Re: [PATCH 01/19] mm: Introduce ARCH_SUPPORTS_HUGE_PFNMAP and special bits to pmd/pud

David Hildenbrand
2024-08-09T16:34:30Z

On 09.08.24 18:08, Peter Xu wrote:
> This patch introduces the option to introduce special pte bit into
> pmd/puds. Archs can start to define pmd_special / pud_special when
> supported by selecting the new option. Per-arch support will be added
> later.
>
> Before that, create fallbacks for these helpers so that they are always
> available.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> include/linux/mm.h | 24 ++++++++++++++++++++++++
> mm/Kconfig | 13 +++++++++++++
> 2 files changed, 37 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 43b40334e9b2..90ca84200800 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2644,6 +2644,30 @@ static inline pte_t pte_mkspecial(pte_t pte)
> }
> #endif
>
> +#ifndef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
> +static inline bool pmd_special(pmd_t pmd)
> +{
> + return false;
> +}
> +
> +static inline pmd_t pmd_mkspecial(pmd_t pmd)
> +{
> + return pmd;
> +}
> +#endif /* CONFIG_ARCH_SUPPORTS_PMD_PFNMAP */
> +
> +#ifndef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
> +static inline bool pud_special(pud_t pud)
> +{
> + return false;
> +}
> +
> +static inline pud_t pud_mkspecial(pud_t pud)
> +{
> + return pud;
> +}
> +#endif /* CONFIG_ARCH_SUPPORTS_PUD_PFNMAP */
> +
> #ifndef CONFIG_ARCH_HAS_PTE_DEVMAP
> static inline int pte_devmap(pte_t pte)
> {
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3936fe4d26d9..3db0eebb53e2 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -881,6 +881,19 @@ endif # TRANSPARENT_HUGEPAGE
> config PGTABLE_HAS_HUGE_LEAVES
> def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE
>
> +# TODO: Allow to be enabled without THP
> +config ARCH_SUPPORTS_HUGE_PFNMAP
> + def_bool n
> + depends on TRANSPARENT_HUGEPAGE
> +
> +config ARCH_SUPPORTS_PMD_PFNMAP
> + def_bool y
> + depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE
> +
> +config ARCH_SUPPORTS_PUD_PFNMAP
> + def_bool y
> + depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
> +
> #
> # UP and nommu archs use km based percpu allocator
> #

As noted in reply to other patches, I think you have to take care of
vm_normal_page_pmd() [if not done in another patch I am missing] and
likely you want to introduce vm_normal_page_pud().

--
Cheers,

David / dhildenb