diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 8ca2032..161f089 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -50,7 +50,7 @@
 #include "hw/i386/ich9.h"
 #include "hw/pci/pci_bus.h"
 #include "hw/pci-host/q35.h"
-#include "hw/i386/intel_iommu.h"
+#include "hw/i386/x86-iommu.h"
 #include "hw/timer/hpet.h"
 
 #include "hw/acpi/aml-build.h"
@@ -2500,12 +2500,7 @@ static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg)
 
 static bool acpi_has_iommu(void)
 {
-    bool ambiguous;
-    Object *intel_iommu;
-
-    intel_iommu = object_resolve_path_type("", TYPE_INTEL_IOMMU_DEVICE,
-                                           &ambiguous);
-    return intel_iommu && !ambiguous;
+    return !!x86_iommu_get_default();
 }
 
 static
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 2734f6b..1936c41 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -26,6 +26,8 @@
 #include "hw/pci/pci.h"
 #include "hw/pci/pci_bus.h"
 #include "hw/i386/pc.h"
+#include "hw/boards.h"
+#include "hw/i386/x86-iommu.h"
 
 /*#define DEBUG_INTEL_IOMMU*/
 #ifdef DEBUG_INTEL_IOMMU
@@ -192,7 +194,7 @@ static void vtd_reset_context_cache(IntelIOMMUState *s)
 
     VTD_DPRINTF(CACHE, "global context_cache_gen=1");
     while (g_hash_table_iter_next (&bus_it, NULL, (void**)&vtd_bus)) {
-        for (devfn_it = 0; devfn_it < VTD_PCI_DEVFN_MAX; ++devfn_it) {
+        for (devfn_it = 0; devfn_it < X86_IOMMU_PCI_DEVFN_MAX; ++devfn_it) {
             vtd_as = vtd_bus->dev_as[devfn_it];
             if (!vtd_as) {
                 continue;
@@ -964,7 +966,7 @@ static void vtd_context_device_invalidate(IntelIOMMUState *s,
     vtd_bus = vtd_find_as_from_bus_num(s, VTD_SID_TO_BUS(source_id));
     if (vtd_bus) {
         devfn = VTD_SID_TO_DEVFN(source_id);
-        for (devfn_it = 0; devfn_it < VTD_PCI_DEVFN_MAX; ++devfn_it) {
+        for (devfn_it = 0; devfn_it < X86_IOMMU_PCI_DEVFN_MAX; ++devfn_it) {
             vtd_as = vtd_bus->dev_as[devfn_it];
             if (vtd_as && ((devfn_it & mask) == (devfn & mask))) {
                 VTD_DPRINTF(INV, "invalidate context-cahce of devfn 0x%"PRIx16,
@@ -1906,7 +1908,8 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, int devfn)
 
     if (!vtd_bus) {
         /* No corresponding free() */
-        vtd_bus = g_malloc0(sizeof(VTDBus) + sizeof(VTDAddressSpace *) * VTD_PCI_DEVFN_MAX);
+        vtd_bus = g_malloc0(sizeof(VTDBus) + sizeof(VTDAddressSpace *) * \
+                            X86_IOMMU_PCI_DEVFN_MAX);
         vtd_bus->bus = bus;
         key = (uintptr_t)bus;
         g_hash_table_insert(s->vtd_as_by_busptr, &key, vtd_bus);
diff --git a/hw/i386/x86-iommu.c b/hw/i386/x86-iommu.c
index d739afb..f395139 100644
--- a/hw/i386/x86-iommu.c
+++ b/hw/i386/x86-iommu.c
@@ -21,6 +21,28 @@
 #include "hw/sysbus.h"
 #include "hw/boards.h"
 #include "hw/i386/x86-iommu.h"
+#include "qemu/error-report.h"
+
+/* Default X86 IOMMU device */
+static X86IOMMUState *x86_iommu_default = NULL;
+
+static void x86_iommu_set_default(X86IOMMUState *x86_iommu)
+{
+    assert(x86_iommu);
+
+    if (x86_iommu_default) {
+        error_report("QEMU does not support multiple vIOMMUs "
+                     "for x86 yet.");
+        exit(1);
+    }
+
+    x86_iommu_default = x86_iommu;
+}
+
+X86IOMMUState *x86_iommu_get_default(void)
+{
+    return x86_iommu_default;
+}
 
 static void x86_iommu_realize(DeviceState *dev, Error **errp)
 {
@@ -28,6 +50,7 @@ static void x86_iommu_realize(DeviceState *dev, Error **errp)
     if (x86_class->realize) {
         x86_class->realize(dev, errp);
     }
+    x86_iommu_set_default(X86_IOMMU_DEVICE(dev));
 }
 
 static void x86_iommu_class_init(ObjectClass *klass, void *data)
diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index 680a0c4..0794309 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -35,7 +35,6 @@
 #define VTD_PCI_BUS_MAX             256
 #define VTD_PCI_SLOT_MAX            32
 #define VTD_PCI_FUNC_MAX            8
-#define VTD_PCI_DEVFN_MAX           256
 #define VTD_PCI_SLOT(devfn)         (((devfn) >> 3) & 0x1f)
 #define VTD_PCI_FUNC(devfn)         ((devfn) & 0x07)
 #define VTD_SID_TO_BUS(sid)         (((sid) >> 8) & 0xff)
diff --git a/include/hw/i386/x86-iommu.h b/include/hw/i386/x86-iommu.h
index 924f39a..d6991cb 100644
--- a/include/hw/i386/x86-iommu.h
+++ b/include/hw/i386/x86-iommu.h
@@ -30,6 +30,9 @@
 #define  X86_IOMMU_GET_CLASS(obj) \
     OBJECT_GET_CLASS(X86IOMMUClass, obj, TYPE_X86_IOMMU_DEVICE)
 
+#define X86_IOMMU_PCI_DEVFN_MAX           256
+#define X86_IOMMU_SID_INVALID             (0xffff)
+
 typedef struct X86IOMMUState X86IOMMUState;
 typedef struct X86IOMMUClass X86IOMMUClass;
 
@@ -43,4 +46,10 @@ struct X86IOMMUState {
     SysBusDevice busdev;
 };
 
+/**
+ * x86_iommu_get_default - get default IOMMU device
+ * @return: pointer to default IOMMU device
+ */
+X86IOMMUState *x86_iommu_get_default(void);
+
 #endif
