diff --git a/hw/display/qxl.c b/hw/display/qxl.c
index ec712d3ca2..2ecaa0643f 100644
--- a/hw/display/qxl.c
+++ b/hw/display/qxl.c
@@ -2224,10 +2224,9 @@ static void qxl_realize_primary(PCIDevice *dev, Error **errp)
     }
     vga_init(vga, OBJECT(dev),
              pci_address_space(dev), pci_address_space_io(dev), false);
-    portio_list_init(&qxl->vga_port_list, OBJECT(dev), qxl_vga_portio_list,
-                     vga, "vga");
-    portio_list_set_flush_coalesced(&qxl->vga_port_list);
-    portio_list_add(&qxl->vga_port_list, pci_address_space_io(dev), 0x3b0);
+    portio_list_register_flush_coalesced(&qxl->vga_port_list, OBJECT(dev),
+                                         qxl_vga_portio_list, vga, "vga",
+                                         pci_address_space_io(dev), 0x3b0);
     qxl->have_vga = true;
 
     vga->con = graphic_console_init(DEVICE(dev), 0, &qxl_ops, qxl);
diff --git a/hw/display/vga.c b/hw/display/vga.c
index 7a5fdff649..98d644922e 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -2309,9 +2309,8 @@ void vga_init(VGACommonState *s, Object *obj, MemoryRegion *address_space,
                                         1);
     memory_region_set_coalescing(vga_io_memory);
     if (init_vga_ports) {
-        portio_list_init(&s->vga_port_list, obj, vga_ports, s, "vga");
-        portio_list_set_flush_coalesced(&s->vga_port_list);
-        portio_list_add(&s->vga_port_list, address_space_io, 0x3b0);
+        portio_list_register_flush_coalesced(&s->vga_port_list, obj, vga_ports,
+                                             s, "vga", address_space_io, 0x3b0);
     }
     if (vbe_ports) {
         portio_list_init(&s->vbe_port_list, obj, vbe_ports, s, "vbe");
diff --git a/include/exec/ioport.h b/include/exec/ioport.h
index e34f668998..eb9882a3ee 100644
--- a/include/exec/ioport.h
+++ b/include/exec/ioport.h
@@ -65,7 +65,10 @@ typedef struct PortioList {
 void portio_list_init(PortioList *piolist, Object *owner,
                       const struct MemoryRegionPortio *callbacks,
                       void *opaque, const char *name);
-void portio_list_set_flush_coalesced(PortioList *piolist);
+void portio_list_register_flush_coalesced(PortioList *piolist, Object *owner,
+                                          const MemoryRegionPortio *callbacks,
+                                          void *opaque, const char *name,
+                                          MemoryRegion *mr, uint32_t offset);
 void portio_list_destroy(PortioList *piolist);
 void portio_list_add(PortioList *piolist,
                      struct MemoryRegion *address_space,
diff --git a/softmmu/ioport.c b/softmmu/ioport.c
index cb8adb0b93..be0c920c5c 100644
--- a/softmmu/ioport.c
+++ b/softmmu/ioport.c
@@ -124,6 +124,7 @@ void portio_list_init(PortioList *piolist,
         ++n;
     }
 
+    assert(owner);
     piolist->ports = callbacks;
     piolist->nr = 0;
     piolist->regions = g_new0(MemoryRegion *, n);
@@ -134,11 +135,6 @@ void portio_list_init(PortioList *piolist,
     piolist->flush_coalesced_mmio = false;
 }
 
-void portio_list_set_flush_coalesced(PortioList *piolist)
-{
-    piolist->flush_coalesced_mmio = true;
-}
-
 void portio_list_destroy(PortioList *piolist)
 {
     MemoryRegionPortioList *mrpio;
@@ -297,3 +293,24 @@ void portio_list_del(PortioList *piolist)
         memory_region_del_subregion(piolist->address_space, &mrpio->mr);
     }
 }
+
+static void do_portio_list_register(PortioList *piolist, Object *owner,
+                                    const MemoryRegionPortio *callbacks,
+                                    void *opaque, const char *name,
+                                    MemoryRegion *mr, uint32_t offset,
+                                    bool flush_coalesced_mmio)
+{
+    assert(piolist && !piolist->owner);
+    portio_list_init(piolist, owner, callbacks, opaque, name);
+    piolist->flush_coalesced_mmio = flush_coalesced_mmio;
+    portio_list_add(piolist, mr, offset);
+}
+
+void portio_list_register_flush_coalesced(PortioList *piolist, Object *owner,
+                                          const MemoryRegionPortio *callbacks,
+                                          void *opaque, const char *name,
+                                          MemoryRegion *mr, uint32_t offset)
+{
+    do_portio_list_register(piolist, owner, callbacks,
+                            opaque, name, mr, offset, true);
+}
