run: add --terminal and explain gem5 pdb

README.adoc

@@ -6982,6 +6982,30 @@ In graphic mode, make sure that you never click inside the QEMU graphic while de
 
 You can still send key presses to QEMU however even without the mouse capture, just either click on the title bar, or alt tab to give it focus.
 
+==== Debug gem5 Python scripts
+
+Start pdb at the first instruction:
+
+....
+./run -g -G='--pdb' --terminal
+....
+
+Requires `--terminal` as we must be on foreground.
+
+Alternatively, you can add to the point of the code where you want to break the usual:
+
+....
+import ipdb; ipdb.set_trace()
+....
+
+and then run with:
+
+....
+./run -g --terminal
+....
+
+TODO test PyCharm: https://stackoverflow.com/questions/51982735/writing-gem5-configuration-scripts-with-pycharm
+
 === Tracing
 
 QEMU can log several different events.