FM / parameters

/sys/module/intel_idle/parameters

Name	Size	Mode	Actions
max_cstate	4096	0444	edit dl rm
no_acpi	4096	0444	edit dl rm
preferred_cstates	4096	0444	edit dl rm
states_off	4096	0444	edit dl rm
use_acpi	4096	0444	edit dl rm

Edit: /sys/module/intel_idle/parameters/preferred_cstates (4096B)