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SubjectRe: [PATCH v17 01/23] mm: Add generic p?d_leaf() macros
Date
Steven Price <steven.price@arm.com> writes:
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
>
> For architectures that don't provide all p?d_leaf() macros, provide
> generic do nothing default that are suitable where there cannot be leaf
> pages at that level. Futher patches will add implementations for
> individual architectures.
>
> The name p?d_leaf() is chosen to minimize the confusion with existing
> uses of "large" pages and "huge" pages which do not necessary mean that
> the entry is a leaf (for example it may be a set of contiguous entries
> that only take 1 TLB slot). For the purpose of walking the page tables
> we don't need to know how it will be represented in the TLB, but we do
> need to know for sure if it is a leaf of the tree.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
> ---
> include/asm-generic/pgtable.h | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 798ea36a0549..e2e2bef07dd2 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -1238,4 +1238,24 @@ static inline bool arch_has_pfn_modify_check(void)
> #define mm_pmd_folded(mm) __is_defined(__PAGETABLE_PMD_FOLDED)
> #endif
>
> +/*
> + * p?d_leaf() - true if this entry is a final mapping to a physical address.
> + * This differs from p?d_huge() by the fact that they are always available (if
> + * the architecture supports large pages at the appropriate level) even
> + * if CONFIG_HUGETLB_PAGE is not defined.
> + * Only meaningful when called on a valid entry.
> + */
> +#ifndef pgd_leaf
> +#define pgd_leaf(x) 0
> +#endif
> +#ifndef p4d_leaf
> +#define p4d_leaf(x) 0
> +#endif
> +#ifndef pud_leaf
> +#define pud_leaf(x) 0
> +#endif
> +#ifndef pmd_leaf
> +#define pmd_leaf(x) 0
> +#endif

Any reason you made these #defines rather than static inlines?

cheers

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