diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
index 402a2d6312..bf1a90f5d7 100644
--- a/backends/tpm/tpm_emulator.c
+++ b/backends/tpm/tpm_emulator.c
@@ -534,11 +534,8 @@ static int tpm_emulator_block_migration(TPMEmulator *tpm_emu)
         error_setg(&tpm_emu->migration_blocker,
                    "Migration disabled: TPM emulator does not support "
                    "migration");
-        if (migrate_add_blocker(tpm_emu->migration_blocker, &err) < 0) {
+        if (migrate_add_blocker(&tpm_emu->migration_blocker, &err) < 0) {
             error_report_err(err);
-            error_free(tpm_emu->migration_blocker);
-            tpm_emu->migration_blocker = NULL;
-
             return -1;
         }
     }
@@ -1016,10 +1013,7 @@ static void tpm_emulator_inst_finalize(Object *obj)
 
     qapi_free_TPMEmulatorOptions(tpm_emu->options);
 
-    if (tpm_emu->migration_blocker) {
-        migrate_del_blocker(tpm_emu->migration_blocker);
-        error_free(tpm_emu->migration_blocker);
-    }
+    migrate_del_blocker(&tpm_emu->migration_blocker);
 
     tpm_sized_buffer_reset(&state_blobs->volatil);
     tpm_sized_buffer_reset(&state_blobs->permanent);
diff --git a/block/parallels.c b/block/parallels.c
index 6b46623241..1d695ce7fb 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -1369,9 +1369,8 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
                bdrv_get_device_or_node_name(bs));
     bdrv_graph_rdunlock_main_loop();
 
-    ret = migrate_add_blocker(s->migration_blocker, errp);
+    ret = migrate_add_blocker(&s->migration_blocker, errp);
     if (ret < 0) {
-        error_setg(errp, "Migration blocker error");
         goto fail;
     }
     qemu_co_mutex_init(&s->lock);
@@ -1406,7 +1405,7 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
         ret = bdrv_check(bs, &res, BDRV_FIX_ERRORS | BDRV_FIX_LEAKS);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Could not repair corrupted image");
-            migrate_del_blocker(s->migration_blocker);
+            migrate_del_blocker(&s->migration_blocker);
             goto fail;
         }
     }
@@ -1423,7 +1422,6 @@ fail:
      */
     parallels_free_used_bitmap(bs);
 
-    error_free(s->migration_blocker);
     g_free(s->bat_dirty_bmap);
     qemu_vfree(s->header);
     return ret;
@@ -1448,8 +1446,7 @@ static void parallels_close(BlockDriverState *bs)
     g_free(s->bat_dirty_bmap);
     qemu_vfree(s->header);
 
-    migrate_del_blocker(s->migration_blocker);
-    error_free(s->migration_blocker);
+    migrate_del_blocker(&s->migration_blocker);
 }
 
 static bool parallels_is_support_dirty_bitmaps(BlockDriverState *bs)
diff --git a/block/qcow.c b/block/qcow.c
index 38a16253b8..fdd4c83948 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -307,9 +307,8 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
                bdrv_get_device_or_node_name(bs));
     bdrv_graph_rdunlock_main_loop();
 
-    ret = migrate_add_blocker(s->migration_blocker, errp);
+    ret = migrate_add_blocker(&s->migration_blocker, errp);
     if (ret < 0) {
-        error_free(s->migration_blocker);
         goto fail;
     }
 
@@ -802,8 +801,7 @@ static void qcow_close(BlockDriverState *bs)
     g_free(s->cluster_cache);
     g_free(s->cluster_data);
 
-    migrate_del_blocker(s->migration_blocker);
-    error_free(s->migration_blocker);
+    migrate_del_blocker(&s->migration_blocker);
 }
 
 static int coroutine_fn GRAPH_UNLOCKED
diff --git a/block/vdi.c b/block/vdi.c
index 3ed43b6f35..fd7e365383 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -498,9 +498,8 @@ static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
                bdrv_get_device_or_node_name(bs));
     bdrv_graph_rdunlock_main_loop();
 
-    ret = migrate_add_blocker(s->migration_blocker, errp);
+    ret = migrate_add_blocker(&s->migration_blocker, errp);
     if (ret < 0) {
-        error_free(s->migration_blocker);
         goto fail_free_bmap;
     }
 
@@ -988,8 +987,7 @@ static void vdi_close(BlockDriverState *bs)
 
     qemu_vfree(s->bmap);
 
-    migrate_del_blocker(s->migration_blocker);
-    error_free(s->migration_blocker);
+    migrate_del_blocker(&s->migration_blocker);
 }
 
 static int vdi_has_zero_init(BlockDriverState *bs)
diff --git a/block/vhdx.c b/block/vhdx.c
index 73cb214fb4..e37f8c0926 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -985,8 +985,7 @@ static void vhdx_close(BlockDriverState *bs)
     s->bat = NULL;
     qemu_vfree(s->parent_entries);
     s->parent_entries = NULL;
-    migrate_del_blocker(s->migration_blocker);
-    error_free(s->migration_blocker);
+    migrate_del_blocker(&s->migration_blocker);
     qemu_vfree(s->log.hdr);
     s->log.hdr = NULL;
     vhdx_region_unregister_all(s);
@@ -1097,9 +1096,8 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The vhdx format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, errp);
+    ret = migrate_add_blocker(&s->migration_blocker, errp);
     if (ret < 0) {
-        error_free(s->migration_blocker);
         goto fail;
     }
 
diff --git a/block/vmdk.c b/block/vmdk.c
index 8a3b152798..1335d39e16 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1386,9 +1386,8 @@ static int vmdk_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The vmdk format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, errp);
+    ret = migrate_add_blocker(&s->migration_blocker, errp);
     if (ret < 0) {
-        error_free(s->migration_blocker);
         goto fail;
     }
 
@@ -2867,8 +2866,7 @@ static void vmdk_close(BlockDriverState *bs)
     vmdk_free_extents(bs);
     g_free(s->create_type);
 
-    migrate_del_blocker(s->migration_blocker);
-    error_free(s->migration_blocker);
+    migrate_del_blocker(&s->migration_blocker);
 }
 
 static int64_t coroutine_fn GRAPH_RDLOCK
diff --git a/block/vpc.c b/block/vpc.c
index 945847fe4a..c30cf8689a 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -452,9 +452,8 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
                bdrv_get_device_or_node_name(bs));
     bdrv_graph_rdunlock_main_loop();
 
-    ret = migrate_add_blocker(s->migration_blocker, errp);
+    ret = migrate_add_blocker(&s->migration_blocker, errp);
     if (ret < 0) {
-        error_free(s->migration_blocker);
         goto fail;
     }
 
@@ -1190,8 +1189,7 @@ static void vpc_close(BlockDriverState *bs)
     g_free(s->pageentry_u8);
 #endif
 
-    migrate_del_blocker(s->migration_blocker);
-    error_free(s->migration_blocker);
+    migrate_del_blocker(&s->migration_blocker);
 }
 
 static QemuOptsList vpc_create_opts = {
diff --git a/block/vvfat.c b/block/vvfat.c
index b0415798c0..266e036dcd 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1268,9 +1268,8 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
                    "The vvfat (rw) format used by node '%s' "
                    "does not support live migration",
                    bdrv_get_device_or_node_name(bs));
-        ret = migrate_add_blocker(s->migration_blocker, errp);
+        ret = migrate_add_blocker(&s->migration_blocker, errp);
         if (ret < 0) {
-            error_free(s->migration_blocker);
             goto fail;
         }
     }
@@ -3239,8 +3238,7 @@ static void vvfat_close(BlockDriverState *bs)
     g_free(s->cluster_buffer);
 
     if (s->qcow) {
-        migrate_del_blocker(s->migration_blocker);
-        error_free(s->migration_blocker);
+        migrate_del_blocker(&s->migration_blocker);
     }
 }
 
diff --git a/dump/dump.c b/dump/dump.c
index d3578ddc62..d355ada62e 100644
--- a/dump/dump.c
+++ b/dump/dump.c
@@ -111,7 +111,7 @@ static int dump_cleanup(DumpState *s)
             qemu_mutex_unlock_iothread();
         }
     }
-    migrate_del_blocker(dump_migration_blocker);
+    migrate_del_blocker(&dump_migration_blocker);
 
     return 0;
 }
@@ -2158,7 +2158,7 @@ void qmp_dump_guest_memory(bool paging, const char *file,
      * Allows even for -only-migratable, but forbid migration during the
      * process of dump guest memory.
      */
-    if (migrate_add_blocker_internal(dump_migration_blocker, errp)) {
+    if (migrate_add_blocker_internal(&dump_migration_blocker, errp)) {
         /* Remember to release the fd before passing it over to dump state */
         close(fd);
         return;
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 323f042e65..af636cfb2d 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -406,11 +406,7 @@ static int coroutine_fn put_fid(V9fsPDU *pdu, V9fsFidState *fidp)
              * delete the migration blocker. Ideally, this
              * should be hooked to transport close notification
              */
-            if (pdu->s->migration_blocker) {
-                migrate_del_blocker(pdu->s->migration_blocker);
-                error_free(pdu->s->migration_blocker);
-                pdu->s->migration_blocker = NULL;
-            }
+            migrate_del_blocker(&pdu->s->migration_blocker);
         }
         return free_fid(pdu, fidp);
     }
@@ -1505,10 +1501,8 @@ static void coroutine_fn v9fs_attach(void *opaque)
         error_setg(&s->migration_blocker,
                    "Migration is disabled when VirtFS export path '%s' is mounted in the guest using mount_tag '%s'",
                    s->ctx.fs_root ? s->ctx.fs_root : "NULL", s->tag);
-        err = migrate_add_blocker(s->migration_blocker, NULL);
+        err = migrate_add_blocker(&s->migration_blocker, NULL);
         if (err < 0) {
-            error_free(s->migration_blocker);
-            s->migration_blocker = NULL;
             clunk_fid(s, fid);
             goto out;
         }
diff --git a/hw/display/virtio-gpu-base.c b/hw/display/virtio-gpu-base.c
index 50c5373b65..37af256219 100644
--- a/hw/display/virtio-gpu-base.c
+++ b/hw/display/virtio-gpu-base.c
@@ -184,8 +184,7 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
 
     if (virtio_gpu_virgl_enabled(g->conf)) {
         error_setg(&g->migration_blocker, "virgl is not yet migratable");
-        if (migrate_add_blocker(g->migration_blocker, errp) < 0) {
-            error_free(g->migration_blocker);
+        if (migrate_add_blocker(&g->migration_blocker, errp) < 0) {
             return false;
         }
     }
@@ -253,10 +252,7 @@ virtio_gpu_base_device_unrealize(DeviceState *qdev)
 {
     VirtIOGPUBase *g = VIRTIO_GPU_BASE(qdev);
 
-    if (g->migration_blocker) {
-        migrate_del_blocker(g->migration_blocker);
-        error_free(g->migration_blocker);
-    }
+    migrate_del_blocker(&g->migration_blocker);
 }
 
 static void
diff --git a/hw/intc/arm_gic_kvm.c b/hw/intc/arm_gic_kvm.c
index 1d588946bc..e0d9e512a3 100644
--- a/hw/intc/arm_gic_kvm.c
+++ b/hw/intc/arm_gic_kvm.c
@@ -516,8 +516,7 @@ static void kvm_arm_gic_realize(DeviceState *dev, Error **errp)
     if (!kvm_arm_gic_can_save_restore(s)) {
         error_setg(&s->migration_blocker, "This operating system kernel does "
                                           "not support vGICv2 migration");
-        if (migrate_add_blocker(s->migration_blocker, errp) < 0) {
-            error_free(s->migration_blocker);
+        if (migrate_add_blocker(&s->migration_blocker, errp) < 0) {
             return;
         }
     }
diff --git a/hw/intc/arm_gicv3_its_kvm.c b/hw/intc/arm_gicv3_its_kvm.c
index 7eda9fb86e..61c1cc7bdb 100644
--- a/hw/intc/arm_gicv3_its_kvm.c
+++ b/hw/intc/arm_gicv3_its_kvm.c
@@ -114,8 +114,7 @@ static void kvm_arm_its_realize(DeviceState *dev, Error **errp)
         GITS_CTLR)) {
         error_setg(&s->migration_blocker, "This operating system kernel "
                    "does not support vITS migration");
-        if (migrate_add_blocker(s->migration_blocker, errp) < 0) {
-            error_free(s->migration_blocker);
+        if (migrate_add_blocker(&s->migration_blocker, errp) < 0) {
             return;
         }
     } else {
diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c
index 72ad916d3d..77eb37e131 100644
--- a/hw/intc/arm_gicv3_kvm.c
+++ b/hw/intc/arm_gicv3_kvm.c
@@ -878,8 +878,7 @@ static void kvm_arm_gicv3_realize(DeviceState *dev, Error **errp)
                                GICD_CTLR)) {
         error_setg(&s->migration_blocker, "This operating system kernel does "
                                           "not support vGICv3 migration");
-        if (migrate_add_blocker(s->migration_blocker, errp) < 0) {
-            error_free(s->migration_blocker);
+        if (migrate_add_blocker(&s->migration_blocker, errp) < 0) {
             return;
         }
     }
diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index d66d912172..0447888029 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -903,8 +903,7 @@ static void ivshmem_common_realize(PCIDevice *dev, Error **errp)
     if (!ivshmem_is_master(s)) {
         error_setg(&s->migration_blocker,
                    "Migration is disabled when using feature 'peer mode' in device 'ivshmem'");
-        if (migrate_add_blocker(s->migration_blocker, errp) < 0) {
-            error_free(s->migration_blocker);
+        if (migrate_add_blocker(&s->migration_blocker, errp) < 0) {
             return;
         }
     }
@@ -922,10 +921,7 @@ static void ivshmem_exit(PCIDevice *dev)
     IVShmemState *s = IVSHMEM_COMMON(dev);
     int i;
 
-    if (s->migration_blocker) {
-        migrate_del_blocker(s->migration_blocker);
-        error_free(s->migration_blocker);
-    }
+    migrate_del_blocker(&s->migration_blocker);
 
     if (memory_region_is_mapped(s->ivshmem_bar2)) {
         if (!s->hostmem) {
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 29e33ea5ed..b85c7946a7 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -3624,8 +3624,8 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
         n->primary_listener.hide_device = failover_hide_primary_device;
         qatomic_set(&n->failover_primary_hidden, true);
         device_listener_register(&n->primary_listener);
-        n->migration_state.notify = virtio_net_migration_state_notifier;
-        add_migration_state_change_notifier(&n->migration_state);
+        migration_add_notifier(&n->migration_state,
+                               virtio_net_migration_state_notifier);
         n->host_features |= (1ULL << VIRTIO_NET_F_STANDBY);
     }
 
@@ -3788,7 +3788,7 @@ static void virtio_net_device_unrealize(DeviceState *dev)
     if (n->failover) {
         qobject_unref(n->primary_opts);
         device_listener_unregister(&n->primary_listener);
-        remove_migration_state_change_notifier(&n->migration_state);
+        migration_remove_notifier(&n->migration_state);
     } else {
         assert(n->primary_opts == NULL);
     }
diff --git a/hw/ppc/pef.c b/hw/ppc/pef.c
index cc44d5e339..d28ed3ba73 100644
--- a/hw/ppc/pef.c
+++ b/hw/ppc/pef.c
@@ -63,7 +63,7 @@ static int kvmppc_svm_init(ConfidentialGuestSupport *cgs, Error **errp)
     /* add migration blocker */
     error_setg(&pef_mig_blocker, "PEF: Migration is not implemented");
     /* NB: This can fail if --only-migratable is used */
-    migrate_add_blocker(pef_mig_blocker, &error_fatal);
+    migrate_add_blocker(&pef_mig_blocker, &error_fatal);
 
     cgs->ready = true;
 
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index cb840676d3..b25093be28 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1761,7 +1761,7 @@ static void spapr_machine_reset(MachineState *machine, ShutdownCause reason)
     /* Signal all vCPUs waiting on this condition */
     qemu_cond_broadcast(&spapr->fwnmi_machine_check_interlock_cond);
 
-    migrate_del_blocker(spapr->fwnmi_migration_blocker);
+    migrate_del_blocker(&spapr->fwnmi_migration_blocker);
 }
 
 static void spapr_create_nvram(SpaprMachineState *spapr)
@@ -2937,13 +2937,6 @@ static void spapr_machine_init(MachineState *machine)
         spapr_create_lmb_dr_connectors(spapr);
     }
 
-    if (spapr_get_cap(spapr, SPAPR_CAP_FWNMI) == SPAPR_CAP_ON) {
-        /* Create the error string for live migration blocker */
-        error_setg(&spapr->fwnmi_migration_blocker,
-            "A machine check is being handled during migration. The handler"
-            "may run and log hardware error on the destination");
-    }
-
     if (mc->nvdimm_supported) {
         spapr_create_nvdimm_dr_connectors(spapr);
     }
diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
index 4508e40814..deb4641505 100644
--- a/hw/ppc/spapr_events.c
+++ b/hw/ppc/spapr_events.c
@@ -920,7 +920,11 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
      * fails when running with -only-migrate.  A proper interface to
      * delay migration completion for a bit could avoid that.
      */
-    ret = migrate_add_blocker(spapr->fwnmi_migration_blocker, NULL);
+    error_setg(&spapr->fwnmi_migration_blocker,
+        "A machine check is being handled during migration. The handler"
+        "may run and log hardware error on the destination");
+
+    ret = migrate_add_blocker(&spapr->fwnmi_migration_blocker, NULL);
     if (ret == -EBUSY) {
         warn_report("Received a fwnmi while migration was in progress");
     }
diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index 7df21581c2..26c384b261 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -496,7 +496,7 @@ static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
     spapr->fwnmi_machine_check_interlock = -1;
     qemu_cond_signal(&spapr->fwnmi_machine_check_interlock_cond);
     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
-    migrate_del_blocker(spapr->fwnmi_migration_blocker);
+    migrate_del_blocker(&spapr->fwnmi_migration_blocker);
 }
 
 static struct rtas_call {
diff --git a/hw/remote/proxy.c b/hw/remote/proxy.c
index 2052d721e5..fbc85a8d36 100644
--- a/hw/remote/proxy.c
+++ b/hw/remote/proxy.c
@@ -107,8 +107,7 @@ static void pci_proxy_dev_realize(PCIDevice *device, Error **errp)
 
     error_setg(&dev->migration_blocker, "%s does not support migration",
                TYPE_PCI_PROXY_DEV);
-    if (migrate_add_blocker(dev->migration_blocker, errp) < 0) {
-        error_free(dev->migration_blocker);
+    if (migrate_add_blocker(&dev->migration_blocker, errp) < 0) {
         object_unref(dev->ioc);
         return;
     }
@@ -134,9 +133,7 @@ static void pci_proxy_dev_exit(PCIDevice *pdev)
         qio_channel_close(dev->ioc, NULL);
     }
 
-    migrate_del_blocker(dev->migration_blocker);
-
-    error_free(dev->migration_blocker);
+    migrate_del_blocker(&dev->migration_blocker);
 
     proxy_memory_listener_deconfigure(&dev->proxy_listener);
 
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 6012165d41..7262725d2e 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -344,8 +344,7 @@ static void s390_machine_unprotect(S390CcwMachineState *ms)
         s390_pv_vm_disable();
     }
     ms->pv = false;
-    migrate_del_blocker(pv_mig_blocker);
-    error_free_or_abort(&pv_mig_blocker);
+    migrate_del_blocker(&pv_mig_blocker);
     ram_block_discard_disable(false);
 }
 
@@ -368,11 +367,10 @@ static int s390_machine_protect(S390CcwMachineState *ms)
 
     error_setg(&pv_mig_blocker,
                "protected VMs are currently not migratable.");
-    rc = migrate_add_blocker(pv_mig_blocker, &local_err);
+    rc = migrate_add_blocker(&pv_mig_blocker, &local_err);
     if (rc) {
         ram_block_discard_disable(false);
         error_report_err(local_err);
-        error_free_or_abort(&pv_mig_blocker);
         return rc;
     }
 
@@ -380,8 +378,7 @@ static int s390_machine_protect(S390CcwMachineState *ms)
     rc = s390_pv_vm_enable();
     if (rc) {
         ram_block_discard_disable(false);
-        migrate_del_blocker(pv_mig_blocker);
-        error_free_or_abort(&pv_mig_blocker);
+        migrate_del_blocker(&pv_mig_blocker);
         return rc;
     }
 
diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
index 443f67daa4..14e23cc5b4 100644
--- a/hw/scsi/vhost-scsi.c
+++ b/hw/scsi/vhost-scsi.c
@@ -208,7 +208,7 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp)
                 "When external environment supports it (Orchestrator migrates "
                 "target SCSI device state or use shared storage over network), "
                 "set 'migratable' property to true to enable migration.");
-        if (migrate_add_blocker(vsc->migration_blocker, errp) < 0) {
+        if (migrate_add_blocker(&vsc->migration_blocker, errp) < 0) {
             goto free_virtio;
         }
     }
@@ -241,10 +241,9 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp)
  free_vqs:
     g_free(vqs);
     if (!vsc->migratable) {
-        migrate_del_blocker(vsc->migration_blocker);
+        migrate_del_blocker(&vsc->migration_blocker);
     }
  free_virtio:
-    error_free(vsc->migration_blocker);
     virtio_scsi_common_unrealize(dev);
  close_fd:
     if (vhostfd >= 0) {
@@ -260,8 +259,7 @@ static void vhost_scsi_unrealize(DeviceState *dev)
     struct vhost_virtqueue *vqs = vsc->dev.vqs;
 
     if (!vsc->migratable) {
-        migrate_del_blocker(vsc->migration_blocker);
-        error_free(vsc->migration_blocker);
+        migrate_del_blocker(&vsc->migration_blocker);
     }
 
     /* This will stop vhost backend. */
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 5ff5acf1d8..d806057b40 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -129,11 +129,7 @@ int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp)
     error_setg(&multiple_devices_migration_blocker,
                "Multiple VFIO devices migration is supported only if all of "
                "them support P2P migration");
-    ret = migrate_add_blocker(multiple_devices_migration_blocker, errp);
-    if (ret < 0) {
-        error_free(multiple_devices_migration_blocker);
-        multiple_devices_migration_blocker = NULL;
-    }
+    ret = migrate_add_blocker(&multiple_devices_migration_blocker, errp);
 
     return ret;
 }
@@ -145,9 +141,7 @@ void vfio_unblock_multiple_devices_migration(void)
         return;
     }
 
-    migrate_del_blocker(multiple_devices_migration_blocker);
-    error_free(multiple_devices_migration_blocker);
-    multiple_devices_migration_blocker = NULL;
+    migrate_del_blocker(&multiple_devices_migration_blocker);
 }
 
 bool vfio_viommu_preset(VFIODevice *vbasedev)
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index da43dcd2fe..28d422b39f 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -872,8 +872,8 @@ static int vfio_migration_init(VFIODevice *vbasedev)
                      NULL;
     migration->vm_state = qdev_add_vm_change_state_handler_full(
         vbasedev->dev, vfio_vmstate_change, prepare_cb, vbasedev);
-    migration->migration_state.notify = vfio_migration_state_notifier;
-    add_migration_state_change_notifier(&migration->migration_state);
+    migration_add_notifier(&migration->migration_state,
+                           vfio_migration_state_notifier);
 
     return 0;
 }
@@ -882,7 +882,7 @@ static void vfio_migration_deinit(VFIODevice *vbasedev)
 {
     VFIOMigration *migration = vbasedev->migration;
 
-    remove_migration_state_change_notifier(&migration->migration_state);
+    migration_remove_notifier(&migration->migration_state);
     qemu_del_vm_change_state_handler(migration->vm_state);
     unregister_savevm(VMSTATE_IF(vbasedev->dev), "vfio", vbasedev);
     vfio_migration_free(vbasedev);
@@ -891,8 +891,6 @@ static void vfio_migration_deinit(VFIODevice *vbasedev)
 
 static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
 {
-    int ret;
-
     if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
         error_propagate(errp, err);
         return -EINVAL;
@@ -901,13 +899,7 @@ static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
     vbasedev->migration_blocker = error_copy(err);
     error_free(err);
 
-    ret = migrate_add_blocker(vbasedev->migration_blocker, errp);
-    if (ret < 0) {
-        error_free(vbasedev->migration_blocker);
-        vbasedev->migration_blocker = NULL;
-    }
-
-    return ret;
+    return migrate_add_blocker(&vbasedev->migration_blocker, errp);
 }
 
 /* ---------------------------------------------------------------------- */
@@ -994,9 +986,5 @@ void vfio_migration_exit(VFIODevice *vbasedev)
         vfio_migration_deinit(vbasedev);
     }
 
-    if (vbasedev->migration_blocker) {
-        migrate_del_blocker(vbasedev->migration_blocker);
-        error_free(vbasedev->migration_blocker);
-        vbasedev->migration_blocker = NULL;
-    }
+    migrate_del_blocker(&vbasedev->migration_blocker);
 }
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 9f37206ba0..d737671028 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1527,9 +1527,8 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     }
 
     if (hdev->migration_blocker != NULL) {
-        r = migrate_add_blocker(hdev->migration_blocker, errp);
+        r = migrate_add_blocker(&hdev->migration_blocker, errp);
         if (r < 0) {
-            error_free(hdev->migration_blocker);
             goto fail_busyloop;
         }
     }
@@ -1597,10 +1596,7 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
         memory_listener_unregister(&hdev->memory_listener);
         QLIST_REMOVE(hdev, entry);
     }
-    if (hdev->migration_blocker) {
-        migrate_del_blocker(hdev->migration_blocker);
-        error_free(hdev->migration_blocker);
-    }
+    migrate_del_blocker(&hdev->migration_blocker);
     g_free(hdev->mem);
     g_free(hdev->mem_sections);
     if (hdev->vhost_ops) {
diff --git a/include/migration/blocker.h b/include/migration/blocker.h
index 9cebe2ba06..b048f301b4 100644
--- a/include/migration/blocker.h
+++ b/include/migration/blocker.h
@@ -17,19 +17,23 @@
 /**
  * @migrate_add_blocker - prevent migration from proceeding
  *
- * @reason - an error to be returned whenever migration is attempted
+ * @reasonp - address of an error to be returned whenever migration is attempted
  *
  * @errp - [out] The reason (if any) we cannot block migration right now.
  *
  * @returns - 0 on success, -EBUSY/-EACCES on failure, with errp set.
+ *
+ * *@reasonp is freed and set to NULL if failure is returned.
+ * On success, the caller must not free @reasonp, except by
+ *   calling migrate_del_blocker.
  */
-int migrate_add_blocker(Error *reason, Error **errp);
+int migrate_add_blocker(Error **reasonp, Error **errp);
 
 /**
  * @migrate_add_blocker_internal - prevent migration from proceeding without
  *                                 only-migrate implications
  *
- * @reason - an error to be returned whenever migration is attempted
+ * @reasonp - address of an error to be returned whenever migration is attempted
  *
  * @errp - [out] The reason (if any) we cannot block migration right now.
  *
@@ -38,14 +42,20 @@ int migrate_add_blocker(Error *reason, Error **errp);
  * Some of the migration blockers can be temporary (e.g., for a few seconds),
  * so it shouldn't need to conflict with "-only-migratable".  For those cases,
  * we can call this function rather than @migrate_add_blocker().
+ *
+ * *@reasonp is freed and set to NULL if failure is returned.
+ * On success, the caller must not free @reasonp, except by
+ *   calling migrate_del_blocker.
  */
-int migrate_add_blocker_internal(Error *reason, Error **errp);
+int migrate_add_blocker_internal(Error **reasonp, Error **errp);
 
 /**
- * @migrate_del_blocker - remove a blocking error from migration
+ * @migrate_del_blocker - remove a blocking error from migration and free it.
  *
- * @reason - the error blocking migration
+ * @reasonp - address of the error blocking migration
+ *
+ * This function frees *@reasonp and sets it to NULL.
  */
-void migrate_del_blocker(Error *reason);
+void migrate_del_blocker(Error **reasonp);
 
 #endif
diff --git a/include/migration/misc.h b/include/migration/misc.h
index 7dcc0b5c2c..673ac490fb 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -60,8 +60,10 @@ void migration_object_init(void);
 void migration_shutdown(void);
 bool migration_is_idle(void);
 bool migration_is_active(MigrationState *);
-void add_migration_state_change_notifier(Notifier *notify);
-void remove_migration_state_change_notifier(Notifier *notify);
+void migration_add_notifier(Notifier *notify,
+                            void (*func)(Notifier *notifier, void *data));
+void migration_remove_notifier(Notifier *notify);
+void migration_call_notifiers(MigrationState *s);
 bool migration_in_setup(MigrationState *);
 bool migration_has_finished(MigrationState *);
 bool migration_has_failed(MigrationState *);
diff --git a/migration/migration.c b/migration/migration.c
index 05c0b801ba..67547eb6a1 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1207,7 +1207,7 @@ static void migrate_fd_cleanup(MigrationState *s)
         /* It is used on info migrate.  We can't free it */
         error_report_err(error_copy(s->error));
     }
-    notifier_list_notify(&migration_state_notifiers, s);
+    migration_call_notifiers(s);
     block_cleanup_parameters();
     yank_unregister_instance(MIGRATION_YANK_INSTANCE);
 }
@@ -1311,14 +1311,24 @@ static void migrate_fd_cancel(MigrationState *s)
     }
 }
 
-void add_migration_state_change_notifier(Notifier *notify)
+void migration_add_notifier(Notifier *notify,
+                            void (*func)(Notifier *notifier, void *data))
 {
+    notify->notify = func;
     notifier_list_add(&migration_state_notifiers, notify);
 }
 
-void remove_migration_state_change_notifier(Notifier *notify)
+void migration_remove_notifier(Notifier *notify)
 {
-    notifier_remove(notify);
+    if (notify->notify) {
+        notifier_remove(notify);
+        notify->notify = NULL;
+    }
+}
+
+void migration_call_notifiers(MigrationState *s)
+{
+    notifier_list_notify(&migration_state_notifiers, s);
 }
 
 bool migration_in_setup(MigrationState *s)
@@ -1465,35 +1475,41 @@ int migrate_init(MigrationState *s, Error **errp)
     return 0;
 }
 
-int migrate_add_blocker_internal(Error *reason, Error **errp)
+int migrate_add_blocker_internal(Error **reasonp, Error **errp)
 {
     /* Snapshots are similar to migrations, so check RUN_STATE_SAVE_VM too. */
     if (runstate_check(RUN_STATE_SAVE_VM) || !migration_is_idle()) {
-        error_propagate_prepend(errp, error_copy(reason),
+        error_propagate_prepend(errp, *reasonp,
                                 "disallowing migration blocker "
                                 "(migration/snapshot in progress) for: ");
+        *reasonp = NULL;
         return -EBUSY;
     }
 
-    migration_blockers = g_slist_prepend(migration_blockers, reason);
+    migration_blockers = g_slist_prepend(migration_blockers, *reasonp);
     return 0;
 }
 
-int migrate_add_blocker(Error *reason, Error **errp)
+int migrate_add_blocker(Error **reasonp, Error **errp)
 {
     if (only_migratable) {
-        error_propagate_prepend(errp, error_copy(reason),
+        error_propagate_prepend(errp, *reasonp,
                                 "disallowing migration blocker "
                                 "(--only-migratable) for: ");
+        *reasonp = NULL;
         return -EACCES;
     }
 
-    return migrate_add_blocker_internal(reason, errp);
+    return migrate_add_blocker_internal(reasonp, errp);
 }
 
-void migrate_del_blocker(Error *reason)
+void migrate_del_blocker(Error **reasonp)
 {
-    migration_blockers = g_slist_remove(migration_blockers, reason);
+    if (*reasonp) {
+        migration_blockers = g_slist_remove(migration_blockers, *reasonp);
+        error_free(*reasonp);
+        *reasonp = NULL;
+    }
 }
 
 void qmp_migrate_incoming(const char *uri, Error **errp)
@@ -2227,7 +2243,7 @@ static int postcopy_start(MigrationState *ms, Error **errp)
      * spice needs to trigger a transition now
      */
     ms->postcopy_after_devices = true;
-    notifier_list_notify(&migration_state_notifiers, ms);
+    migration_call_notifiers(ms);
 
     ms->downtime =  qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - time_at_stop;
 
@@ -3307,7 +3323,7 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
         rate_limit = migrate_max_bandwidth();
 
         /* Notify before starting migration thread */
-        notifier_list_notify(&migration_state_notifiers, s);
+        migration_call_notifiers(s);
     }
 
     migration_rate_set(rate_limit);
diff --git a/migration/multifd.c b/migration/multifd.c
index 1fe53d3b98..e2a45c667a 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -743,9 +743,6 @@ static void *multifd_send_thread(void *opaque)
             if (flags & MULTIFD_FLAG_SYNC) {
                 qemu_sem_post(&p->sem_sync);
             }
-        } else if (p->quit) {
-            qemu_mutex_unlock(&p->mutex);
-            break;
         } else {
             qemu_mutex_unlock(&p->mutex);
             /* sometimes there are spurious wakeups */
diff --git a/migration/ram.c b/migration/ram.c
index 16c30a9d7a..92769902bb 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3873,6 +3873,7 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
         ret = qemu_ram_resize(block, length, &local_err);
         if (local_err) {
             error_report_err(local_err);
+            return ret;
         }
     }
     /* For postcopy we need to check hugepage sizes match */
@@ -3883,7 +3884,7 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
             error_report("Mismatched RAM page size %s "
                          "(local) %zd != %" PRId64, block->idstr,
                          block->page_size, remote_page_size);
-            ret = -EINVAL;
+            return -EINVAL;
         }
     }
     if (migrate_ignore_shared()) {
@@ -3893,7 +3894,7 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
             error_report("Mismatched GPAs for block %s "
                          "%" PRId64 "!= %" PRId64, block->idstr,
                          (uint64_t)addr, (uint64_t)block->mr->addr);
-            ret = -EINVAL;
+            return -EINVAL;
         }
     }
     ret = rdma_block_notification_handle(f, block->idstr);
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 939c984d5b..0f2e6fc58e 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -339,7 +339,8 @@ static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
 {
     struct vhost_vdpa *v = &s->vhost_vdpa;
 
-    add_migration_state_change_notifier(&s->migration_state);
+    migration_add_notifier(&s->migration_state,
+                           vdpa_net_migration_state_notifier);
     if (v->shadow_vqs_enabled) {
         v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
                                            v->iova_range.last);
@@ -399,7 +400,7 @@ static void vhost_vdpa_net_client_stop(NetClientState *nc)
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
 
     if (s->vhost_vdpa.index == 0) {
-        remove_migration_state_change_notifier(&s->migration_state);
+        migration_remove_notifier(&s->migration_state);
     }
 
     dev = s->vhost_vdpa.dev;
@@ -1456,7 +1457,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
     s->vhost_vdpa.device_fd = vdpa_device_fd;
     s->vhost_vdpa.index = queue_pair_index;
     s->always_svq = svq;
-    s->migration_state.notify = vdpa_net_migration_state_notifier;
+    s->migration_state.notify = NULL;
     s->vhost_vdpa.shadow_vqs_enabled = svq;
     s->vhost_vdpa.iova_range = iova_range;
     s->vhost_vdpa.shadow_data = svq;
diff --git a/stubs/migr-blocker.c b/stubs/migr-blocker.c
index 5676a2f93c..17a5dbf87b 100644
--- a/stubs/migr-blocker.c
+++ b/stubs/migr-blocker.c
@@ -1,11 +1,11 @@
 #include "qemu/osdep.h"
 #include "migration/blocker.h"
 
-int migrate_add_blocker(Error *reason, Error **errp)
+int migrate_add_blocker(Error **reasonp, Error **errp)
 {
     return 0;
 }
 
-void migrate_del_blocker(Error *reason)
+void migrate_del_blocker(Error **reasonp)
 {
 }
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ab72bcdfad..e7c054cc16 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1603,7 +1603,7 @@ static int hyperv_init_vcpu(X86CPU *cpu)
         error_setg(&hv_passthrough_mig_blocker,
                    "'hv-passthrough' CPU flag prevents migration, use explicit"
                    " set of hv-* flags instead");
-        ret = migrate_add_blocker(hv_passthrough_mig_blocker, &local_err);
+        ret = migrate_add_blocker(&hv_passthrough_mig_blocker, &local_err);
         if (ret < 0) {
             error_report_err(local_err);
             return ret;
@@ -1617,7 +1617,7 @@ static int hyperv_init_vcpu(X86CPU *cpu)
                    " use explicit 'hv-no-nonarch-coresharing=on' instead (but"
                    " make sure SMT is disabled and/or that vCPUs are properly"
                    " pinned)");
-        ret = migrate_add_blocker(hv_no_nonarch_cs_mig_blocker, &local_err);
+        ret = migrate_add_blocker(&hv_no_nonarch_cs_mig_blocker, &local_err);
         if (ret < 0) {
             error_report_err(local_err);
             return ret;
@@ -2213,7 +2213,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
             error_setg(&invtsc_mig_blocker,
                        "State blocked by non-migratable CPU device"
                        " (invtsc flag)");
-            r = migrate_add_blocker(invtsc_mig_blocker, &local_err);
+            r = migrate_add_blocker(&invtsc_mig_blocker, &local_err);
             if (r < 0) {
                 error_report_err(local_err);
                 return r;
@@ -2271,7 +2271,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
     return 0;
 
  fail:
-    migrate_del_blocker(invtsc_mig_blocker);
+    migrate_del_blocker(&invtsc_mig_blocker);
 
     return r;
 }
diff --git a/target/i386/nvmm/nvmm-all.c b/target/i386/nvmm/nvmm-all.c
index fb769868f2..7d752bc5e0 100644
--- a/target/i386/nvmm/nvmm-all.c
+++ b/target/i386/nvmm/nvmm-all.c
@@ -929,9 +929,8 @@ nvmm_init_vcpu(CPUState *cpu)
         error_setg(&nvmm_migration_blocker,
             "NVMM: Migration not supported");
 
-        if (migrate_add_blocker(nvmm_migration_blocker, &local_error) < 0) {
+        if (migrate_add_blocker(&nvmm_migration_blocker, &local_error) < 0) {
             error_report_err(local_error);
-            error_free(nvmm_migration_blocker);
             return -EINVAL;
         }
     }
diff --git a/target/i386/sev.c b/target/i386/sev.c
index fe2144c038..9a71246682 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -891,7 +891,7 @@ sev_launch_finish(SevGuestState *sev)
     /* add migration blocker */
     error_setg(&sev_mig_blocker,
                "SEV: Migration is not implemented");
-    migrate_add_blocker(sev_mig_blocker, &error_fatal);
+    migrate_add_blocker(&sev_mig_blocker, &error_fatal);
 }
 
 static void
diff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c
index df3aba2642..d29ba916a0 100644
--- a/target/i386/whpx/whpx-all.c
+++ b/target/i386/whpx/whpx-all.c
@@ -2160,9 +2160,8 @@ int whpx_init_vcpu(CPUState *cpu)
                "State blocked due to non-migratable CPUID feature support,"
                "dirty memory tracking support, and XSAVE/XRSTOR support");
 
-        if (migrate_add_blocker(whpx_migration_blocker, &local_error) < 0) {
+        if (migrate_add_blocker(&whpx_migration_blocker, &local_error) < 0) {
             error_report_err(local_error);
-            error_free(whpx_migration_blocker);
             ret = -EINVAL;
             goto error;
         }
diff --git a/tests/qtest/libqtest.c b/tests/qtest/libqtest.c
index dc7a55634c..f33a210861 100644
--- a/tests/qtest/libqtest.c
+++ b/tests/qtest/libqtest.c
@@ -91,6 +91,7 @@ struct QTestState
 
 static GHookList abrt_hooks;
 static void (*sighandler_old)(int);
+static bool silence_spawn_log;
 
 static int qtest_query_target_endianness(QTestState *s);
 
@@ -336,10 +337,17 @@ void qtest_remove_abrt_handler(void *data)
     }
 }
 
-static const char *qtest_qemu_binary(void)
+static const char *qtest_qemu_binary(const char *var)
 {
     const char *qemu_bin;
 
+    if (var) {
+        qemu_bin = getenv(var);
+        if (qemu_bin) {
+            return qemu_bin;
+        }
+    }
+
     qemu_bin = getenv("QTEST_QEMU_BINARY");
     if (!qemu_bin) {
         fprintf(stderr, "Environment variable QTEST_QEMU_BINARY required\n");
@@ -381,7 +389,8 @@ static pid_t qtest_create_process(char *cmd)
 }
 #endif /* _WIN32 */
 
-static QTestState *G_GNUC_PRINTF(1, 2) qtest_spawn_qemu(const char *fmt, ...)
+static QTestState *G_GNUC_PRINTF(2, 3) qtest_spawn_qemu(const char *qemu_bin,
+                                                        const char *fmt, ...)
 {
     va_list ap;
     QTestState *s = g_new0(QTestState, 1);
@@ -391,14 +400,15 @@ static QTestState *G_GNUC_PRINTF(1, 2) qtest_spawn_qemu(const char *fmt, ...)
     g_autoptr(GString) command = g_string_new("");
 
     va_start(ap, fmt);
-    g_string_append_printf(command, CMD_EXEC "%s %s",
-                           qtest_qemu_binary(), tracearg);
+    g_string_append_printf(command, CMD_EXEC "%s %s", qemu_bin, tracearg);
     g_string_append_vprintf(command, fmt, ap);
     va_end(ap);
 
     qtest_add_abrt_handler(kill_qemu_hook_func, s);
 
-    g_test_message("starting QEMU: %s", command->str);
+    if (!silence_spawn_log) {
+        g_test_message("starting QEMU: %s", command->str);
+    }
 
 #ifndef _WIN32
     s->qemu_pid = fork();
@@ -431,7 +441,8 @@ static QTestState *G_GNUC_PRINTF(1, 2) qtest_spawn_qemu(const char *fmt, ...)
     return s;
 }
 
-QTestState *qtest_init_without_qmp_handshake(const char *extra_args)
+static QTestState *qtest_init_internal(const char *qemu_bin,
+                                       const char *extra_args)
 {
     QTestState *s;
     int sock, qmpsock, i;
@@ -456,7 +467,8 @@ QTestState *qtest_init_without_qmp_handshake(const char *extra_args)
     sock = init_socket(socket_path);
     qmpsock = init_socket(qmp_socket_path);
 
-    s = qtest_spawn_qemu("-qtest unix:%s "
+    s = qtest_spawn_qemu(qemu_bin,
+                         "-qtest unix:%s "
                          "-qtest-log %s "
                          "-chardev socket,path=%s,id=char0 "
                          "-mon chardev=char0,mode=control "
@@ -509,9 +521,14 @@ QTestState *qtest_init_without_qmp_handshake(const char *extra_args)
     return s;
 }
 
-QTestState *qtest_init(const char *extra_args)
+QTestState *qtest_init_without_qmp_handshake(const char *extra_args)
 {
-    QTestState *s = qtest_init_without_qmp_handshake(extra_args);
+    return qtest_init_internal(qtest_qemu_binary(NULL), extra_args);
+}
+
+QTestState *qtest_init_with_env(const char *var, const char *extra_args)
+{
+    QTestState *s = qtest_init_internal(qtest_qemu_binary(var), extra_args);
     QDict *greeting;
 
     /* Read the QMP greeting and then do the handshake */
@@ -522,6 +539,11 @@ QTestState *qtest_init(const char *extra_args)
     return s;
 }
 
+QTestState *qtest_init(const char *extra_args)
+{
+    return qtest_init_with_env(NULL, extra_args);
+}
+
 QTestState *qtest_vinitf(const char *fmt, va_list ap)
 {
     char *args = g_strdup_vprintf(fmt, ap);
@@ -905,7 +927,7 @@ char *qtest_hmp(QTestState *s, const char *fmt, ...)
 
 const char *qtest_get_arch(void)
 {
-    const char *qemu = qtest_qemu_binary();
+    const char *qemu = qtest_qemu_binary(NULL);
     const char *end = strrchr(qemu, '-');
 
     if (!end) {
@@ -1449,13 +1471,26 @@ struct MachInfo {
     char *alias;
 };
 
+static void qtest_free_machine_list(struct MachInfo *machines)
+{
+    if (machines) {
+        for (int i = 0; machines[i].name != NULL; i++) {
+            g_free(machines[i].name);
+            g_free(machines[i].alias);
+        }
+
+        g_free(machines);
+    }
+}
+
 /*
  * Returns an array with pointers to the available machine names.
  * The terminating entry has the name set to NULL.
  */
-static struct MachInfo *qtest_get_machines(void)
+static struct MachInfo *qtest_get_machines(const char *var)
 {
     static struct MachInfo *machines;
+    static char *qemu_var;
     QDict *response, *minfo;
     QList *list;
     const QListEntry *p;
@@ -1464,11 +1499,21 @@ static struct MachInfo *qtest_get_machines(void)
     QTestState *qts;
     int idx;
 
+    if (g_strcmp0(qemu_var, var)) {
+        qemu_var = g_strdup(var);
+
+        /* new qemu, clear the cache */
+        qtest_free_machine_list(machines);
+        machines = NULL;
+    }
+
     if (machines) {
         return machines;
     }
 
-    qts = qtest_init("-machine none");
+    silence_spawn_log = !g_test_verbose();
+
+    qts = qtest_init_with_env(qemu_var, "-machine none");
     response = qtest_qmp(qts, "{ 'execute': 'query-machines' }");
     g_assert(response);
     list = qdict_get_qlist(response, "return");
@@ -1499,6 +1544,8 @@ static struct MachInfo *qtest_get_machines(void)
     qtest_quit(qts);
     qobject_unref(response);
 
+    silence_spawn_log = false;
+
     memset(&machines[idx], 0, sizeof(struct MachInfo)); /* Terminating entry */
     return machines;
 }
@@ -1509,7 +1556,7 @@ void qtest_cb_for_every_machine(void (*cb)(const char *machine),
     struct MachInfo *machines;
     int i;
 
-    machines = qtest_get_machines();
+    machines = qtest_get_machines(NULL);
 
     for (i = 0; machines[i].name != NULL; i++) {
         /* Ignore machines that cannot be used for qtests */
@@ -1525,12 +1572,28 @@ void qtest_cb_for_every_machine(void (*cb)(const char *machine),
     }
 }
 
-bool qtest_has_machine(const char *machine)
+char *qtest_resolve_machine_alias(const char *var, const char *alias)
 {
     struct MachInfo *machines;
     int i;
 
-    machines = qtest_get_machines();
+    machines = qtest_get_machines(var);
+
+    for (i = 0; machines[i].name != NULL; i++) {
+        if (machines[i].alias && g_str_equal(alias, machines[i].alias)) {
+            return g_strdup(machines[i].name);
+        }
+    }
+
+    return NULL;
+}
+
+bool qtest_has_machine_with_env(const char *var, const char *machine)
+{
+    struct MachInfo *machines;
+    int i;
+
+    machines = qtest_get_machines(var);
 
     for (i = 0; machines[i].name != NULL; i++) {
         if (g_str_equal(machine, machines[i].name) ||
@@ -1542,6 +1605,11 @@ bool qtest_has_machine(const char *machine)
     return false;
 }
 
+bool qtest_has_machine(const char *machine)
+{
+    return qtest_has_machine_with_env(NULL, machine);
+}
+
 bool qtest_has_device(const char *device)
 {
     static QList *list;
diff --git a/tests/qtest/libqtest.h b/tests/qtest/libqtest.h
index 5fe3d13466..6e3d3525bf 100644
--- a/tests/qtest/libqtest.h
+++ b/tests/qtest/libqtest.h
@@ -55,6 +55,19 @@ QTestState *qtest_vinitf(const char *fmt, va_list ap) G_GNUC_PRINTF(1, 0);
  */
 QTestState *qtest_init(const char *extra_args);
 
+/**
+ * qtest_init_with_env:
+ * @var: Environment variable from where to take the QEMU binary
+ * @extra_args: Other arguments to pass to QEMU.  CAUTION: these
+ * arguments are subject to word splitting and shell evaluation.
+ *
+ * Like qtest_init(), but use a different environment variable for the
+ * QEMU binary.
+ *
+ * Returns: #QTestState instance.
+ */
+QTestState *qtest_init_with_env(const char *var, const char *extra_args);
+
 /**
  * qtest_init_without_qmp_handshake:
  * @extra_args: other arguments to pass to QEMU.  CAUTION: these
@@ -909,6 +922,16 @@ void qtest_qmp_fds_assert_success(QTestState *qts, int *fds, size_t nfds,
 void qtest_cb_for_every_machine(void (*cb)(const char *machine),
                                 bool skip_old_versioned);
 
+/**
+ * qtest_resolve_machine_alias:
+ * @var: Environment variable from where to take the QEMU binary
+ * @alias: The alias to resolve
+ *
+ * Returns: the machine type corresponding to the alias if any,
+ * otherwise NULL.
+ */
+char *qtest_resolve_machine_alias(const char *var, const char *alias);
+
 /**
  * qtest_has_machine:
  * @machine: The machine to look for
@@ -917,6 +940,15 @@ void qtest_cb_for_every_machine(void (*cb)(const char *machine),
  */
 bool qtest_has_machine(const char *machine);
 
+/**
+ * qtest_has_machine_with_env:
+ * @var: Environment variable from where to take the QEMU binary
+ * @machine: The machine to look for
+ *
+ * Returns: true if the machine is available in the specified binary.
+ */
+bool qtest_has_machine_with_env(const char *var, const char *machine);
+
 /**
  * qtest_has_device:
  * @device: The device to look for
diff --git a/tests/qtest/migration-helpers.c b/tests/qtest/migration-helpers.c
index 0c185db450..24fb7b3525 100644
--- a/tests/qtest/migration-helpers.c
+++ b/tests/qtest/migration-helpers.c
@@ -11,6 +11,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/ctype.h"
 #include "qapi/qmp/qjson.h"
 
 #include "migration-helpers.h"
@@ -240,3 +241,54 @@ void wait_for_migration_fail(QTestState *from, bool allow_active)
     g_assert(qdict_get_bool(rsp_return, "running"));
     qobject_unref(rsp_return);
 }
+
+char *find_common_machine_version(const char *mtype, const char *var1,
+                                  const char *var2)
+{
+    g_autofree char *type1 = qtest_resolve_machine_alias(var1, mtype);
+    g_autofree char *type2 = qtest_resolve_machine_alias(var2, mtype);
+
+    g_assert(type1 && type2);
+
+    if (g_str_equal(type1, type2)) {
+        /* either can be used */
+        return g_strdup(type1);
+    }
+
+    if (qtest_has_machine_with_env(var2, type1)) {
+        return g_strdup(type1);
+    }
+
+    if (qtest_has_machine_with_env(var1, type2)) {
+        return g_strdup(type2);
+    }
+
+    g_test_message("No common machine version for machine type '%s' between "
+                   "binaries %s and %s", mtype, getenv(var1), getenv(var2));
+    g_assert_not_reached();
+}
+
+char *resolve_machine_version(const char *alias, const char *var1,
+                              const char *var2)
+{
+    const char *mname = g_getenv("QTEST_QEMU_MACHINE_TYPE");
+    g_autofree char *machine_name = NULL;
+
+    if (mname) {
+        const char *dash = strrchr(mname, '-');
+        const char *dot = strrchr(mname, '.');
+
+        machine_name = g_strdup(mname);
+
+        if (dash && dot) {
+            assert(qtest_has_machine(machine_name));
+            return g_steal_pointer(&machine_name);
+        }
+        /* else: probably an alias, let it be resolved below */
+    } else {
+        /* use the hardcoded alias */
+        machine_name = g_strdup(alias);
+    }
+
+    return find_common_machine_version(machine_name, var1, var2);
+}
diff --git a/tests/qtest/migration-helpers.h b/tests/qtest/migration-helpers.h
index 4f51d0f8bc..e31dc85cc7 100644
--- a/tests/qtest/migration-helpers.h
+++ b/tests/qtest/migration-helpers.h
@@ -43,4 +43,8 @@ void wait_for_migration_complete(QTestState *who);
 
 void wait_for_migration_fail(QTestState *from, bool allow_active);
 
+char *find_common_machine_version(const char *mtype, const char *var1,
+                                  const char *var2);
+char *resolve_machine_version(const char *alias, const char *var1,
+                              const char *var2);
 #endif /* MIGRATION_HELPERS_H */
diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index 241b409857..bc70a14642 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -71,6 +71,8 @@ static bool got_dst_resume;
 #define QEMU_VM_FILE_MAGIC 0x5145564d
 #define FILE_TEST_FILENAME "migfile"
 #define FILE_TEST_OFFSET 0x1000
+#define QEMU_ENV_SRC "QTEST_QEMU_BINARY_SRC"
+#define QEMU_ENV_DST "QTEST_QEMU_BINARY_DST"
 
 #if defined(__linux__)
 #include <sys/syscall.h>
@@ -743,6 +745,8 @@ static int test_migrate_start(QTestState **from, QTestState **to,
     const char *kvm_opts = NULL;
     const char *arch = qtest_get_arch();
     const char *memory_size;
+    const char *machine_alias, *machine_opts = "";
+    g_autofree char *machine = NULL;
 
     if (args->use_shmem) {
         if (!g_file_test("/dev/shm", G_FILE_TEST_IS_DIR)) {
@@ -755,11 +759,20 @@ static int test_migrate_start(QTestState **from, QTestState **to,
     got_dst_resume = false;
     if (strcmp(arch, "i386") == 0 || strcmp(arch, "x86_64") == 0) {
         memory_size = "150M";
-        arch_opts = g_strdup_printf("-drive file=%s,format=raw", bootpath);
+
+        if (g_str_equal(arch, "i386")) {
+            machine_alias = "pc";
+        } else {
+            machine_alias = "q35";
+        }
+        arch_opts = g_strdup_printf(
+            "-drive if=none,id=d0,file=%s,format=raw "
+            "-device ide-hd,drive=d0,secs=1,cyls=1,heads=1", bootpath);
         start_address = X86_TEST_MEM_START;
         end_address = X86_TEST_MEM_END;
     } else if (g_str_equal(arch, "s390x")) {
         memory_size = "128M";
+        machine_alias = "s390-ccw-virtio";
         arch_opts = g_strdup_printf("-bios %s", bootpath);
         start_address = S390_TEST_MEM_START;
         end_address = S390_TEST_MEM_END;
@@ -771,11 +784,14 @@ static int test_migrate_start(QTestState **from, QTestState **to,
                                       "'nvramrc=hex .\" _\" begin %x %x "
                                       "do i c@ 1 + i c! 1000 +loop .\" B\" 0 "
                                       "until'", end_address, start_address);
-        arch_opts = g_strdup("-nodefaults -machine vsmt=8");
+        machine_alias = "pseries";
+        machine_opts = "vsmt=8";
+        arch_opts = g_strdup("-nodefaults");
     } else if (strcmp(arch, "aarch64") == 0) {
         memory_size = "150M";
-        arch_opts = g_strdup_printf("-machine virt,gic-version=max -cpu max "
-                                    "-kernel %s", bootpath);
+        machine_alias = "virt";
+        machine_opts = "gic-version=max";
+        arch_opts = g_strdup_printf("-cpu max -kernel %s", bootpath);
         start_address = ARM_TEST_MEM_START;
         end_address = ARM_TEST_MEM_END;
     } else {
@@ -809,12 +825,19 @@ static int test_migrate_start(QTestState **from, QTestState **to,
         kvm_opts = ",dirty-ring-size=4096";
     }
 
+    machine = resolve_machine_version(machine_alias, QEMU_ENV_SRC,
+                                      QEMU_ENV_DST);
+
+    g_test_message("Using machine type: %s", machine);
+
     cmd_source = g_strdup_printf("-accel kvm%s -accel tcg "
+                                 "-machine %s,%s "
                                  "-name source,debug-threads=on "
                                  "-m %s "
                                  "-serial file:%s/src_serial "
                                  "%s %s %s %s %s",
                                  kvm_opts ? kvm_opts : "",
+                                 machine, machine_opts,
                                  memory_size, tmpfs,
                                  arch_opts ? arch_opts : "",
                                  arch_source ? arch_source : "",
@@ -822,26 +845,28 @@ static int test_migrate_start(QTestState **from, QTestState **to,
                                  args->opts_source ? args->opts_source : "",
                                  ignore_stderr);
     if (!args->only_target) {
-        *from = qtest_init(cmd_source);
+        *from = qtest_init_with_env(QEMU_ENV_SRC, cmd_source);
         qtest_qmp_set_event_callback(*from,
                                      migrate_watch_for_stop,
                                      &got_src_stop);
     }
 
     cmd_target = g_strdup_printf("-accel kvm%s -accel tcg "
+                                 "-machine %s,%s "
                                  "-name target,debug-threads=on "
                                  "-m %s "
                                  "-serial file:%s/dest_serial "
                                  "-incoming %s "
                                  "%s %s %s %s %s",
                                  kvm_opts ? kvm_opts : "",
+                                 machine, machine_opts,
                                  memory_size, tmpfs, uri,
                                  arch_opts ? arch_opts : "",
                                  arch_target ? arch_target : "",
                                  shmem_opts ? shmem_opts : "",
                                  args->opts_target ? args->opts_target : "",
                                  ignore_stderr);
-    *to = qtest_init(cmd_target);
+    *to = qtest_init_with_env(QEMU_ENV_DST, cmd_target);
     qtest_qmp_set_event_callback(*to,
                                  migrate_watch_for_resume,
                                  &got_dst_resume);
@@ -2972,10 +2997,23 @@ int main(int argc, char **argv)
     bool has_uffd;
     const char *arch;
     g_autoptr(GError) err = NULL;
+    const char *qemu_src = getenv(QEMU_ENV_SRC);
+    const char *qemu_dst = getenv(QEMU_ENV_DST);
     int ret;
 
     g_test_init(&argc, &argv, NULL);
 
+    /*
+     * The default QTEST_QEMU_BINARY must always be provided because
+     * that is what helpers use to query the accel type and
+     * architecture.
+     */
+    if (qemu_src && qemu_dst) {
+        g_test_message("Only one of %s, %s is allowed",
+                       QEMU_ENV_SRC, QEMU_ENV_DST);
+        exit(1);
+    }
+
     has_kvm = qtest_has_accel("kvm");
     has_tcg = qtest_has_accel("tcg");
 
diff --git a/ui/spice-core.c b/ui/spice-core.c
index 52a59386d7..db21db2c94 100644
--- a/ui/spice-core.c
+++ b/ui/spice-core.c
@@ -821,8 +821,7 @@ static void qemu_spice_init(void)
     };
     using_spice = 1;
 
-    migration_state.notify = migration_state_notifier;
-    add_migration_state_change_notifier(&migration_state);
+    migration_add_notifier(&migration_state, migration_state_notifier);
     spice_migrate.base.sif = &migrate_interface.base;
     qemu_spice.add_interface(&spice_migrate.base);
 
diff --git a/ui/vdagent.c b/ui/vdagent.c
index 706d6d97bd..64d7ab245a 100644
--- a/ui/vdagent.c
+++ b/ui/vdagent.c
@@ -671,7 +671,7 @@ static void vdagent_chr_open(Chardev *chr,
     return;
 #endif
 
-    if (migrate_add_blocker(vd->migration_blocker, errp) != 0) {
+    if (migrate_add_blocker(&vd->migration_blocker, errp) != 0) {
         return;
     }
 
@@ -924,13 +924,12 @@ static void vdagent_chr_fini(Object *obj)
 {
     VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(obj);
 
-    migrate_del_blocker(vd->migration_blocker);
+    migrate_del_blocker(&vd->migration_blocker);
     vdagent_disconnect(vd);
     if (vd->mouse_hs) {
         qemu_input_handler_unregister(vd->mouse_hs);
     }
     buffer_free(&vd->outbuf);
-    error_free(vd->migration_blocker);
 }
 
 static const TypeInfo vdagent_chr_type_info = {