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>

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 7c21572..ac3a2b1 100644 (file)
--- 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);