Messages in this thread |  | | From | Michael Ellerman <> | Subject | Re: [PATCH v17 01/23] mm: Add generic p?d_leaf() macros | Date | Sat, 21 Dec 2019 21:35:58 +1100 |
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Steven Price <steven.price@arm.com> writes: > On 19/12/2019 11:43, Michael Ellerman wrote: >> 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? > > No strong reason - but these have to be #defines in the arch overrides > so the #ifndef works, so I was being consistent here.
We handle that usually just with eg:
static inline bool pgd_leaf(pgd_t pgd) { ... } #define pgd_leaf pgd_leaf
> I guess a static inline might avoid warnings although I haven't seen > any.
If anything I'd expect it to cause warnings, for example if someone is doing pgd_leaf(pmd), but that would be good to catch.
cheers
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