1 files changed, 14 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 03d1251a915e..5190f1706414 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1984,6 +1984,20 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
         nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
 
+        cpu0_hotplug    [X86] Turn on CPU0 hotplug feature when
+                        CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
+                        Some features depend on CPU0. Known dependencies are:
+                        1. Resume from suspend/hibernate depends on CPU0.
+                        Suspend/hibernate will fail if CPU0 is offline and you
+                        need to online CPU0 before suspend/hibernate.
+                        2. PIC interrupts also depend on CPU0. CPU0 can't be
+                        removed if a PIC interrupt is detected.
+                        It's said poweroff/reboot may depend on CPU0 on some
+                        machines although I haven't seen such issues so far
+                        after CPU0 is offline on a few tested machines.
+                        If the dependencies are under your control, you can
+                        turn on cpu0_hotplug.
+
         nptcg=          [IA-64] Override max number of concurrent global TLB
                         purges which is reported from either PAL_VM_SUMMARY or
                         SAL PALO.