Linux 3.17-rc2

[linux/fpc-iii.git] / arch / tile / mm / init.c

/*
 * Copyright (C) 1995  Linus Torvalds
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/module.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/poison.h>
#include <linux/bootmem.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/efi.h>
#include <linux/memory_hotplug.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/processor.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/dma.h>
#include <asm/fixmap.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/homecache.h>
#include <hv/hypervisor.h>
#include <arch/chip.h>

#include "migrate.h"

#define clear_pgd(pmdptr) (*(pmdptr) = hv_pte(0))

#ifndef __tilegx__
unsigned long VMALLOC_RESERVE = CONFIG_VMALLOC_RESERVE;
EXPORT_SYMBOL(VMALLOC_RESERVE);
#endif

/* Create an L2 page table */
static pte_t * __init alloc_pte(void)
{
        return __alloc_bootmem(L2_KERNEL_PGTABLE_SIZE, HV_PAGE_TABLE_ALIGN, 0);
}

/*
 * L2 page tables per controller.  We allocate these all at once from
 * the bootmem allocator and store them here.  This saves on kernel L2
 * page table memory, compared to allocating a full 64K page per L2
 * page table, and also means that in cases where we use huge pages,
 * we are guaranteed to later be able to shatter those huge pages and
 * switch to using these page tables instead, without requiring
 * further allocation.  Each l2_ptes[] entry points to the first page
 * table for the first hugepage-size piece of memory on the
 * controller; other page tables are just indexed directly, i.e. the
 * L2 page tables are contiguous in memory for each controller.
 */
static pte_t *l2_ptes[MAX_NUMNODES];
static int num_l2_ptes[MAX_NUMNODES];

static void init_prealloc_ptes(int node, int pages)
{
        BUG_ON(pages & (PTRS_PER_PTE - 1));
        if (pages) {
                num_l2_ptes[node] = pages;
                l2_ptes[node] = __alloc_bootmem(pages * sizeof(pte_t),
                                                HV_PAGE_TABLE_ALIGN, 0);
        }
}

pte_t *get_prealloc_pte(unsigned long pfn)
{
        int node = pfn_to_nid(pfn);
        pfn &= ~(-1UL << (NR_PA_HIGHBIT_SHIFT - PAGE_SHIFT));
        BUG_ON(node >= MAX_NUMNODES);
        BUG_ON(pfn >= num_l2_ptes[node]);
        return &l2_ptes[node][pfn];
}

/*
 * What caching do we expect pages from the heap to have when
 * they are allocated during bootup?  (Once we've installed the
 * "real" swapper_pg_dir.)
 */
static int initial_heap_home(void)
{
        if (hash_default)
                return PAGE_HOME_HASH;
        return smp_processor_id();
}

/*
 * Place a pointer to an L2 page table in a middle page
 * directory entry.
 */
static void __init assign_pte(pmd_t *pmd, pte_t *page_table)
{
        phys_addr_t pa = __pa(page_table);
        unsigned long l2_ptfn = pa >> HV_LOG2_PAGE_TABLE_ALIGN;
        pte_t pteval = hv_pte_set_ptfn(__pgprot(_PAGE_TABLE), l2_ptfn);
        BUG_ON((pa & (HV_PAGE_TABLE_ALIGN-1)) != 0);
        pteval = pte_set_home(pteval, initial_heap_home());
        *(pte_t *)pmd = pteval;
        if (page_table != (pte_t *)pmd_page_vaddr(*pmd))
                BUG();
}

#ifdef __tilegx__

static inline pmd_t *alloc_pmd(void)
{
        return __alloc_bootmem(L1_KERNEL_PGTABLE_SIZE, HV_PAGE_TABLE_ALIGN, 0);
}

static inline void assign_pmd(pud_t *pud, pmd_t *pmd)
{
        assign_pte((pmd_t *)pud, (pte_t *)pmd);
}

#endif /* __tilegx__ */

/* Replace the given pmd with a full PTE table. */
void __init shatter_pmd(pmd_t *pmd)
{
        pte_t *pte = get_prealloc_pte(pte_pfn(*(pte_t *)pmd));
        assign_pte(pmd, pte);
}

#ifdef __tilegx__
static pmd_t *__init get_pmd(pgd_t pgtables[], unsigned long va)
{
        pud_t *pud = pud_offset(&pgtables[pgd_index(va)], va);
        if (pud_none(*pud))
                assign_pmd(pud, alloc_pmd());
        return pmd_offset(pud, va);
}
#else
static pmd_t *__init get_pmd(pgd_t pgtables[], unsigned long va)
{
        return pmd_offset(pud_offset(&pgtables[pgd_index(va)], va), va);
}
#endif

/*
 * This function initializes a certain range of kernel virtual memory
 * with new bootmem page tables, everywhere page tables are missing in
 * the given range.
 */

/*
 * NOTE: The pagetables are allocated contiguous on the physical space
 * so we can cache the place of the first one and move around without
 * checking the pgd every time.
 */
static void __init page_table_range_init(unsigned long start,
                                         unsigned long end, pgd_t *pgd)
{
        unsigned long vaddr;
        start = round_down(start, PMD_SIZE);
        end = round_up(end, PMD_SIZE);
        for (vaddr = start; vaddr < end; vaddr += PMD_SIZE) {
                pmd_t *pmd = get_pmd(pgd, vaddr);
                if (pmd_none(*pmd))
                        assign_pte(pmd, alloc_pte());
        }
}


static int __initdata ktext_hash = 1;  /* .text pages */
static int __initdata kdata_hash = 1;  /* .data and .bss pages */
int __write_once hash_default = 1;     /* kernel allocator pages */
EXPORT_SYMBOL(hash_default);
int __write_once kstack_hash = 1;      /* if no homecaching, use h4h */

/*
 * CPUs to use to for striping the pages of kernel data.  If hash-for-home
 * is available, this is only relevant if kcache_hash sets up the
 * .data and .bss to be page-homed, and we don't want the default mode
 * of using the full set of kernel cpus for the striping.
 */
static __initdata struct cpumask kdata_mask;
static __initdata int kdata_arg_seen;

int __write_once kdata_huge;       /* if no homecaching, small pages */


/* Combine a generic pgprot_t with cache home to get a cache-aware pgprot. */
static pgprot_t __init construct_pgprot(pgprot_t prot, int home)
{
        prot = pte_set_home(prot, home);
        if (home == PAGE_HOME_IMMUTABLE) {
                if (ktext_hash)
                        prot = hv_pte_set_mode(prot, HV_PTE_MODE_CACHE_HASH_L3);
                else
                        prot = hv_pte_set_mode(prot, HV_PTE_MODE_CACHE_NO_L3);
        }
        return prot;
}

/*
 * For a given kernel data VA, how should it be cached?
 * We return the complete pgprot_t with caching bits set.
 */
static pgprot_t __init init_pgprot(ulong address)
{
        int cpu;
        unsigned long page;
        enum { CODE_DELTA = MEM_SV_START - PAGE_OFFSET };

        /* For kdata=huge, everything is just hash-for-home. */
        if (kdata_huge)
                return construct_pgprot(PAGE_KERNEL, PAGE_HOME_HASH);

        /* We map the aliased pages of permanent text inaccessible. */
        if (address < (ulong) _sinittext - CODE_DELTA)
                return PAGE_NONE;

        /* We map read-only data non-coherent for performance. */
        if ((address >= (ulong) __start_rodata &&
             address < (ulong) __end_rodata) ||
            address == (ulong) empty_zero_page) {
                return construct_pgprot(PAGE_KERNEL_RO, PAGE_HOME_IMMUTABLE);
        }

#ifndef __tilegx__
        /* Force the atomic_locks[] array page to be hash-for-home. */
        if (address == (ulong) atomic_locks)
                return construct_pgprot(PAGE_KERNEL, PAGE_HOME_HASH);
#endif

        /*
         * Everything else that isn't data or bss is heap, so mark it
         * with the initial heap home (hash-for-home, or this cpu).  This
         * includes any addresses after the loaded image and any address before
         * _einitdata, since we already captured the case of text before
         * _sinittext, and __pa(einittext) is approximately __pa(sinitdata).
         *
         * All the LOWMEM pages that we mark this way will get their
         * struct page homecache properly marked later, in set_page_homes().
         * The HIGHMEM pages we leave with a default zero for their
         * homes, but with a zero free_time we don't have to actually
         * do a flush action the first time we use them, either.
         */
        if (address >= (ulong) _end || address < (ulong) _einitdata)
                return construct_pgprot(PAGE_KERNEL, initial_heap_home());

        /* Use hash-for-home if requested for data/bss. */
        if (kdata_hash)
                return construct_pgprot(PAGE_KERNEL, PAGE_HOME_HASH);

        /*
         * Otherwise we just hand out consecutive cpus.  To avoid
         * requiring this function to hold state, we just walk forward from
         * __end_rodata by PAGE_SIZE, skipping the readonly and init data, to
         * reach the requested address, while walking cpu home around
         * kdata_mask. This is typically no more than a dozen or so iterations.
         */
        page = (((ulong)__end_rodata) + PAGE_SIZE - 1) & PAGE_MASK;
        BUG_ON(address < page || address >= (ulong)_end);
        cpu = cpumask_first(&kdata_mask);
        for (; page < address; page += PAGE_SIZE) {
                if (page >= (ulong)&init_thread_union &&
                    page < (ulong)&init_thread_union + THREAD_SIZE)
                        continue;
                if (page == (ulong)empty_zero_page)
                        continue;
#ifndef __tilegx__
                if (page == (ulong)atomic_locks)
                        continue;
#endif
                cpu = cpumask_next(cpu, &kdata_mask);
                if (cpu == NR_CPUS)
                        cpu = cpumask_first(&kdata_mask);
        }
        return construct_pgprot(PAGE_KERNEL, cpu);
}

/*
 * This function sets up how we cache the kernel text.  If we have
 * hash-for-home support, normally that is used instead (see the
 * kcache_hash boot flag for more information).  But if we end up
 * using a page-based caching technique, this option sets up the
 * details of that.  In addition, the "ktext=nocache" option may
 * always be used to disable local caching of text pages, if desired.
 */

static int __initdata ktext_arg_seen;
static int __initdata ktext_small;
static int __initdata ktext_local;
static int __initdata ktext_all;
static int __initdata ktext_nondataplane;
static int __initdata ktext_nocache;
static struct cpumask __initdata ktext_mask;

static int __init setup_ktext(char *str)
{
        if (str == NULL)
                return -EINVAL;

        /* If you have a leading "nocache", turn off ktext caching */
        if (strncmp(str, "nocache", 7) == 0) {
                ktext_nocache = 1;
                pr_info("ktext: disabling local caching of kernel text\n");
                str += 7;
                if (*str == ',')
                        ++str;
                if (*str == '\0')
                        return 0;
        }

        ktext_arg_seen = 1;

        /* Default setting: use a huge page */
        if (strcmp(str, "huge") == 0)
                pr_info("ktext: using one huge locally cached page\n");

        /* Pay TLB cost but get no cache benefit: cache small pages locally */
        else if (strcmp(str, "local") == 0) {
                ktext_small = 1;
                ktext_local = 1;
                pr_info("ktext: using small pages with local caching\n");
        }

        /* Neighborhood cache ktext pages on all cpus. */
        else if (strcmp(str, "all") == 0) {
                ktext_small = 1;
                ktext_all = 1;
                pr_info("ktext: using maximal caching neighborhood\n");
        }


        /* Neighborhood ktext pages on specified mask */
        else if (cpulist_parse(str, &ktext_mask) == 0) {
                char buf[NR_CPUS * 5];
                cpulist_scnprintf(buf, sizeof(buf), &ktext_mask);
                if (cpumask_weight(&ktext_mask) > 1) {
                        ktext_small = 1;
                        pr_info("ktext: using caching neighborhood %s "
                               "with small pages\n", buf);
                } else {
                        pr_info("ktext: caching on cpu %s with one huge page\n",
                               buf);
                }
        }

        else if (*str)
                return -EINVAL;

        return 0;
}

early_param("ktext", setup_ktext);


static inline pgprot_t ktext_set_nocache(pgprot_t prot)
{
        if (!ktext_nocache)
                prot = hv_pte_set_nc(prot);
        else
                prot = hv_pte_set_no_alloc_l2(prot);
        return prot;
}

/* Temporary page table we use for staging. */
static pgd_t pgtables[PTRS_PER_PGD]
 __attribute__((aligned(HV_PAGE_TABLE_ALIGN)));

/*
 * This maps the physical memory to kernel virtual address space, a total
 * of max_low_pfn pages, by creating page tables starting from address
 * PAGE_OFFSET.
 *
 * This routine transitions us from using a set of compiled-in large
 * pages to using some more precise caching, including removing access
 * to code pages mapped at PAGE_OFFSET (executed only at MEM_SV_START)
 * marking read-only data as locally cacheable, striping the remaining
 * .data and .bss across all the available tiles, and removing access
 * to pages above the top of RAM (thus ensuring a page fault from a bad
 * virtual address rather than a hypervisor shoot down for accessing
 * memory outside the assigned limits).
 */
static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
{
        unsigned long long irqmask;
        unsigned long address, pfn;
        pmd_t *pmd;
        pte_t *pte;
        int pte_ofs;
        const struct cpumask *my_cpu_mask = cpumask_of(smp_processor_id());
        struct cpumask kstripe_mask;
        int rc, i;

        if (ktext_arg_seen && ktext_hash) {
                pr_warning("warning: \"ktext\" boot argument ignored"
                           " if \"kcache_hash\" sets up text hash-for-home\n");
                ktext_small = 0;
        }

        if (kdata_arg_seen && kdata_hash) {
                pr_warning("warning: \"kdata\" boot argument ignored"
                           " if \"kcache_hash\" sets up data hash-for-home\n");
        }

        if (kdata_huge && !hash_default) {
                pr_warning("warning: disabling \"kdata=huge\"; requires"
                          " kcache_hash=all or =allbutstack\n");
                kdata_huge = 0;
        }

        /*
         * Set up a mask for cpus to use for kernel striping.
         * This is normally all cpus, but minus dataplane cpus if any.
         * If the dataplane covers the whole chip, we stripe over
         * the whole chip too.
         */
        cpumask_copy(&kstripe_mask, cpu_possible_mask);
        if (!kdata_arg_seen)
                kdata_mask = kstripe_mask;

        /* Allocate and fill in L2 page tables */
        for (i = 0; i < MAX_NUMNODES; ++i) {
#ifdef CONFIG_HIGHMEM
                unsigned long end_pfn = node_lowmem_end_pfn[i];
#else
                unsigned long end_pfn = node_end_pfn[i];
#endif
                unsigned long end_huge_pfn = 0;

                /* Pre-shatter the last huge page to allow per-cpu pages. */
                if (kdata_huge)
                        end_huge_pfn = end_pfn - (HPAGE_SIZE >> PAGE_SHIFT);

                pfn = node_start_pfn[i];

                /* Allocate enough memory to hold L2 page tables for node. */
                init_prealloc_ptes(i, end_pfn - pfn);

                address = (unsigned long) pfn_to_kaddr(pfn);
                while (pfn < end_pfn) {
                        BUG_ON(address & (HPAGE_SIZE-1));
                        pmd = get_pmd(pgtables, address);
                        pte = get_prealloc_pte(pfn);
                        if (pfn < end_huge_pfn) {
                                pgprot_t prot = init_pgprot(address);
                                *(pte_t *)pmd = pte_mkhuge(pfn_pte(pfn, prot));
                                for (pte_ofs = 0; pte_ofs < PTRS_PER_PTE;
                                     pfn++, pte_ofs++, address += PAGE_SIZE)
                                        pte[pte_ofs] = pfn_pte(pfn, prot);
                        } else {
                                if (kdata_huge)
                                        printk(KERN_DEBUG "pre-shattered huge"
                                               " page at %#lx\n", address);
                                for (pte_ofs = 0; pte_ofs < PTRS_PER_PTE;
                                     pfn++, pte_ofs++, address += PAGE_SIZE) {
                                        pgprot_t prot = init_pgprot(address);
                                        pte[pte_ofs] = pfn_pte(pfn, prot);
                                }
                                assign_pte(pmd, pte);
                        }
                }
        }

        /*
         * Set or check ktext_map now that we have cpu_possible_mask
         * and kstripe_mask to work with.
         */
        if (ktext_all)
                cpumask_copy(&ktext_mask, cpu_possible_mask);
        else if (ktext_nondataplane)
                ktext_mask = kstripe_mask;
        else if (!cpumask_empty(&ktext_mask)) {
                /* Sanity-check any mask that was requested */
                struct cpumask bad;
                cpumask_andnot(&bad, &ktext_mask, cpu_possible_mask);
                cpumask_and(&ktext_mask, &ktext_mask, cpu_possible_mask);
                if (!cpumask_empty(&bad)) {
                        char buf[NR_CPUS * 5];
                        cpulist_scnprintf(buf, sizeof(buf), &bad);
                        pr_info("ktext: not using unavailable cpus %s\n", buf);
                }
                if (cpumask_empty(&ktext_mask)) {
                        pr_warning("ktext: no valid cpus; caching on %d.\n",
                                   smp_processor_id());
                        cpumask_copy(&ktext_mask,
                                     cpumask_of(smp_processor_id()));
                }
        }

        address = MEM_SV_START;
        pmd = get_pmd(pgtables, address);
        pfn = 0;  /* code starts at PA 0 */
        if (ktext_small) {
                /* Allocate an L2 PTE for the kernel text */
                int cpu = 0;
                pgprot_t prot = construct_pgprot(PAGE_KERNEL_EXEC,
                                                 PAGE_HOME_IMMUTABLE);

                if (ktext_local) {
                        if (ktext_nocache)
                                prot = hv_pte_set_mode(prot,
                                                       HV_PTE_MODE_UNCACHED);
                        else
                                prot = hv_pte_set_mode(prot,
                                                       HV_PTE_MODE_CACHE_NO_L3);
                } else {
                        prot = hv_pte_set_mode(prot,
                                               HV_PTE_MODE_CACHE_TILE_L3);
                        cpu = cpumask_first(&ktext_mask);

                        prot = ktext_set_nocache(prot);
                }

                BUG_ON(address != (unsigned long)_text);
                pte = NULL;
                for (; address < (unsigned long)_einittext;
                     pfn++, address += PAGE_SIZE) {
                        pte_ofs = pte_index(address);
                        if (pte_ofs == 0) {
                                if (pte)
                                        assign_pte(pmd++, pte);
                                pte = alloc_pte();
                        }
                        if (!ktext_local) {
                                prot = set_remote_cache_cpu(prot, cpu);
                                cpu = cpumask_next(cpu, &ktext_mask);
                                if (cpu == NR_CPUS)
                                        cpu = cpumask_first(&ktext_mask);
                        }
                        pte[pte_ofs] = pfn_pte(pfn, prot);
                }
                if (pte)
                        assign_pte(pmd, pte);
        } else {
                pte_t pteval = pfn_pte(0, PAGE_KERNEL_EXEC);
                pteval = pte_mkhuge(pteval);
                if (ktext_hash) {
                        pteval = hv_pte_set_mode(pteval,
                                                 HV_PTE_MODE_CACHE_HASH_L3);
                        pteval = ktext_set_nocache(pteval);
                } else
                if (cpumask_weight(&ktext_mask) == 1) {
                        pteval = set_remote_cache_cpu(pteval,
                                              cpumask_first(&ktext_mask));
                        pteval = hv_pte_set_mode(pteval,
                                                 HV_PTE_MODE_CACHE_TILE_L3);
                        pteval = ktext_set_nocache(pteval);
                } else if (ktext_nocache)
                        pteval = hv_pte_set_mode(pteval,
                                                 HV_PTE_MODE_UNCACHED);
                else
                        pteval = hv_pte_set_mode(pteval,
                                                 HV_PTE_MODE_CACHE_NO_L3);
                for (; address < (unsigned long)_einittext;
                     pfn += PFN_DOWN(HPAGE_SIZE), address += HPAGE_SIZE)
                        *(pte_t *)(pmd++) = pfn_pte(pfn, pteval);
        }

        /* Set swapper_pgprot here so it is flushed to memory right away. */
        swapper_pgprot = init_pgprot((unsigned long)swapper_pg_dir);

        /*
         * Since we may be changing the caching of the stack and page
         * table itself, we invoke an assembly helper to do the
         * following steps:
         *
         *  - flush the cache so we start with an empty slate
         *  - install pgtables[] as the real page table
         *  - flush the TLB so the new page table takes effect
         */
        irqmask = interrupt_mask_save_mask();
        interrupt_mask_set_mask(-1ULL);
        rc = flush_and_install_context(__pa(pgtables),
                                       init_pgprot((unsigned long)pgtables),
                                       __get_cpu_var(current_asid),
                                       cpumask_bits(my_cpu_mask));
        interrupt_mask_restore_mask(irqmask);
        BUG_ON(rc != 0);

        /* Copy the page table back to the normal swapper_pg_dir. */
        memcpy(pgd_base, pgtables, sizeof(pgtables));
        __install_page_table(pgd_base, __get_cpu_var(current_asid),
                             swapper_pgprot);

        /*
         * We just read swapper_pgprot and thus brought it into the cache,
         * with its new home & caching mode.  When we start the other CPUs,
         * they're going to reference swapper_pgprot via their initial fake
         * VA-is-PA mappings, which cache everything locally.  At that
         * time, if it's in our cache with a conflicting home, the
         * simulator's coherence checker will complain.  So, flush it out
         * of our cache; we're not going to ever use it again anyway.
         */
        __insn_finv(&swapper_pgprot);
}

/*
 * devmem_is_allowed() checks to see if /dev/mem access to a certain address
 * is valid. The argument is a physical page number.
 *
 * On Tile, the only valid things for which we can just hand out unchecked
 * PTEs are the kernel code and data.  Anything else might change its
 * homing with time, and we wouldn't know to adjust the /dev/mem PTEs.
 * Note that init_thread_union is released to heap soon after boot,
 * so we include it in the init data.
 *
 * For TILE-Gx, we might want to consider allowing access to PA
 * regions corresponding to PCI space, etc.
 */
int devmem_is_allowed(unsigned long pagenr)
{
        return pagenr < kaddr_to_pfn(_end) &&
                !(pagenr >= kaddr_to_pfn(&init_thread_union) ||
                  pagenr < kaddr_to_pfn(_einitdata)) &&
                !(pagenr >= kaddr_to_pfn(_sinittext) ||
                  pagenr <= kaddr_to_pfn(_einittext-1));
}

#ifdef CONFIG_HIGHMEM
static void __init permanent_kmaps_init(pgd_t *pgd_base)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;
        unsigned long vaddr;

        vaddr = PKMAP_BASE;
        page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base);

        pgd = swapper_pg_dir + pgd_index(vaddr);
        pud = pud_offset(pgd, vaddr);
        pmd = pmd_offset(pud, vaddr);
        pte = pte_offset_kernel(pmd, vaddr);
        pkmap_page_table = pte;
}
#endif /* CONFIG_HIGHMEM */


#ifndef CONFIG_64BIT
static void __init init_free_pfn_range(unsigned long start, unsigned long end)
{
        unsigned long pfn;
        struct page *page = pfn_to_page(start);

        for (pfn = start; pfn < end; ) {
                /* Optimize by freeing pages in large batches */
                int order = __ffs(pfn);
                int count, i;
                struct page *p;

                if (order >= MAX_ORDER)
                        order = MAX_ORDER-1;
                count = 1 << order;
                while (pfn + count > end) {
                        count >>= 1;
                        --order;
                }
                for (p = page, i = 0; i < count; ++i, ++p) {
                        __ClearPageReserved(p);
                        /*
                         * Hacky direct set to avoid unnecessary
                         * lock take/release for EVERY page here.
                         */
                        p->_count.counter = 0;
                        p->_mapcount.counter = -1;
                }
                init_page_count(page);
                __free_pages(page, order);
                adjust_managed_page_count(page, count);

                page += count;
                pfn += count;
        }
}

static void __init set_non_bootmem_pages_init(void)
{
        struct zone *z;
        for_each_zone(z) {
                unsigned long start, end;
                int nid = z->zone_pgdat->node_id;
#ifdef CONFIG_HIGHMEM
                int idx = zone_idx(z);
#endif

                start = z->zone_start_pfn;
                end = start + z->spanned_pages;
                start = max(start, node_free_pfn[nid]);
                start = max(start, max_low_pfn);

#ifdef CONFIG_HIGHMEM
                if (idx == ZONE_HIGHMEM)
                        totalhigh_pages += z->spanned_pages;
#endif
                if (kdata_huge) {
                        unsigned long percpu_pfn = node_percpu_pfn[nid];
                        if (start < percpu_pfn && end > percpu_pfn)
                                end = percpu_pfn;
                }
#ifdef CONFIG_PCI
                if (start <= pci_reserve_start_pfn &&
                    end > pci_reserve_start_pfn) {
                        if (end > pci_reserve_end_pfn)
                                init_free_pfn_range(pci_reserve_end_pfn, end);
                        end = pci_reserve_start_pfn;
                }
#endif
                init_free_pfn_range(start, end);
        }
}
#endif

/*
 * paging_init() sets up the page tables - note that all of lowmem is
 * already mapped by head.S.
 */
void __init paging_init(void)
{
#ifdef __tilegx__
        pud_t *pud;
#endif
        pgd_t *pgd_base = swapper_pg_dir;

        kernel_physical_mapping_init(pgd_base);

        /* Fixed mappings, only the page table structure has to be created. */
        page_table_range_init(fix_to_virt(__end_of_fixed_addresses - 1),
                              FIXADDR_TOP, pgd_base);

#ifdef CONFIG_HIGHMEM
        permanent_kmaps_init(pgd_base);
#endif

#ifdef __tilegx__
        /*
         * Since GX allocates just one pmd_t array worth of vmalloc space,
         * we go ahead and allocate it statically here, then share it
         * globally.  As a result we don't have to worry about any task
         * changing init_mm once we get up and running, and there's no
         * need for e.g. vmalloc_sync_all().
         */
        BUILD_BUG_ON(pgd_index(VMALLOC_START) != pgd_index(VMALLOC_END - 1));
        pud = pud_offset(pgd_base + pgd_index(VMALLOC_START), VMALLOC_START);
        assign_pmd(pud, alloc_pmd());
#endif
}


/*
 * Walk the kernel page tables and derive the page_home() from
 * the PTEs, so that set_pte() can properly validate the caching
 * of all PTEs it sees.
 */
void __init set_page_homes(void)
{
}

static void __init set_max_mapnr_init(void)
{
#ifdef CONFIG_FLATMEM
        max_mapnr = max_low_pfn;
#endif
}

void __init mem_init(void)
{
        int i;
#ifndef __tilegx__
        void *last;
#endif

#ifdef CONFIG_FLATMEM
        BUG_ON(!mem_map);
#endif

#ifdef CONFIG_HIGHMEM
        /* check that fixmap and pkmap do not overlap */
        if (PKMAP_ADDR(LAST_PKMAP-1) >= FIXADDR_START) {
                pr_err("fixmap and kmap areas overlap"
                       " - this will crash\n");
                pr_err("pkstart: %lxh pkend: %lxh fixstart %lxh\n",
                       PKMAP_BASE, PKMAP_ADDR(LAST_PKMAP-1),
                       FIXADDR_START);
                BUG();
        }
#endif

        set_max_mapnr_init();

        /* this will put all bootmem onto the freelists */
        free_all_bootmem();

#ifndef CONFIG_64BIT
        /* count all remaining LOWMEM and give all HIGHMEM to page allocator */
        set_non_bootmem_pages_init();
#endif

        mem_init_print_info(NULL);

        /*
         * In debug mode, dump some interesting memory mappings.
         */
#ifdef CONFIG_HIGHMEM
        printk(KERN_DEBUG "  KMAP    %#lx - %#lx\n",
               FIXADDR_START, FIXADDR_TOP + PAGE_SIZE - 1);
        printk(KERN_DEBUG "  PKMAP   %#lx - %#lx\n",
               PKMAP_BASE, PKMAP_ADDR(LAST_PKMAP) - 1);
#endif
        printk(KERN_DEBUG "  VMALLOC %#lx - %#lx\n",
               _VMALLOC_START, _VMALLOC_END - 1);
#ifdef __tilegx__
        for (i = MAX_NUMNODES-1; i >= 0; --i) {
                struct pglist_data *node = &node_data[i];
                if (node->node_present_pages) {
                        unsigned long start = (unsigned long)
                                pfn_to_kaddr(node->node_start_pfn);
                        unsigned long end = start +
                                (node->node_present_pages << PAGE_SHIFT);
                        printk(KERN_DEBUG "  MEM%d    %#lx - %#lx\n",
                               i, start, end - 1);
                }
        }
#else
        last = high_memory;
        for (i = MAX_NUMNODES-1; i >= 0; --i) {
                if ((unsigned long)vbase_map[i] != -1UL) {
                        printk(KERN_DEBUG "  LOWMEM%d %#lx - %#lx\n",
                               i, (unsigned long) (vbase_map[i]),
                               (unsigned long) (last-1));
                        last = vbase_map[i];
                }
        }
#endif

#ifndef __tilegx__
        /*
         * Convert from using one lock for all atomic operations to
         * one per cpu.
         */
        __init_atomic_per_cpu();
#endif
}

/*
 * this is for the non-NUMA, single node SMP system case.
 * Specifically, in the case of x86, we will always add
 * memory to the highmem for now.
 */
#ifndef CONFIG_NEED_MULTIPLE_NODES
int arch_add_memory(u64 start, u64 size)
{
        struct pglist_data *pgdata = &contig_page_data;
        struct zone *zone = pgdata->node_zones + MAX_NR_ZONES-1;
        unsigned long start_pfn = start >> PAGE_SHIFT;
        unsigned long nr_pages = size >> PAGE_SHIFT;

        return __add_pages(zone, start_pfn, nr_pages);
}

int remove_memory(u64 start, u64 size)
{
        return -EINVAL;
}

#ifdef CONFIG_MEMORY_HOTREMOVE
int arch_remove_memory(u64 start, u64 size)
{
        /* TODO */
        return -EBUSY;
}
#endif
#endif

struct kmem_cache *pgd_cache;

void __init pgtable_cache_init(void)
{
        pgd_cache = kmem_cache_create("pgd", SIZEOF_PGD, SIZEOF_PGD, 0, NULL);
        if (!pgd_cache)
                panic("pgtable_cache_init(): Cannot create pgd cache");
}

#ifdef CONFIG_DEBUG_PAGEALLOC
static long __write_once initfree;
#else
static long __write_once initfree = 1;
#endif

/* Select whether to free (1) or mark unusable (0) the __init pages. */
static int __init set_initfree(char *str)
{
        long val;
        if (kstrtol(str, 0, &val) == 0) {
                initfree = val;
                pr_info("initfree: %s free init pages\n",
                        initfree ? "will" : "won't");
        }
        return 1;
}
__setup("initfree=", set_initfree);

static void free_init_pages(char *what, unsigned long begin, unsigned long end)
{
        unsigned long addr = (unsigned long) begin;

        if (kdata_huge && !initfree) {
                pr_warning("Warning: ignoring initfree=0:"
                           " incompatible with kdata=huge\n");
                initfree = 1;
        }
        end = (end + PAGE_SIZE - 1) & PAGE_MASK;
        local_flush_tlb_pages(NULL, begin, PAGE_SIZE, end - begin);
        for (addr = begin; addr < end; addr += PAGE_SIZE) {
                /*
                 * Note we just reset the home here directly in the
                 * page table.  We know this is safe because our caller
                 * just flushed the caches on all the other cpus,
                 * and they won't be touching any of these pages.
                 */
                int pfn = kaddr_to_pfn((void *)addr);
                struct page *page = pfn_to_page(pfn);
                pte_t *ptep = virt_to_kpte(addr);
                if (!initfree) {
                        /*
                         * If debugging page accesses then do not free
                         * this memory but mark them not present - any
                         * buggy init-section access will create a
                         * kernel page fault:
                         */
                        pte_clear(&init_mm, addr, ptep);
                        continue;
                }
                if (pte_huge(*ptep))
                        BUG_ON(!kdata_huge);
                else
                        set_pte_at(&init_mm, addr, ptep,
                                   pfn_pte(pfn, PAGE_KERNEL));
                memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
                free_reserved_page(page);
        }
        pr_info("Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
}

void free_initmem(void)
{
        const unsigned long text_delta = MEM_SV_START - PAGE_OFFSET;

        /*
         * Evict the cache on all cores to avoid incoherence.
         * We are guaranteed that no one will touch the init pages any more.
         */
        homecache_evict(&cpu_cacheable_map);

        /* Free the data pages that we won't use again after init. */
        free_init_pages("unused kernel data",
                        (unsigned long)_sinitdata,
                        (unsigned long)_einitdata);

        /*
         * Free the pages mapped from 0xc0000000 that correspond to code
         * pages from MEM_SV_START that we won't use again after init.
         */
        free_init_pages("unused kernel text",
                        (unsigned long)_sinittext - text_delta,
                        (unsigned long)_einittext - text_delta);
        /* Do a global TLB flush so everyone sees the changes. */
        flush_tlb_all();
}