[PATCH 05/20] x86/mm/pat: Change reserve_memtype() for Write-Through type

[Borislav Petkov <bp@alien8.de>]

From: Toshi Kani <toshi.kani@hp.com>

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@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: arnd@arndb.de
Cc: Elliott@hp.com
Cc: hch@lst.de
Cc: hmh@hmh.eng.br
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: jgross@suse.com
Cc: konrad.wilk@oracle.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: linux-nvdimm@lists.01.org
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: stefan.bader@canonical.com
Cc: x86-ml <x86@kernel.org>
Cc: yigal@plexistor.com
Link: http://lkml.kernel.org/r/1433187393-22688-3-git-send-email-toshi.kani@hp.com
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 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 59ab1a0fe21b..6311193fd1a2 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
-- 
2.3.5