OMPI: btl openib: fix detection of max registarable memory

Deal with the case when mlx4 module is loaded but device
is not present

cmr=v1.8.3:reviewer=miked

This commit was SVN r32734.

opal/mca/btl/openib/btl_openib.c

@@ -635,12 +635,17 @@ static uint64_t calculate_max_reg (void)
         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) {
-            /* NTH: is 19 a minimum? when log_num_mtt is set to 0 use 19 */
-            num_mtt = 1 << 20;
+            if (0  == stat("/sys/module/mlx5_core", &statinfo)) {
+                max_reg = 2 * mem_total;
+            } else {
+                /* NTH: is 19 a minimum? when log_num_mtt is set to 0 use 19 */
+                num_mtt = 1 << 19;
+                max_reg = (num_mtt - reserved_mtt) * opal_getpagesize () * mtts_per_seg;
+            }
+        } else  {
+            max_reg = (num_mtt - reserved_mtt) * opal_getpagesize () * mtts_per_seg;
         }
 
-        max_reg = (num_mtt - reserved_mtt) * opal_getpagesize () * mtts_per_seg;
-
     } 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);