Commit f89b399e authored by Ryan Roberts's avatar Ryan Roberts Committed by Will Deacon
Browse files

arm64/mm: Hoist barriers out of set_ptes_anysz() loop 



set_ptes_anysz() previously called __set_pte() for each PTE in the
range, which would conditionally issue a DSB and ISB to make the new PTE
value immediately visible to the table walker if the new PTE was valid
and for kernel space.

We can do better than this; let's hoist those barriers out of the loop
so that they are only issued once at the end of the loop. We then reduce
the cost by the number of PTEs in the range.

Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Tested-by: default avatarLuiz Capitulino <luizcap@redhat.com>
Link: https://lore.kernel.org/r/20250422081822.1836315-7-ryan.roberts@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent a899b7d0

arch/arm64/include/asm/pgtable.h

+11 −5
Original line number Diff line number Diff line
@@ -320,13 +320,11 @@ static inline void __set_pte_nosync(pte_t *ptep, pte_t pte) 
	WRITE_ONCE(*ptep, pte);

}



static inline void __set_pte(pte_t *ptep, pte_t pte)

static inline void __set_pte_complete(pte_t pte)

{

	__set_pte_nosync(ptep, pte);



	/*

	 * Only if the new pte is valid and kernel, otherwise TLB maintenance

	 * or update_mmu_cache() have the necessary barriers.

	 * has the necessary barriers.

	 */

	if (pte_valid_not_user(pte)) {

		dsb(ishst);
@@ -334,6 +332,12 @@ static inline void __set_pte(pte_t *ptep, pte_t pte) 
	}

}



static inline void __set_pte(pte_t *ptep, pte_t pte)

{

	__set_pte_nosync(ptep, pte);

	__set_pte_complete(pte);

}



static inline pte_t __ptep_get(pte_t *ptep)

{

	return READ_ONCE(*ptep);
@@ -658,12 +662,14 @@ static inline void __set_ptes_anysz(struct mm_struct *mm, pte_t *ptep, 


	for (;;) {

		__check_safe_pte_update(mm, ptep, pte);

		__set_pte(ptep, pte);

		__set_pte_nosync(ptep, pte);

		if (--nr == 0)

			break;

		ptep++;

		pte = pte_advance_pfn(pte, stride);

	}



	__set_pte_complete(pte);

}



static inline void __set_ptes(struct mm_struct *mm,