1 files changed, 7 insertions, 2 deletions

diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index e71bc6cbbc5e..57a09f99ecb0 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -46,10 +46,12 @@ maxcpus=n    Restrict boot time cpus to n. Say if you have 4 cpus, using
              maxcpus=2 will only boot 2. You can choose to bring the
              other cpus later online, read FAQ's for more info.
 
-additional_cpus=n       [x86_64, s390 only] use this to limit hotpluggable cpus.
-                          This option sets
+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, s390
+
 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
@@ -57,6 +59,9 @@ apicid values in those tables for disabled apics. In the event BIOS doesnt
 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.
 
+s390 uses the number of cpus it detects at IPL time to also the number of bits
+in cpu_possible_map. If it is desired to add additional cpus at a later time
+the number should be specified using this option or the possible_cpus option.
 
 possible_cpus=n         [s390 only] use this to set hotpluggable cpus.
                         This option sets possible_cpus bits in