diff -r bf74d9c31674 xen/include/asm-x86/guest_pt.h
--- a/xen/include/asm-x86/guest_pt.h	Mon Apr 12 07:23:21 2010 +0100
+++ b/xen/include/asm-x86/guest_pt.h	Mon Apr 12 15:36:41 2010 +0200
@@ -29,6 +29,10 @@
 #ifndef _XEN_ASM_GUEST_PT_H
 #define _XEN_ASM_GUEST_PT_H
 
+#if !defined(GUEST_PAGING_LEVELS)
+#error GUEST_PAGING_LEVELS not defined
+#endif
+
 /* Type of the guest's frame numbers */
 TYPE_SAFE(unsigned long,gfn)
 #define PRI_gfn "05lx"