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    Subject[PATCHv4 04/12] arm64: Provide pmdp_establish() helper
    Date
    From: Catalin Marinas <catalin.marinas@arm.com>

    We need an atomic way to setup pmd page table entry, avoiding races with
    CPU setting dirty/accessed bits. This is required to implement
    pmdp_invalidate() that doesn't lose these bits.

    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    arch/arm64/include/asm/pgtable.h | 7 +++++++
    1 file changed, 7 insertions(+)

    diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
    index 149d05fb9421..116d610a2620 100644
    --- a/arch/arm64/include/asm/pgtable.h
    +++ b/arch/arm64/include/asm/pgtable.h
    @@ -676,6 +676,13 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
    {
    ptep_set_wrprotect(mm, address, (pte_t *)pmdp);
    }
    +
    +#define pmdp_establish pmdp_establish
    +static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
    + unsigned long address, pmd_t *pmdp, pmd_t pmd)
    +{
    + return __pmd(xchg_relaxed(&pmd_val(*pmdp), pmd_val(pmd)));
    +}
    #endif

    extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
    --
    2.15.0
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