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x86, Kconfig: Add config switch for CPU0 hotplug

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New config switch CONFIG_BOOTPARAM_HOTPLUG_CPU0 sets default state of whether
the CPU0 hotplug is on or off.

If the switch is off, CPU0 is not hotpluggable by default. But the CPU0 hotplug
feature can still be turned on by kernel parameter cpu0_hotplug at boot.

If the switch is on, CPU0 is always hotpluggable.

The default value of the switch is off.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1352835171-3958-3-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Fenghua Yu 2012-11-13 11:32:39 -08:00 committed by H. Peter Anvin
parent f78cff48c3
commit 80aa1dff65
1 changed files with 29 additions and 0 deletions
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arch/x86/Kconfig
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@ -1698,6 +1698,35 @@ config HOTPLUG_CPU
automatically on SMP systems. )
Say N if you want to disable CPU hotplug.
config BOOTPARAM_HOTPLUG_CPU0
bool "Set default setting of cpu0_hotpluggable"
default n
depends on HOTPLUG_CPU && EXPERIMENTAL
---help---
Set whether default state of cpu0_hotpluggable is on or off.
Say Y here to enable CPU0 hotplug by default. If this switch
is turned on, there is no need to give cpu0_hotplug kernel
parameter and the CPU0 hotplug feature is enabled by default.
Please note: there are two known CPU0 dependencies if you want
to enable the CPU0 hotplug feature either by this switch or by
cpu0_hotplug kernel parameter.
First, resume from hibernate or suspend always starts from CPU0.
So hibernate and suspend are prevented if CPU0 is offline.
Second dependency is PIC interrupts always go to CPU0. CPU0 can not
offline if any interrupt can not migrate out of CPU0. There may
be other CPU0 dependencies.
Please make sure the dependencies are under your control before
you enable this feature.
Say N if you don't want to enable CPU0 hotplug feature by default.
You still can enable the CPU0 hotplug feature at boot by kernel
parameter cpu0_hotplug.
config COMPAT_VDSO
def_bool y
prompt "Compat VDSO support"