diff --git a/hw/char/serial-isa.c b/hw/char/serial-isa.c
index 1c793b20f7..329b352b9a 100644
--- a/hw/char/serial-isa.c
+++ b/hw/char/serial-isa.c
@@ -184,3 +184,17 @@ void serial_hds_isa_init(ISABus *bus, int from, int to)
         }
     }
 }
+
+void isa_serial_set_iobase(ISADevice *serial, hwaddr iobase)
+{
+    ISASerialState *s = ISA_SERIAL(serial);
+
+    serial->ioport_id = iobase;
+    s->iobase = iobase;
+    memory_region_set_address(&s->state.io, s->iobase);
+}
+
+void isa_serial_set_enabled(ISADevice *serial, bool enabled)
+{
+    memory_region_set_enabled(&ISA_SERIAL(serial)->state.io, enabled);
+}
diff --git a/include/hw/char/serial.h b/include/hw/char/serial.h
index 8ba7eca3d6..6e14099ee7 100644
--- a/include/hw/char/serial.h
+++ b/include/hw/char/serial.h
@@ -112,5 +112,7 @@ SerialMM *serial_mm_init(MemoryRegion *address_space,
 
 #define TYPE_ISA_SERIAL "isa-serial"
 void serial_hds_isa_init(ISABus *bus, int from, int to);
+void isa_serial_set_iobase(ISADevice *serial, hwaddr iobase);
+void isa_serial_set_enabled(ISADevice *serial, bool enabled);
 
 #endif