diff -r 5f3c40a4c214 include/xen/interface/platform.h
--- a/include/xen/interface/platform.h	Thu Sep 18 10:44:15 2008 +0100
+++ b/include/xen/interface/platform.h	Mon Sep 22 12:07:54 2008 +0800
@@ -312,6 +312,17 @@
 typedef struct xenpf_set_processor_pminfo xenpf_set_processor_pminfo_t;
 DEFINE_XEN_GUEST_HANDLE(xenpf_set_processor_pminfo_t);
 
+#define XENPF_cpu_hotplug               55
+struct xenpf_cpu_hotplug {
+    /* IN variables */
+    uint32_t cpu;   /* Physical cpu. */
+#define CPU_HOTPLUG_ONLINE              0
+#define CPU_HOTPLUG_OFFLINE             1
+    uint64_t ops;   /* hotplug opscode */
+};
+typedef struct xenpf_cpu_hotplug xenpf_cpu_hotplug_t;
+DEFINE_XEN_GUEST_HANDLE(xenpf_cpu_hotplug_t);
+
 struct xen_platform_op {
     uint32_t cmd;
     uint32_t interface_version; /* XENPF_INTERFACE_VERSION */
@@ -327,6 +338,7 @@
         struct xenpf_change_freq       change_freq;
         struct xenpf_getidletime       getidletime;
         struct xenpf_set_processor_pminfo set_pminfo;
+        struct xenpf_cpu_hotplug       cpu_hotplug;
         uint8_t                        pad[128];
     } u;
 };