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    Subject[RFC PATCH 11/26] hugetlb: add hugetlb_walk_to to do PT walks
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    This adds it for architectures that use GENERAL_HUGETLB, including x86.

    Signed-off-by: James Houghton <jthoughton@google.com>
    ---
    include/linux/hugetlb.h | 2 ++
    mm/hugetlb.c | 45 +++++++++++++++++++++++++++++++++++++++++
    2 files changed, 47 insertions(+)

    diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
    index e7a6b944d0cc..605aa19d8572 100644
    --- a/include/linux/hugetlb.h
    +++ b/include/linux/hugetlb.h
    @@ -258,6 +258,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
    unsigned long addr, unsigned long sz);
    pte_t *huge_pte_offset(struct mm_struct *mm,
    unsigned long addr, unsigned long sz);
    +int hugetlb_walk_to(struct mm_struct *mm, struct hugetlb_pte *hpte,
    + unsigned long addr, unsigned long sz, bool stop_at_none);
    int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
    unsigned long *addr, pte_t *ptep);
    void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
    diff --git a/mm/hugetlb.c b/mm/hugetlb.c
    index 557b0afdb503..3ec2a921ee6f 100644
    --- a/mm/hugetlb.c
    +++ b/mm/hugetlb.c
    @@ -6981,6 +6981,51 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
    return (pte_t *)pmd;
    }

    +int hugetlb_walk_to(struct mm_struct *mm, struct hugetlb_pte *hpte,
    + unsigned long addr, unsigned long sz, bool stop_at_none)
    +{
    + pte_t *ptep;
    +
    + if (!hpte->ptep) {
    + pgd_t *pgd = pgd_offset(mm, addr);
    +
    + if (!pgd)
    + return -ENOMEM;
    + ptep = (pte_t *)p4d_alloc(mm, pgd, addr);
    + if (!ptep)
    + return -ENOMEM;
    + hugetlb_pte_populate(hpte, ptep, P4D_SHIFT);
    + }
    +
    + while (hugetlb_pte_size(hpte) > sz &&
    + !hugetlb_pte_present_leaf(hpte) &&
    + !(stop_at_none && hugetlb_pte_none(hpte))) {
    + if (hpte->shift == PMD_SHIFT) {
    + ptep = pte_alloc_map(mm, (pmd_t *)hpte->ptep, addr);
    + if (!ptep)
    + return -ENOMEM;
    + hpte->shift = PAGE_SHIFT;
    + hpte->ptep = ptep;
    + } else if (hpte->shift == PUD_SHIFT) {
    + ptep = (pte_t *)pmd_alloc(mm, (pud_t *)hpte->ptep,
    + addr);
    + if (!ptep)
    + return -ENOMEM;
    + hpte->shift = PMD_SHIFT;
    + hpte->ptep = ptep;
    + } else if (hpte->shift == P4D_SHIFT) {
    + ptep = (pte_t *)pud_alloc(mm, (p4d_t *)hpte->ptep,
    + addr);
    + if (!ptep)
    + return -ENOMEM;
    + hpte->shift = PUD_SHIFT;
    + hpte->ptep = ptep;
    + } else
    + BUG();
    + }
    + return 0;
    +}
    +
    #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */

    #ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
    --
    2.37.0.rc0.161.g10f37bed90-goog
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