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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));
page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
if (page)
return page_address(page);
return NULL;
} else
return __earlyonly_bootmem_alloc(node, size, size,
/* 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,
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))
map_map[pnum] = sparse_mem_map_populate(pnum, nodeid);
if (map_map[pnum])
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;
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