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Date: Tue, 6 Jan 2015 13:49:47 -0700 From: Toshi Kani <toshi.kani@...com> To: hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org, arnd@...db.de Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, jgross@...e.com, stefan.bader@...onical.com, luto@...capital.net, hmh@....eng.br, yigal@...xistor.com, konrad.wilk@...cle.com, Elliott@...com, Toshi Kani <toshi.kani@...com> Subject: [PATCH v7 2/7] x86, mm, pat: Change reserve_memtype() to handle WT This patch changes reserve_memtype() to handle the WT cache mode with PAT. When PAT is not enabled, WB and UC- are the only types supported. When a target range is in RAM, reserve_ram_pages_type() verifies the requested type. In this case, WT and WP requests fail with -EINVAL and UC gets redirected to UC- since set_page_memtype() is limited to handle three types, WB, WC and UC-. Signed-off-by: Toshi Kani <toshi.kani@...com> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> --- arch/x86/mm/pat.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index 3d9da74..99d2eb0 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -360,6 +360,8 @@ 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-. * 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 @@ -371,6 +373,13 @@ 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 (new_type) + *new_type = _PAGE_CACHE_MODE_UC_MINUS; + return -EINVAL; + } + if (req_type == _PAGE_CACHE_MODE_UC) { /* We do not support strong UC */ WARN_ON_ONCE(1); @@ -420,6 +429,7 @@ static int free_ram_pages_type(u64 start, u64 end) * - _PAGE_CACHE_MODE_WC * - _PAGE_CACHE_MODE_UC_MINUS * - _PAGE_CACHE_MODE_UC + * - _PAGE_CACHE_MODE_WT * * If new_type is NULL, function will return an error if it cannot reserve the * region with req_type. If new_type is non-NULL, function will return @@ -437,12 +447,12 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type, BUG_ON(start >= end); /* end is exclusive */ if (!pat_enabled) { - /* This is identical to page table setting without PAT */ + /* WB and UC- are the only types supported without PAT */ if (new_type) { - if (req_type == _PAGE_CACHE_MODE_WC) - *new_type = _PAGE_CACHE_MODE_UC_MINUS; + if (req_type == _PAGE_CACHE_MODE_WB) + *new_type = _PAGE_CACHE_MODE_WB; else - *new_type = req_type; + *new_type = _PAGE_CACHE_MODE_UC_MINUS; } return 0; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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