xen/acpi: ACPI cpu hotplug

This patch implement real Xen ACPI cpu hotplug driver as module.
When loaded, it replaces Xen stub driver.

For booting existed cpus, the driver enumerates them.
For hotadded cpus, which added at runtime and notify OS via
device or container event, the driver is invoked to add them,
parsing cpu information, hypercalling to Xen hypervisor to add
them, and finally setting up new /sys interface for them.

Signed-off-by: Liu Jinsong <jinsong.liu@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/Kconfig

@@ -202,6 +202,18 @@ config XEN_ACPI_HOTPLUG_MEMORY
 	  to hot-add memory at runtime (the hot-added memory cannot be
 	  removed until machine stop), select Y/M here, otherwise select N.
 
+config XEN_ACPI_HOTPLUG_CPU
+	tristate "Xen ACPI cpu hotplug"
+	depends on XEN_DOM0 && XEN_STUB && ACPI
+	select ACPI_CONTAINER
+	default n
+	help
+	  Xen ACPI cpu enumerating and hotplugging
+
+	  For hotplugging, currently Xen only support ACPI cpu hotadd.
+	  If you want to hotadd cpu at runtime (the hotadded cpu cannot
+	  be removed until machine stop), select Y/M here.
+
 config XEN_ACPI_PROCESSOR
 	tristate "Xen ACPI processor"
 	depends on XEN && X86 && ACPI_PROCESSOR && CPU_FREQ