diff -r a8dcfc92f53c linux-2.6-xen-sparse/arch/ia64/kernel/iosapic.c
--- a/linux-2.6-xen-sparse/arch/ia64/kernel/iosapic.c	Mon Dec 04 15:40:32 2006 +0900
+++ b/linux-2.6-xen-sparse/arch/ia64/kernel/iosapic.c	Mon Dec 04 15:41:29 2006 +0900
@@ -197,6 +197,17 @@ int xen_assign_irq_vector(int irq)
 
 	return irq_op.vector;
 }
+
+void xen_free_irq_vector(int vector)
+{
+	struct physdev_irq irq_op;
+
+	irq_op.vector = vector;
+	if (HYPERVISOR_physdev_op(PHYSDEVOP_free_irq_vector, &irq_op))
+		printk(KERN_WARNING "%s: xen_free_irq_vecotr fail vector=%d\n", __FUNCTION__, vector);
+
+	return;
+}
 #endif /* XEN */
 
 /*
diff -r a8dcfc92f53c linux-2.6-xen-sparse/arch/ia64/kernel/irq_ia64.c
--- a/linux-2.6-xen-sparse/arch/ia64/kernel/irq_ia64.c	Mon Dec 04 15:40:32 2006 +0900
+++ b/linux-2.6-xen-sparse/arch/ia64/kernel/irq_ia64.c	Mon Dec 04 15:41:29 2006 +0900
@@ -94,6 +94,13 @@ free_irq_vector (int vector)
 	if (vector < IA64_FIRST_DEVICE_VECTOR || vector > IA64_LAST_DEVICE_VECTOR)
 		return;
 
+#ifdef CONFIG_XEN
+	if (is_running_on_xen()) {
+		extern void xen_free_irq_vector(int);
+		xen_free_irq_vector(vector);
+		return;
+	}
+#endif
 	pos = vector - IA64_FIRST_DEVICE_VECTOR;
 	if (!test_and_clear_bit(pos, ia64_vector_mask))
 		printk(KERN_WARNING "%s: double free!\n", __FUNCTION__);
diff -r a8dcfc92f53c xen/arch/ia64/xen/hypercall.c
--- a/xen/arch/ia64/xen/hypercall.c	Mon Dec 04 15:40:32 2006 +0900
+++ b/xen/arch/ia64/xen/hypercall.c	Mon Dec 04 15:41:29 2006 +0900
@@ -372,6 +372,7 @@ static long do_physdev_op(int cmd, XEN_G
 static long do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
 {
     int irq;
+    int vector;
     long ret;
 
     switch ( cmd )
@@ -454,6 +455,27 @@ static long do_physdev_op(int cmd, XEN_G
         break;
     }
 
+    case PHYSDEVOP_free_irq_vector: {
+        struct physdev_irq irq_op;
+
+        ret = -EFAULT;
+        if ( copy_from_guest(&irq_op, arg, 1) != 0 )
+            break;
+
+        ret = -EPERM;
+        if ( !IS_PRIV(current->domain) )
+            break;
+
+        ret = -EINVAL;
+        vector = irq_op.vector;
+        if (vector < IA64_FIRST_DEVICE_VECTOR || vector > IA64_LAST_DEVICE_VECTOR)
+            break;
+        
+        free_irq_vector(vector);
+	ret = 0;
+        break;
+    }
+
     default:
         ret = -ENOSYS;
         break;
diff -r a8dcfc92f53c xen/include/public/physdev.h
--- a/xen/include/public/physdev.h	Mon Dec 04 15:40:32 2006 +0900
+++ b/xen/include/public/physdev.h	Mon Dec 04 15:41:29 2006 +0900
@@ -152,6 +152,7 @@ DEFINE_XEN_GUEST_HANDLE(physdev_op_t);
 #define PHYSDEVOP_APIC_READ              PHYSDEVOP_apic_read
 #define PHYSDEVOP_APIC_WRITE             PHYSDEVOP_apic_write
 #define PHYSDEVOP_ASSIGN_VECTOR          PHYSDEVOP_alloc_irq_vector
+#define PHYSDEVOP_FREE_VECTOR            PHYSDEVOP_free_irq_vector
 #define PHYSDEVOP_IRQ_NEEDS_UNMASK_NOTIFY XENIRQSTAT_needs_eoi
 #define PHYSDEVOP_IRQ_SHARED             XENIRQSTAT_shared