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    Subject[PATCH v2 18/24] hugetlb/userfaultfd: Handle UFFDIO_WRITEPROTECT
    Date
    This starts from passing cp_flags into hugetlb_change_protection() so hugetlb
    will be able to handle MM_CP_UFFD_WP[_RESOLVE] requests.

    huge_pte_clear_uffd_wp() is introduced to handle the case where the
    UFFDIO_WRITEPROTECT is requested upon migrating huge page entries.

    Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
    Signed-off-by: Peter Xu <peterx@redhat.com>
    ---
    include/asm-generic/hugetlb.h | 5 +++++
    include/linux/hugetlb.h | 6 ++++--
    mm/hugetlb.c | 13 ++++++++++++-
    mm/mprotect.c | 3 ++-
    mm/userfaultfd.c | 8 ++++++++
    5 files changed, 31 insertions(+), 4 deletions(-)

    diff --git a/include/asm-generic/hugetlb.h b/include/asm-generic/hugetlb.h
    index 548212eccbd61..181cdc3297e7b 100644
    --- a/include/asm-generic/hugetlb.h
    +++ b/include/asm-generic/hugetlb.h
    @@ -32,6 +32,11 @@ static inline pte_t huge_pte_mkuffd_wp(pte_t pte)
    return pte_mkuffd_wp(pte);
    }

    +static inline pte_t huge_pte_clear_uffd_wp(pte_t pte)
    +{
    + return pte_clear_uffd_wp(pte);
    +}
    +
    static inline pte_t huge_pte_modify(pte_t pte, pgprot_t newprot)
    {
    return pte_modify(pte, newprot);
    diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
    index e38077918330f..652660fd6ec8a 100644
    --- a/include/linux/hugetlb.h
    +++ b/include/linux/hugetlb.h
    @@ -187,7 +187,8 @@ struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address,
    int pmd_huge(pmd_t pmd);
    int pud_huge(pud_t pud);
    unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
    - unsigned long address, unsigned long end, pgprot_t newprot);
    + unsigned long address, unsigned long end, pgprot_t newprot,
    + unsigned long cp_flags);

    bool is_hugetlb_entry_migration(pte_t pte);
    void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
    @@ -349,7 +350,8 @@ static inline void move_hugetlb_state(struct page *oldpage,

    static inline unsigned long hugetlb_change_protection(
    struct vm_area_struct *vma, unsigned long address,
    - unsigned long end, pgprot_t newprot)
    + unsigned long end, pgprot_t newprot,
    + unsigned long cp_flags)
    {
    return 0;
    }
    diff --git a/mm/hugetlb.c b/mm/hugetlb.c
    index 20ee8fdf6507d..3cad5d7726614 100644
    --- a/mm/hugetlb.c
    +++ b/mm/hugetlb.c
    @@ -5222,7 +5222,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
    }

    unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
    - unsigned long address, unsigned long end, pgprot_t newprot)
    + unsigned long address, unsigned long end,
    + pgprot_t newprot, unsigned long cp_flags)
    {
    struct mm_struct *mm = vma->vm_mm;
    unsigned long start = address;
    @@ -5232,6 +5233,8 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
    unsigned long pages = 0;
    bool shared_pmd = false;
    struct mmu_notifier_range range;
    + bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
    + bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;

    /*
    * In the case of shared PMDs, the area to flush could be beyond
    @@ -5272,6 +5275,10 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,

    make_migration_entry_read(&entry);
    newpte = swp_entry_to_pte(entry);
    + if (uffd_wp)
    + newpte = pte_swp_mkuffd_wp(newpte);
    + else if (uffd_wp_resolve)
    + newpte = pte_swp_clear_uffd_wp(newpte);
    set_huge_swap_pte_at(mm, address, ptep,
    newpte, huge_page_size(h));
    pages++;
    @@ -5285,6 +5292,10 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
    old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
    pte = pte_mkhuge(huge_pte_modify(old_pte, newprot));
    pte = arch_make_huge_pte(pte, vma, NULL, 0);
    + if (uffd_wp)
    + pte = huge_pte_mkuffd_wp(huge_pte_wrprotect(pte));
    + else if (uffd_wp_resolve)
    + pte = huge_pte_clear_uffd_wp(pte);
    huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
    pages++;
    }
    diff --git a/mm/mprotect.c b/mm/mprotect.c
    index 51c954afa4069..fe5a5b96a61f9 100644
    --- a/mm/mprotect.c
    +++ b/mm/mprotect.c
    @@ -416,7 +416,8 @@ unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
    BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);

    if (is_vm_hugetlb_page(vma))
    - pages = hugetlb_change_protection(vma, start, end, newprot);
    + pages = hugetlb_change_protection(vma, start, end, newprot,
    + cp_flags);
    else
    pages = change_protection_range(vma, start, end, newprot,
    cp_flags);
    diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
    index 4f716838f1fdb..ceb77ea24497e 100644
    --- a/mm/userfaultfd.c
    +++ b/mm/userfaultfd.c
    @@ -653,6 +653,7 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
    unsigned long len, bool enable_wp, bool *mmap_changing)
    {
    struct vm_area_struct *dst_vma;
    + unsigned long page_mask;
    pgprot_t newprot;
    int err;

    @@ -689,6 +690,13 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
    if (!vma_is_anonymous(dst_vma))
    goto out_unlock;

    + if (is_vm_hugetlb_page(dst_vma)) {
    + err = -EINVAL;
    + page_mask = vma_kernel_pagesize(dst_vma) - 1;
    + if ((start & page_mask) || (len & page_mask))
    + goto out_unlock;
    + }
    +
    if (enable_wp)
    newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
    else
    --
    2.26.2
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