arch/powerpc/mm/pgtable-hash64.c - arm/linux - Git at Google

 /*
  * Copyright 2005, Paul Mackerras, IBM Corporation.
  * Copyright 2009, Benjamin Herrenschmidt, IBM Corporation.
  * Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
  *
  * 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/sched.h>
 #include <linux/mm_types.h>

 #include <asm/pgalloc.h>
 #include <asm/tlb.h>

 #include "mmu_decl.h"

 #define CREATE_TRACE_POINTS
 #include <trace/events/thp.h>

 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 /*
  * On hash-based CPUs, the vmemmap is bolted in the hash table.
  *
  */
 int __meminit hash__vmemmap_create_mapping(unsigned long start,
 				       unsigned long page_size,
 				       unsigned long phys)
 {
 	int rc = htab_bolt_mapping(start, start + page_size, phys,
 				   pgprot_val(PAGE_KERNEL),
 				   mmu_vmemmap_psize, mmu_kernel_ssize);
 	if (rc < 0) {
 		int rc2 = htab_remove_mapping(start, start + page_size,
 					      mmu_vmemmap_psize,
 					      mmu_kernel_ssize);
 		BUG_ON(rc2 && (rc2 != -ENOENT));
 	}
 	return rc;
 }

 #ifdef CONFIG_MEMORY_HOTPLUG
 void hash__vmemmap_remove_mapping(unsigned long start,
 			      unsigned long page_size)
 {
 	int rc = htab_remove_mapping(start, start + page_size,
 				     mmu_vmemmap_psize,
 				     mmu_kernel_ssize);
 	BUG_ON((rc < 0) && (rc != -ENOENT));
 	WARN_ON(rc == -ENOENT);
 }
 #endif
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */

 /*
  * 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 hash__map_kernel_page(unsigned long ea, unsigned long pa, unsigned long flags)
 {
 	pgd_t *pgdp;
 	pud_t *pudp;
 	pmd_t *pmdp;
 	pte_t *ptep;

 	BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE);
 	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 {
 		/*
 		 * 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;
 		}
 	}

 	smp_wmb();
 	return 0;
 }

 #ifdef CONFIG_TRANSPARENT_HUGEPAGE

 unsigned long hash__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 				    pmd_t *pmdp, unsigned long clr,
 				    unsigned long set)
 {
 	__be64 old_be, tmp;
 	unsigned long old;

 #ifdef CONFIG_DEBUG_VM
 	WARN_ON(!pmd_trans_huge(*pmdp));
 	assert_spin_locked(&mm->page_table_lock);
 #endif

 	__asm__ __volatile__(
 	"1:	ldarx	%0,0,%3\n\
 		and.	%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_be), "=&r" (tmp), "=m" (*pmdp)
 	: "r" (pmdp), "r" (cpu_to_be64(clr)), "m" (*pmdp),
 	  "r" (cpu_to_be64(H_PAGE_BUSY)), "r" (cpu_to_be64(set))
 	: "cc" );

 	old = be64_to_cpu(old_be);

 	trace_hugepage_update(addr, old, clr, set);
 	if (old & H_PAGE_HASHPTE)
 		hpte_do_hugepage_flush(mm, addr, pmdp, old);
 	return old;
 }

 pmd_t hash__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;
 }

 /*
  * We want to put the pgtable in pmd and use pgtable for tracking
  * the base page size hptes
  */
 void hash__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 hash__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 hash__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, 0, _PAGE_PRIVILEGED);
 }

 /*
  * 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 & H_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);
 }

 pmd_t hash__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 hash__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 */
	/*
	* Copyright 2005, Paul Mackerras, IBM Corporation.
	* Copyright 2009, Benjamin Herrenschmidt, IBM Corporation.
	* Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
	*
	* 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/sched.h>
	#include <linux/mm_types.h>

	#include <asm/pgalloc.h>
	#include <asm/tlb.h>

	#include "mmu_decl.h"

	#define CREATE_TRACE_POINTS
	#include <trace/events/thp.h>

	#ifdef CONFIG_SPARSEMEM_VMEMMAP
	/*
	* On hash-based CPUs, the vmemmap is bolted in the hash table.
	*
	*/
	int __meminit hash__vmemmap_create_mapping(unsigned long start,
	unsigned long page_size,
	unsigned long phys)
	{
	int rc = htab_bolt_mapping(start, start + page_size, phys,
	pgprot_val(PAGE_KERNEL),
	mmu_vmemmap_psize, mmu_kernel_ssize);
	if (rc < 0) {
	int rc2 = htab_remove_mapping(start, start + page_size,
	mmu_vmemmap_psize,
	mmu_kernel_ssize);
	BUG_ON(rc2 && (rc2 != -ENOENT));
	}
	return rc;
	}

	#ifdef CONFIG_MEMORY_HOTPLUG
	void hash__vmemmap_remove_mapping(unsigned long start,
	unsigned long page_size)
	{
	int rc = htab_remove_mapping(start, start + page_size,
	mmu_vmemmap_psize,
	mmu_kernel_ssize);
	BUG_ON((rc < 0) && (rc != -ENOENT));
	WARN_ON(rc == -ENOENT);
	}
	#endif
	#endif /* CONFIG_SPARSEMEM_VMEMMAP */

	/*
	* 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 hash__map_kernel_page(unsigned long ea, unsigned long pa, unsigned long flags)
	{
	pgd_t *pgdp;
	pud_t *pudp;
	pmd_t *pmdp;
	pte_t *ptep;

	BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE);
	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 {
	/*
	* 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;
	}
	}

	smp_wmb();
	return 0;
	}

	#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	unsigned long hash__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
	pmd_t *pmdp, unsigned long clr,
	unsigned long set)
	{
	__be64 old_be, tmp;
	unsigned long old;

	#ifdef CONFIG_DEBUG_VM
	WARN_ON(!pmd_trans_huge(*pmdp));
	assert_spin_locked(&mm->page_table_lock);
	#endif

	__asm__ __volatile__(
	"1: ldarx %0,0,%3\n\
	and. %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_be), "=&r" (tmp), "=m" (*pmdp)
	: "r" (pmdp), "r" (cpu_to_be64(clr)), "m" (*pmdp),
	"r" (cpu_to_be64(H_PAGE_BUSY)), "r" (cpu_to_be64(set))
	: "cc" );

	old = be64_to_cpu(old_be);

	trace_hugepage_update(addr, old, clr, set);
	if (old & H_PAGE_HASHPTE)
	hpte_do_hugepage_flush(mm, addr, pmdp, old);
	return old;
	}

	pmd_t hash__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;
	}

	/*
	* We want to put the pgtable in pmd and use pgtable for tracking
	* the base page size hptes
	*/
	void hash__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 hash__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 hash__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, 0, _PAGE_PRIVILEGED);
	}

	/*
	* 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 & H_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);
	}

	pmd_t hash__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 hash__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 */