arch/arm64/mm/hugetlbpage.c - linux - Git at Google

 /*
  * arch/arm64/mm/hugetlbpage.c
  *
  * Copyright (C) 2013 Linaro Ltd.
  *
  * Based on arch/x86/mm/hugetlbpage.c.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  */

 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
 #include <linux/pagemap.h>
 #include <linux/err.h>
 #include <linux/sysctl.h>
 #include <asm/mman.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/pgalloc.h>

 int pmd_huge(pmd_t pmd)
 {
 	return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT);
 }

 int pud_huge(pud_t pud)
 {
 #ifndef __PAGETABLE_PMD_FOLDED
 	return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT);
 #else
 	return 0;
 #endif
 }

 /*
  * Select all bits except the pfn
  */
 static inline pgprot_t pte_pgprot(pte_t pte)
 {
 	unsigned long pfn = pte_pfn(pte);

 	return __pgprot(pte_val(pfn_pte(pfn, __pgprot(0))) ^ pte_val(pte));
 }

 static int find_num_contig(struct mm_struct *mm, unsigned long addr,
 			   pte_t *ptep, size_t *pgsize)
 {
 	pgd_t *pgdp = pgd_offset(mm, addr);
 	pud_t *pudp;
 	pmd_t *pmdp;

 	*pgsize = PAGE_SIZE;
 	pudp = pud_offset(pgdp, addr);
 	pmdp = pmd_offset(pudp, addr);
 	if ((pte_t *)pmdp == ptep) {
 		*pgsize = PMD_SIZE;
 		return CONT_PMDS;
 	}
 	return CONT_PTES;
 }

 static inline int num_contig_ptes(unsigned long size, size_t *pgsize)
 {
 	int contig_ptes = 0;

 	*pgsize = size;

 	switch (size) {
 #ifdef CONFIG_ARM64_4K_PAGES
 	case PUD_SIZE:
 #endif
 	case PMD_SIZE:
 		contig_ptes = 1;
 		break;
 	case CONT_PMD_SIZE:
 		*pgsize = PMD_SIZE;
 		contig_ptes = CONT_PMDS;
 		break;
 	case CONT_PTE_SIZE:
 		*pgsize = PAGE_SIZE;
 		contig_ptes = CONT_PTES;
 		break;
 	}

 	return contig_ptes;
 }

 /*
  * Changing some bits of contiguous entries requires us to follow a
  * Break-Before-Make approach, breaking the whole contiguous set
  * before we can change any entries. See ARM DDI 0487A.k_iss10775,
  * "Misprogramming of the Contiguous bit", page D4-1762.
  *
  * This helper performs the break step.
  */
 static pte_t get_clear_flush(struct mm_struct *mm,
 			     unsigned long addr,
 			     pte_t *ptep,
 			     unsigned long pgsize,
 			     unsigned long ncontig)
 {
 	pte_t orig_pte = huge_ptep_get(ptep);
 	bool valid = pte_valid(orig_pte);
 	unsigned long i, saddr = addr;

 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
 		pte_t pte = ptep_get_and_clear(mm, addr, ptep);

 		/*
 		 * If HW_AFDBM is enabled, then the HW could turn on
 		 * the dirty or accessed bit for any page in the set,
 		 * so check them all.
 		 */
 		if (pte_dirty(pte))
 			orig_pte = pte_mkdirty(orig_pte);

 		if (pte_young(pte))
 			orig_pte = pte_mkyoung(orig_pte);
 	}

 	if (valid) {
 		struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
 		flush_tlb_range(&vma, saddr, addr);
 	}
 	return orig_pte;
 }

 /*
  * Changing some bits of contiguous entries requires us to follow a
  * Break-Before-Make approach, breaking the whole contiguous set
  * before we can change any entries. See ARM DDI 0487A.k_iss10775,
  * "Misprogramming of the Contiguous bit", page D4-1762.
  *
  * This helper performs the break step for use cases where the
  * original pte is not needed.
  */
 static void clear_flush(struct mm_struct *mm,
 			     unsigned long addr,
 			     pte_t *ptep,
 			     unsigned long pgsize,
 			     unsigned long ncontig)
 {
 	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
 	unsigned long i, saddr = addr;

 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
 		pte_clear(mm, addr, ptep);

 	flush_tlb_range(&vma, saddr, addr);
 }

 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 			    pte_t *ptep, pte_t pte)
 {
 	size_t pgsize;
 	int i;
 	int ncontig;
 	unsigned long pfn, dpfn;
 	pgprot_t hugeprot;

 	/*
 	 * Code needs to be expanded to handle huge swap and migration
 	 * entries. Needed for HUGETLB and MEMORY_FAILURE.
 	 */
 	WARN_ON(!pte_present(pte));

 	if (!pte_cont(pte)) {
 		set_pte_at(mm, addr, ptep, pte);
 		return;
 	}

 	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
 	pfn = pte_pfn(pte);
 	dpfn = pgsize >> PAGE_SHIFT;
 	hugeprot = pte_pgprot(pte);

 	clear_flush(mm, addr, ptep, pgsize, ncontig);

 	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
 		set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
 }

 void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
 			  pte_t *ptep, pte_t pte, unsigned long sz)
 {
 	int i, ncontig;
 	size_t pgsize;

 	ncontig = num_contig_ptes(sz, &pgsize);

 	for (i = 0; i < ncontig; i++, ptep++)
 		set_pte(ptep, pte);
 }

 pte_t *huge_pte_alloc(struct mm_struct *mm,
 		      unsigned long addr, unsigned long sz)
 {
 	pgd_t *pgdp;
 	pud_t *pudp;
 	pmd_t *pmdp;
 	pte_t *ptep = NULL;

 	pgdp = pgd_offset(mm, addr);
 	pudp = pud_alloc(mm, pgdp, addr);
 	if (!pudp)
 		return NULL;

 	if (sz == PUD_SIZE) {
 		ptep = (pte_t *)pudp;
 	} else if (sz == (PAGE_SIZE * CONT_PTES)) {
 		pmdp = pmd_alloc(mm, pudp, addr);

 		WARN_ON(addr & (sz - 1));
 		/*
 		 * Note that if this code were ever ported to the
 		 * 32-bit arm platform then it will cause trouble in
 		 * the case where CONFIG_HIGHPTE is set, since there
 		 * will be no pte_unmap() to correspond with this
 		 * pte_alloc_map().
 		 */
 		ptep = pte_alloc_map(mm, pmdp, addr);
 	} else if (sz == PMD_SIZE) {
 		if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) &&
 		    pud_none(READ_ONCE(*pudp)))
 			ptep = huge_pmd_share(mm, addr, pudp);
 		else
 			ptep = (pte_t *)pmd_alloc(mm, pudp, addr);
 	} else if (sz == (PMD_SIZE * CONT_PMDS)) {
 		pmdp = pmd_alloc(mm, pudp, addr);
 		WARN_ON(addr & (sz - 1));
 		return (pte_t *)pmdp;
 	}

 	return ptep;
 }

 pte_t *huge_pte_offset(struct mm_struct *mm,
 		       unsigned long addr, unsigned long sz)
 {
 	pgd_t *pgdp;
 	pud_t *pudp, pud;
 	pmd_t *pmdp, pmd;

 	pgdp = pgd_offset(mm, addr);
 	if (!pgd_present(READ_ONCE(*pgdp)))
 		return NULL;

 	pudp = pud_offset(pgdp, addr);
 	pud = READ_ONCE(*pudp);
 	if (sz != PUD_SIZE && pud_none(pud))
 		return NULL;
 	/* hugepage or swap? */
 	if (pud_huge(pud) || !pud_present(pud))
 		return (pte_t *)pudp;
 	/* table; check the next level */

 	if (sz == CONT_PMD_SIZE)
 		addr &= CONT_PMD_MASK;

 	pmdp = pmd_offset(pudp, addr);
 	pmd = READ_ONCE(*pmdp);
 	if (!(sz == PMD_SIZE || sz == CONT_PMD_SIZE) &&
 	    pmd_none(pmd))
 		return NULL;
 	if (pmd_huge(pmd) || !pmd_present(pmd))
 		return (pte_t *)pmdp;

 	if (sz == CONT_PTE_SIZE)
 		return pte_offset_kernel(pmdp, (addr & CONT_PTE_MASK));

 	return NULL;
 }

 pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
 			 struct page *page, int writable)
 {
 	size_t pagesize = huge_page_size(hstate_vma(vma));

 	if (pagesize == CONT_PTE_SIZE) {
 		entry = pte_mkcont(entry);
 	} else if (pagesize == CONT_PMD_SIZE) {
 		entry = pmd_pte(pmd_mkcont(pte_pmd(entry)));
 	} else if (pagesize != PUD_SIZE && pagesize != PMD_SIZE) {
 		pr_warn("%s: unrecognized huge page size 0x%lx\n",
 			__func__, pagesize);
 	}
 	return entry;
 }

 void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
 		    pte_t *ptep, unsigned long sz)
 {
 	int i, ncontig;
 	size_t pgsize;

 	ncontig = num_contig_ptes(sz, &pgsize);

 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
 		pte_clear(mm, addr, ptep);
 }

 pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 			      unsigned long addr, pte_t *ptep)
 {
 	int ncontig;
 	size_t pgsize;
 	pte_t orig_pte = huge_ptep_get(ptep);

 	if (!pte_cont(orig_pte))
 		return ptep_get_and_clear(mm, addr, ptep);

 	ncontig = find_num_contig(mm, addr, ptep, &pgsize);

 	return get_clear_flush(mm, addr, ptep, pgsize, ncontig);
 }

 /*
  * huge_ptep_set_access_flags will update access flags (dirty, accesssed)
  * and write permission.
  *
  * For a contiguous huge pte range we need to check whether or not write
  * permission has to change only on the first pte in the set. Then for
  * all the contiguous ptes we need to check whether or not there is a
  * discrepancy between dirty or young.
  */
 static int __cont_access_flags_changed(pte_t *ptep, pte_t pte, int ncontig)
 {
 	int i;

 	if (pte_write(pte) != pte_write(huge_ptep_get(ptep)))
 		return 1;

 	for (i = 0; i < ncontig; i++) {
 		pte_t orig_pte = huge_ptep_get(ptep + i);

 		if (pte_dirty(pte) != pte_dirty(orig_pte))
 			return 1;

 		if (pte_young(pte) != pte_young(orig_pte))
 			return 1;
 	}

 	return 0;
 }

 int huge_ptep_set_access_flags(struct vm_area_struct *vma,
 			       unsigned long addr, pte_t *ptep,
 			       pte_t pte, int dirty)
 {
 	int ncontig, i;
 	size_t pgsize = 0;
 	unsigned long pfn = pte_pfn(pte), dpfn;
 	pgprot_t hugeprot;
 	pte_t orig_pte;

 	if (!pte_cont(pte))
 		return ptep_set_access_flags(vma, addr, ptep, pte, dirty);

 	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
 	dpfn = pgsize >> PAGE_SHIFT;

 	if (!__cont_access_flags_changed(ptep, pte, ncontig))
 		return 0;

 	orig_pte = get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);

 	/* Make sure we don't lose the dirty or young state */
 	if (pte_dirty(orig_pte))
 		pte = pte_mkdirty(pte);

 	if (pte_young(orig_pte))
 		pte = pte_mkyoung(pte);

 	hugeprot = pte_pgprot(pte);
 	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
 		set_pte_at(vma->vm_mm, addr, ptep, pfn_pte(pfn, hugeprot));

 	return 1;
 }

 void huge_ptep_set_wrprotect(struct mm_struct *mm,
 			     unsigned long addr, pte_t *ptep)
 {
 	unsigned long pfn, dpfn;
 	pgprot_t hugeprot;
 	int ncontig, i;
 	size_t pgsize;
 	pte_t pte;

 	if (!pte_cont(READ_ONCE(*ptep))) {
 		ptep_set_wrprotect(mm, addr, ptep);
 		return;
 	}

 	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
 	dpfn = pgsize >> PAGE_SHIFT;

 	pte = get_clear_flush(mm, addr, ptep, pgsize, ncontig);
 	pte = pte_wrprotect(pte);

 	hugeprot = pte_pgprot(pte);
 	pfn = pte_pfn(pte);

 	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
 		set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
 }

 void huge_ptep_clear_flush(struct vm_area_struct *vma,
 			   unsigned long addr, pte_t *ptep)
 {
 	size_t pgsize;
 	int ncontig;

 	if (!pte_cont(READ_ONCE(*ptep))) {
 		ptep_clear_flush(vma, addr, ptep);
 		return;
 	}

 	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
 	clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
 }

 static __init int setup_hugepagesz(char *opt)
 {
 	unsigned long ps = memparse(opt, &opt);

 	switch (ps) {
 #ifdef CONFIG_ARM64_4K_PAGES
 	case PUD_SIZE:
 #endif
 	case PMD_SIZE * CONT_PMDS:
 	case PMD_SIZE:
 	case PAGE_SIZE * CONT_PTES:
 		hugetlb_add_hstate(ilog2(ps) - PAGE_SHIFT);
 		return 1;
 	}

 	hugetlb_bad_size();
 	pr_err("hugepagesz: Unsupported page size %lu K\n", ps >> 10);
 	return 0;
 }
 __setup("hugepagesz=", setup_hugepagesz);

 #ifdef CONFIG_ARM64_64K_PAGES
 static __init int add_default_hugepagesz(void)
 {
 	if (size_to_hstate(CONT_PTES * PAGE_SIZE) == NULL)
 		hugetlb_add_hstate(CONT_PTE_SHIFT);
 	return 0;
 }
 arch_initcall(add_default_hugepagesz);
 #endif
	/*
	* arch/arm64/mm/hugetlbpage.c
	*
	* Copyright (C) 2013 Linaro Ltd.
	*
	* Based on arch/x86/mm/hugetlbpage.c.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*/

	#include <linux/init.h>
	#include <linux/fs.h>
	#include <linux/mm.h>
	#include <linux/hugetlb.h>
	#include <linux/pagemap.h>
	#include <linux/err.h>
	#include <linux/sysctl.h>
	#include <asm/mman.h>
	#include <asm/tlb.h>
	#include <asm/tlbflush.h>
	#include <asm/pgalloc.h>

	int pmd_huge(pmd_t pmd)
	{
	return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT);
	}

	int pud_huge(pud_t pud)
	{
	#ifndef __PAGETABLE_PMD_FOLDED
	return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT);
	#else
	return 0;
	#endif
	}

	/*
	* Select all bits except the pfn
	*/
	static inline pgprot_t pte_pgprot(pte_t pte)
	{
	unsigned long pfn = pte_pfn(pte);

	return __pgprot(pte_val(pfn_pte(pfn, __pgprot(0))) ^ pte_val(pte));
	}

	static int find_num_contig(struct mm_struct *mm, unsigned long addr,
	pte_t ptep, size_t pgsize)
	{
	pgd_t *pgdp = pgd_offset(mm, addr);
	pud_t *pudp;
	pmd_t *pmdp;

	*pgsize = PAGE_SIZE;
	pudp = pud_offset(pgdp, addr);
	pmdp = pmd_offset(pudp, addr);
	if ((pte_t *)pmdp == ptep) {
	*pgsize = PMD_SIZE;
	return CONT_PMDS;
	}
	return CONT_PTES;
	}

	static inline int num_contig_ptes(unsigned long size, size_t *pgsize)
	{
	int contig_ptes = 0;

	*pgsize = size;

	switch (size) {
	#ifdef CONFIG_ARM64_4K_PAGES
	case PUD_SIZE:
	#endif
	case PMD_SIZE:
	contig_ptes = 1;
	break;
	case CONT_PMD_SIZE:
	*pgsize = PMD_SIZE;
	contig_ptes = CONT_PMDS;
	break;
	case CONT_PTE_SIZE:
	*pgsize = PAGE_SIZE;
	contig_ptes = CONT_PTES;
	break;
	}

	return contig_ptes;
	}

	/*
	* Changing some bits of contiguous entries requires us to follow a
	* Break-Before-Make approach, breaking the whole contiguous set
	* before we can change any entries. See ARM DDI 0487A.k_iss10775,
	* "Misprogramming of the Contiguous bit", page D4-1762.
	*
	* This helper performs the break step.
	*/
	static pte_t get_clear_flush(struct mm_struct *mm,
	unsigned long addr,
	pte_t *ptep,
	unsigned long pgsize,
	unsigned long ncontig)
	{
	pte_t orig_pte = huge_ptep_get(ptep);
	bool valid = pte_valid(orig_pte);
	unsigned long i, saddr = addr;

	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
	pte_t pte = ptep_get_and_clear(mm, addr, ptep);

	/*
	* If HW_AFDBM is enabled, then the HW could turn on
	* the dirty or accessed bit for any page in the set,
	* so check them all.
	*/
	if (pte_dirty(pte))
	orig_pte = pte_mkdirty(orig_pte);

	if (pte_young(pte))
	orig_pte = pte_mkyoung(orig_pte);
	}

	if (valid) {
	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
	flush_tlb_range(&vma, saddr, addr);
	}
	return orig_pte;
	}

	/*
	* Changing some bits of contiguous entries requires us to follow a
	* Break-Before-Make approach, breaking the whole contiguous set
	* before we can change any entries. See ARM DDI 0487A.k_iss10775,
	* "Misprogramming of the Contiguous bit", page D4-1762.
	*
	* This helper performs the break step for use cases where the
	* original pte is not needed.
	*/
	static void clear_flush(struct mm_struct *mm,
	unsigned long addr,
	pte_t *ptep,
	unsigned long pgsize,
	unsigned long ncontig)
	{
	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
	unsigned long i, saddr = addr;

	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
	pte_clear(mm, addr, ptep);

	flush_tlb_range(&vma, saddr, addr);
	}

	void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, pte_t pte)
	{
	size_t pgsize;
	int i;
	int ncontig;
	unsigned long pfn, dpfn;
	pgprot_t hugeprot;

	/*
	* Code needs to be expanded to handle huge swap and migration
	* entries. Needed for HUGETLB and MEMORY_FAILURE.
	*/
	WARN_ON(!pte_present(pte));

	if (!pte_cont(pte)) {
	set_pte_at(mm, addr, ptep, pte);
	return;
	}

	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
	pfn = pte_pfn(pte);
	dpfn = pgsize >> PAGE_SHIFT;
	hugeprot = pte_pgprot(pte);

	clear_flush(mm, addr, ptep, pgsize, ncontig);

	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
	set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
	}

	void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, pte_t pte, unsigned long sz)
	{
	int i, ncontig;
	size_t pgsize;

	ncontig = num_contig_ptes(sz, &pgsize);

	for (i = 0; i < ncontig; i++, ptep++)
	set_pte(ptep, pte);
	}

	pte_t huge_pte_alloc(struct mm_struct mm,
	unsigned long addr, unsigned long sz)
	{
	pgd_t *pgdp;
	pud_t *pudp;
	pmd_t *pmdp;
	pte_t *ptep = NULL;

	pgdp = pgd_offset(mm, addr);
	pudp = pud_alloc(mm, pgdp, addr);
	if (!pudp)
	return NULL;

	if (sz == PUD_SIZE) {
	ptep = (pte_t *)pudp;
	} else if (sz == (PAGE_SIZE * CONT_PTES)) {
	pmdp = pmd_alloc(mm, pudp, addr);

	WARN_ON(addr & (sz - 1));
	/*
	* Note that if this code were ever ported to the
	* 32-bit arm platform then it will cause trouble in
	* the case where CONFIG_HIGHPTE is set, since there
	* will be no pte_unmap() to correspond with this
	* pte_alloc_map().
	*/
	ptep = pte_alloc_map(mm, pmdp, addr);
	} else if (sz == PMD_SIZE) {
	if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) &&
	pud_none(READ_ONCE(*pudp)))
	ptep = huge_pmd_share(mm, addr, pudp);
	else
	ptep = (pte_t *)pmd_alloc(mm, pudp, addr);
	} else if (sz == (PMD_SIZE * CONT_PMDS)) {
	pmdp = pmd_alloc(mm, pudp, addr);
	WARN_ON(addr & (sz - 1));
	return (pte_t *)pmdp;
	}

	return ptep;
	}

	pte_t huge_pte_offset(struct mm_struct mm,
	unsigned long addr, unsigned long sz)
	{
	pgd_t *pgdp;
	pud_t *pudp, pud;
	pmd_t *pmdp, pmd;

	pgdp = pgd_offset(mm, addr);
	if (!pgd_present(READ_ONCE(*pgdp)))
	return NULL;

	pudp = pud_offset(pgdp, addr);
	pud = READ_ONCE(*pudp);
	if (sz != PUD_SIZE && pud_none(pud))
	return NULL;
	/* hugepage or swap? */
	if (pud_huge(pud) \|\| !pud_present(pud))
	return (pte_t *)pudp;
	/* table; check the next level */

	if (sz == CONT_PMD_SIZE)
	addr &= CONT_PMD_MASK;

	pmdp = pmd_offset(pudp, addr);
	pmd = READ_ONCE(*pmdp);
	if (!(sz == PMD_SIZE \|\| sz == CONT_PMD_SIZE) &&
	pmd_none(pmd))
	return NULL;
	if (pmd_huge(pmd) \|\| !pmd_present(pmd))
	return (pte_t *)pmdp;

	if (sz == CONT_PTE_SIZE)
	return pte_offset_kernel(pmdp, (addr & CONT_PTE_MASK));

	return NULL;
	}

	pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
	struct page *page, int writable)
	{
	size_t pagesize = huge_page_size(hstate_vma(vma));

	if (pagesize == CONT_PTE_SIZE) {
	entry = pte_mkcont(entry);
	} else if (pagesize == CONT_PMD_SIZE) {
	entry = pmd_pte(pmd_mkcont(pte_pmd(entry)));
	} else if (pagesize != PUD_SIZE && pagesize != PMD_SIZE) {
	pr_warn("%s: unrecognized huge page size 0x%lx\n",
	__func__, pagesize);
	}
	return entry;
	}

	void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, unsigned long sz)
	{
	int i, ncontig;
	size_t pgsize;

	ncontig = num_contig_ptes(sz, &pgsize);

	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
	pte_clear(mm, addr, ptep);
	}

	pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
	unsigned long addr, pte_t *ptep)
	{
	int ncontig;
	size_t pgsize;
	pte_t orig_pte = huge_ptep_get(ptep);

	if (!pte_cont(orig_pte))
	return ptep_get_and_clear(mm, addr, ptep);

	ncontig = find_num_contig(mm, addr, ptep, &pgsize);

	return get_clear_flush(mm, addr, ptep, pgsize, ncontig);
	}

	/*
	* huge_ptep_set_access_flags will update access flags (dirty, accesssed)
	* and write permission.
	*
	* For a contiguous huge pte range we need to check whether or not write
	* permission has to change only on the first pte in the set. Then for
	* all the contiguous ptes we need to check whether or not there is a
	* discrepancy between dirty or young.
	*/
	static int __cont_access_flags_changed(pte_t *ptep, pte_t pte, int ncontig)
	{
	int i;

	if (pte_write(pte) != pte_write(huge_ptep_get(ptep)))
	return 1;

	for (i = 0; i < ncontig; i++) {
	pte_t orig_pte = huge_ptep_get(ptep + i);

	if (pte_dirty(pte) != pte_dirty(orig_pte))
	return 1;

	if (pte_young(pte) != pte_young(orig_pte))
	return 1;
	}

	return 0;
	}

	int huge_ptep_set_access_flags(struct vm_area_struct *vma,
	unsigned long addr, pte_t *ptep,
	pte_t pte, int dirty)
	{
	int ncontig, i;
	size_t pgsize = 0;
	unsigned long pfn = pte_pfn(pte), dpfn;
	pgprot_t hugeprot;
	pte_t orig_pte;

	if (!pte_cont(pte))
	return ptep_set_access_flags(vma, addr, ptep, pte, dirty);

	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
	dpfn = pgsize >> PAGE_SHIFT;

	if (!__cont_access_flags_changed(ptep, pte, ncontig))
	return 0;

	orig_pte = get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);

	/* Make sure we don't lose the dirty or young state */
	if (pte_dirty(orig_pte))
	pte = pte_mkdirty(pte);

	if (pte_young(orig_pte))
	pte = pte_mkyoung(pte);

	hugeprot = pte_pgprot(pte);
	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
	set_pte_at(vma->vm_mm, addr, ptep, pfn_pte(pfn, hugeprot));

	return 1;
	}

	void huge_ptep_set_wrprotect(struct mm_struct *mm,
	unsigned long addr, pte_t *ptep)
	{
	unsigned long pfn, dpfn;
	pgprot_t hugeprot;
	int ncontig, i;
	size_t pgsize;
	pte_t pte;

	if (!pte_cont(READ_ONCE(*ptep))) {
	ptep_set_wrprotect(mm, addr, ptep);
	return;
	}

	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
	dpfn = pgsize >> PAGE_SHIFT;

	pte = get_clear_flush(mm, addr, ptep, pgsize, ncontig);
	pte = pte_wrprotect(pte);

	hugeprot = pte_pgprot(pte);
	pfn = pte_pfn(pte);

	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
	set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
	}

	void huge_ptep_clear_flush(struct vm_area_struct *vma,
	unsigned long addr, pte_t *ptep)
	{
	size_t pgsize;
	int ncontig;

	if (!pte_cont(READ_ONCE(*ptep))) {
	ptep_clear_flush(vma, addr, ptep);
	return;
	}

	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
	clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
	}

	static __init int setup_hugepagesz(char *opt)
	{
	unsigned long ps = memparse(opt, &opt);

	switch (ps) {
	#ifdef CONFIG_ARM64_4K_PAGES
	case PUD_SIZE:
	#endif
	case PMD_SIZE * CONT_PMDS:
	case PMD_SIZE:
	case PAGE_SIZE * CONT_PTES:
	hugetlb_add_hstate(ilog2(ps) - PAGE_SHIFT);
	return 1;
	}

	hugetlb_bad_size();
	pr_err("hugepagesz: Unsupported page size %lu K\n", ps >> 10);
	return 0;
	}
	__setup("hugepagesz=", setup_hugepagesz);

	#ifdef CONFIG_ARM64_64K_PAGES
	static __init int add_default_hugepagesz(void)
	{
	if (size_to_hstate(CONT_PTES * PAGE_SIZE) == NULL)
	hugetlb_add_hstate(CONT_PTE_SHIFT);
	return 0;
	}
	arch_initcall(add_default_hugepagesz);
	#endif