xen: add support for callbackops hypercall

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/asm-x86/xen/hypercall.h b/include/asm-x86/xen/hypercall.h
index bc0ee7d..c2ccd99 100644
--- a/include/asm-x86/xen/hypercall.h
+++ b/include/asm-x86/xen/hypercall.h
@@ -164,6 +164,12 @@
 }
 
 static inline int
+HYPERVISOR_callback_op(int cmd, void *arg)
+{
+	return _hypercall2(int, callback_op, cmd, arg);
+}
+
+static inline int
 HYPERVISOR_fpu_taskswitch(int set)
 {
 	return _hypercall1(int, fpu_taskswitch, set);