diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 347580e..3e57d5f 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -151,20 +151,12 @@
     pci_device_reset(pbdev->pdev);
 }
 
-static void s390_pci_reset_cb(void *opaque)
-{
-    S390PCIBusDevice *pbdev = opaque;
-
-    pci_device_reset(pbdev->pdev);
-}
-
 static void s390_pci_perform_unplug(S390PCIBusDevice *pbdev)
 {
     HotplugHandler *hotplug_ctrl;
 
     if (pbdev->pft == ZPCI_PFT_ISM) {
         notifier_remove(&pbdev->shutdown_notifier);
-        qemu_unregister_reset(s390_pci_reset_cb, pbdev);
     }
 
     /* Unplug the PCI device */
@@ -1132,7 +1124,6 @@
             if (pbdev->pft == ZPCI_PFT_ISM) {
                 pbdev->shutdown_notifier.notify = s390_pci_shutdown_notifier;
                 qemu_register_shutdown_notifier(&pbdev->shutdown_notifier);
-                qemu_register_reset(s390_pci_reset_cb, pbdev);
             }
         } else {
             pbdev->fh |= FH_SHM_EMUL;
@@ -1279,6 +1270,23 @@
     pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, s->bus_no, 1);
 }
 
+void s390_pci_ism_reset(void)
+{
+    S390pciState *s = s390_get_phb();
+
+    S390PCIBusDevice *pbdev, *next;
+
+    /* Trigger reset event for each passthrough ISM device currently in-use */
+    QTAILQ_FOREACH_SAFE(pbdev, &s->zpci_devs, link, next) {
+        if (pbdev->interp && pbdev->pft == ZPCI_PFT_ISM &&
+            pbdev->fh & FH_MASK_ENABLE) {
+            s390_pci_kvm_aif_disable(pbdev);
+
+            pci_device_reset(pbdev->pdev);
+        }
+    }
+}
+
 static void s390_pcihost_reset(DeviceState *dev)
 {
     S390pciState *s = S390_PCI_HOST_BRIDGE(dev);
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index eaf61d3..c99682b 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -118,6 +118,14 @@
     DeviceState *dev;
     int i;
 
+    /*
+     * ISM firmware is sensitive to unexpected changes to the IOMMU, which can
+     * occur during reset of the vfio-pci device (unmap of entire aperture).
+     * Ensure any passthrough ISM devices are reset now, while CPUs are paused
+     * but before vfio-pci cleanup occurs.
+     */
+    s390_pci_ism_reset();
+
     for (i = 0; i < ARRAY_SIZE(reset_dev_types); i++) {
         dev = DEVICE(object_resolve_path_type("", reset_dev_types[i], NULL));
         if (dev) {
diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-pci-bus.h
index 435e788..2c43ea1 100644
--- a/include/hw/s390x/s390-pci-bus.h
+++ b/include/hw/s390x/s390-pci-bus.h
@@ -401,5 +401,6 @@
                                               const char *target);
 S390PCIBusDevice *s390_pci_find_next_avail_dev(S390pciState *s,
                                                S390PCIBusDevice *pbdev);
+void s390_pci_ism_reset(void);
 
 #endif