diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index b000017..3989fa5 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -624,11 +624,32 @@ static int __assign_irq_vector(int irq, 
 	if (irq_vector[irq] > 0)
 		old_vector = irq_vector[irq];
 	if (old_vector > 0) {
+		cpumask_t domain, new_mask, old_mask;
+		int new_cpu, old_cpu;
 		cpus_and(*result, irq_domain[irq], mask);
 		if (!cpus_empty(*result))
 			return old_vector;
+
+		/* try to reuse vector for phys flat */
+		domain = vector_allocation_domain(cpu);
+		cpus_and(new_mask, domain, cpu_online_map);
+		for_each_cpu_mask(new_cpu, new_mask)
+			if (per_cpu(vector_irq, new_cpu)[old_vector] != -1)
+				goto new_vector;
+		/* We can reuse it */	
+		cpus_and(old_mask, irq_domain[irq], cpu_online_map);
+		for_each_cpu_mask(old_cpu, old_mask);
+			per_cpu(vector_irq, old_cpu)[old_vector] = -1;
+		for_each_cpu_mask(new_cpu, new_mask)
+			per_cpu(vector_irq, new_cpu)[old_vector] = irq;
+		irq_domain[irq] = domain;
+		cpus_and(*result, domain, mask);
+		return old_vector;
+		
 	}
 
+new_vector:
+
 	for_each_cpu_mask(cpu, mask) {
 		cpumask_t domain;
 		int first, new_cpu;