diff --git a/include/hw/sysbus.h b/include/hw/sysbus.h
index 3564b7b6a2..14dbc22d0c 100644
--- a/include/hw/sysbus.h
+++ b/include/hw/sysbus.h
@@ -83,8 +83,6 @@ void sysbus_mmio_map(SysBusDevice *dev, int n, hwaddr addr);
 void sysbus_mmio_map_overlap(SysBusDevice *dev, int n, hwaddr addr,
                              int priority);
 void sysbus_mmio_unmap(SysBusDevice *dev, int n);
-void sysbus_add_io(SysBusDevice *dev, hwaddr addr,
-                   MemoryRegion *mem);
 MemoryRegion *sysbus_address_space(SysBusDevice *dev);
 
 bool sysbus_realize(SysBusDevice *dev, Error **errp);
diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
index 35f902b582..9f1d5b2d6d 100644
--- a/hw/core/sysbus.c
+++ b/hw/core/sysbus.c
@@ -298,12 +298,6 @@ static char *sysbus_get_fw_dev_path(DeviceState *dev)
     return g_strdup(qdev_fw_name(dev));
 }
 
-void sysbus_add_io(SysBusDevice *dev, hwaddr addr,
-                       MemoryRegion *mem)
-{
-    memory_region_add_subregion(get_system_io(), addr, mem);
-}
-
 MemoryRegion *sysbus_address_space(SysBusDevice *dev)
 {
     return get_system_memory();
diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
index f2b0aff479..20b0300357 100644
--- a/hw/i386/kvmvapic.c
+++ b/hw/i386/kvmvapic.c
@@ -16,6 +16,7 @@
 #include "sysemu/hw_accel.h"
 #include "sysemu/kvm.h"
 #include "sysemu/runstate.h"
+#include "exec/address-spaces.h"
 #include "hw/i386/apic_internal.h"
 #include "hw/sysbus.h"
 #include "hw/boards.h"
@@ -727,7 +728,7 @@ static void vapic_realize(DeviceState *dev, Error **errp)
     VAPICROMState *s = VAPIC(dev);
 
     memory_region_init_io(&s->io, OBJECT(s), &vapic_ops, s, "kvmvapic", 2);
-    sysbus_add_io(sbd, VAPIC_IO_PORT, &s->io);
+    memory_region_add_subregion(get_system_io(), VAPIC_IO_PORT, &s->io);
     sysbus_init_ioports(sbd, VAPIC_IO_PORT, 2);
 
     option_rom[nb_option_roms].name = "kvmvapic.bin";
diff --git a/hw/mips/mipssim.c b/hw/mips/mipssim.c
index a12427b6c8..9170d6c474 100644
--- a/hw/mips/mipssim.c
+++ b/hw/mips/mipssim.c
@@ -28,6 +28,7 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu/datadir.h"
+#include "exec/address-spaces.h"
 #include "hw/clock.h"
 #include "hw/mips/mips.h"
 #include "hw/char/serial.h"
@@ -226,7 +227,7 @@ mips_mipssim_init(MachineState *machine)
         qdev_prop_set_uint8(dev, "endianness", DEVICE_LITTLE_ENDIAN);
         sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
         sysbus_connect_irq(SYS_BUS_DEVICE(dev), 0, env->irq[4]);
-        sysbus_add_io(SYS_BUS_DEVICE(dev), 0x3f8,
+        memory_region_add_subregion(get_system_io(), 0x3f8,
                       sysbus_mmio_get_region(SYS_BUS_DEVICE(dev), 0));
     }
 
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index e85493d513..fc0263f349 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -27,6 +27,7 @@
 #include "sysemu/sysemu.h"
 #include "sysemu/dma.h"
 #include "sysemu/reset.h"
+#include "exec/address-spaces.h"
 #include "hw/boards.h"
 #include "hw/nvram/fw_cfg.h"
 #include "hw/qdev-properties.h"
@@ -1142,6 +1143,7 @@ FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
     SysBusDevice *sbd;
     FWCfgIoState *ios;
     FWCfgState *s;
+    MemoryRegion *iomem = get_system_io();
     bool dma_requested = dma_iobase && dma_as;
 
     dev = qdev_new(TYPE_FW_CFG_IO);
@@ -1155,7 +1157,7 @@ FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
     sbd = SYS_BUS_DEVICE(dev);
     sysbus_realize_and_unref(sbd, &error_fatal);
     ios = FW_CFG_IO(dev);
-    sysbus_add_io(sbd, iobase, &ios->comb_iomem);
+    memory_region_add_subregion(iomem, iobase, &ios->comb_iomem);
 
     s = FW_CFG(dev);
 
@@ -1163,7 +1165,7 @@ FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
         /* 64 bits for the address field */
         s->dma_as = dma_as;
         s->dma_addr = 0;
-        sysbus_add_io(sbd, dma_iobase, &s->dma_iomem);
+        memory_region_add_subregion(iomem, dma_iobase, &s->dma_iomem);
     }
 
     return s;
