diff -r 6c0a0284d9cb xen/common/timer.c
--- a/xen/common/timer.c	Mon May 19 13:47:12 2014 +0100
+++ b/xen/common/timer.c	Mon May 19 13:49:26 2014 +0100
@@ -493,7 +493,7 @@
     if ( (ts->list != NULL) && (ts->list->expires < deadline) )
         deadline = ts->list->expires;
     this_cpu(timer_deadline) =
-        (deadline == STIME_MAX) ? 0 : deadline + timer_slop;
+        (deadline == STIME_MAX) ? 0 : MAX(deadline, now + timer_slop);
 
     if ( !reprogram_timer(this_cpu(timer_deadline)) )
         raise_softirq(TIMER_SOFTIRQ);