| Message ID | 1431551151-19124-8-git-send-email-toshi.kani@hp.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
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
On Fri, 2015-05-22 at 09:35 +0200, Thomas Gleixner wrote: > 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? Sounds good. I will update as suggested. > > * Note we do not support _PAGE_CACHE_MODE_UC here. > > This can be removed as it is completely redundant. Will remove this sentence. > > */ > > > > -#define _PGMT_DEFAULT 0 > > +#define _PGMT_WB 0 /* default */ > > We just established two lines above that this is the default Will remove this comment as well. > > #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 */ I was trying to preserve the original name of "_PGMT_DEFAULT" with the comment because _PGMT_WB takes the place of _PGMT_DEFAULT with this change. But I agree that this may be redundant. I will remove this comment as well. > Aside of the, please do not use tail comments. They make code harder > to parse. Got it. > > /* > > * 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. I will change it to "Setting a new memory type is only allowed to a page mapped with the default WB type." > > @@ -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. Will do. Thanks, -Toshi
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index aee5cdf..ed191e0 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -69,18 +69,18 @@ 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). + * 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. * Note we do not support _PAGE_CACHE_MODE_UC here. */ -#define _PGMT_DEFAULT 0 +#define _PGMT_WB 0 /* 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 */ break; } @@ -365,8 +366,9 @@ static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end) /* * 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. * Here we do two pass: * - Find the memtype of all the pages in the range, look for any conflicts * - In case of no conflicts, set the new memtype for pages in the range @@ -378,8 +380,7 @@ static int reserve_ram_pages_type(u64 start, u64 end, struct page *page; u64 pfn; - if ((req_type == _PAGE_CACHE_MODE_WT) || - (req_type == _PAGE_CACHE_MODE_WP)) { + if (req_type == _PAGE_CACHE_MODE_WP) { if (new_type) *new_type = _PAGE_CACHE_MODE_UC_MINUS; return -EINVAL; @@ -396,7 +397,7 @@ static int reserve_ram_pages_type(u64 start, u64 end, page = pfn_to_page(pfn); type = get_page_memtype(page); - if (type != -1) { + if (type != _PAGE_CACHE_MODE_WB) { pr_info("reserve_ram_pages_type failed [mem %#010Lx-%#010Lx], track 0x%x, req 0x%x\n", start, end - 1, type, req_type); if (new_type) @@ -423,7 +424,7 @@ static int free_ram_pages_type(u64 start, u64 end) for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) { page = pfn_to_page(pfn); - set_page_memtype(page, -1); + set_page_memtype(page, _PAGE_CACHE_MODE_WB); } return 0; } @@ -568,7 +569,7 @@ int free_memtype(u64 start, u64 end) * Only to be called when PAT is enabled * * Returns _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC, _PAGE_CACHE_MODE_UC_MINUS - * or _PAGE_CACHE_MODE_UC + * or _PAGE_CACHE_MODE_WT. */ static enum page_cache_mode lookup_memtype(u64 paddr) { @@ -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); - /* - * -1 from get_page_memtype() implies RAM page is in its - * default state and not reserved, and hence of type WB - */ - if (rettype == -1) - rettype = _PAGE_CACHE_MODE_WB; - return rettype; }
As set_memory_wb() calls free_ram_pages_type(), which then calls set_page_memtype() with -1, _PGMT_DEFAULT is used for tracking the WB type. _PGMT_WB is defined but unused. Hence, this patch renames _PGMT_DEFAULT to _PGMT_WB to clarify the usage, and releases the slot used by _PGMT_WB before. free_ram_pages_type() is changed to call set_page_memtype() with _PGMT_WB, and get_page_memtype() returns _PAGE_CACHE_MODE_WB for _PGMT_WB. This patch then defines _PGMT_WT to the released slot. This enables set_page_memtype() to track the WT type. Signed-off-by: Toshi Kani <toshi.kani@hp.com> --- arch/x86/mm/pat.c | 48 +++++++++++++++++++++--------------------------- 1 file changed, 21 insertions(+), 27 deletions(-)