text: /*
   *  This file contains ioremap and related functions for 64-bit machines.
   *
   *  Derived from arch/ppc64/mm/init.c
   *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   *
   *  Modifications by Paul Mackerras (PowerMac) (paulus@samba.org)
   *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
   *    Copyright (C) 1996 Paul Mackerras
   *
   *  Derived from "arch/i386/mm/init.c"
   *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   *
   *  Dave Engebretsen <engebret@us.ibm.com>
   *      Rework for PPC64 port.
   *
   *  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; either version
   *  2 of the License, or (at your option) any later version.
   *
   */
  
  #include <linux/signal.h>
  #include <linux/sched.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/export.h>
  #include <linux/types.h>
  #include <linux/mman.h>
  #include <linux/mm.h>
  #include <linux/swap.h>
  #include <linux/stddef.h>
  #include <linux/vmalloc.h>
  #include <linux/memblock.h>
  #include <linux/slab.h>
  #include <linux/hugetlb.h>
  
  #include <asm/pgalloc.h>
  #include <asm/page.h>
  #include <asm/prom.h>
  #include <asm/io.h>
  #include <asm/mmu_context.h>
  #include <asm/pgtable.h>
  #include <asm/mmu.h>
  #include <asm/smp.h>
  #include <asm/machdep.h>
  #include <asm/tlb.h>
  #include <asm/processor.h>
  #include <asm/cputable.h>
  #include <asm/sections.h>
  #include <asm/firmware.h>
  #include <asm/dma.h>
  
  #include "mmu_decl.h"
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/thp.h>
  
  /* Some sanity checking */
  #if TASK_SIZE_USER64 > PGTABLE_RANGE
  #error TASK_SIZE_USER64 exceeds pagetable range
  #endif
  
  #ifdef CONFIG_PPC_STD_MMU_64
  #if TASK_SIZE_USER64 > (1UL << (ESID_BITS + SID_SHIFT))
  #error TASK_SIZE_USER64 exceeds user VSID range
  #endif
  #endif
  
  unsigned long ioremap_bot = IOREMAP_BASE;
  
  #ifdef CONFIG_PPC_MMU_NOHASH
  static __ref void *early_alloc_pgtable(unsigned long size)
  {
  	void *pt;
  
  	pt = __va(memblock_alloc_base(size, size, __pa(MAX_DMA_ADDRESS)));
  	memset(pt, 0, size);
  
  	return pt;
  }
  #endif /* CONFIG_PPC_MMU_NOHASH */
  
  /*
   * map_kernel_page currently only called by __ioremap
   * map_kernel_page adds an entry to the ioremap page table
   * and adds an entry to the HPT, possibly bolting it
   */
  int map_kernel_page(unsigned long ea, unsigned long pa, int flags)
  {
  	pgd_t *pgdp;
  	pud_t *pudp;
  	pmd_t *pmdp;
  	pte_t *ptep;
  
  	if (slab_is_available()) {
  		pgdp = pgd_offset_k(ea);
  		pudp = pud_alloc(&init_mm, pgdp, ea);
  		if (!pudp)
  			return -ENOMEM;
  		pmdp = pmd_alloc(&init_mm, pudp, ea);
  		if (!pmdp)
  			return -ENOMEM;
  		ptep = pte_alloc_kernel(pmdp, ea);
  		if (!ptep)
  			return -ENOMEM;
  		set_pte_at(&init_mm, ea, ptep, pfn_pte(pa >> PAGE_SHIFT,
  							  __pgprot(flags)));
  	} else {
  #ifdef CONFIG_PPC_MMU_NOHASH
  		pgdp = pgd_offset_k(ea);
  #ifdef PUD_TABLE_SIZE
  		if (pgd_none(*pgdp)) {
  			pudp = early_alloc_pgtable(PUD_TABLE_SIZE);
  			BUG_ON(pudp == NULL);
  			pgd_populate(&init_mm, pgdp, pudp);
  		}
  #endif /* PUD_TABLE_SIZE */
  		pudp = pud_offset(pgdp, ea);
  		if (pud_none(*pudp)) {
  			pmdp = early_alloc_pgtable(PMD_TABLE_SIZE);
  			BUG_ON(pmdp == NULL);
  			pud_populate(&init_mm, pudp, pmdp);
  		}
  		pmdp = pmd_offset(pudp, ea);
  		if (!pmd_present(*pmdp)) {
  			ptep = early_alloc_pgtable(PAGE_SIZE);
  			BUG_ON(ptep == NULL);
  			pmd_populate_kernel(&init_mm, pmdp, ptep);
  		}
  		ptep = pte_offset_kernel(pmdp, ea);
  		set_pte_at(&init_mm, ea, ptep, pfn_pte(pa >> PAGE_SHIFT,
  							  __pgprot(flags)));
  #else /* CONFIG_PPC_MMU_NOHASH */
  		/*
  		 * If the mm subsystem is not fully up, we cannot create a
  		 * linux page table entry for this mapping.  Simply bolt an
  		 * entry in the hardware page table.
  		 *
  		 */
  		if (htab_bolt_mapping(ea, ea + PAGE_SIZE, pa, flags,
  				      mmu_io_psize, mmu_kernel_ssize)) {
  			printk(KERN_ERR "Failed to do bolted mapping IO "
  			       "memory at %016lx !\n", pa);
  			return -ENOMEM;
  		}
  #endif /* !CONFIG_PPC_MMU_NOHASH */
  	}
  
  	smp_wmb();
  	return 0;
  }
  
  
  /**
   * __ioremap_at - Low level function to establish the page tables
   *                for an IO mapping
   */
  void __iomem * __ioremap_at(phys_addr_t pa, void *ea, unsigned long size,
  			    unsigned long flags)
  {
  	unsigned long i;
  
  	/* Make sure we have the base flags */
  	if ((flags & _PAGE_PRESENT) == 0)
  		flags |= pgprot_val(PAGE_KERNEL);
  
  	/* Non-cacheable page cannot be coherent */
  	if (flags & _PAGE_NO_CACHE)
  		flags &= ~_PAGE_COHERENT;
  
  	/* We don't support the 4K PFN hack with ioremap */
  	if (flags & _PAGE_4K_PFN)
  		return NULL;
  
  	WARN_ON(pa & ~PAGE_MASK);
  	WARN_ON(((unsigned long)ea) & ~PAGE_MASK);
  	WARN_ON(size & ~PAGE_MASK);
  
  	for (i = 0; i < size; i += PAGE_SIZE)
  		if (map_kernel_page((unsigned long)ea+i, pa+i, flags))
  			return NULL;
  
  	return (void __iomem *)ea;
  }
  
  /**
   * __iounmap_from - Low level function to tear down the page tables
   *                  for an IO mapping. This is used for mappings that
   *                  are manipulated manually, like partial unmapping of
   *                  PCI IOs or ISA space.
   */
  void __iounmap_at(void *ea, unsigned long size)
  {
  	WARN_ON(((unsigned long)ea) & ~PAGE_MASK);
  	WARN_ON(size & ~PAGE_MASK);
  
  	unmap_kernel_range((unsigned long)ea, size);
  }
  
  void __iomem * __ioremap_caller(phys_addr_t addr, unsigned long size,
  				unsigned long flags, void *caller)
  {
  	phys_addr_t paligned;
  	void __iomem *ret;
  
  	/*
  	 * Choose an address to map it to.
  	 * Once the imalloc system is running, we use it.
  	 * Before that, we map using addresses going
  	 * up from ioremap_bot.  imalloc will use
  	 * the addresses from ioremap_bot through
  	 * IMALLOC_END
  	 * 
  	 */
  	paligned = addr & PAGE_MASK;
  	size = PAGE_ALIGN(addr + size) - paligned;
  
  	if ((size == 0) || (paligned == 0))
  		return NULL;
  
  	if (slab_is_available()) {
  		struct vm_struct *area;
  
  		area = __get_vm_area_caller(size, VM_IOREMAP,
  					    ioremap_bot, IOREMAP_END,
  					    caller);
  		if (area == NULL)
  			return NULL;
  
  		area->phys_addr = paligned;
  		ret = __ioremap_at(paligned, area->addr, size, flags);
  		if (!ret)
  			vunmap(area->addr);
  	} else {
  		ret = __ioremap_at(paligned, (void *)ioremap_bot, size, flags);
  		if (ret)
  			ioremap_bot += size;
  	}
  
  	if (ret)
  		ret += addr & ~PAGE_MASK;
  	return ret;
  }
  
  void __iomem * __ioremap(phys_addr_t addr, unsigned long size,
  			 unsigned long flags)
  {
  	return __ioremap_caller(addr, size, flags, __builtin_return_address(0));
  }
  
  void __iomem * ioremap(phys_addr_t addr, unsigned long size)
  {
  	unsigned long flags = _PAGE_NO_CACHE | _PAGE_GUARDED;
  	void *caller = __builtin_return_address(0);
  
  	if (ppc_md.ioremap)
  		return ppc_md.ioremap(addr, size, flags, caller);
  	return __ioremap_caller(addr, size, flags, caller);
  }
  
  void __iomem * ioremap_wc(phys_addr_t addr, unsigned long size)
  {
  	unsigned long flags = _PAGE_NO_CACHE;
  	void *caller = __builtin_return_address(0);
  
  	if (ppc_md.ioremap)
  		return ppc_md.ioremap(addr, size, flags, caller);
  	return __ioremap_caller(addr, size, flags, caller);
  }
  
  void __iomem * ioremap_prot(phys_addr_t addr, unsigned long size,
  			     unsigned long flags)
  {
  	void *caller = __builtin_return_address(0);
  
  	/* writeable implies dirty for kernel addresses */
  	if (flags & _PAGE_RW)
  		flags |= _PAGE_DIRTY;
  
  	/* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
  	flags &= ~(_PAGE_USER | _PAGE_EXEC);
  
  #ifdef _PAGE_BAP_SR
  	/* _PAGE_USER contains _PAGE_BAP_SR on BookE using the new PTE format
  	 * which means that we just cleared supervisor access... oops ;-) This
  	 * restores it
  	 */
  	flags |= _PAGE_BAP_SR;
  #endif
  
  	if (ppc_md.ioremap)
  		return ppc_md.ioremap(addr, size, flags, caller);
  	return __ioremap_caller(addr, size, flags, caller);
  }
  
  
  /*  
   * Unmap an IO region and remove it from imalloc'd list.
   * Access to IO memory should be serialized by driver.
   */
  void __iounmap(volatile void __iomem *token)
  {
  	void *addr;
  
  	if (!slab_is_available())
  		return;
  	
  	addr = (void *) ((unsigned long __force)
  			 PCI_FIX_ADDR(token) & PAGE_MASK);
  	if ((unsigned long)addr < ioremap_bot) {
  		printk(KERN_WARNING "Attempt to iounmap early bolted mapping"
  		       " at 0x%p\n", addr);
  		return;
  	}
  	vunmap(addr);
  }
  
  void iounmap(volatile void __iomem *token)
  {
  	if (ppc_md.iounmap)
  		ppc_md.iounmap(token);
  	else
  		__iounmap(token);
  }
  
  EXPORT_SYMBOL(ioremap);
  EXPORT_SYMBOL(ioremap_wc);
  EXPORT_SYMBOL(ioremap_prot);
  EXPORT_SYMBOL(__ioremap);
  EXPORT_SYMBOL(__ioremap_at);
  EXPORT_SYMBOL(iounmap);
  EXPORT_SYMBOL(__iounmap);
  EXPORT_SYMBOL(__iounmap_at);
  
  #ifndef __PAGETABLE_PUD_FOLDED
  /* 4 level page table */
  struct page *pgd_page(pgd_t pgd)
  {
  	if (pgd_huge(pgd))
  		return pte_page(pgd_pte(pgd));
  	return virt_to_page(pgd_page_vaddr(pgd));
  }
  #endif
  
  struct page *pud_page(pud_t pud)
  {
  	if (pud_huge(pud))
  		return pte_page(pud_pte(pud));
  	return virt_to_page(pud_page_vaddr(pud));
  }
  
  /*
   * For hugepage we have pfn in the pmd, we use PTE_RPN_SHIFT bits for flags
   * For PTE page, we have a PTE_FRAG_SIZE (4K) aligned virtual address.
   */
  struct page *pmd_page(pmd_t pmd)
  {
  	if (pmd_trans_huge(pmd) || pmd_huge(pmd))
  		return pte_page(pmd_pte(pmd));
  	return virt_to_page(pmd_page_vaddr(pmd));
  }
  
  #ifdef CONFIG_PPC_64K_PAGES
  static pte_t *get_from_cache(struct mm_struct *mm)
  {
  	void *pte_frag, *ret;
  
  	spin_lock(&mm->page_table_lock);
  	ret = mm->context.pte_frag;
  	if (ret) {
  		pte_frag = ret + PTE_FRAG_SIZE;
  		/*
  		 * If we have taken up all the fragments mark PTE page NULL
  		 */
  		if (((unsigned long)pte_frag & ~PAGE_MASK) == 0)
  			pte_frag = NULL;
  		mm->context.pte_frag = pte_frag;
  	}
  	spin_unlock(&mm->page_table_lock);
  	return (pte_t *)ret;
  }
  
  static pte_t *__alloc_for_cache(struct mm_struct *mm, int kernel)
  {
  	void *ret = NULL;
  	struct page *page = alloc_page(GFP_KERNEL | __GFP_NOTRACK |
  				       __GFP_REPEAT | __GFP_ZERO);
  	if (!page)
  		return NULL;
  	if (!kernel && !pgtable_page_ctor(page)) {
  		__free_page(page);
  		return NULL;
  	}
  
  	ret = page_address(page);
  	spin_lock(&mm->page_table_lock);
  	/*
  	 * If we find pgtable_page set, we return
  	 * the allocated page with single fragement
  	 * count.
  	 */
  	if (likely(!mm->context.pte_frag)) {
  		atomic_set(&page->_count, PTE_FRAG_NR);
  		mm->context.pte_frag = ret + PTE_FRAG_SIZE;
  	}
  	spin_unlock(&mm->page_table_lock);
  
  	return (pte_t *)ret;
  }
  
  pte_t *page_table_alloc(struct mm_struct *mm, unsigned long vmaddr, int kernel)
  {
  	pte_t *pte;
  
  	pte = get_from_cache(mm);
  	if (pte)
  		return pte;
  
  	return __alloc_for_cache(mm, kernel);
  }
  
  void page_table_free(struct mm_struct *mm, unsigned long *table, int kernel)
  {
  	struct page *page = virt_to_page(table);
  	if (put_page_testzero(page)) {
  		if (!kernel)
  			pgtable_page_dtor(page);
  		free_hot_cold_page(page, 0);
  	}
  }
  
  #ifdef CONFIG_SMP
  static void page_table_free_rcu(void *table)
  {
  	struct page *page = virt_to_page(table);
  	if (put_page_testzero(page)) {
  		pgtable_page_dtor(page);
  		free_hot_cold_page(page, 0);
  	}
  }
  
  void pgtable_free_tlb(struct mmu_gather *tlb, void *table, int shift)
  {
  	unsigned long pgf = (unsigned long)table;
  
  	BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
  	pgf |= shift;
  	tlb_remove_table(tlb, (void *)pgf);
  }
  
  void __tlb_remove_table(void *_table)
  {
  	void *table = (void *)((unsigned long)_table & ~MAX_PGTABLE_INDEX_SIZE);
  	unsigned shift = (unsigned long)_table & MAX_PGTABLE_INDEX_SIZE;
  
  	if (!shift)
  		/* PTE page needs special handling */
  		page_table_free_rcu(table);
  	else {
  		BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
  		kmem_cache_free(PGT_CACHE(shift), table);
  	}
  }
  #else
  void pgtable_free_tlb(struct mmu_gather *tlb, void *table, int shift)
  {
  	if (!shift) {
  		/* PTE page needs special handling */
  		struct page *page = virt_to_page(table);
  		if (put_page_testzero(page)) {
  			pgtable_page_dtor(page);
  			free_hot_cold_page(page, 0);
  		}
  	} else {
  		BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
  		kmem_cache_free(PGT_CACHE(shift), table);
  	}
  }
  #endif
  #endif /* CONFIG_PPC_64K_PAGES */
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  
  /*
   * This is called when relaxing access to a hugepage. It's also called in the page
   * fault path when we don't hit any of the major fault cases, ie, a minor
   * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have
   * handled those two for us, we additionally deal with missing execute
   * permission here on some processors
   */
  int pmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
  			  pmd_t *pmdp, pmd_t entry, int dirty)
  {
  	int changed;
  #ifdef CONFIG_DEBUG_VM
  	WARN_ON(!pmd_trans_huge(*pmdp));
  	assert_spin_locked(&vma->vm_mm->page_table_lock);
  #endif
  	changed = !pmd_same(*(pmdp), entry);
  	if (changed) {
  		__ptep_set_access_flags(pmdp_ptep(pmdp), pmd_pte(entry));
  		/*
  		 * Since we are not supporting SW TLB systems, we don't
  		 * have any thing similar to flush_tlb_page_nohash()
  		 */
  	}
  	return changed;
  }
  
  unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
  				  pmd_t *pmdp, unsigned long clr,
  				  unsigned long set)
  {
  
  	unsigned long old, tmp;
  
  #ifdef CONFIG_DEBUG_VM
  	WARN_ON(!pmd_trans_huge(*pmdp));
  	assert_spin_locked(&mm->page_table_lock);
  #endif
  
  #ifdef PTE_ATOMIC_UPDATES
  	__asm__ __volatile__(
  	"1:	ldarx	%0,0,%3\n\
  		andi.	%1,%0,%6\n\
  		bne-	1b \n\
  		andc	%1,%0,%4 \n\
  		or	%1,%1,%7\n\
  		stdcx.	%1,0,%3 \n\
  		bne-	1b"
  	: "=&r" (old), "=&r" (tmp), "=m" (*pmdp)
  	: "r" (pmdp), "r" (clr), "m" (*pmdp), "i" (_PAGE_BUSY), "r" (set)
  	: "cc" );
  #else
  	old = pmd_val(*pmdp);
  	*pmdp = __pmd((old & ~clr) | set);
  #endif
  	trace_hugepage_update(addr, old, clr, set);
  	if (old & _PAGE_HASHPTE)
  		hpte_do_hugepage_flush(mm, addr, pmdp, old);
  	return old;
  }
  
  pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
  			  pmd_t *pmdp)
  {
  	pmd_t pmd;
  
  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
  	VM_BUG_ON(pmd_trans_huge(*pmdp));
  
  	pmd = *pmdp;
  	pmd_clear(pmdp);
  	/*
  	 * Wait for all pending hash_page to finish. This is needed
  	 * in case of subpage collapse. When we collapse normal pages
  	 * to hugepage, we first clear the pmd, then invalidate all
  	 * the PTE entries. The assumption here is that any low level
  	 * page fault will see a none pmd and take the slow path that
  	 * will wait on mmap_sem. But we could very well be in a
  	 * hash_page with local ptep pointer value. Such a hash page
  	 * can result in adding new HPTE entries for normal subpages.
  	 * That means we could be modifying the page content as we
  	 * copy them to a huge page. So wait for parallel hash_page
  	 * to finish before invalidating HPTE entries. We can do this
  	 * by sending an IPI to all the cpus and executing a dummy
  	 * function there.
  	 */
  	kick_all_cpus_sync();
  	/*
  	 * Now invalidate the hpte entries in the range
  	 * covered by pmd. This make sure we take a
  	 * fault and will find the pmd as none, which will
  	 * result in a major fault which takes mmap_sem and
  	 * hence wait for collapse to complete. Without this
  	 * the __collapse_huge_page_copy can result in copying
  	 * the old content.
  	 */
  	flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
  	return pmd;
  }
  
  int pmdp_test_and_clear_young(struct vm_area_struct *vma,
  			      unsigned long address, pmd_t *pmdp)
  {
  	return __pmdp_test_and_clear_young(vma->vm_mm, address, pmdp);
  }
  
  /*
   * We currently remove entries from the hashtable regardless of whether
   * the entry was young or dirty. The generic routines only flush if the
   * entry was young or dirty which is not good enough.
   *
   * We should be more intelligent about this but for the moment we override
   * these functions and force a tlb flush unconditionally
   */
  int pmdp_clear_flush_young(struct vm_area_struct *vma,
  				  unsigned long address, pmd_t *pmdp)
  {
  	return __pmdp_test_and_clear_young(vma->vm_mm, address, pmdp);
  }
  
  /*
   * We want to put the pgtable in pmd and use pgtable for tracking
   * the base page size hptes
   */
  void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
  				pgtable_t pgtable)
  {
  	pgtable_t *pgtable_slot;
  	assert_spin_locked(&mm->page_table_lock);
  	/*
  	 * we store the pgtable in the second half of PMD
  	 */
  	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
  	*pgtable_slot = pgtable;
  	/*
  	 * expose the deposited pgtable to other cpus.
  	 * before we set the hugepage PTE at pmd level
  	 * hash fault code looks at the deposted pgtable
  	 * to store hash index values.
  	 */
  	smp_wmb();
  }
  
  pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
  {
  	pgtable_t pgtable;
  	pgtable_t *pgtable_slot;
  
  	assert_spin_locked(&mm->page_table_lock);
  	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
  	pgtable = *pgtable_slot;
  	/*
  	 * Once we withdraw, mark the entry NULL.
  	 */
  	*pgtable_slot = NULL;
  	/*
  	 * We store HPTE information in the deposited PTE fragment.
  	 * zero out the content on withdraw.
  	 */
  	memset(pgtable, 0, PTE_FRAG_SIZE);
  	return pgtable;
  }
  
  void pmdp_huge_split_prepare(struct vm_area_struct *vma,
  			     unsigned long address, pmd_t *pmdp)
  {
  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
  	VM_BUG_ON(REGION_ID(address) != USER_REGION_ID);
  
  	/*
  	 * We can't mark the pmd none here, because that will cause a race
  	 * against exit_mmap. We need to continue mark pmd TRANS HUGE, while
  	 * we spilt, but at the same time we wan't rest of the ppc64 code
  	 * not to insert hash pte on this, because we will be modifying
  	 * the deposited pgtable in the caller of this function. Hence
  	 * clear the _PAGE_USER so that we move the fault handling to
  	 * higher level function and that will serialize against ptl.
  	 * We need to flush existing hash pte entries here even though,
  	 * the translation is still valid, because we will withdraw
  	 * pgtable_t after this.
  	 */
  	pmd_hugepage_update(vma->vm_mm, address, pmdp, _PAGE_USER, 0);
  }
  
  
  /*
   * set a new huge pmd. We should not be called for updating
   * an existing pmd entry. That should go via pmd_hugepage_update.
   */
  void set_pmd_at(struct mm_struct *mm, unsigned long addr,
  		pmd_t *pmdp, pmd_t pmd)
  {
  #ifdef CONFIG_DEBUG_VM
  	WARN_ON((pmd_val(*pmdp) & (_PAGE_PRESENT | _PAGE_USER)) ==
  		(_PAGE_PRESENT | _PAGE_USER));
  	assert_spin_locked(&mm->page_table_lock);
  	WARN_ON(!pmd_trans_huge(pmd));
  #endif
  	trace_hugepage_set_pmd(addr, pmd_val(pmd));
  	return set_pte_at(mm, addr, pmdp_ptep(pmdp), pmd_pte(pmd));
  }
  
  /*
   * We use this to invalidate a pmdp entry before switching from a
   * hugepte to regular pmd entry.
   */
  void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
  		     pmd_t *pmdp)
  {
  	pmd_hugepage_update(vma->vm_mm, address, pmdp, _PAGE_PRESENT, 0);
  
  	/*
  	 * This ensures that generic code that rely on IRQ disabling
  	 * to prevent a parallel THP split work as expected.
  	 */
  	kick_all_cpus_sync();
  }
  
  /*
   * A linux hugepage PMD was changed and the corresponding hash table entries
   * neesd to be flushed.
   */
  void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
  			    pmd_t *pmdp, unsigned long old_pmd)
  {
  	int ssize;
  	unsigned int psize;
  	unsigned long vsid;
  	unsigned long flags = 0;
  	const struct cpumask *tmp;
  
  	/* get the base page size,vsid and segment size */
  #ifdef CONFIG_DEBUG_VM
  	psize = get_slice_psize(mm, addr);
  	BUG_ON(psize == MMU_PAGE_16M);
  #endif
  	if (old_pmd & _PAGE_COMBO)
  		psize = MMU_PAGE_4K;
  	else
  		psize = MMU_PAGE_64K;
  
  	if (!is_kernel_addr(addr)) {
  		ssize = user_segment_size(addr);
  		vsid = get_vsid(mm->context.id, addr, ssize);
  		WARN_ON(vsid == 0);
  	} else {
  		vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
  		ssize = mmu_kernel_ssize;
  	}
  
  	tmp = cpumask_of(smp_processor_id());
  	if (cpumask_equal(mm_cpumask(mm), tmp))
  		flags |= HPTE_LOCAL_UPDATE;
  
  	return flush_hash_hugepage(vsid, addr, pmdp, psize, ssize, flags);
  }
  
  static pmd_t pmd_set_protbits(pmd_t pmd, pgprot_t pgprot)
  {
  	return __pmd(pmd_val(pmd) | pgprot_val(pgprot));
  }
  
  pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
  {
  	unsigned long pmdv;
  
  	pmdv = pfn << PTE_RPN_SHIFT;
  	return pmd_set_protbits(__pmd(pmdv), pgprot);
  }
  
  pmd_t mk_pmd(struct page *page, pgprot_t pgprot)
  {
  	return pfn_pmd(page_to_pfn(page), pgprot);
  }
  
  pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
  {
  	unsigned long pmdv;
  
  	pmdv = pmd_val(pmd);
  	pmdv &= _HPAGE_CHG_MASK;
  	return pmd_set_protbits(__pmd(pmdv), newprot);
  }
  
  /*
   * This is called at the end of handling a user page fault, when the
   * fault has been handled by updating a HUGE PMD entry in the linux page tables.
   * We use it to preload an HPTE into the hash table corresponding to
   * the updated linux HUGE PMD entry.
   */
  void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
  			  pmd_t *pmd)
  {
  	return;
  }
  
  pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
  			      unsigned long addr, pmd_t *pmdp)
  {
  	pmd_t old_pmd;
  	pgtable_t pgtable;
  	unsigned long old;
  	pgtable_t *pgtable_slot;
  
  	old = pmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
  	old_pmd = __pmd(old);
  	/*
  	 * We have pmd == none and we are holding page_table_lock.
  	 * So we can safely go and clear the pgtable hash
  	 * index info.
  	 */
  	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
  	pgtable = *pgtable_slot;
  	/*
  	 * Let's zero out old valid and hash index details
  	 * hash fault look at them.
  	 */
  	memset(pgtable, 0, PTE_FRAG_SIZE);
  	/*
  	 * Serialize against find_linux_pte_or_hugepte which does lock-less
  	 * lookup in page tables with local interrupts disabled. For huge pages
  	 * it casts pmd_t to pte_t. Since format of pte_t is different from
  	 * pmd_t we want to prevent transit from pmd pointing to page table
  	 * to pmd pointing to huge page (and back) while interrupts are disabled.
  	 * We clear pmd to possibly replace it with page table pointer in
  	 * different code paths. So make sure we wait for the parallel
  	 * find_linux_pte_or_hugepage to finish.
  	 */
  	kick_all_cpus_sync();
  	return old_pmd;
  }
  
  int has_transparent_hugepage(void)
  {
  	if (!mmu_has_feature(MMU_FTR_16M_PAGE))
  		return 0;
  	/*
  	 * We support THP only if PMD_SIZE is 16MB.
  	 */
  	if (mmu_psize_defs[MMU_PAGE_16M].shift != PMD_SHIFT)
  		return 0;
  	/*
  	 * We need to make sure that we support 16MB hugepage in a segement
  	 * with base page size 64K or 4K. We only enable THP with a PAGE_SIZE
  	 * of 64K.
  	 */
  	/*
  	 * If we have 64K HPTE, we will be using that by default
  	 */
  	if (mmu_psize_defs[MMU_PAGE_64K].shift &&
  	    (mmu_psize_defs[MMU_PAGE_64K].penc[MMU_PAGE_16M] == -1))
  		return 0;
  	/*
  	 * Ok we only have 4K HPTE
  	 */
  	if (mmu_psize_defs[MMU_PAGE_4K].penc[MMU_PAGE_16M] == -1)
  		return 0;
  
  	return 1;
  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  