diff options
Diffstat (limited to 'arch/x86/mm/pat.c')
| -rw-r--r-- | arch/x86/mm/pat.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index 4c601276a556..25d2c58489e0 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -67,6 +67,75 @@ __setup("debugpat", pat_debug_setup); static u64 __read_mostly boot_pat_state; +#ifdef CONFIG_X86_PAT +/* + * X86 PAT uses page flags WC and Uncached together to keep track of + * memory type of pages that have backing page struct. X86 PAT supports 3 + * different memory types, _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC and + * _PAGE_CACHE_MODE_UC_MINUS and fourth state where page's memory type has not + * been changed from its default (value of -1 used to denote this). + * Note we do not support _PAGE_CACHE_MODE_UC here. + */ + +#define _PGMT_DEFAULT 0 +#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_MASK (1UL << PG_uncached | 1UL << PG_arch_1) +#define _PGMT_CLEAR_MASK (~_PGMT_MASK) + +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; + 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; +} + +static inline void set_page_memtype(struct page *pg, + enum page_cache_mode memtype) +{ + unsigned long memtype_flags; + unsigned long old_flags; + unsigned long new_flags; + + switch (memtype) { + case _PAGE_CACHE_MODE_WC: + memtype_flags = _PGMT_WC; + break; + case _PAGE_CACHE_MODE_UC_MINUS: + memtype_flags = _PGMT_UC_MINUS; + break; + case _PAGE_CACHE_MODE_WB: + memtype_flags = _PGMT_WB; + break; + default: + memtype_flags = _PGMT_DEFAULT; + break; + } + + do { + old_flags = pg->flags; + new_flags = (old_flags & _PGMT_CLEAR_MASK) | memtype_flags; + } while (cmpxchg(&pg->flags, old_flags, new_flags) != old_flags); +} +#else +static inline enum page_cache_mode get_page_memtype(struct page *pg) +{ + return -1; +} +static inline void set_page_memtype(struct page *pg, + enum page_cache_mode memtype) +{ +} +#endif + enum { PAT_UC = 0, /* uncached */ PAT_WC = 1, /* Write combining */ |