Messages in this thread Patch in this message | | | Date | Fri, 22 May 2015 09:35:59 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v9 7/10] x86, mm, asm: Add WT support to set_page_memtype() |
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On Wed, 13 May 2015, Toshi Kani wrote: > + * X86 PAT uses page flags arch_1 and uncached together to keep track of > + * memory type of pages that have backing page struct. X86 PAT supports 4 > + * different memory types, _PAGE_CACHE_MODE_WT, _PAGE_CACHE_MODE_WC, > + * _PAGE_CACHE_MODE_UC_MINUS and _PAGE_CACHE_MODE_WB where page's memory > + * type has not been changed from its default.
This is a horrible sentence.
* X86 PAT supports 4 different memory types: * - _PAGE_CACHE_MODE_WB * - _PAGE_CACHE_MODE_WC * - _PAGE_CACHE_MODE_UC_MINUS * - _PAGE_CACHE_MODE_WT * * _PAGE_CACHE_MODE_WB is the default type. */ Hmm?
> * Note we do not support _PAGE_CACHE_MODE_UC here.
This can be removed as it is completely redundant.
> */ > > -#define _PGMT_DEFAULT 0 > +#define _PGMT_WB 0 /* default */
We just established two lines above that this is the default
> #define _PGMT_WC (1UL << PG_arch_1) > #define _PGMT_UC_MINUS (1UL << PG_uncached) > -#define _PGMT_WB (1UL << PG_uncached | 1UL << PG_arch_1) > +#define _PGMT_WT (1UL << PG_uncached | 1UL << PG_arch_1) > #define _PGMT_MASK (1UL << PG_uncached | 1UL << PG_arch_1) > #define _PGMT_CLEAR_MASK (~_PGMT_MASK) > > @@ -88,14 +88,14 @@ static inline enum page_cache_mode get_page_memtype(struct page *pg) > { > unsigned long pg_flags = pg->flags & _PGMT_MASK; > > - if (pg_flags == _PGMT_DEFAULT) > - return -1; > + if (pg_flags == _PGMT_WB) > + return _PAGE_CACHE_MODE_WB; > else if (pg_flags == _PGMT_WC) > return _PAGE_CACHE_MODE_WC; > else if (pg_flags == _PGMT_UC_MINUS) > return _PAGE_CACHE_MODE_UC_MINUS; > else > - return _PAGE_CACHE_MODE_WB; > + return _PAGE_CACHE_MODE_WT; > } > > static inline void set_page_memtype(struct page *pg, > @@ -112,11 +112,12 @@ static inline void set_page_memtype(struct page *pg, > case _PAGE_CACHE_MODE_UC_MINUS: > memtype_flags = _PGMT_UC_MINUS; > break; > - case _PAGE_CACHE_MODE_WB: > - memtype_flags = _PGMT_WB; > + case _PAGE_CACHE_MODE_WT: > + memtype_flags = _PGMT_WT; > break; > + case _PAGE_CACHE_MODE_WB: > default: > - memtype_flags = _PGMT_DEFAULT; > + memtype_flags = _PGMT_WB; /* default */
What's the value of that comment?
default: /* default */
Aside of the, please do not use tail comments. They make code harder to parse.
> /* > * For RAM pages, we use page flags to mark the pages with appropriate type. > - * The page flags are limited to three types, WB, WC and UC-. > - * WT and WP requests fail with -EINVAL, and UC gets redirected to UC-. > + * The page flags are limited to four types, WB (default), WC, WT and UC-. > + * WP request fails with -EINVAL, and UC gets redirected to UC-.
> + * A new memtype can only be set to the default memtype WB.
I have no idea what that line means.
> @@ -582,13 +583,6 @@ static enum page_cache_mode lookup_memtype(u64 paddr) > struct page *page; > page = pfn_to_page(paddr >> PAGE_SHIFT); > rettype = get_page_memtype(page);
return get_page_memtype(page);
And while you are at it please add the missing newline between the variable declaration and code.
Thanks,
tglx
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