simultaneous runs: could not set gem5 ports explicitly

README.adoc

@@ -1194,8 +1194,18 @@ Like <<cpu-architecture>>, you will need to pass the `-n` option to anything tha
 
 Implementation note: we create multiple namespaces for two things:
 
-* ports: gem5 automatically increments ports until it finds a free one, but QEMU does not, and just crashes
 * run output directory
+* ports
+** QEMU allows setting all ports explicitly.
++
+If a port is not free, it just crashes.
++
+We assign a contiguous port range for each run ID.
+** gem5 automatically increments ports until it finds a free one.
++
+gem5 60600f09c25255b3c8f72da7fb49100e2682093a does not seem to expose a way to set the terminal and VNC ports from `fs.py`, so we just let gem5 assign the ports itself, and use `-n` only to match what it assigned. Those ports both appear on `config.ini`.
++
+The GDB port can be assigned on `gem5.opt --remote-gdb-port`, but it does not appear on `config.ini`.
 
 [[gdb]]
 == GDB step debug