diff --git a/hw/alpha/typhoon.c b/hw/alpha/typhoon.c
index 60987ed..71a5a37 100644
--- a/hw/alpha/typhoon.c
+++ b/hw/alpha/typhoon.c
@@ -934,11 +934,9 @@ static int typhoon_pcihost_init(SysBusDevice *dev)
 
 static void typhoon_pcihost_class_init(ObjectClass *klass, void *data)
 {
-    DeviceClass *dc = DEVICE_CLASS(klass);
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = typhoon_pcihost_init;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo typhoon_pcihost_info = {
diff --git a/hw/arm/versatilepb.c b/hw/arm/versatilepb.c
index bb0c0ba..aef2bde 100644
--- a/hw/arm/versatilepb.c
+++ b/hw/arm/versatilepb.c
@@ -390,7 +390,6 @@ static void vpb_sic_class_init(ObjectClass *klass, void *data)
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = vpb_sic_init;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->vmsd = &vmstate_vpb_sic;
 }
 
diff --git a/hw/audio/pl041.c b/hw/audio/pl041.c
index 8ba661a..ed82be5 100644
--- a/hw/audio/pl041.c
+++ b/hw/audio/pl041.c
@@ -632,7 +632,6 @@ static void pl041_device_class_init(ObjectClass *klass, void *data)
 
     k->init = pl041_init;
     set_bit(DEVICE_CATEGORY_SOUND, dc->categories);
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->reset = pl041_device_reset;
     dc->vmsd = &vmstate_pl041;
     dc->props = pl041_device_properties;
diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
index 146f50a..f4e760d 100644
--- a/hw/core/sysbus.c
+++ b/hw/core/sysbus.c
@@ -257,6 +257,13 @@ static void sysbus_device_class_init(ObjectClass *klass, void *data)
     DeviceClass *k = DEVICE_CLASS(klass);
     k->init = sysbus_device_init;
     k->bus_type = TYPE_SYSTEM_BUS;
+    /*
+     * device_add plugs devices into suitable bus.  For "real" buses,
+     * that actually connects the device.  For sysbus, the connections
+     * need to be made separately, and device_add can't do that.  The
+     * device would be left unconnected, and could not possibly work.
+     */
+    k->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo sysbus_device_type_info = {
diff --git a/hw/display/pl110.c b/hw/display/pl110.c
index 7ad5972..ab689e9 100644
--- a/hw/display/pl110.c
+++ b/hw/display/pl110.c
@@ -496,7 +496,6 @@ static void pl110_class_init(ObjectClass *klass, void *data)
 
     k->init = pl110_initfn;
     set_bit(DEVICE_CATEGORY_DISPLAY, dc->categories);
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->vmsd = &vmstate_pl110;
 }
 
diff --git a/hw/dma/pl080.c b/hw/dma/pl080.c
index a515621..cb7bda9 100644
--- a/hw/dma/pl080.c
+++ b/hw/dma/pl080.c
@@ -381,7 +381,6 @@ static void pl080_class_init(ObjectClass *oc, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(oc);
 
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->vmsd = &vmstate_pl080;
 }
 
diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
index abd2ce8..892aa02 100644
--- a/hw/i386/kvm/clock.c
+++ b/hw/i386/kvm/clock.c
@@ -114,7 +114,6 @@ static void kvmclock_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->realize = kvmclock_realize;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->vmsd = &kvmclock_vmsd;
 }
 
diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
index f1a0a9d..44ee62a 100644
--- a/hw/i386/kvmvapic.c
+++ b/hw/i386/kvmvapic.c
@@ -827,7 +827,6 @@ static void vapic_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
 
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->reset   = vapic_reset;
     dc->vmsd    = &vmstate_vapic;
     dc->realize = vapic_realize;
diff --git a/hw/intc/arm_gic.c b/hw/intc/arm_gic.c
index 24ad276..f13a927 100644
--- a/hw/intc/arm_gic.c
+++ b/hw/intc/arm_gic.c
@@ -704,7 +704,6 @@ static void arm_gic_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
     ARMGICClass *agc = ARM_GIC_CLASS(klass);
 
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     agc->parent_realize = dc->realize;
     dc->realize = arm_gic_realize;
 }
diff --git a/hw/intc/arm_gic_common.c b/hw/intc/arm_gic_common.c
index 214a585..a47004b 100644
--- a/hw/intc/arm_gic_common.c
+++ b/hw/intc/arm_gic_common.c
@@ -156,7 +156,6 @@ static void arm_gic_common_class_init(ObjectClass *klass, void *data)
     dc->realize = arm_gic_common_realize;
     dc->props = arm_gic_common_properties;
     dc->vmsd = &vmstate_gic;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo arm_gic_common_type = {
diff --git a/hw/intc/arm_gic_kvm.c b/hw/intc/arm_gic_kvm.c
index a0bbf12..59a3da5 100644
--- a/hw/intc/arm_gic_kvm.c
+++ b/hw/intc/arm_gic_kvm.c
@@ -150,7 +150,6 @@ static void kvm_arm_gic_class_init(ObjectClass *klass, void *data)
     kgc->parent_reset = dc->reset;
     dc->realize = kvm_arm_gic_realize;
     dc->reset = kvm_arm_gic_reset;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo kvm_arm_gic_info = {
diff --git a/hw/intc/ioapic_common.c b/hw/intc/ioapic_common.c
index cc5a80d..9ba1a26 100644
--- a/hw/intc/ioapic_common.c
+++ b/hw/intc/ioapic_common.c
@@ -98,7 +98,6 @@ static void ioapic_common_class_init(ObjectClass *klass, void *data)
 
     dc->realize = ioapic_common_realize;
     dc->vmsd = &vmstate_ioapic_common;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo ioapic_common_type = {
diff --git a/hw/intc/pl190.c b/hw/intc/pl190.c
index b16bc02..2bf359a 100644
--- a/hw/intc/pl190.c
+++ b/hw/intc/pl190.c
@@ -273,7 +273,6 @@ static void pl190_class_init(ObjectClass *klass, void *data)
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = pl190_init;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->reset = pl190_reset;
     dc->vmsd = &vmstate_pl190;
 }
diff --git a/hw/isa/isa-bus.c b/hw/isa/isa-bus.c
index 6b2114d..55d0100 100644
--- a/hw/isa/isa-bus.c
+++ b/hw/isa/isa-bus.c
@@ -197,7 +197,6 @@ static void isabus_bridge_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->fw_name = "isa";
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo isabus_bridge_info = {
diff --git a/hw/misc/arm_l2x0.c b/hw/misc/arm_l2x0.c
index ceea99d..9e220c9 100644
--- a/hw/misc/arm_l2x0.c
+++ b/hw/misc/arm_l2x0.c
@@ -179,7 +179,6 @@ static void l2x0_class_init(ObjectClass *klass, void *data)
 
     k->init = l2x0_priv_init;
     dc->vmsd = &vmstate_l2x0;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->props = l2x0_properties;
     dc->reset = l2x0_priv_reset;
 }
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 6075bfc..ee96c16 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -599,7 +599,6 @@ static void fw_cfg_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->realize = fw_cfg_realize;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->reset = fw_cfg_reset;
     dc->vmsd = &vmstate_fw_cfg;
     dc->props = fw_cfg_properties;
diff --git a/hw/pci-host/bonito.c b/hw/pci-host/bonito.c
index 2e08e9d..bfb9820 100644
--- a/hw/pci-host/bonito.c
+++ b/hw/pci-host/bonito.c
@@ -819,11 +819,9 @@ static const TypeInfo bonito_info = {
 
 static void bonito_pcihost_class_init(ObjectClass *klass, void *data)
 {
-    DeviceClass *dc = DEVICE_CLASS(klass);
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = bonito_pcihost_initfn;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo bonito_pcihost_info = {
diff --git a/hw/pci-host/grackle.c b/hw/pci-host/grackle.c
index ba6017f..b0da33d 100644
--- a/hw/pci-host/grackle.c
+++ b/hw/pci-host/grackle.c
@@ -143,10 +143,8 @@ static const TypeInfo grackle_pci_info = {
 static void pci_grackle_class_init(ObjectClass *klass, void *data)
 {
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
-    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init = pci_grackle_init_device;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo grackle_pci_host_info = {
diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index 333358e..98ebe6c 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -727,7 +727,6 @@ static void i440fx_pcihost_class_init(ObjectClass *klass, void *data)
     hc->root_bus_path = i440fx_pcihost_root_bus_path;
     dc->realize = i440fx_pcihost_realize;
     dc->fw_name = "pci";
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->props = i440fx_props;
 }
 
diff --git a/hw/pci-host/prep.c b/hw/pci-host/prep.c
index 58b8c5e..ebc40c6 100644
--- a/hw/pci-host/prep.c
+++ b/hw/pci-host/prep.c
@@ -215,7 +215,6 @@ static void raven_pcihost_class_init(ObjectClass *klass, void *data)
     set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
     dc->realize = raven_pcihost_realizefn;
     dc->fw_name = "pci";
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo raven_pcihost_info = {
diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
index e328f53..4e33f46 100644
--- a/hw/ppc/spapr_vio.c
+++ b/hw/ppc/spapr_vio.c
@@ -528,11 +528,9 @@ static int spapr_vio_bridge_init(SysBusDevice *dev)
 
 static void spapr_vio_bridge_class_init(ObjectClass *klass, void *data)
 {
-    DeviceClass *dc = DEVICE_CLASS(klass);
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = spapr_vio_bridge_init;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo spapr_vio_bridge_info = {
diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 26a717c..1a6397b 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -182,7 +182,6 @@ static void s390_ipl_class_init(ObjectClass *klass, void *data)
     k->init = s390_ipl_init;
     dc->props = s390_ipl_properties;
     dc->reset = s390_ipl_reset;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo s390_ipl_info = {
diff --git a/hw/s390x/s390-virtio-bus.c b/hw/s390x/s390-virtio-bus.c
index eccc3e7..46c5ff1 100644
--- a/hw/s390x/s390-virtio-bus.c
+++ b/hw/s390x/s390-virtio-bus.c
@@ -676,11 +676,9 @@ static int s390_virtio_bridge_init(SysBusDevice *dev)
 
 static void s390_virtio_bridge_class_init(ObjectClass *klass, void *data)
 {
-    DeviceClass *dc = DEVICE_CLASS(klass);
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = s390_virtio_bridge_init;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo s390_virtio_bridge_info = {
diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 3be9268..4b6250d 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -1283,11 +1283,9 @@ static int virtual_css_bridge_init(SysBusDevice *dev)
 
 static void virtual_css_bridge_class_init(ObjectClass *klass, void *data)
 {
-    DeviceClass *dc = DEVICE_CLASS(klass);
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = virtual_css_bridge_init;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo virtual_css_bridge_info = {
diff --git a/hw/sd/pl181.c b/hw/sd/pl181.c
index d830188..462558b 100644
--- a/hw/sd/pl181.c
+++ b/hw/sd/pl181.c
@@ -506,7 +506,6 @@ static void pl181_class_init(ObjectClass *klass, void *data)
     sdc->init = pl181_init;
     k->vmsd = &vmstate_pl181;
     k->reset = pl181_reset;
-    k->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
 }
 
 static const TypeInfo pl181_info = {
diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
index 1dc44cd..35a0a23 100644
--- a/hw/timer/arm_mptimer.c
+++ b/hw/timer/arm_mptimer.c
@@ -274,7 +274,6 @@ static void arm_mptimer_class_init(ObjectClass *klass, void *data)
     dc->realize = arm_mptimer_realize;
     dc->vmsd = &vmstate_arm_mptimer;
     dc->reset = arm_mptimer_reset;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->props = arm_mptimer_properties;
 }
 
diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c
index 74e0297..2fbbeb1 100644
--- a/hw/timer/hpet.c
+++ b/hw/timer/hpet.c
@@ -765,7 +765,6 @@ static void hpet_device_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->realize = hpet_realize;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->reset = hpet_reset;
     dc->vmsd = &vmstate_hpet;
     dc->props = hpet_device_properties;
diff --git a/hw/timer/pl031.c b/hw/timer/pl031.c
index 2f7360c..34d9b44 100644
--- a/hw/timer/pl031.c
+++ b/hw/timer/pl031.c
@@ -251,7 +251,6 @@ static void pl031_class_init(ObjectClass *klass, void *data)
     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 
     k->init = pl031_init;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->vmsd = &vmstate_pl031;
 }
 
