diff --git a/hw/i386/kvm/ioapic.c b/hw/i386/kvm/ioapic.c
index 772a712..36f7de2 100644
--- a/hw/i386/kvm/ioapic.c
+++ b/hw/i386/kvm/ioapic.c
@@ -15,6 +15,8 @@
 #include "hw/i386/apic_internal.h"
 #include "sysemu/kvm.h"
 
+#define TYPE_KVM_IOAPIC "kvm-ioapic"
+
 /* PC Utility function */
 void kvm_pc_setup_irq_routing(bool pci_enabled)
 {
@@ -127,12 +129,12 @@ static void kvm_ioapic_set_irq(void *opaque, int irq, int level)
     apic_report_irq_delivered(delivered);
 }
 
-static void kvm_ioapic_init(IOAPICCommonState *s, int instance_no)
+static void kvm_ioapic_realize(DeviceState *dev, Error **errp)
 {
-    DeviceState *dev = DEVICE(s);
-
-    memory_region_init_reservation(&s->io_memory, NULL, "kvm-ioapic", 0x1000);
+    IOAPICCommonState *s = IOAPIC_COMMON(dev);
 
+    memory_region_init_reservation(&s->io_memory, NULL,
+                                   TYPE_KVM_IOAPIC, 0x1000);
     qdev_init_gpio_in(dev, kvm_ioapic_set_irq, IOAPIC_NUM_PINS);
 }
 
@@ -143,10 +145,11 @@ static Property kvm_ioapic_properties[] = {
 
 static void kvm_ioapic_class_init(ObjectClass *klass, void *data)
 {
+
     IOAPICCommonClass *k = IOAPIC_COMMON_CLASS(klass);
     DeviceClass *dc = DEVICE_CLASS(klass);
 
-    k->init      = kvm_ioapic_init;
+    k->realize   = kvm_ioapic_realize;
     k->pre_save  = kvm_ioapic_get;
     k->post_load = kvm_ioapic_put;
     dc->reset    = kvm_ioapic_reset;
@@ -154,7 +157,7 @@ static void kvm_ioapic_class_init(ObjectClass *klass, void *data)
 }
 
 static const TypeInfo kvm_ioapic_info = {
-    .name  = "kvm-ioapic",
+    .name  = TYPE_KVM_IOAPIC,
     .parent = TYPE_IOAPIC_COMMON,
     .instance_size = sizeof(KVMIOAPICState),
     .class_init = kvm_ioapic_class_init,
diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index 8842845..885f385 100644
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -36,6 +36,10 @@
 
 static IOAPICCommonState *ioapics[MAX_IOAPICS];
 
+#define TYPE_IOAPIC "ioapic"
+/* global variable from ioapic_common.c */
+extern int ioapic_no;
+
 static void ioapic_service(IOAPICCommonState *s)
 {
     uint8_t i;
@@ -225,16 +229,19 @@ static const MemoryRegionOps ioapic_io_ops = {
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
-static void ioapic_init(IOAPICCommonState *s, int instance_no)
+static void ioapic_realize(DeviceState *dev, Error **errp)
 {
-    DeviceState *dev = DEVICE(s);
+    IOAPICCommonState *s = IOAPIC_COMMON(dev);
 
     memory_region_init_io(&s->io_memory, OBJECT(s), &ioapic_io_ops, s,
-                          "ioapic", 0x1000);
+                          TYPE_IOAPIC, 0x1000);
 
     qdev_init_gpio_in(dev, ioapic_set_irq, IOAPIC_NUM_PINS);
 
-    ioapics[instance_no] = s;
+    ioapics[ioapic_no] = s;
+
+    /* increase the counter */
+    ioapic_no++;
 }
 
 static void ioapic_class_init(ObjectClass *klass, void *data)
@@ -242,12 +249,12 @@ static void ioapic_class_init(ObjectClass *klass, void *data)
     IOAPICCommonClass *k = IOAPIC_COMMON_CLASS(klass);
     DeviceClass *dc = DEVICE_CLASS(klass);
 
-    k->init = ioapic_init;
+    k->realize = ioapic_realize;
     dc->reset = ioapic_reset_common;
 }
 
 static const TypeInfo ioapic_info = {
-    .name          = "ioapic",
+    .name          = TYPE_IOAPIC,
     .parent        = TYPE_IOAPIC_COMMON,
     .instance_size = sizeof(IOAPICCommonState),
     .class_init    = ioapic_class_init,
diff --git a/hw/intc/ioapic_common.c b/hw/intc/ioapic_common.c
index e55c6d1..aac0402 100644
--- a/hw/intc/ioapic_common.c
+++ b/hw/intc/ioapic_common.c
@@ -23,6 +23,14 @@
 #include "hw/i386/ioapic_internal.h"
 #include "hw/sysbus.h"
 
+/* ioapic_no count start from 0 to MAX_IOAPICS,
+ * remove as static variable from ioapic_common_init.
+ * now as a global variable, let child to increase the counter
+ * then we can drop the 'instance_no' argument
+ * and convert to our QOM's realize function
+ */
+int ioapic_no;
+
 void ioapic_reset_common(DeviceState *dev)
 {
     IOAPICCommonState *s = IOAPIC_COMMON(dev);
@@ -61,7 +69,6 @@ static void ioapic_common_realize(DeviceState *dev, Error **errp)
 {
     IOAPICCommonState *s = IOAPIC_COMMON(dev);
     IOAPICCommonClass *info;
-    static int ioapic_no;
 
     if (ioapic_no >= MAX_IOAPICS) {
         error_setg(errp, "Only %d ioapics allowed", MAX_IOAPICS);
@@ -69,10 +76,10 @@ static void ioapic_common_realize(DeviceState *dev, Error **errp)
     }
 
     info = IOAPIC_COMMON_GET_CLASS(s);
-    info->init(s, ioapic_no);
+    info->realize(dev, errp);
 
     sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->io_memory);
-    ioapic_no++;
+
 }
 
 static const VMStateDescription vmstate_ioapic_common = {
diff --git a/include/hw/i386/ioapic_internal.h b/include/hw/i386/ioapic_internal.h
index 25576c8..cbe4744 100644
--- a/include/hw/i386/ioapic_internal.h
+++ b/include/hw/i386/ioapic_internal.h
@@ -83,7 +83,8 @@ typedef struct IOAPICCommonState IOAPICCommonState;
 
 typedef struct IOAPICCommonClass {
     SysBusDeviceClass parent_class;
-    void (*init)(IOAPICCommonState *s, int instance_no);
+    /* QOM realize */
+    DeviceRealize realize;
     void (*pre_save)(IOAPICCommonState *s);
     void (*post_load)(IOAPICCommonState *s);
 } IOAPICCommonClass;
