If specified, z/VM IUCV HVC accepts connections
from listed z/VM user IDs only.
+ hwthread_map= [METAG] Comma-separated list of Linux cpu id to
+ hardware thread id mappings.
+ Format: <cpu>:<hwthread>
+
keep_bootcon [KNL]
Do not unregister boot console at start. This is only
useful for debugging when something happens in the window