x86: PAT: change pgprot_noncached to uc_minus instead of strong uc - v3

Impact: mm behavior change.

Make pgprot_noncached uc_minus instead of strong UC. This will make
pgprot_noncached to be in line with ioremap_nocache() and all the other
APIs that map page uc_minus on uc request.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/pgtable.h

@@ -158,6 +158,14 @@
 #define PGD_IDENT_ATTR	 0x001		/* PRESENT (no other attributes) */
 #endif
 
+/*
+ * Macro to mark a page protection value as UC-
+ */
+#define pgprot_noncached(prot)					\
+	((boot_cpu_data.x86 > 3)				\
+	 ? (__pgprot(pgprot_val(prot) | _PAGE_CACHE_UC_MINUS))	\
+	 : (prot))
+
 #ifndef __ASSEMBLY__
 
 /*

arch/x86/include/asm/pgtable_32.h

@@ -100,15 +100,6 @@ extern unsigned long pg0[];
 # include <asm/pgtable-2level.h>
 #endif
 
-/*
- * Macro to mark a page protection value as "uncacheable".
- * On processors which do not support it, this is a no-op.
- */
-#define pgprot_noncached(prot)					\
-	((boot_cpu_data.x86 > 3)				\
-	 ? (__pgprot(pgprot_val(prot) | _PAGE_PCD | _PAGE_PWT))	\
-	 : (prot))
-
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.

arch/x86/include/asm/pgtable_64.h

@@ -176,12 +176,6 @@ static inline int pmd_bad(pmd_t pmd)
 
 #define pages_to_mb(x)	((x) >> (20 - PAGE_SHIFT))   /* FIXME: is this right? */
 
-/*
- * Macro to mark a page protection value as "uncacheable".
- */
-#define pgprot_noncached(prot)					\
-	(__pgprot(pgprot_val((prot)) | _PAGE_PCD | _PAGE_PWT))
-
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.