diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index 9f401350f502..67f733d6f848 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -370,8 +370,10 @@ A: There is no clear spec defined way from ACPI that can give us that CPUs in MADT as hotpluggable CPUS. In the case there are no disabled CPUS we assume 1/2 the number of CPUs currently present can be hotplugged. - Caveat: Today's ACPI MADT can only provide 256 entries since the apicid field - in MADT is only 8 bits. + Caveat: ACPI MADT can only provide 256 entries in systems with only ACPI 2.0c + or earlier ACPI version supported, because the apicid field in MADT is only + 8 bits. From ACPI 3.0, this limitation was removed since the apicid field + was extended to 32 bits with x2APIC introduced. User Space Notification