diff -r c0bdfda5183d xen/arch/x86/hvm/vpt.c
--- a/xen/arch/x86/hvm/vpt.c	Thu Nov 08 14:50:01 2007 +0000
+++ b/xen/arch/x86/hvm/vpt.c	Fri Nov 09 09:08:59 2007 -0500
@@ -45,6 +45,26 @@ static void pt_unlock(struct periodic_ti
     spin_unlock(&pt->vcpu->arch.hvm_vcpu.tm_lock);
 }
 
+#include <xen/keyhandler.h>
+#define PT_MISSED_OPTION_SYNC 0
+#define PT_MISSED_OPTION_ASYNC 1
+int pt_missed_option = 0;
+static void pt_missed_option_fn(unsigned char key)
+{
+    pt_missed_option = pt_missed_option ^ 1;
+    if(pt_missed_option == PT_MISSED_OPTION_SYNC)
+	printk("pt_missed_option = 0 (SYNC)\n");
+    else
+	printk("pt_missed_option = 1 (ASYNC)\n");
+}
+static int __init pt_missed_option_init(void)
+{
+    register_keyhandler('D', pt_missed_option_fn, "pt_missed_option");
+    return 0;
+}
+
+__initcall(pt_missed_option_init);
+
 static void pt_process_missed_ticks(struct periodic_time *pt)
 {
     s_time_t missed_ticks, now = NOW();
@@ -56,9 +76,20 @@ static void pt_process_missed_ticks(stru
     if ( missed_ticks <= 0 )
         return;
 
-    missed_ticks = missed_ticks / (s_time_t) pt->period + 1;
-    pt->pending_intr_nr += missed_ticks;
-    pt->scheduled += missed_ticks * pt->period;
+    if ( mode_is(pt->vcpu->domain, no_missed_tick_accounting)  && (pt_missed_option == PT_MISSED_OPTION_ASYNC) )
+    {
+        pt->pending_intr_nr = 1;
+        pt->scheduled = now + pt->period;
+    }
+    else
+    {
+        missed_ticks = missed_ticks / (s_time_t) pt->period + 1;
+	if ( !mode_is(pt->vcpu->domain, no_missed_tick_accounting) )
+	    pt->pending_intr_nr += missed_ticks;
+	else
+	    pt->run_timer = 1;
+        pt->scheduled += missed_ticks * pt->period;
+    }
 }
 
 static void pt_freeze_time(struct vcpu *v)
@@ -91,8 +122,10 @@ void pt_save_timer(struct vcpu *v)
 
     spin_lock(&v->arch.hvm_vcpu.tm_lock);
 
-    list_for_each_entry ( pt, head, list )
-        stop_timer(&pt->timer);
+    list_for_each_entry ( pt, head, list ) {
+	if(!pt->run_timer)
+	    stop_timer(&pt->timer);
+    }
 
     pt_freeze_time(v);
 
@@ -123,7 +156,12 @@ static void pt_timer_fn(void *data)
 
     pt_lock(pt);
 
-    pt->pending_intr_nr++;
+    if ( mode_is(pt->vcpu->domain, no_missed_tick_accounting) ) {
+        pt->pending_intr_nr = 1;
+	pt->run_timer = 0;
+    }
+    else
+        pt->pending_intr_nr++;
 
     if ( !pt->one_shot )
     {
@@ -224,16 +262,11 @@ void pt_intr_post(struct vcpu *v, struct
     }
     else
     {
+        pt->pending_intr_nr--;
         if ( mode_is(v->domain, no_missed_tick_accounting) )
-        {
             pt->last_plt_gtime = hvm_get_guest_time(v);
-            pt->pending_intr_nr = 0; /* 'collapse' all missed ticks */
-        }
         else
-        {
             pt->last_plt_gtime += pt->period_cycles;
-            pt->pending_intr_nr--;
-        }
     }
 
     if ( mode_is(v->domain, delay_for_missed_ticks) &&
diff -r c0bdfda5183d xen/include/asm-x86/hvm/vpt.h
--- a/xen/include/asm-x86/hvm/vpt.h	Thu Nov 08 14:50:01 2007 +0000
+++ b/xen/include/asm-x86/hvm/vpt.h	Fri Nov 09 08:53:14 2007 -0500
@@ -84,6 +84,7 @@ struct periodic_time {
     struct timer timer;         /* ac_timer */
     time_cb *cb;
     void *priv;                 /* point back to platform time source */
+    u32 run_timer;
 };