linux-kernel - [tip:x86/mm] x86/mm/pat: Change reserve

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Message-ID: <tip-0d69bdff451a10aa48f80509e8bf18fb24683c06@git.kernel.org>
Date:	Sun, 7 Jun 2015 10:40:40 -0700
From:	tip-bot for Toshi Kani <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, akpm@...ux-foundation.org, linux-mm@...ck.org,
	luto@...capital.net, torvalds@...ux-foundation.org,
	toshi.kani@...com, peterz@...radead.org, mingo@...nel.org,
	mcgrof@...e.com, linux-kernel@...r.kernel.org, bp@...e.de,
	tglx@...utronix.de
Subject: [tip:x86/mm] x86/mm/pat: Change reserve_memtype()
  for Write-Through type

Commit-ID:  0d69bdff451a10aa48f80509e8bf18fb24683c06
Gitweb:     http://git.kernel.org/tip/0d69bdff451a10aa48f80509e8bf18fb24683c06
Author:     Toshi Kani <toshi.kani@...com>
AuthorDate: Thu, 4 Jun 2015 18:55:13 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 7 Jun 2015 15:28:55 +0200

x86/mm/pat: Change reserve_memtype() for Write-Through type

When a target range is in RAM, reserve_ram_pages_type() verifies
the requested type. Change it to fail WT and WP requests with
-EINVAL since set_page_memtype() is limited to handle three
types: WB, WC and UC-.

Signed-off-by: Toshi Kani <toshi.kani@...com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Elliott@...com
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: arnd@...db.de
Cc: hch@....de
Cc: hmh@....eng.br
Cc: jgross@...e.com
Cc: konrad.wilk@...cle.com
Cc: linux-mm <linux-mm@...ck.org>
Cc: linux-nvdimm@...ts.01.org
Cc: stefan.bader@...onical.com
Cc: yigal@...xistor.com
Link: http://lkml.kernel.org/r/1433436928-31903-6-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/mm/pat.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 59ab1a0f..6311193 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -401,9 +401,12 @@ 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.
- * 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
+ * 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 passes:
+ * - 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.
  */
 static int reserve_ram_pages_type(u64 start, u64 end,
 				  enum page_cache_mode req_type,
@@ -412,6 +415,13 @@ 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);
@@ -461,6 +471,7 @@ 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
--
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