text: /*
   * Virtual Memory Map support
   *
   * (C) 2007 sgi. Christoph Lameter <clameter@sgi.com>.
   *
   * 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 memmory 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/module.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(NODE_DATA(node), size, align, goal);
  }
  
  
  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 = alloc_pages_node(node,
  				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));
  }
  
  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 (actual_node != node)
  		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(PAGE_SIZE, node);
  		if (!p)
  			return 0;
  		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 0;
  		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 0;
  		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 0;
  		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;
  }
  