diff -r dedfadeadf86 xen/drivers/passthrough/io.c
--- a/xen/drivers/passthrough/io.c	Fri Jun 20 18:42:45 2008 +0100
+++ b/xen/drivers/passthrough/io.c	Wed Jul 02 18:15:10 2008 +0200
@@ -253,10 +253,12 @@ void hvm_dpci_eoi(struct domain *d, unsi
     {
         spin_unlock(&hvm_irq_dpci->dirq_lock);
 
-        stop_timer(&hvm_irq_dpci->hvm_timer[
-            domain_irq_to_vector(d, machine_gsi)]);
         if ( (ent == NULL) || !ent->fields.mask )
+        {
+            stop_timer(&hvm_irq_dpci->hvm_timer[
+                domain_irq_to_vector(d, machine_gsi)]);
             pirq_guest_eoi(d, machine_gsi);
+        }
     }
     else
         spin_unlock(&hvm_irq_dpci->dirq_lock);