gem5: fix -X-b, fs_bigLITTLE checkpoint restore, checkpoints are just dirs on backend

Author: cirosantilli

README.adoc

@@ -6162,6 +6162,10 @@ Checkpoints are stored inside the `m5out` directory at:
 out/<arch>/gem5/<gem5-variant>/<run-id>/m5out/cpt.<checkpoint-time>
 ....
 
+and TODO confirm the `-r N` tag takes the N-th checkpoint with the longest running time, which is not necessarily the last one that was taken, unless you take the second one on the same simulation as the first one.
+
+This integer value is just pure `fs.py` sugar, the backend at `m5.instantiate` just takes the actual tracepoint directory as input.
+
 [[gem5-restore-new-scrip]]
 ==== gem5 checkpoint restore and run a different script
 
@@ -6545,6 +6549,12 @@ then:
 ./run -aA -g -X-b
 ....
 
+Checkpoints can be restored with:
+
+....
+./run -aA -g -X-b -- --restore-from=out/aarch64/gem5/default/0/m5ou5/cpt.*
+....
+
 Advantages over `fs.py`:
 
 * more representative of mobile ARM SoCs, which almost always have  big little cluster

run

@@ -134,7 +134,7 @@ done
 shift "$(($OPTIND - 1))"
 extra_flags="$extra_flags $@"
 OPTIND=1
-while getopts b OPT "$extra_opts"; do
+while getopts b OPT $extra_opts; do
   case "$OPT" in
     b)
       gem5_fsbiglittle=true