diff -r ad9bbd103034 xen/arch/x86/domctl.c
--- a/xen/arch/x86/domctl.c	Fri Feb 09 18:19:24 2007 +0000
+++ b/xen/arch/x86/domctl.c	Wed Feb 14 15:42:34 2007 +0100
@@ -398,6 +398,7 @@ long arch_do_domctl(
 
         put_domain(d);
     }
+    break;
 
     case XEN_DOMCTL_get_address_size:
     {
@@ -407,11 +408,16 @@ long arch_do_domctl(
         if ( (d = get_domain_by_id(domctl->domain)) == NULL )
             break;
 
+	printk("%s: offset %zd\n", __FUNCTION__, offsetof(struct xen_domctl, u.address_size.size));
         domctl->u.address_size.size = BITS_PER_GUEST_LONG(d);
 
         ret = 0;
         put_domain(d);
-    }
+
+        if (copy_to_guest(u_domctl, domctl, 1))
+            ret = -EFAULT;
+    }
+    break;
 
     default:
         ret = -ENOSYS;