diff -r c1c549c4fe9e xen/arch/x86/time.c
--- a/xen/arch/x86/time.c	Mon Oct 15 16:51:44 2012 +0100
+++ b/xen/arch/x86/time.c	Wed Oct 17 17:13:22 2012 +0100
@@ -523,11 +523,12 @@ static s_time_t __read_platform_stime(u6
 static void plt_overflow(void *unused)
 {
     int i;
-    u64 count;
+    u64 count, old_stamp, tsc;
     s_time_t now, plt_now, plt_wrap;
 
     spin_lock_irq(&platform_timer_lock);
 
+    old_stamp = plt_stamp;
     count = plt_src.read_counter();
     plt_stamp64 += (count - plt_stamp) & plt_mask;
     plt_stamp = count;
@@ -540,6 +541,14 @@ static void plt_overflow(void *unused)
         plt_wrap = __read_platform_stime(plt_stamp64 + plt_mask + 1);
         if ( ABS(plt_wrap - now) > ABS(plt_now - now) )
             break;
+        rdtscll(tsc);
+        printk("XXX plt_overflow: plt_now=%"PRIx64" plt_wrap=%"PRIx64
+               " now=%"PRIx64" old_stamp=%"PRIx64" new_stamp=%"PRIx64
+               " plt_stamp64=%"PRIx64" plt_mask=%"PRIx64
+               " tsc=%"PRIx64" tsc_stamp=%"PRIx64"\n",
+               plt_now, plt_wrap, now, old_stamp, plt_stamp, plt_stamp64,
+               plt_mask, tsc, this_cpu(cpu_time).local_tsc_stamp);
+        break;
         plt_stamp64 += plt_mask + 1;
     }
     if ( i != 0 )