diff -r 253cc5185fb5 -r 281e5488ee97 xen/arch/x86/domctl.c
--- a/xen/arch/x86/domctl.c	Wed Jan 05 18:49:34 2011 -0800
+++ b/xen/arch/x86/domctl.c	Wed Jan 05 18:50:54 2011 -0800
@@ -1566,6 +1566,26 @@ long arch_do_domctl(
     break;
 #endif /* __x86_64__ */
 
+    case XEN_DOMCTL_set_access_required:
+    {
+        struct domain *d;
+        struct p2m_domain* p2m;
+        
+        ret = -EPERM;
+        if ( current->domain->domain_id == domctl->domain )
+            break;
+
+        ret = -ESRCH;
+        d = rcu_lock_domain_by_id(domctl->domain);
+        if ( d != NULL )
+        {
+            p2m = p2m_get_hostp2m(d);
+            p2m->access_required = domctl->u.access_required.access_required;
+            rcu_unlock_domain(d);
+        } 
+    }
+    break;
+
     default:
         ret = -ENOSYS;
         break;
diff -r 253cc5185fb5 -r 281e5488ee97 xen/include/public/domctl.h
--- a/xen/include/public/domctl.h	Wed Jan 05 18:49:34 2011 -0800
+++ b/xen/include/public/domctl.h	Wed Jan 05 18:50:54 2011 -0800
@@ -820,6 +820,16 @@ typedef struct xen_domctl_vcpuextstate x
 DEFINE_XEN_GUEST_HANDLE(xen_domctl_vcpuextstate_t);
 #endif
 
+/* XEN_DOMCTL_set_access_required: sets whether a memory event listener
+ * must be present to handle page access events: if false, the page
+ * access will revert to full permissions if no one is listening;
+ *  */
+struct xen_domctl_set_access_required {
+    uint8_t access_required;
+};
+typedef struct xen_domctl_set_access_required xen_domctl_set_access_required_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_set_access_required_t);
+
 struct xen_domctl {
     uint32_t cmd;
 #define XEN_DOMCTL_createdomain                   1
@@ -882,6 +892,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_getpageframeinfo3             61
 #define XEN_DOMCTL_setvcpuextstate               62
 #define XEN_DOMCTL_getvcpuextstate               63
+#define XEN_DOMCTL_set_access_required           64
 #define XEN_DOMCTL_gdbsx_guestmemio            1000
 #define XEN_DOMCTL_gdbsx_pausevcpu             1001
 #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
@@ -934,6 +945,7 @@ struct xen_domctl {
         struct xen_domctl_cpuid             cpuid;
         struct xen_domctl_vcpuextstate      vcpuextstate;
 #endif
+        struct xen_domctl_set_access_required access_required;
         struct xen_domctl_gdbsx_memio       gdbsx_guest_memio;
         struct xen_domctl_gdbsx_pauseunp_vcpu gdbsx_pauseunp_vcpu;
         struct xen_domctl_gdbsx_domstatus   gdbsx_domstatus;