openib/btl: better detect max reg memory. OFED has no runtime versioning API :(

based on http://www.open-mpi.org/community/lists/users/2014/08/25048.php

reviewed by AlexM
cmr=v1.8.2:reviewer=ompi-rm1.8

This commit was SVN r32569.

opal/mca/btl/openib/btl_openib.c

@@ -620,6 +620,7 @@ static uint64_t calculate_total_mem (void)
 #endif
 }
 
+
 static uint64_t calculate_max_reg (void) 
 {
     struct stat statinfo;
@@ -630,11 +631,7 @@ static uint64_t calculate_max_reg (void)
 
     mem_total = calculate_total_mem ();
 
-    if (0 == stat("/sys/module/mlx5_core", &statinfo)) {
-        /* mlx5 means that we have ofed 2.0 and it can always register 2xmem_total for any mlx hca */
-        max_reg = 2 * mem_total;
-    }
-    else if (0 == stat("/sys/module/mlx4_core/parameters", &statinfo)) {
+    if (0 == stat("/sys/module/mlx4_core/parameters/log_num_mtt", &statinfo)) {
         mtts_per_seg = 1 << read_module_param("/sys/module/mlx4_core/parameters/log_mtts_per_seg", 1);
         num_mtt = 1 << read_module_param("/sys/module/mlx4_core/parameters/log_num_mtt", 20);
         if (1 == num_mtt) {
@@ -643,12 +640,22 @@ static uint64_t calculate_max_reg (void)
         }
 
         max_reg = (num_mtt - reserved_mtt) * opal_getpagesize () * mtts_per_seg;
-    } else if (0 == stat("/sys/module/ib_mthca/parameters", &statinfo)) {
+
+    } else if (0 == stat("/sys/module/ib_mthca/parameters/num_mtt", &statinfo)) {
         mtts_per_seg = 1 << read_module_param("/sys/module/ib_mthca/parameters/log_mtts_per_seg", 1);
         num_mtt = read_module_param("/sys/module/ib_mthca/parameters/num_mtt", 1 << 20);
         reserved_mtt = read_module_param("/sys/module/ib_mthca/parameters/fmr_reserved_mtts", 0);
 
         max_reg = (num_mtt - reserved_mtt) * opal_getpagesize () * mtts_per_seg;
+
+    } else if (
+            (0 == stat("/sys/module/mlx5_core", &statinfo)) ||
+            (0 == stat("/sys/module/mlx4_core/parameters", &statinfo)) ||
+            (0 == stat("/sys/module/ib_mthca/parameters", &statinfo))
+            ) {
+        /* mlx5 means that we have ofed 2.0 and it can always register 2xmem_total for any mlx hca */
+        max_reg = 2 * mem_total;
+
     } else {
         /* Need to update to determine the registration limit for this
            configuration */