[PATCH] x86_64: CPU hotplug support

  Experimental CPU hotplug patch for x86_64
  -----------------------------------------
This supports logical CPU online and offline.
- Test with maxcpus=1, and then kick other cpu's off to test if init code
  is all cleaned up. CONFIG_SCHED_SMT works as well.
- idle threads are forked on demand from keventd threads for clean startup

TBD:
1. Not tested on a real NUMA machine (tested with numa=fake=2)
2. Handle ACPI pieces for physical hotplug support.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Acked-by: Andi Kleen <ak@muc.de>
Acked-by: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: Shaohua.li<shaohua.li@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index db259757dc8a..92f5a5266023 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -313,6 +313,15 @@ config NR_CPUS
           This is purely to save memory - each supported CPU requires
           memory in the static kernel configuration.
 
+config HOTPLUG_CPU
+        bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"
+        depends on SMP && HOTPLUG && EXPERIMENTAL
+        help
+                Say Y here to experiment with turning CPUs off and on.  CPUs
+                can be controlled through /sys/devices/system/cpu/cpu#.
+                Say N if you want to disable CPU hotplug.
+
+
 config HPET_TIMER
         bool
         default y