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

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2023 ARM Ltd.
  */

 #include <linux/mm.h>
 #include <linux/efi.h>
 #include <linux/export.h>
 #include <asm/tlbflush.h>

 static inline bool mm_is_user(struct mm_struct *mm)
 {
 	/*
 	 * Don't attempt to apply the contig bit to kernel mappings, because
 	 * dynamically adding/removing the contig bit can cause page faults.
 	 * These racing faults are ok for user space, since they get serialized
 	 * on the PTL. But kernel mappings can't tolerate faults.
 	 */
 	if (unlikely(mm_is_efi(mm)))
 		return false;
 	return mm != &init_mm;
 }

 static inline pte_t *contpte_align_down(pte_t *ptep)
 {
 	return PTR_ALIGN_DOWN(ptep, sizeof(*ptep) * CONT_PTES);
 }

 static void contpte_try_unfold_partial(struct mm_struct *mm, unsigned long addr,
 					pte_t *ptep, unsigned int nr)
 {
 	/*
 	 * Unfold any partially covered contpte block at the beginning and end
 	 * of the range.
 	 */

 	if (ptep != contpte_align_down(ptep) || nr < CONT_PTES)
 		contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep));

 	if (ptep + nr != contpte_align_down(ptep + nr)) {
 		unsigned long last_addr = addr + PAGE_SIZE * (nr - 1);
 		pte_t *last_ptep = ptep + nr - 1;

 		contpte_try_unfold(mm, last_addr, last_ptep,
 				   __ptep_get(last_ptep));
 	}
 }

 static void contpte_convert(struct mm_struct *mm, unsigned long addr,
 			    pte_t *ptep, pte_t pte)
 {
 	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
 	unsigned long start_addr;
 	pte_t *start_ptep;
 	int i;

 	start_ptep = ptep = contpte_align_down(ptep);
 	start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
 	pte = pfn_pte(ALIGN_DOWN(pte_pfn(pte), CONT_PTES), pte_pgprot(pte));

 	for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) {
 		pte_t ptent = __ptep_get_and_clear(mm, addr, ptep);

 		if (pte_dirty(ptent))
 			pte = pte_mkdirty(pte);

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

 	__flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3);

 	__set_ptes(mm, start_addr, start_ptep, pte, CONT_PTES);
 }

 void __contpte_try_fold(struct mm_struct *mm, unsigned long addr,
 			pte_t *ptep, pte_t pte)
 {
 	/*
 	 * We have already checked that the virtual and pysical addresses are
 	 * correctly aligned for a contpte mapping in contpte_try_fold() so the
 	 * remaining checks are to ensure that the contpte range is fully
 	 * covered by a single folio, and ensure that all the ptes are valid
 	 * with contiguous PFNs and matching prots. We ignore the state of the
 	 * access and dirty bits for the purpose of deciding if its a contiguous
 	 * range; the folding process will generate a single contpte entry which
 	 * has a single access and dirty bit. Those 2 bits are the logical OR of
 	 * their respective bits in the constituent pte entries. In order to
 	 * ensure the contpte range is covered by a single folio, we must
 	 * recover the folio from the pfn, but special mappings don't have a
 	 * folio backing them. Fortunately contpte_try_fold() already checked
 	 * that the pte is not special - we never try to fold special mappings.
 	 * Note we can't use vm_normal_page() for this since we don't have the
 	 * vma.
 	 */

 	unsigned long folio_start, folio_end;
 	unsigned long cont_start, cont_end;
 	pte_t expected_pte, subpte;
 	struct folio *folio;
 	struct page *page;
 	unsigned long pfn;
 	pte_t *orig_ptep;
 	pgprot_t prot;

 	int i;

 	if (!mm_is_user(mm))
 		return;

 	page = pte_page(pte);
 	folio = page_folio(page);
 	folio_start = addr - (page - &folio->page) * PAGE_SIZE;
 	folio_end = folio_start + folio_nr_pages(folio) * PAGE_SIZE;
 	cont_start = ALIGN_DOWN(addr, CONT_PTE_SIZE);
 	cont_end = cont_start + CONT_PTE_SIZE;

 	if (folio_start > cont_start || folio_end < cont_end)
 		return;

 	pfn = ALIGN_DOWN(pte_pfn(pte), CONT_PTES);
 	prot = pte_pgprot(pte_mkold(pte_mkclean(pte)));
 	expected_pte = pfn_pte(pfn, prot);
 	orig_ptep = ptep;
 	ptep = contpte_align_down(ptep);

 	for (i = 0; i < CONT_PTES; i++) {
 		subpte = pte_mkold(pte_mkclean(__ptep_get(ptep)));
 		if (!pte_same(subpte, expected_pte))
 			return;
 		expected_pte = pte_advance_pfn(expected_pte, 1);
 		ptep++;
 	}

 	pte = pte_mkcont(pte);
 	contpte_convert(mm, addr, orig_ptep, pte);
 }
 EXPORT_SYMBOL_GPL(__contpte_try_fold);

 void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
 			pte_t *ptep, pte_t pte)
 {
 	/*
 	 * We have already checked that the ptes are contiguous in
 	 * contpte_try_unfold(), so just check that the mm is user space.
 	 */
 	if (!mm_is_user(mm))
 		return;

 	pte = pte_mknoncont(pte);
 	contpte_convert(mm, addr, ptep, pte);
 }
 EXPORT_SYMBOL_GPL(__contpte_try_unfold);

 pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
 {
 	/*
 	 * Gather access/dirty bits, which may be populated in any of the ptes
 	 * of the contig range. We are guaranteed to be holding the PTL, so any
 	 * contiguous range cannot be unfolded or otherwise modified under our
 	 * feet.
 	 */

 	pte_t pte;
 	int i;

 	ptep = contpte_align_down(ptep);

 	for (i = 0; i < CONT_PTES; i++, ptep++) {
 		pte = __ptep_get(ptep);

 		if (pte_dirty(pte))
 			orig_pte = pte_mkdirty(orig_pte);

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

 	return orig_pte;
 }
 EXPORT_SYMBOL_GPL(contpte_ptep_get);

 pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
 {
 	/*
 	 * The ptep_get_lockless() API requires us to read and return *orig_ptep
 	 * so that it is self-consistent, without the PTL held, so we may be
 	 * racing with other threads modifying the pte. Usually a READ_ONCE()
 	 * would suffice, but for the contpte case, we also need to gather the
 	 * access and dirty bits from across all ptes in the contiguous block,
 	 * and we can't read all of those neighbouring ptes atomically, so any
 	 * contiguous range may be unfolded/modified/refolded under our feet.
 	 * Therefore we ensure we read a _consistent_ contpte range by checking
 	 * that all ptes in the range are valid and have CONT_PTE set, that all
 	 * pfns are contiguous and that all pgprots are the same (ignoring
 	 * access/dirty). If we find a pte that is not consistent, then we must
 	 * be racing with an update so start again. If the target pte does not
 	 * have CONT_PTE set then that is considered consistent on its own
 	 * because it is not part of a contpte range.
 	 */

 	pgprot_t orig_prot;
 	unsigned long pfn;
 	pte_t orig_pte;
 	pgprot_t prot;
 	pte_t *ptep;
 	pte_t pte;
 	int i;

 retry:
 	orig_pte = __ptep_get(orig_ptep);

 	if (!pte_valid_cont(orig_pte))
 		return orig_pte;

 	orig_prot = pte_pgprot(pte_mkold(pte_mkclean(orig_pte)));
 	ptep = contpte_align_down(orig_ptep);
 	pfn = pte_pfn(orig_pte) - (orig_ptep - ptep);

 	for (i = 0; i < CONT_PTES; i++, ptep++, pfn++) {
 		pte = __ptep_get(ptep);
 		prot = pte_pgprot(pte_mkold(pte_mkclean(pte)));

 		if (!pte_valid_cont(pte) ||
 		   pte_pfn(pte) != pfn ||
 		   pgprot_val(prot) != pgprot_val(orig_prot))
 			goto retry;

 		if (pte_dirty(pte))
 			orig_pte = pte_mkdirty(orig_pte);

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

 	return orig_pte;
 }
 EXPORT_SYMBOL_GPL(contpte_ptep_get_lockless);

 void contpte_set_ptes(struct mm_struct *mm, unsigned long addr,
 					pte_t *ptep, pte_t pte, unsigned int nr)
 {
 	unsigned long next;
 	unsigned long end;
 	unsigned long pfn;
 	pgprot_t prot;

 	/*
 	 * The set_ptes() spec guarantees that when nr > 1, the initial state of
 	 * all ptes is not-present. Therefore we never need to unfold or
 	 * otherwise invalidate a range before we set the new ptes.
 	 * contpte_set_ptes() should never be called for nr < 2.
 	 */
 	VM_WARN_ON(nr == 1);

 	if (!mm_is_user(mm))
 		return __set_ptes(mm, addr, ptep, pte, nr);

 	end = addr + (nr << PAGE_SHIFT);
 	pfn = pte_pfn(pte);
 	prot = pte_pgprot(pte);

 	do {
 		next = pte_cont_addr_end(addr, end);
 		nr = (next - addr) >> PAGE_SHIFT;
 		pte = pfn_pte(pfn, prot);

 		if (((addr | next | (pfn << PAGE_SHIFT)) & ~CONT_PTE_MASK) == 0)
 			pte = pte_mkcont(pte);
 		else
 			pte = pte_mknoncont(pte);

 		__set_ptes(mm, addr, ptep, pte, nr);

 		addr = next;
 		ptep += nr;
 		pfn += nr;

 	} while (addr != end);
 }
 EXPORT_SYMBOL_GPL(contpte_set_ptes);

 void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, unsigned int nr, int full)
 {
 	contpte_try_unfold_partial(mm, addr, ptep, nr);
 	__clear_full_ptes(mm, addr, ptep, nr, full);
 }
 EXPORT_SYMBOL_GPL(contpte_clear_full_ptes);

 pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm,
 				unsigned long addr, pte_t *ptep,
 				unsigned int nr, int full)
 {
 	contpte_try_unfold_partial(mm, addr, ptep, nr);
 	return __get_and_clear_full_ptes(mm, addr, ptep, nr, full);
 }
 EXPORT_SYMBOL_GPL(contpte_get_and_clear_full_ptes);

 int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma,
 					unsigned long addr, pte_t *ptep)
 {
 	/*
 	 * ptep_clear_flush_young() technically requires us to clear the access
 	 * flag for a _single_ pte. However, the core-mm code actually tracks
 	 * access/dirty per folio, not per page. And since we only create a
 	 * contig range when the range is covered by a single folio, we can get
 	 * away with clearing young for the whole contig range here, so we avoid
 	 * having to unfold.
 	 */

 	int young = 0;
 	int i;

 	ptep = contpte_align_down(ptep);
 	addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);

 	for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE)
 		young |= __ptep_test_and_clear_young(vma, addr, ptep);

 	return young;
 }
 EXPORT_SYMBOL_GPL(contpte_ptep_test_and_clear_young);

 int contpte_ptep_clear_flush_young(struct vm_area_struct *vma,
 					unsigned long addr, pte_t *ptep)
 {
 	int young;

 	young = contpte_ptep_test_and_clear_young(vma, addr, ptep);

 	if (young) {
 		/*
 		 * See comment in __ptep_clear_flush_young(); same rationale for
 		 * eliding the trailing DSB applies here.
 		 */
 		addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
 		__flush_tlb_range_nosync(vma, addr, addr + CONT_PTE_SIZE,
 					 PAGE_SIZE, true, 3);
 	}

 	return young;
 }
 EXPORT_SYMBOL_GPL(contpte_ptep_clear_flush_young);

 void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
 					pte_t *ptep, unsigned int nr)
 {
 	/*
 	 * If wrprotecting an entire contig range, we can avoid unfolding. Just
 	 * set wrprotect and wait for the later mmu_gather flush to invalidate
 	 * the tlb. Until the flush, the page may or may not be wrprotected.
 	 * After the flush, it is guaranteed wrprotected. If it's a partial
 	 * range though, we must unfold, because we can't have a case where
 	 * CONT_PTE is set but wrprotect applies to a subset of the PTEs; this
 	 * would cause it to continue to be unpredictable after the flush.
 	 */

 	contpte_try_unfold_partial(mm, addr, ptep, nr);
 	__wrprotect_ptes(mm, addr, ptep, nr);
 }
 EXPORT_SYMBOL_GPL(contpte_wrprotect_ptes);

 void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
 				    unsigned long addr, pte_t *ptep,
 				    unsigned int nr, cydp_t flags)
 {
 	/*
 	 * We can safely clear access/dirty without needing to unfold from
 	 * the architectures perspective, even when contpte is set. If the
 	 * range starts or ends midway through a contpte block, we can just
 	 * expand to include the full contpte block. While this is not
 	 * exactly what the core-mm asked for, it tracks access/dirty per
 	 * folio, not per page. And since we only create a contpte block
 	 * when it is covered by a single folio, we can get away with
 	 * clearing access/dirty for the whole block.
 	 */
 	unsigned long start = addr;
 	unsigned long end = start + nr * PAGE_SIZE;

 	if (pte_cont(__ptep_get(ptep + nr - 1)))
 		end = ALIGN(end, CONT_PTE_SIZE);

 	if (pte_cont(__ptep_get(ptep))) {
 		start = ALIGN_DOWN(start, CONT_PTE_SIZE);
 		ptep = contpte_align_down(ptep);
 	}

 	__clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, flags);
 }
 EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);

 int contpte_ptep_set_access_flags(struct vm_area_struct *vma,
 					unsigned long addr, pte_t *ptep,
 					pte_t entry, int dirty)
 {
 	unsigned long start_addr;
 	pte_t orig_pte;
 	int i;

 	/*
 	 * Gather the access/dirty bits for the contiguous range. If nothing has
 	 * changed, its a noop.
 	 */
 	orig_pte = pte_mknoncont(ptep_get(ptep));
 	if (pte_val(orig_pte) == pte_val(entry))
 		return 0;

 	/*
 	 * We can fix up access/dirty bits without having to unfold the contig
 	 * range. But if the write bit is changing, we must unfold.
 	 */
 	if (pte_write(orig_pte) == pte_write(entry)) {
 		/*
 		 * For HW access management, we technically only need to update
 		 * the flag on a single pte in the range. But for SW access
 		 * management, we need to update all the ptes to prevent extra
 		 * faults. Avoid per-page tlb flush in __ptep_set_access_flags()
 		 * and instead flush the whole range at the end.
 		 */
 		ptep = contpte_align_down(ptep);
 		start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);

 		/*
 		 * We are not advancing entry because __ptep_set_access_flags()
 		 * only consumes access flags from entry. And since we have checked
 		 * for the whole contpte block and returned early, pte_same()
 		 * within __ptep_set_access_flags() is likely false.
 		 */
 		for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE)
 			__ptep_set_access_flags(vma, addr, ptep, entry, 0);

 		if (dirty)
 			__flush_tlb_range(vma, start_addr, addr,
 							PAGE_SIZE, true, 3);
 	} else {
 		__contpte_try_unfold(vma->vm_mm, addr, ptep, orig_pte);
 		__ptep_set_access_flags(vma, addr, ptep, entry, dirty);
 	}

 	return 1;
 }
 EXPORT_SYMBOL_GPL(contpte_ptep_set_access_flags);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2023 ARM Ltd.
	*/

	#include <linux/mm.h>
	#include <linux/efi.h>
	#include <linux/export.h>
	#include <asm/tlbflush.h>

	static inline bool mm_is_user(struct mm_struct *mm)
	{
	/*
	* Don't attempt to apply the contig bit to kernel mappings, because
	* dynamically adding/removing the contig bit can cause page faults.
	* These racing faults are ok for user space, since they get serialized
	* on the PTL. But kernel mappings can't tolerate faults.
	*/
	if (unlikely(mm_is_efi(mm)))
	return false;
	return mm != &init_mm;
	}

	static inline pte_t contpte_align_down(pte_t ptep)
	{
	return PTR_ALIGN_DOWN(ptep, sizeof(ptep) CONT_PTES);
	}

	static void contpte_try_unfold_partial(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, unsigned int nr)
	{
	/*
	* Unfold any partially covered contpte block at the beginning and end
	* of the range.
	*/

	if (ptep != contpte_align_down(ptep) \|\| nr < CONT_PTES)
	contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep));

	if (ptep + nr != contpte_align_down(ptep + nr)) {
	unsigned long last_addr = addr + PAGE_SIZE * (nr - 1);
	pte_t *last_ptep = ptep + nr - 1;

	contpte_try_unfold(mm, last_addr, last_ptep,
	__ptep_get(last_ptep));
	}
	}

	static void contpte_convert(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, pte_t pte)
	{
	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
	unsigned long start_addr;
	pte_t *start_ptep;
	int i;

	start_ptep = ptep = contpte_align_down(ptep);
	start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
	pte = pfn_pte(ALIGN_DOWN(pte_pfn(pte), CONT_PTES), pte_pgprot(pte));

	for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) {
	pte_t ptent = __ptep_get_and_clear(mm, addr, ptep);

	if (pte_dirty(ptent))
	pte = pte_mkdirty(pte);

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

	__flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3);

	__set_ptes(mm, start_addr, start_ptep, pte, CONT_PTES);
	}

	void __contpte_try_fold(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, pte_t pte)
	{
	/*
	* We have already checked that the virtual and pysical addresses are
	* correctly aligned for a contpte mapping in contpte_try_fold() so the
	* remaining checks are to ensure that the contpte range is fully
	* covered by a single folio, and ensure that all the ptes are valid
	* with contiguous PFNs and matching prots. We ignore the state of the
	* access and dirty bits for the purpose of deciding if its a contiguous
	* range; the folding process will generate a single contpte entry which
	* has a single access and dirty bit. Those 2 bits are the logical OR of
	* their respective bits in the constituent pte entries. In order to
	* ensure the contpte range is covered by a single folio, we must
	* recover the folio from the pfn, but special mappings don't have a
	* folio backing them. Fortunately contpte_try_fold() already checked
	* that the pte is not special - we never try to fold special mappings.
	* Note we can't use vm_normal_page() for this since we don't have the
	* vma.
	*/

	unsigned long folio_start, folio_end;
	unsigned long cont_start, cont_end;
	pte_t expected_pte, subpte;
	struct folio *folio;
	struct page *page;
	unsigned long pfn;
	pte_t *orig_ptep;
	pgprot_t prot;

	int i;

	if (!mm_is_user(mm))
	return;

	page = pte_page(pte);
	folio = page_folio(page);
	folio_start = addr - (page - &folio->page) * PAGE_SIZE;
	folio_end = folio_start + folio_nr_pages(folio) * PAGE_SIZE;
	cont_start = ALIGN_DOWN(addr, CONT_PTE_SIZE);
	cont_end = cont_start + CONT_PTE_SIZE;

	if (folio_start > cont_start \|\| folio_end < cont_end)
	return;

	pfn = ALIGN_DOWN(pte_pfn(pte), CONT_PTES);
	prot = pte_pgprot(pte_mkold(pte_mkclean(pte)));
	expected_pte = pfn_pte(pfn, prot);
	orig_ptep = ptep;
	ptep = contpte_align_down(ptep);

	for (i = 0; i < CONT_PTES; i++) {
	subpte = pte_mkold(pte_mkclean(__ptep_get(ptep)));
	if (!pte_same(subpte, expected_pte))
	return;
	expected_pte = pte_advance_pfn(expected_pte, 1);
	ptep++;
	}

	pte = pte_mkcont(pte);
	contpte_convert(mm, addr, orig_ptep, pte);
	}
	EXPORT_SYMBOL_GPL(__contpte_try_fold);

	void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, pte_t pte)
	{
	/*
	* We have already checked that the ptes are contiguous in
	* contpte_try_unfold(), so just check that the mm is user space.
	*/
	if (!mm_is_user(mm))
	return;

	pte = pte_mknoncont(pte);
	contpte_convert(mm, addr, ptep, pte);
	}
	EXPORT_SYMBOL_GPL(__contpte_try_unfold);

	pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
	{
	/*
	* Gather access/dirty bits, which may be populated in any of the ptes
	* of the contig range. We are guaranteed to be holding the PTL, so any
	* contiguous range cannot be unfolded or otherwise modified under our
	* feet.
	*/

	pte_t pte;
	int i;

	ptep = contpte_align_down(ptep);

	for (i = 0; i < CONT_PTES; i++, ptep++) {
	pte = __ptep_get(ptep);

	if (pte_dirty(pte))
	orig_pte = pte_mkdirty(orig_pte);

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

	return orig_pte;
	}
	EXPORT_SYMBOL_GPL(contpte_ptep_get);

	pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
	{
	/*
	* The ptep_get_lockless() API requires us to read and return *orig_ptep
	* so that it is self-consistent, without the PTL held, so we may be
	* racing with other threads modifying the pte. Usually a READ_ONCE()
	* would suffice, but for the contpte case, we also need to gather the
	* access and dirty bits from across all ptes in the contiguous block,
	* and we can't read all of those neighbouring ptes atomically, so any
	* contiguous range may be unfolded/modified/refolded under our feet.
	* Therefore we ensure we read a _consistent_ contpte range by checking
	* that all ptes in the range are valid and have CONT_PTE set, that all
	* pfns are contiguous and that all pgprots are the same (ignoring
	* access/dirty). If we find a pte that is not consistent, then we must
	* be racing with an update so start again. If the target pte does not
	* have CONT_PTE set then that is considered consistent on its own
	* because it is not part of a contpte range.
	*/

	pgprot_t orig_prot;
	unsigned long pfn;
	pte_t orig_pte;
	pgprot_t prot;
	pte_t *ptep;
	pte_t pte;
	int i;

	retry:
	orig_pte = __ptep_get(orig_ptep);

	if (!pte_valid_cont(orig_pte))
	return orig_pte;

	orig_prot = pte_pgprot(pte_mkold(pte_mkclean(orig_pte)));
	ptep = contpte_align_down(orig_ptep);
	pfn = pte_pfn(orig_pte) - (orig_ptep - ptep);

	for (i = 0; i < CONT_PTES; i++, ptep++, pfn++) {
	pte = __ptep_get(ptep);
	prot = pte_pgprot(pte_mkold(pte_mkclean(pte)));

	if (!pte_valid_cont(pte) \|\|
	pte_pfn(pte) != pfn \|\|
	pgprot_val(prot) != pgprot_val(orig_prot))
	goto retry;

	if (pte_dirty(pte))
	orig_pte = pte_mkdirty(orig_pte);

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

	return orig_pte;
	}
	EXPORT_SYMBOL_GPL(contpte_ptep_get_lockless);

	void contpte_set_ptes(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, pte_t pte, unsigned int nr)
	{
	unsigned long next;
	unsigned long end;
	unsigned long pfn;
	pgprot_t prot;

	/*
	* The set_ptes() spec guarantees that when nr > 1, the initial state of
	* all ptes is not-present. Therefore we never need to unfold or
	* otherwise invalidate a range before we set the new ptes.
	* contpte_set_ptes() should never be called for nr < 2.
	*/
	VM_WARN_ON(nr == 1);

	if (!mm_is_user(mm))
	return __set_ptes(mm, addr, ptep, pte, nr);

	end = addr + (nr << PAGE_SHIFT);
	pfn = pte_pfn(pte);
	prot = pte_pgprot(pte);

	do {
	next = pte_cont_addr_end(addr, end);
	nr = (next - addr) >> PAGE_SHIFT;
	pte = pfn_pte(pfn, prot);

	if (((addr \| next \| (pfn << PAGE_SHIFT)) & ~CONT_PTE_MASK) == 0)
	pte = pte_mkcont(pte);
	else
	pte = pte_mknoncont(pte);

	__set_ptes(mm, addr, ptep, pte, nr);

	addr = next;
	ptep += nr;
	pfn += nr;

	} while (addr != end);
	}
	EXPORT_SYMBOL_GPL(contpte_set_ptes);

	void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, unsigned int nr, int full)
	{
	contpte_try_unfold_partial(mm, addr, ptep, nr);
	__clear_full_ptes(mm, addr, ptep, nr, full);
	}
	EXPORT_SYMBOL_GPL(contpte_clear_full_ptes);

	pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm,
	unsigned long addr, pte_t *ptep,
	unsigned int nr, int full)
	{
	contpte_try_unfold_partial(mm, addr, ptep, nr);
	return __get_and_clear_full_ptes(mm, addr, ptep, nr, full);
	}
	EXPORT_SYMBOL_GPL(contpte_get_and_clear_full_ptes);

	int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma,
	unsigned long addr, pte_t *ptep)
	{
	/*
	* ptep_clear_flush_young() technically requires us to clear the access
	* flag for a _single_ pte. However, the core-mm code actually tracks
	* access/dirty per folio, not per page. And since we only create a
	* contig range when the range is covered by a single folio, we can get
	* away with clearing young for the whole contig range here, so we avoid
	* having to unfold.
	*/

	int young = 0;
	int i;

	ptep = contpte_align_down(ptep);
	addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);

	for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE)
	young \|= __ptep_test_and_clear_young(vma, addr, ptep);

	return young;
	}
	EXPORT_SYMBOL_GPL(contpte_ptep_test_and_clear_young);

	int contpte_ptep_clear_flush_young(struct vm_area_struct *vma,
	unsigned long addr, pte_t *ptep)
	{
	int young;

	young = contpte_ptep_test_and_clear_young(vma, addr, ptep);

	if (young) {
	/*
	* See comment in __ptep_clear_flush_young(); same rationale for
	* eliding the trailing DSB applies here.
	*/
	addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
	__flush_tlb_range_nosync(vma, addr, addr + CONT_PTE_SIZE,
	PAGE_SIZE, true, 3);
	}

	return young;
	}
	EXPORT_SYMBOL_GPL(contpte_ptep_clear_flush_young);

	void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, unsigned int nr)
	{
	/*
	* If wrprotecting an entire contig range, we can avoid unfolding. Just
	* set wrprotect and wait for the later mmu_gather flush to invalidate
	* the tlb. Until the flush, the page may or may not be wrprotected.
	* After the flush, it is guaranteed wrprotected. If it's a partial
	* range though, we must unfold, because we can't have a case where
	* CONT_PTE is set but wrprotect applies to a subset of the PTEs; this
	* would cause it to continue to be unpredictable after the flush.
	*/

	contpte_try_unfold_partial(mm, addr, ptep, nr);
	__wrprotect_ptes(mm, addr, ptep, nr);
	}
	EXPORT_SYMBOL_GPL(contpte_wrprotect_ptes);

	void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
	unsigned long addr, pte_t *ptep,
	unsigned int nr, cydp_t flags)
	{
	/*
	* We can safely clear access/dirty without needing to unfold from
	* the architectures perspective, even when contpte is set. If the
	* range starts or ends midway through a contpte block, we can just
	* expand to include the full contpte block. While this is not
	* exactly what the core-mm asked for, it tracks access/dirty per
	* folio, not per page. And since we only create a contpte block
	* when it is covered by a single folio, we can get away with
	* clearing access/dirty for the whole block.
	*/
	unsigned long start = addr;
	unsigned long end = start + nr * PAGE_SIZE;

	if (pte_cont(__ptep_get(ptep + nr - 1)))
	end = ALIGN(end, CONT_PTE_SIZE);

	if (pte_cont(__ptep_get(ptep))) {
	start = ALIGN_DOWN(start, CONT_PTE_SIZE);
	ptep = contpte_align_down(ptep);
	}

	__clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, flags);
	}
	EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);

	int contpte_ptep_set_access_flags(struct vm_area_struct *vma,
	unsigned long addr, pte_t *ptep,
	pte_t entry, int dirty)
	{
	unsigned long start_addr;
	pte_t orig_pte;
	int i;

	/*
	* Gather the access/dirty bits for the contiguous range. If nothing has
	* changed, its a noop.
	*/
	orig_pte = pte_mknoncont(ptep_get(ptep));
	if (pte_val(orig_pte) == pte_val(entry))
	return 0;

	/*
	* We can fix up access/dirty bits without having to unfold the contig
	* range. But if the write bit is changing, we must unfold.
	*/
	if (pte_write(orig_pte) == pte_write(entry)) {
	/*
	* For HW access management, we technically only need to update
	* the flag on a single pte in the range. But for SW access
	* management, we need to update all the ptes to prevent extra
	* faults. Avoid per-page tlb flush in __ptep_set_access_flags()
	* and instead flush the whole range at the end.
	*/
	ptep = contpte_align_down(ptep);
	start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);

	/*
	* We are not advancing entry because __ptep_set_access_flags()
	* only consumes access flags from entry. And since we have checked
	* for the whole contpte block and returned early, pte_same()
	* within __ptep_set_access_flags() is likely false.
	*/
	for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE)
	__ptep_set_access_flags(vma, addr, ptep, entry, 0);

	if (dirty)
	__flush_tlb_range(vma, start_addr, addr,
	PAGE_SIZE, true, 3);
	} else {
	__contpte_try_unfold(vma->vm_mm, addr, ptep, orig_pte);
	__ptep_set_access_flags(vma, addr, ptep, entry, dirty);
	}

	return 1;
	}
	EXPORT_SYMBOL_GPL(contpte_ptep_set_access_flags);