[PATCH] s390: additional_cpus parameter

[~andy/linux] / Documentation / cpu-hotplug.txt

diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index 08c5d04f308600fca7688eeb0ae51cda9e1d3006..4d3355da0e268c5d1cdd93921301272b25e4a920 100644 (file)
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -11,6 +11,8 @@
                        Joel Schopp <jschopp@austin.ibm.com>
                ia64/x86_64:
                        Ashok Raj <ashok.raj@intel.com>
+               s390:
+                       Heiko Carstens <heiko.carstens@de.ibm.com>
 
 Authors: Ashok Raj <ashok.raj@intel.com>
 Lots of feedback: Nathan Lynch <nathanl@austin.ibm.com>,
@@ -44,9 +46,17 @@ 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 only] use this to limit hotpluggable cpus.
-                        This option sets
-                       cpu_possible_map = cpu_present_map + additional_cpus
+additional_cpus=n      [x86_64, s390 only] use this to limit hotpluggable cpus.
+                          This option sets
+                       cpu_possible_map = cpu_present_map + additional_cpus
+
+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 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.
+
 
 CPU maps and such
 -----------------