x86: PAT: make pat_x_mtrr_type() more readable

Clean up over-complications in pat_x_mtrr_type().
And if reserve_memtype() ignores stray req_type bits when
pat_enabled, it's better to mask them off when not also.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 12 insertions, 35 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 7c21572bbdda..ac3a2b11eb38 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -159,47 +159,31 @@ static DEFINE_SPINLOCK(memtype_lock); 	/* protects memtype list */
  * The intersection is based on "Effective Memory Type" tables in IA-32
  * SDM vol 3a
  */
-static int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
-                                unsigned long *ret_prot)
+static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
 {
-        unsigned long pat_type;
         u8 mtrr_type;
 
-        pat_type = prot & _PAGE_CACHE_MASK;
-        prot &= (~_PAGE_CACHE_MASK);
-
         /*
          * 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 (pat_type == _PAGE_CACHE_WC) {
-                *ret_prot = prot | _PAGE_CACHE_WC;
-                return 0;
-        } else if (pat_type == _PAGE_CACHE_UC_MINUS) {
-                *ret_prot = prot | _PAGE_CACHE_UC_MINUS;
-                return 0;
-        } else if (pat_type == _PAGE_CACHE_UC) {
-                *ret_prot = prot | _PAGE_CACHE_UC;
-                return 0;
-        }
+        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) {
-                *ret_prot = prot | _PAGE_CACHE_UC;
-        } else if (mtrr_type == MTRR_TYPE_WRCOMB) {
-                *ret_prot = prot | _PAGE_CACHE_WC;
-        } else {
-                *ret_prot = prot | _PAGE_CACHE_WB;
-        }
-
-        return 0;
+        if (mtrr_type == MTRR_TYPE_UNCACHABLE)
+                return _PAGE_CACHE_UC;
+        if (mtrr_type == MTRR_TYPE_WRCOMB)
+                return _PAGE_CACHE_WC;
+        return _PAGE_CACHE_WB;
 }
 
 /*
@@ -232,7 +216,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
                         if (req_type == -1) {
                                 *ret_type = _PAGE_CACHE_WB;
                         } else {
-                                *ret_type = req_type;
+                                *ret_type = req_type & _PAGE_CACHE_MASK;
                         }
                 }
                 return 0;
@@ -264,14 +248,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
                 }
         } else {
                 req_type &= _PAGE_CACHE_MASK;
-                err = pat_x_mtrr_type(start, end, req_type, &actual_type);
-        }
-
-        if (err) {
-                if (ret_type)
-                        *ret_type = actual_type;
-
-                return -EINVAL;
+                actual_type = pat_x_mtrr_type(start, end, req_type);
         }
 
         new_entry  = kmalloc(sizeof(struct memtype), GFP_KERNEL);