-additional_cpus=n [x86_64 only] use this to limit hotpluggable cpus.
- This option sets
- cpu_possible_map = cpu_present_map + additional_cpus
+additional_cpus=n (*) Use this to limit hotpluggable cpus. This option sets
+ cpu_possible_map = cpu_present_map + additional_cpus
+
+(*) Option valid only for following architectures
+- x86_64, ia64
+
+ia64 and x86_64 use the number of disabled local apics in ACPI tables MADT
+to determine the number of potentially hot-pluggable cpus. The implementation
+should only rely on this to count the # of cpus, but *MUST* not rely on the
+apicid values in those tables for disabled apics. In the event BIOS doesn't
+mark such hot-pluggable cpus as disabled entries, one could use this
+parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.
+
+possible_cpus=n [s390 only] use this to set hotpluggable cpus.
+ This option sets possible_cpus bits in
+ cpu_possible_map. Thus keeping the numbers of bits set
+ constant even if the machine gets rebooted.