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Date: Mon, 27 Oct 2014 16:55:40 -0600
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,
Toshi Kani <toshi.kani@...com>
Subject: [PATCH v4 2/7] x86, mm, pat: Change reserve_memtype() to handle WT
This patch changes reserve_memtype() to handle the WT cache mode.
When PAT is not enabled, it continues to set UC- to *new_type for
any non-WB request.
When a target range is RAM, reserve_ram_pages_type() fails for WT
for now. This function may not reserve a RAM range for WT since
reserve_ram_pages_type() uses the page flags limited to three memory
types, WB, WC and UC.
Signed-off-by: Toshi Kani <toshi.kani@...com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
arch/x86/include/asm/cacheflush.h | 4 ++++
arch/x86/mm/pat.c | 16 +++++++++++++---
2 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index 157644b..c912680 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -53,6 +53,10 @@ static inline void set_page_memtype(struct page *pg,
case _PAGE_CACHE_MODE_WB:
memtype_flags = _PGMT_WB;
break;
+ case _PAGE_CACHE_MODE_WT:
+ case _PAGE_CACHE_MODE_WP:
+ pr_err("set_page_memtype: unsupported cachemode %d\n", memtype);
+ BUG();
default:
memtype_flags = _PGMT_DEFAULT;
break;
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index db687c3..a214f5a 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -289,6 +289,8 @@ 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 currently limited to three types, WB, WC and UC. Hence,
+ * any request to WT or WP will fail with -EINVAL.
* 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
@@ -300,6 +302,13 @@ 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);
@@ -349,6 +358,7 @@ 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
@@ -368,10 +378,10 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
if (!pat_enabled) {
/* This is identical to page table setting 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;
}
--
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