x86: irq_move_cleanup_interrupt() must ignore legacy vectors

Since the main loop in the function includes legacy vectors, and since
vector_irq[] gets set up for legacy vectors regardless of whether those
get handled through the IO-APIC, it must not do anything on this vector
range. In fact, we should never get here for IRQs not handled through
the IO-APIC, so add a respective warning at once (could probably as
well be an ASSERT()).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -625,6 +625,12 @@ void irq_move_cleanup_interrupt(struct c
         if ((int)irq < 0)
             continue;
 
+        if ( vector >= FIRST_LEGACY_VECTOR && vector <= LAST_LEGACY_VECTOR )
+        {
+            WARN_ON(!IO_APIC_IRQ(irq));
+            continue;
+        }
+
         desc = irq_to_desc(irq);
         if (!desc)
             continue;