sparse-vmemmap.c

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/*
 * Virtual Memory Map support
 *
 * (C) 2007 sgi. Christoph Lameter.
 *
 * Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn,
 * virt_to_page, page_address() to be implemented as a base offset
 * calculation without memory access.
 *
 * However, virtual mappings need a page table and TLBs. Many Linux
 * architectures already map their physical space using 1-1 mappings
 * via TLBs. For those arches the virtual memory map is essentially
 * for free if we use the same page size as the 1-1 mappings. In that
 * case the overhead consists of a few additional pages that are
 * allocated to create a view of memory for vmemmap.
 *
 * The architecture is expected to provide a vmemmap_populate() function
 * to instantiate the mapping.
 */
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/bootmem.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include <linux/sched.h>
#include <asm/dma.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>

/*
 * Allocate a block of memory to be used to back the virtual memory map
 * or to back the page tables that are used to create the mapping.
 * Uses the main allocators if they are available, else bootmem.
 */

static void * __init_refok __earlyonly_bootmem_alloc(int node,
                unsigned long size,
                unsigned long align,
                unsigned long goal)
{
    return __alloc_bootmem_node_high(NODE_DATA(node), size, align, goal);
}

static void *vmemmap_buf;
static void *vmemmap_buf_end;

void * __meminit vmemmap_alloc_block(unsigned long size, int node)
{
    /* If the main allocator is up use that, fallback to bootmem. */
    if (slab_is_available()) {
        struct page *page;

        if (node_state(node, N_HIGH_MEMORY))
            page = alloc_pages_node(node,
                GFP_KERNEL | __GFP_ZERO, get_order(size));
        else
            page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
                get_order(size));
        if (page)
            return page_address(page);
        return NULL;
    } else
        return __earlyonly_bootmem_alloc(node, size, size,
                __pa(MAX_DMA_ADDRESS));
}

/* need to make sure size is all the same during early stage */
void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node)
{
    void *ptr;

    if (!vmemmap_buf)
        return vmemmap_alloc_block(size, node);

    /* take the from buf */
    ptr = (void *)ALIGN((unsigned long)vmemmap_buf, size);
    if (ptr + size > vmemmap_buf_end)
        return vmemmap_alloc_block(size, node);

    vmemmap_buf = ptr + size;

    return ptr;
}

void __meminit vmemmap_verify(pte_t *pte, int node,
                unsigned long start, unsigned long end)
{
    unsigned long pfn = pte_pfn(*pte);
    int actual_node = early_pfn_to_nid(pfn);

    if (node_distance(actual_node, node) > LOCAL_DISTANCE)
        printk(KERN_WARNING "[%lx-%lx] potential offnode "
            "page_structs\n", start, end - 1);
}

pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node)
{
    pte_t *pte = pte_offset_kernel(pmd, addr);
    if (pte_none(*pte)) {
        pte_t entry;
        void *p = vmemmap_alloc_block_buf(PAGE_SIZE, node);
        if (!p)
            return NULL;
        entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL);
        set_pte_at(&init_mm, addr, pte, entry);
    }
    return pte;
}

pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
{
    pmd_t *pmd = pmd_offset(pud, addr);
    if (pmd_none(*pmd)) {
        void *p = vmemmap_alloc_block(PAGE_SIZE, node);
        if (!p)
            return NULL;
        pmd_populate_kernel(&init_mm, pmd, p);
    }
    return pmd;
}

pud_t * __meminit vmemmap_pud_populate(pgd_t *pgd, unsigned long addr, int node)
{
    pud_t *pud = pud_offset(pgd, addr);
    if (pud_none(*pud)) {
        void *p = vmemmap_alloc_block(PAGE_SIZE, node);
        if (!p)
            return NULL;
        pud_populate(&init_mm, pud, p);
    }
    return pud;
}

pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
{
    pgd_t *pgd = pgd_offset_k(addr);
    if (pgd_none(*pgd)) {
        void *p = vmemmap_alloc_block(PAGE_SIZE, node);
        if (!p)
            return NULL;
        pgd_populate(&init_mm, pgd, p);
    }
    return pgd;
}

int __meminit vmemmap_populate_basepages(struct page *start_page,
                        unsigned long size, int node)
{
    unsigned long addr = (unsigned long)start_page;
    unsigned long end = (unsigned long)(start_page + size);
    pgd_t *pgd;
    pud_t *pud;
    pmd_t *pmd;
    pte_t *pte;

    for (; addr < end; addr += PAGE_SIZE) {
        pgd = vmemmap_pgd_populate(addr, node);
        if (!pgd)
            return -ENOMEM;
        pud = vmemmap_pud_populate(pgd, addr, node);
        if (!pud)
            return -ENOMEM;
        pmd = vmemmap_pmd_populate(pud, addr, node);
        if (!pmd)
            return -ENOMEM;
        pte = vmemmap_pte_populate(pmd, addr, node);
        if (!pte)
            return -ENOMEM;
        vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);
    }

    return 0;
}

struct page * __meminit sparse_mem_map_populate(unsigned long pnum, int nid)
{
    struct page *map = pfn_to_page(pnum * PAGES_PER_SECTION);
    int error = vmemmap_populate(map, PAGES_PER_SECTION, nid);
    if (error)
        return NULL;

    return map;
}

void __init sparse_mem_maps_populate_node(struct page **map_map,
                      unsigned long pnum_begin,
                      unsigned long pnum_end,
                      unsigned long map_count, int nodeid)
{
    unsigned long pnum;
    unsigned long size = sizeof(struct page) * PAGES_PER_SECTION;
    void *vmemmap_buf_start;

    size = ALIGN(size, PMD_SIZE);
    vmemmap_buf_start = __earlyonly_bootmem_alloc(nodeid, size * map_count,
             PMD_SIZE, __pa(MAX_DMA_ADDRESS));

    if (vmemmap_buf_start) {
        vmemmap_buf = vmemmap_buf_start;
        vmemmap_buf_end = vmemmap_buf_start + size * map_count;
    }

    for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
        struct mem_section *ms;

        if (!present_section_nr(pnum))
            continue;

        map_map[pnum] = sparse_mem_map_populate(pnum, nodeid);
        if (map_map[pnum])
            continue;
        ms = __nr_to_section(pnum);
        printk(KERN_ERR "%s: sparsemem memory map backing failed "
            "some memory will not be available.\n", __func__);
        ms->section_mem_map = 0;
    }

    if (vmemmap_buf_start) {
        /* need to free left buf */
        free_bootmem(__pa(vmemmap_buf), vmemmap_buf_end - vmemmap_buf);
        vmemmap_buf = NULL;
        vmemmap_buf_end = NULL;
    }
}