more verbose about forgetting ./configure options when making the simgrid version

doc/doxygen/chapters/470_simgrid.doxy

@@ -61,7 +61,8 @@ run several times before the model is calibrated.
 \section Simulation Simulation
 
 Then, recompile StarPU, passing \ref enable-simgrid "--enable-simgrid"
-to <c>./configure</c>.
+to <c>./configure</c>. Make sure to keep all other <c>./configure</c> options
+the same, and notably options such as <c>--enable-maxcudadev</c>.
 
 \verbatim
 $ ./configure --enable-simgrid

src/core/perfmodel/perfmodel_bus.c

@@ -1030,7 +1030,7 @@ static int load_bus_latency_file_content(void)
 			n = _starpu_read_double(f, "%le", &latency);
 			if (n != 1)
 			{
-				_STARPU_DISP("Error while reading latency file <%s>. Expected a number\n", path);
+				_STARPU_DISP("Error while reading latency file <%s>. Expected a number. Did you change the maximum number of GPUs at ./configure time?\n", path);
 				fclose(f);
 				return 0;
 			}
@@ -1069,7 +1069,7 @@ static int load_bus_latency_file_content(void)
 			n = _starpu_read_double(f, "%le", &latency);
 			if (n && !isnan(latency))
 			{
-				_STARPU_DISP("Too many nodes in latency file %s for this configuration (%d)\n", path, STARPU_MAXNODES);
+				_STARPU_DISP("Too many nodes in latency file %s for this configuration (%d). Did you change the maximum number of GPUs at ./configure time?\n", path, STARPU_MAXNODES);
 				fclose(f);
 				return 0;
 			}