On Thu, Jun 29, 2023 at 01:50:37PM -0700, Axel Rasmussen wrote:
> The behavior here is the same as it is for anon/shmem. This is done
> separately because hugetlb pte marker handling is a bit different.
>
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
> ---
> mm/hugetlb.c | 33 +++++++++++++++++++++++++++++++--
> mm/userfaultfd.c | 6 +-----
> 2 files changed, 32 insertions(+), 7 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 38711d49e4db..05abe88986b6 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6090,14 +6090,24 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> }
>
> entry = huge_ptep_get(ptep);
> - /* PTE markers should be handled the same way as none pte */
> - if (huge_pte_none_mostly(entry))
> + if (huge_pte_none_mostly(entry)) {
> + if (is_pte_marker(entry)) {
> + unsigned long marker = pte_marker_get(pte_to_swp_entry(entry));
> +
> + if (marker & PTE_MARKER_UFFD_POISON) {
> + ret = VM_FAULT_HWPOISON_LARGE;
> + goto out_mutex;
> + }
> + }
> /*
> + * Other PTE markers should be handled the same way as none PTE.
> + *
> * hugetlb_no_page will drop vma lock and hugetlb fault
> * mutex internally, which make us return immediately.
> */
> return hugetlb_no_page(mm, vma, mapping, idx, address, ptep,
> entry, flags);
> + }
>
> ret = 0;
>
> @@ -6253,6 +6263,25 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
> int writable;
> bool folio_in_pagecache = false;
>
> + if (uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) {
> + ptl = huge_pte_lock(h, dst_mm, dst_pte);
> +
> + /* Don't overwrite any existing PTEs (even markers) */
> + if (!huge_pte_none(huge_ptep_get(dst_pte))) {
> + spin_unlock(ptl);
> + return -EEXIST;
> + }
> +
> + _dst_pte = make_pte_marker(PTE_MARKER_UFFD_POISON);
> + set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
> +
> + /* No need to invalidate - it was non-present before */
> + update_mmu_cache(dst_vma, dst_addr, dst_pte);
> +
> + spin_unlock(ptl);
> + return 0;
> + }
> +
> if (is_continue) {
> ret = -EFAULT;
> folio = filemap_lock_folio(mapping, idx);
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index 87b62ca1e09e..4436cae1c7a8 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -381,12 +381,8 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
> * supported by hugetlb. A PMD_SIZE huge pages may exist as used
> * by THP. Since we can not reliably insert a zero page, this
> * feature is not supported.
> - *
> - * PTE marker handling for hugetlb is a bit special, so for now
> - * UFFDIO_POISON is not supported.
> */
> - if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE) ||
> - uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) {
> + if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
> mmap_read_unlock(dst_mm);
> return -EINVAL;
If we have the last patch declaring the feature bits and so on, IIUC we
don'tt need this change back and forth. Other than that looks good.
Thanks,
> }
> --
> 2.41.0.255.g8b1d071c50-goog
>
--
Peter Xu
