {
                        /*
                         * add map entry to overlap list (> 1 entry
                         * implies an overlap)
                         */
                        overlap_list[overlap_entries++] =
                                change_point[chgidx]->pbios;
                } else {
                        /*
                         * remove entry from list (order independent,
                         * so swap with last)
                         */
                        for (i = 0; i < overlap_entries; i++) {
                                if (overlap_list[i] ==
                                    change_point[chgidx]->pbios)
                                        overlap_list[i] =
                                                overlap_list[overlap_entries-1];
                        }
                        overlap_entries--;
                }
                /*
                 * if there are overlapping entries, decide which
                 * "type" to use (larger value takes precedence --
                 * 1=usable, 2,3,4,4+=unusable)
                 */
                current_type = 0;
                for (i = 0; i < overlap_entries; i++)
                        if (overlap_list[i]->type > current_type)
                                current_type = overlap_list[i]->type;
                /*
                 * continue building up new bios map based on this
                 * information
                 */
                if (current_type != last_type)  {
                        if (last_type != 0)      {
                                new_bios[new_bios_entry].size =
                                        change_point[chgidx]->addr - last_addr;
                                /*
                                 * move forward only if the new size
                                 * was non-zero
                                 */
                                if (new_bios[new_bios_entry].size != 0)
                                        /*
                                         * no more space left for new
                                         * bios entries ?
                                         */
                                        if (++new_bios_entry >= max_nr_map)
                                                break;
                        }
                        if (current_type != 0)  {
                                new_bios[new_bios_entry].addr =
                                        change_point[chgidx]->addr;
                                new_bios[new_bios_entry].type = current_type;
                                last_addr = change_point[chgidx]->addr;
                        }
                        last_type = current_type;
                }
        }
        /* retain count for new bios entries */
        new_nr = new_bios_entry;

        /* copy new bios mapping into original location */
        memcpy(biosmap, new_bios, new_nr * sizeof(struct e820entry));
        *pnr_map = new_nr;

        return 0;
}

/*
 * Copy the BIOS e820 map into a safe place.
 *
 * Sanity-check it while we're at it..
 *
 * If we're lucky and live on a modern system, the setup code
 * will have given us a memory map that we can use to properly
 * set up memory.  If we aren't, we'll fake a memory map.
 */
int __init copy_e820_map(struct e820entry *biosmap, int nr_map)
{
        /* Only one memory region (or negative)? Ignore it */
        if (nr_map < 2)
                return -1;

        do {
                u64 start = biosmap->addr;
                u64 size = biosmap->size;
                u64 end = start + size;
                u32 type = biosmap->type;

                /* Overflow in 64 bits? Ignore the memory map. */
                if (start > end)
                        return -1;

                add_memory_region(start, size, type);
        } while (biosmap++, --nr_map);
        return 0;
}

u64 __init update_memory_range(u64 start, u64 size, unsigned old_type,
                                unsigned new_type)
{
        int i;
        u64 real_updated_size = 0;

        BUG_ON(old_type == new_type);

        for (i = 0; i < e820.nr_map; i++) {
                struct e820entry *ei = &e820.map[i];
                u64 final_start, final_end;
                if (ei->type != old_type)
                        continue;
                /* totally covered? */
                if (ei->addr >= start &&
                    (ei->addr + ei->size) <= (start + size)) {
                        ei->type = new_type;
                        real_updated_size += ei->size;
                        continue;
                }
                /* partially covered */
                final_start = max(start, ei->addr);
                final_end = min(start + size, ei->addr + ei->size);
                if (final_start >= final_end)
                        continue;
                add_memory_region(final_start, final_end - final_start,
                                         new_type);
                real_updated_size += final_end - final_start;
        }
        return real_updated_size;
}

void __init update_e820(void)
{
        int nr_map;

        nr_map = e820.nr_map;
        if (sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &nr_map))
                return;
        e820.nr_map = nr_map;
        printk(KERN_INFO "modified physical RAM map:\n");
        e820_print_map("modified");
}

/*
 * Search for the biggest gap in the low 32 bits of the e820
 * memory space.  We pass this space to PCI to assign MMIO resources
 * for hotplug or unconfigured devices in.
 * Hopefully the BIOS let enough space left.
 */
__init void e820_setup_gap(void)
{
        unsigned long gapstart, gapsize, round;
        unsigned long long last;
        int i;
        int found = 0;

        last = 0x100000000ull;
        gapstart = 0x10000000;
        gapsize = 0x400000;
        i = e820.nr_map;
        while (--i >= 0) {
                unsigned long long start = e820.map[i].addr;
                unsigned long long end = start + e820.map[i].size;

                /*
                 * Since "last" is at most 4GB, we know we'll
                 * fit in 32 bits if this condition is true
                 */
                if (last > end) {
                        unsigned long gap = last - end;

                        if (gap > gapsize) {
                                gapsize = gap;
                                gapstart = end;
                                found = 1;
                        }
                }
                if (start < last)
                        last = start;
        }

#ifdef CONFIG_X86_64
        if (!found) {
                gapstart = (end_pfn << PAGE_SHIFT) + 1024*1024;
                printk(KERN_ERR "PCI: Warning: Cannot find a gap in the 32bit "
                       "address range\n"
                       KERN_ERR "PCI: Unassigned devices with 32bit resource "
                       "registers may break!\n");
        }
#endif

        /*
         * See how much we want to round up: start off with
         * rounding to the next 1MB area.
         */
        round = 0x100000;
        while ((gapsize >> 4) > round)
                round += round;
        /* Fun with two's complement */
        pci_mem_start = (gapstart + round) & -round;

        printk(KERN_INFO
               "Allocating PCI resources starting at %lx (gap: %lx:%lx)\n",
               pci_mem_start, gapstart, gapsize);
}