Commit 0aa3657d authored by Dev Jain's avatar Dev Jain Committed by Andrew Morton
Browse files

mm: add batched versions of ptep_modify_prot_start/commit 

Batch ptep_modify_prot_start/commit in preparation for optimizing
mprotect, implementing them as a simple loop over the corresponding single
pte helpers.  Architecture may override these helpers.

Link: https://lkml.kernel.org/r/20250718090244.21092-4-dev.jain@arm.com


Signed-off-by: default avatarDev Jain <dev.jain@arm.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: default avatarBarry Song <baohua@kernel.org>
Reviewed-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 1d40f4e3

include/linux/pgtable.h

+83 −1
Original line number Diff line number Diff line
@@ -1331,7 +1331,9 @@ static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma, 


/*

 * Commit an update to a pte, leaving any hardware-controlled bits in

 * the PTE unmodified.

 * the PTE unmodified. The pte returned from ptep_modify_prot_start() may

 * additionally have young and/or dirty bits set where previously they were not,

 * so the updated pte may have these additional changes.

 */

static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,

					   unsigned long addr,
@@ -1340,6 +1342,86 @@ static inline void ptep_modify_prot_commit(struct vm_area_struct *vma, 
	__ptep_modify_prot_commit(vma, addr, ptep, pte);

}

#endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */



/**

 * modify_prot_start_ptes - Start a pte protection read-modify-write transaction

 * over a batch of ptes, which protects against asynchronous hardware

 * modifications to the ptes. The intention is not to prevent the hardware from

 * making pte updates, but to prevent any updates it may make from being lost.

 * Please see the comment above ptep_modify_prot_start() for full description.

 *

 * @vma: The virtual memory area the pages are mapped into.

 * @addr: Address the first page is mapped at.

 * @ptep: Page table pointer for the first entry.

 * @nr: Number of entries.

 *

 * May be overridden by the architecture; otherwise, implemented as a simple

 * loop over ptep_modify_prot_start(), collecting the a/d bits from each pte

 * in the batch.

 *

 * Note that PTE bits in the PTE batch besides the PFN can differ.

 *

 * Context: The caller holds the page table lock.  The PTEs map consecutive

 * pages that belong to the same folio. All other PTE bits must be identical for

 * all PTEs in the batch except for young and dirty bits.  The PTEs are all in

 * the same PMD.

 */

#ifndef modify_prot_start_ptes

static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,

		unsigned long addr, pte_t *ptep, unsigned int nr)

{

	pte_t pte, tmp_pte;



	pte = ptep_modify_prot_start(vma, addr, ptep);

	while (--nr) {

		ptep++;

		addr += PAGE_SIZE;

		tmp_pte = ptep_modify_prot_start(vma, addr, ptep);

		if (pte_dirty(tmp_pte))

			pte = pte_mkdirty(pte);

		if (pte_young(tmp_pte))

			pte = pte_mkyoung(pte);

	}

	return pte;

}

#endif



/**

 * modify_prot_commit_ptes - Commit an update to a batch of ptes, leaving any

 * hardware-controlled bits in the PTE unmodified.

 *

 * @vma: The virtual memory area the pages are mapped into.

 * @addr: Address the first page is mapped at.

 * @ptep: Page table pointer for the first entry.

 * @old_pte: Old page table entry (for the first entry) which is now cleared.

 * @pte: New page table entry to be set.

 * @nr: Number of entries.

 *

 * May be overridden by the architecture; otherwise, implemented as a simple

 * loop over ptep_modify_prot_commit().

 *

 * Context: The caller holds the page table lock. The PTEs are all in the same

 * PMD. On exit, the set ptes in the batch map the same folio. The ptes set by

 * ptep_modify_prot_start() may additionally have young and/or dirty bits set

 * where previously they were not, so the updated ptes may have these

 * additional changes.

 */

#ifndef modify_prot_commit_ptes

static inline void modify_prot_commit_ptes(struct vm_area_struct *vma, unsigned long addr,

		pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)

{

	int i;



	for (i = 0; i < nr; ++i, ++ptep, addr += PAGE_SIZE) {

		ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);



		/* Advance PFN only, set same prot */

		old_pte = pte_next_pfn(old_pte);

		pte = pte_next_pfn(pte);

	}

}

#endif



#endif /* CONFIG_MMU */



/*

mm/mprotect.c

+2 −2
Original line number Diff line number Diff line
@@ -204,7 +204,7 @@ static long change_pte_range(struct mmu_gather *tlb, 
				}

			}



			oldpte = ptep_modify_prot_start(vma, addr, pte);

			oldpte = modify_prot_start_ptes(vma, addr, pte, nr_ptes);

			ptent = pte_modify(oldpte, newprot);



			if (uffd_wp)
@@ -230,7 +230,7 @@ static long change_pte_range(struct mmu_gather *tlb, 
			    can_change_pte_writable(vma, addr, ptent))

				ptent = pte_mkwrite(ptent, vma);



			ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);

			modify_prot_commit_ptes(vma, addr, pte, oldpte, ptent, nr_ptes);

			if (pte_needs_flush(oldpte, ptent))

				tlb_flush_pte_range(tlb, addr, PAGE_SIZE);

			pages++;