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>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 7dcd94c29044..6968d4f6be3e 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/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__
 
 /*