diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index c749d00de8..b934fc80c2 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -478,19 +478,22 @@ static const MemoryRegionOps s390_msi_ctrl_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
 
-void s390_pcihost_iommu_configure(S390PCIBusDevice *pbdev, bool enable)
+void s390_pci_iommu_enable(S390PCIBusDevice *pbdev)
 {
     pbdev->configured = false;
+    uint64_t size = pbdev->pal - pbdev->pba + 1;
 
-    if (enable) {
-        uint64_t size = pbdev->pal - pbdev->pba + 1;
-        memory_region_init_iommu(&pbdev->iommu_mr, OBJECT(&pbdev->mr),
-                                 &s390_iommu_ops, "iommu-s390", size);
-        memory_region_add_subregion(&pbdev->mr, pbdev->pba, &pbdev->iommu_mr);
-    } else {
-        memory_region_del_subregion(&pbdev->mr, &pbdev->iommu_mr);
-    }
+    memory_region_init_iommu(&pbdev->iommu_mr, OBJECT(&pbdev->mr),
+                             &s390_iommu_ops, "iommu-s390", size);
+    memory_region_add_subregion(&pbdev->mr, pbdev->pba, &pbdev->iommu_mr);
+    pbdev->configured = true;
+}
 
+void s390_pci_iommu_disable(S390PCIBusDevice *pbdev)
+{
+    pbdev->configured = false;
+    memory_region_del_subregion(&pbdev->mr, &pbdev->iommu_mr);
+    object_unparent(OBJECT(&pbdev->iommu_mr));
     pbdev->configured = true;
 }
 
diff --git a/hw/s390x/s390-pci-bus.h b/hw/s390x/s390-pci-bus.h
index d6e17d2eeb..426f690bba 100644
--- a/hw/s390x/s390-pci-bus.h
+++ b/hw/s390x/s390-pci-bus.h
@@ -249,7 +249,8 @@ int chsc_sei_nt2_get_event(void *res);
 int chsc_sei_nt2_have_event(void);
 void s390_pci_sclp_configure(SCCB *sccb);
 void s390_pci_sclp_deconfigure(SCCB *sccb);
-void s390_pcihost_iommu_configure(S390PCIBusDevice *pbdev, bool enable);
+void s390_pci_iommu_enable(S390PCIBusDevice *pbdev);
+void s390_pci_iommu_disable(S390PCIBusDevice *pbdev);
 S390PCIBusDevice *s390_pci_find_dev_by_idx(uint32_t idx);
 S390PCIBusDevice *s390_pci_find_dev_by_fh(uint32_t fh);
 S390PCIBusDevice *s390_pci_find_dev_by_fid(uint32_t fid);
diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
index 90d9fda77c..eb03f480c4 100644
--- a/hw/s390x/s390-pci-inst.c
+++ b/hw/s390x/s390-pci-inst.c
@@ -705,18 +705,17 @@ static int reg_ioat(CPUS390XState *env, S390PCIBusDevice *pbdev, ZpciFib fib)
     pbdev->pal = pal;
     pbdev->g_iota = g_iota;
 
-    s390_pcihost_iommu_configure(pbdev, true);
+    s390_pci_iommu_enable(pbdev);
 
     return 0;
 }
 
 static void dereg_ioat(S390PCIBusDevice *pbdev)
 {
+    s390_pci_iommu_disable(pbdev);
     pbdev->pba = 0;
     pbdev->pal = 0;
     pbdev->g_iota = 0;
-
-    s390_pcihost_iommu_configure(pbdev, false);
 }
 
 int mpcifc_service_call(S390CPU *cpu, uint8_t r1, uint64_t fiba, uint8_t ar)