sched: make early bootup sched_clock() use safer

[wrt350n-kernel.git] / arch / x86 / kernel / e820_64.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/suspend.h>
#include <linux/pfn.h>

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

struct e820map e820;

/*
 * PFN of last memory page.
 */
unsigned long end_pfn;

/*
 * end_pfn only includes RAM, while end_pfn_map includes all e820 entries.
 * The direct mapping extends to end_pfn_map, so that we can directly access
 * apertures, ACPI and other tables without having to play with fixmaps.
 */
unsigned long end_pfn_map;

/*
 * Last pfn which the user wants to use.
 */
static unsigned long __initdata end_user_pfn = MAXMEM>>PAGE_SHIFT;

/*
 * Early reserved memory areas.
 */
#define MAX_EARLY_RES 20

struct early_res {
        unsigned long start, end;
        char name[16];
};
static struct early_res early_res[MAX_EARLY_RES] __initdata = {
        { 0, PAGE_SIZE, "BIOS data page" },                     /* BIOS data page */
#ifdef CONFIG_SMP
        { SMP_TRAMPOLINE_BASE, SMP_TRAMPOLINE_BASE + 2*PAGE_SIZE, "SMP_TRAMPOLINE" },
#endif
        {}
};

void __init reserve_early(unsigned long start, unsigned long end, char *name)
{
        int i;
        struct early_res *r;
        for (i = 0; i < MAX_EARLY_RES && early_res[i].end; i++) {
                r = &early_res[i];
                if (end > r->start && start < r->end)
                        panic("Overlapping early reservations %lx-%lx %s to %lx-%lx %s\n",
                              start, end - 1, name?name:"", r->start, r->end - 1, r->name);
        }
        if (i >= MAX_EARLY_RES)
                panic("Too many early reservations");
        r = &early_res[i];
        r->start = start;
        r->end = end;
        if (name)
                strncpy(r->name, name, sizeof(r->name) - 1);
}

void __init early_res_to_bootmem(void)
{
        int i;
        for (i = 0; i < MAX_EARLY_RES && early_res[i].end; i++) {
                struct early_res *r = &early_res[i];
                printk(KERN_INFO "early res: %d [%lx-%lx] %s\n", i,
                        r->start, r->end - 1, r->name);
                reserve_bootmem_generic(r->start, r->end - r->start);
        }
}

/* Check for already reserved areas */
static inline int bad_addr(unsigned long *addrp, unsigned long size)
{
        int i;
        unsigned long addr = *addrp, last;
        int changed = 0;
again:
        last = addr + size;
        for (i = 0; i < MAX_EARLY_RES && early_res[i].end; i++) {
                struct early_res *r = &early_res[i];
                if (last >= r->start && addr < r->end) {
                        *addrp = addr = r->end;
                        changed = 1;
                        goto again;
                }
        }
        return changed;
}

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

/*
 * Find a free area with specified alignment in a specific range.
 */
unsigned long __init find_e820_area(unsigned long start, unsigned long end,
                                    unsigned size, unsigned long align)
{
        int i;
        unsigned long mask = ~(align - 1);

        for (i = 0; i < e820.nr_map; i++) {
                struct e820entry *ei = &e820.map[i];
                unsigned long addr = ei->addr, last;

                if (ei->type != E820_RAM)
                        continue;
                if (addr < start)
                        addr = start;
                if (addr > ei->addr + ei->size)
                        continue;
                while (bad_addr(&addr, size) && addr+size <= ei->addr+ei->size)
                        ;
                addr = (addr + align - 1) & mask;
                last = addr + size;
                if (last > ei->addr + ei->size)
                        continue;
                if (last > end)
                        continue;
                return addr;
        }
        return -1UL;
}

/*
 * Find the highest page frame number we have available
 */
unsigned long __init e820_end_of_ram(void)
{
        unsigned long end_pfn;

        end_pfn = find_max_pfn_with_active_regions();

        if (end_pfn > end_pfn_map)
                end_pfn_map = end_pfn;
        if (end_pfn_map > MAXMEM>>PAGE_SHIFT)
                end_pfn_map = MAXMEM>>PAGE_SHIFT;
        if (end_pfn > end_user_pfn)
                end_pfn = end_user_pfn;
        if (end_pfn > end_pfn_map)
                end_pfn = end_pfn_map;

        printk(KERN_INFO "end_pfn_map = %lu\n", end_pfn_map);
        return end_pfn;
}

/*
 * Mark e820 reserved areas as busy for the resource manager.
 */
void __init e820_reserve_resources(struct resource *code_resource,
                struct resource *data_resource, struct resource *bss_resource)
{
        int i;
        for (i = 0; i < e820.nr_map; i++) {
                struct resource *res;
                res = alloc_bootmem_low(sizeof(struct resource));
                switch (e820.map[i].type) {
                case E820_RAM:  res->name = "System RAM"; break;
                case E820_ACPI: res->name = "ACPI Tables"; break;
                case E820_NVS:  res->name = "ACPI Non-volatile Storage"; break;
                default:        res->name = "reserved";
                }
                res->start = e820.map[i].addr;
                res->end = res->start + e820.map[i].size - 1;
                res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
                request_resource(&iomem_resource, res);
                if (e820.map[i].type == E820_RAM) {
                        /*
                         * We don't know which RAM region contains kernel data,
                         * so we try it repeatedly and let the resource manager
                         * test it.
                         */
                        request_resource(res, code_resource);
                        request_resource(res, data_resource);
                        request_resource(res, bss_resource);
#ifdef CONFIG_KEXEC
                        if (crashk_res.start != crashk_res.end)
                                request_resource(res, &crashk_res);
#endif
                }
        }
}

/*
 * Find the ranges of physical addresses that do not correspond to
 * e820 RAM areas and mark the corresponding pages as nosave for software
 * suspend and suspend to RAM.
 *
 * This function requires the e820 map to be sorted and without any
 * overlapping entries and assumes the first e820 area to be RAM.
 */
void __init e820_mark_nosave_regions(void)
{
        int i;
        unsigned long paddr;

        paddr = round_down(e820.map[0].addr + e820.map[0].size, PAGE_SIZE);
        for (i = 1; i < e820.nr_map; i++) {
                struct e820entry *ei = &e820.map[i];

                if (paddr < ei->addr)
                        register_nosave_region(PFN_DOWN(paddr),
                                                PFN_UP(ei->addr));

                paddr = round_down(ei->addr + ei->size, PAGE_SIZE);
                if (ei->type != E820_RAM)
                        register_nosave_region(PFN_UP(ei->addr),
                                                PFN_DOWN(paddr));

                if (paddr >= (end_pfn << PAGE_SHIFT))
                        break;
        }
}

/*
 * Finds an active region in the address range from start_pfn to end_pfn and
 * returns its range in ei_startpfn and ei_endpfn for the e820 entry.
 */
static int __init e820_find_active_region(const struct e820entry *ei,
                                          unsigned long start_pfn,
                                          unsigned long end_pfn,
                                          unsigned long *ei_startpfn,
                                          unsigned long *ei_endpfn)
{
        *ei_startpfn = round_up(ei->addr, PAGE_SIZE) >> PAGE_SHIFT;
        *ei_endpfn = round_down(ei->addr + ei->size, PAGE_SIZE) >> PAGE_SHIFT;

        /* Skip map entries smaller than a page */
        if (*ei_startpfn >= *ei_endpfn)
                return 0;

        /* Check if end_pfn_map should be updated */
        if (ei->type != E820_RAM && *ei_endpfn > end_pfn_map)
                end_pfn_map = *ei_endpfn;

        /* Skip if map is outside the node */
        if (ei->type != E820_RAM || *ei_endpfn <= start_pfn ||
                                    *ei_startpfn >= end_pfn)
                return 0;

        /* Check for overlaps */
        if (*ei_startpfn < start_pfn)
                *ei_startpfn = start_pfn;
        if (*ei_endpfn > end_pfn)
                *ei_endpfn = end_pfn;

        /* Obey end_user_pfn to save on memmap */
        if (*ei_startpfn >= end_user_pfn)
                return 0;
        if (*ei_endpfn > end_user_pfn)
                *ei_endpfn = end_user_pfn;

        return 1;
}

/* Walk the e820 map and register active regions within a node */
void __init
e820_register_active_regions(int nid, unsigned long start_pfn,
                                                        unsigned long end_pfn)
{
        unsigned long ei_startpfn;
        unsigned long ei_endpfn;
        int i;

        for (i = 0; i < e820.nr_map; i++)
                if (e820_find_active_region(&e820.map[i],
                                            start_pfn, end_pfn,
                                            &ei_startpfn, &ei_endpfn))
                        add_active_range(nid, ei_startpfn, ei_endpfn);
}

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

        if (x == E820MAX) {
                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++;
}

/*
 * Find the hole size (in bytes) in the memory range.
 * @start: starting address of the memory range to scan
 * @end: ending address of the memory range to scan
 */
unsigned long __init e820_hole_size(unsigned long start, unsigned long end)
{
        unsigned long start_pfn = start >> PAGE_SHIFT;
        unsigned long end_pfn = end >> PAGE_SHIFT;
        unsigned long ei_startpfn, ei_endpfn, ram = 0;
        int i;

        for (i = 0; i < e820.nr_map; i++) {
                if (e820_find_active_region(&e820.map[i],
                                            start_pfn, end_pfn,
                                            &ei_startpfn, &ei_endpfn))
                        ram += ei_endpfn - ei_startpfn;
        }
        return end - start - (ram << PAGE_SHIFT);
}

static 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.
 *
 */
static int __init sanitize_e820_map(struct e820entry *biosmap, char *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*E820MAX] __initdata;
        static struct change_member *change_point[2*E820MAX] __initdata;
        static struct e820entry *overlap_list[E820MAX] __initdata;
        static struct e820entry new_bios[E820MAX] __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;

        /*
                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_
        */

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

        old_nr = *pnr_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 >= E820MAX)
                                                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.
 */
static 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 {
                unsigned long start = biosmap->addr;
                unsigned long size = biosmap->size;
                unsigned long end = start + size;
                unsigned long 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;
}

static void early_panic(char *msg)
{
        early_printk(msg);
        panic(msg);
}

/* We're not void only for x86 32-bit compat */
char * __init machine_specific_memory_setup(void)
{
        char *who = "BIOS-e820";
        /*
         * Try to copy the BIOS-supplied E820-map.
         *
         * Otherwise fake a memory map; one section from 0k->640k,
         * the next section from 1mb->appropriate_mem_k
         */
        sanitize_e820_map(boot_params.e820_map, &boot_params.e820_entries);
        if (copy_e820_map(boot_params.e820_map, boot_params.e820_entries) < 0)
                early_panic("Cannot find a valid memory map");
        printk(KERN_INFO "BIOS-provided physical RAM map:\n");
        e820_print_map(who);

        /* In case someone cares... */
        return who;
}

static int __init parse_memopt(char *p)
{
        if (!p)
                return -EINVAL;
        end_user_pfn = memparse(p, &p);
        end_user_pfn >>= PAGE_SHIFT;
        return 0;
}
early_param("mem", parse_memopt);

static int userdef __initdata;

static int __init parse_memmap_opt(char *p)
{
        char *oldp;
        unsigned long long start_at, mem_size;

        if (!strcmp(p, "exactmap")) {
#ifdef CONFIG_CRASH_DUMP
                /*
                 * If we are doing a crash dump, we still need to know
                 * the real mem size before original memory map is
                 * reset.
                 */
                e820_register_active_regions(0, 0, -1UL);
                saved_max_pfn = e820_end_of_ram();
                remove_all_active_ranges();
#endif
                end_pfn_map = 0;
                e820.nr_map = 0;
                userdef = 1;
                return 0;
        }

        oldp = p;
        mem_size = memparse(p, &p);
        if (p == oldp)
                return -EINVAL;

        userdef = 1;
        if (*p == '@') {
                start_at = memparse(p+1, &p);
                add_memory_region(start_at, mem_size, E820_RAM);
        } else if (*p == '#') {
                start_at = memparse(p+1, &p);
                add_memory_region(start_at, mem_size, E820_ACPI);
        } else if (*p == '$') {
                start_at = memparse(p+1, &p);
                add_memory_region(start_at, mem_size, E820_RESERVED);
        } else {
                end_user_pfn = (mem_size >> PAGE_SHIFT);
        }
        return *p == '\0' ? 0 : -EINVAL;
}
early_param("memmap", parse_memmap_opt);

void __init finish_e820_parsing(void)
{
        if (userdef) {
                char nr = e820.nr_map;

                if (sanitize_e820_map(e820.map, &nr) < 0)
                        early_panic("Invalid user supplied memory map");
                e820.nr_map = nr;

                printk(KERN_INFO "user-defined physical RAM map:\n");
                e820_print_map("user");
        }
}

void __init update_e820(void)
{
        u8 nr_map;

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

unsigned long pci_mem_start = 0xaeedbabe;
EXPORT_SYMBOL(pci_mem_start);

/*
 * 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 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;
        }

        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");
        }

        /*
         * 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);
}

int __init arch_get_ram_range(int slot, u64 *addr, u64 *size)
{
        int i;

        if (slot < 0 || slot >= e820.nr_map)
                return -1;
        for (i = slot; i < e820.nr_map; i++) {
                if (e820.map[i].type != E820_RAM)
                        continue;
                break;
        }
        if (i == e820.nr_map || e820.map[i].addr > (max_pfn << PAGE_SHIFT))
                return -1;
        *addr = e820.map[i].addr;
        *size = min_t(u64, e820.map[i].size + e820.map[i].addr,
                max_pfn << PAGE_SHIFT) - *addr;
        return i + 1;
}