Re: [PATCH v2 16/46] hugetlb: make default arch_make_huge_pte understand small mappings

[Mina Almasry]

On Fri, Feb 17, 2023 at 4:28 PM James Houghton <jthoughton@xxxxxxxxxx> wrote:
>
> This is a simple change: don't create a "huge" PTE if we are making a
> regular, PAGE_SIZE PTE. All architectures that want to implement HGM
> likely need to be changed in a similar way if they implement their own
> version of arch_make_huge_pte.
>
> Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 726d581158b1..b767b6889dea 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -899,7 +899,7 @@ static inline void arch_clear_hugepage_flags(struct page *page) { }
>  static inline pte_t arch_make_huge_pte(pte_t entry, unsigned int shift,
>                                        vm_flags_t flags)
>  {
> -       return pte_mkhuge(entry);
> +       return shift > PAGE_SHIFT ? pte_mkhuge(entry) : entry;
>  }
>  #endif
>

How are contig_pte's handled here? Will shift show that it's actually
a contig_pte and not just PAGE_SHIFT? Or is that arm64 specific so it
exists only in the arm64 version of this function? Do we need to worry
about it here?

> --
> 2.39.2.637.g21b0678d19-goog
>