x86: shrink pat_x_mtrr_type to its essentials

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Suresh B Siddha <suresh.b.siddha@intel.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 19 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index ac3a2b11eb38..227df3ca9bfd 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -161,29 +161,21 @@ static DEFINE_SPINLOCK(memtype_lock); 	/* protects memtype list */
  */
 static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
 {
-        u8 mtrr_type;
-
-        /*
-         * We return the PAT request directly for types where PAT takes
-         * precedence with respect to MTRR and for UC_MINUS.
-         * Consistency checks with other PAT requests is done later
-         * while going through memtype list.
-         */
-        if (req_type == _PAGE_CACHE_WC ||
-            req_type == _PAGE_CACHE_UC_MINUS ||
-            req_type == _PAGE_CACHE_UC)
-                return req_type;
-
         /*
          * Look for MTRR hint to get the effective type in case where PAT
          * request is for WB.
          */
-        mtrr_type = mtrr_type_lookup(start, end);
-        if (mtrr_type == MTRR_TYPE_UNCACHABLE)
-                return _PAGE_CACHE_UC;
-        if (mtrr_type == MTRR_TYPE_WRCOMB)
-                return _PAGE_CACHE_WC;
-        return _PAGE_CACHE_WB;
+        if (req_type == _PAGE_CACHE_WB) {
+                u8 mtrr_type;
+
+                mtrr_type = mtrr_type_lookup(start, end);
+                if (mtrr_type == MTRR_TYPE_UNCACHABLE)
+                        return _PAGE_CACHE_UC;
+                if (mtrr_type == MTRR_TYPE_WRCOMB)
+                        return _PAGE_CACHE_WC;
+        }
+
+        return req_type;
 }
 
 /*