[PATCH v3 1/6] arm64: make huge_ptep_get handled unaligned addresses

[Andrew Morton]

On Fri,  3 Jul 2026 11:41:54 +0000 Dev Jain <dev.jain at arm.com> wrote:

> huge_ptep_get() can be handed a virtual address pointing to the middle of
> a contpmd/contpte mapped hugetlb folio (examples of callers are
> pagemap_hugetlb_range, page_mapped_in_vma).
> 
> The arm64 helper rewalks the pgtables in find_num_contig to answer whether
> the huge pte we have maps a contpmd or a contpte hugetlb folio, and
> returns CONT_PMDS or CONT_PTES, so that it can collect a/d bits over the
> contiguous ptes. We can falsely return CONT_PTES instead of CONT_PMDS
> if the addr is not aligned.
> 
> Fix this by aligning the pmdp pointer down to a contpmd base before
> checking equality with the passed huge pte pointer, to correctly answer
> whether the huge pte is the base of a contpmd block.
> 
> Fixes: 29cb80519689 ("arm64: hugetlb: Cleanup huge_pte size discovery mechanisms")
> Cc: stable at vger.kernel.org

Please describe the userspace-visible effects of bugs when fixing them.
Particularly when cc:stable is proposed.  Thanks.