diff --git a/hw/mips/gt64xxx_pci.c b/hw/mips/gt64xxx_pci.c
index 3da2e67098..6398514c99 100644
--- a/hw/mips/gt64xxx_pci.c
+++ b/hw/mips/gt64xxx_pci.c
@@ -1151,12 +1151,18 @@ static int gt64120_pci_init(PCIDevice *d)
 static void gt64120_pci_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init = gt64120_pci_init;
     k->vendor_id = PCI_VENDOR_ID_MARVELL;
     k->device_id = PCI_DEVICE_ID_MARVELL_GT6412X;
     k->revision = 0x10;
     k->class_id = PCI_CLASS_BRIDGE_HOST;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo gt64120_pci_info = {
diff --git a/hw/pci-bridge/dec.c b/hw/pci-bridge/dec.c
index e5e3be829f..a6ca940d55 100644
--- a/hw/pci-bridge/dec.c
+++ b/hw/pci-bridge/dec.c
@@ -116,6 +116,7 @@ static int dec_21154_pci_host_init(PCIDevice *d)
 static void dec_21154_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init = dec_21154_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_DEC;
@@ -123,6 +124,11 @@ static void dec_21154_pci_host_class_init(ObjectClass *klass, void *data)
     k->revision = 0x02;
     k->class_id = PCI_CLASS_BRIDGE_PCI;
     k->is_bridge = 1;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo dec_21154_pci_host_info = {
diff --git a/hw/pci-host/apb.c b/hw/pci-host/apb.c
index 92f289f8f9..1b399ddbc3 100644
--- a/hw/pci-host/apb.c
+++ b/hw/pci-host/apb.c
@@ -516,11 +516,17 @@ static int pbm_pci_host_init(PCIDevice *d)
 static void pbm_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init = pbm_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_SUN;
     k->device_id = PCI_DEVICE_ID_SUN_SABRE;
     k->class_id = PCI_CLASS_BRIDGE_HOST;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo pbm_pci_host_info = {
diff --git a/hw/pci-host/bonito.c b/hw/pci-host/bonito.c
index bfb9820336..902441f10b 100644
--- a/hw/pci-host/bonito.c
+++ b/hw/pci-host/bonito.c
@@ -806,8 +806,12 @@ static void bonito_class_init(ObjectClass *klass, void *data)
     k->revision = 0x01;
     k->class_id = PCI_CLASS_BRIDGE_HOST;
     dc->desc = "Host bridge";
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->vmsd = &vmstate_bonito;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo bonito_info = {
diff --git a/hw/pci-host/grackle.c b/hw/pci-host/grackle.c
index b0da33dbe8..6c7cfdbeb2 100644
--- a/hw/pci-host/grackle.c
+++ b/hw/pci-host/grackle.c
@@ -130,7 +130,11 @@ static void grackle_pci_class_init(ObjectClass *klass, void *data)
     k->device_id = PCI_DEVICE_ID_MOTOROLA_MPC106;
     k->revision  = 0x00;
     k->class_id  = PCI_CLASS_BRIDGE_HOST;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo grackle_pci_info = {
diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index 98ebe6cd00..0a8f6c1d6e 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -689,8 +689,12 @@ static void i440fx_class_init(ObjectClass *klass, void *data)
     k->revision = 0x02;
     k->class_id = PCI_CLASS_BRIDGE_HOST;
     dc->desc = "Host bridge";
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
     dc->vmsd = &vmstate_i440fx;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo i440fx_info = {
diff --git a/hw/pci-host/ppce500.c b/hw/pci-host/ppce500.c
index f00793d819..c80b7cb2f5 100644
--- a/hw/pci-host/ppce500.c
+++ b/hw/pci-host/ppce500.c
@@ -387,6 +387,11 @@ static void e500_host_bridge_class_init(ObjectClass *klass, void *data)
     k->device_id = PCI_DEVICE_ID_MPC8533E;
     k->class_id = PCI_CLASS_PROCESSOR_POWERPC;
     dc->desc = "Host bridge";
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo e500_host_bridge_info = {
diff --git a/hw/pci-host/prep.c b/hw/pci-host/prep.c
index ebc40c6ab8..042dc8f225 100644
--- a/hw/pci-host/prep.c
+++ b/hw/pci-host/prep.c
@@ -198,7 +198,11 @@ static void raven_class_init(ObjectClass *klass, void *data)
     k->class_id = PCI_CLASS_BRIDGE_HOST;
     dc->desc = "PReP Host Bridge - Motorola Raven";
     dc->vmsd = &vmstate_raven;
-    dc->cannot_instantiate_with_device_add_yet = true; /* FIXME explain why */
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo raven_info = {
diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
index 81c82404d6..4bc2e0118e 100644
--- a/hw/pci-host/q35.c
+++ b/hw/pci-host/q35.c
@@ -403,6 +403,11 @@ static void mch_class_init(ObjectClass *klass, void *data)
     k->device_id = PCI_DEVICE_ID_INTEL_Q35_MCH;
     k->revision = MCH_HOST_BRIDGE_REVISION_DEFAULT;
     k->class_id = PCI_CLASS_BRIDGE_HOST;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo mch_info = {
diff --git a/hw/pci-host/uninorth.c b/hw/pci-host/uninorth.c
index adc1d89010..e72fe2a70b 100644
--- a/hw/pci-host/uninorth.c
+++ b/hw/pci-host/uninorth.c
@@ -351,12 +351,18 @@ static int unin_internal_pci_host_init(PCIDevice *d)
 static void unin_main_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init      = unin_main_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_APPLE;
     k->device_id = PCI_DEVICE_ID_APPLE_UNI_N_PCI;
     k->revision  = 0x00;
     k->class_id  = PCI_CLASS_BRIDGE_HOST;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo unin_main_pci_host_info = {
@@ -369,12 +375,18 @@ static const TypeInfo unin_main_pci_host_info = {
 static void u3_agp_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init      = u3_agp_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_APPLE;
     k->device_id = PCI_DEVICE_ID_APPLE_U3_AGP;
     k->revision  = 0x00;
     k->class_id  = PCI_CLASS_BRIDGE_HOST;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo u3_agp_pci_host_info = {
@@ -387,12 +399,18 @@ static const TypeInfo u3_agp_pci_host_info = {
 static void unin_agp_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init      = unin_agp_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_APPLE;
     k->device_id = PCI_DEVICE_ID_APPLE_UNI_N_AGP;
     k->revision  = 0x00;
     k->class_id  = PCI_CLASS_BRIDGE_HOST;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo unin_agp_pci_host_info = {
@@ -405,12 +423,18 @@ static const TypeInfo unin_agp_pci_host_info = {
 static void unin_internal_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init      = unin_internal_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_APPLE;
     k->device_id = PCI_DEVICE_ID_APPLE_UNI_N_I_PCI;
     k->revision  = 0x00;
     k->class_id  = PCI_CLASS_BRIDGE_HOST;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo unin_internal_pci_host_info = {
diff --git a/hw/pci-host/versatile.c b/hw/pci-host/versatile.c
index 6b28929d26..71ff0de303 100644
--- a/hw/pci-host/versatile.c
+++ b/hw/pci-host/versatile.c
@@ -467,11 +467,17 @@ static int versatile_pci_host_init(PCIDevice *d)
 static void versatile_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init = versatile_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_XILINX;
     k->device_id = PCI_DEVICE_ID_XILINX_XC2VP30;
     k->class_id = PCI_CLASS_PROCESSOR_CO;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo versatile_pci_host_info = {
diff --git a/hw/ppc/ppc4xx_pci.c b/hw/ppc/ppc4xx_pci.c
index d2d6f65e6c..4cb78518a3 100644
--- a/hw/ppc/ppc4xx_pci.c
+++ b/hw/ppc/ppc4xx_pci.c
@@ -380,6 +380,11 @@ static void ppc4xx_host_bridge_class_init(ObjectClass *klass, void *data)
     k->vendor_id    = PCI_VENDOR_ID_IBM;
     k->device_id    = PCI_DEVICE_ID_IBM_440GX;
     k->class_id     = PCI_CLASS_BRIDGE_OTHER;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo ppc4xx_host_bridge_info = {
diff --git a/hw/sh4/sh_pci.c b/hw/sh4/sh_pci.c
index e81176a11e..a2f6d9e0b6 100644
--- a/hw/sh4/sh_pci.c
+++ b/hw/sh4/sh_pci.c
@@ -162,10 +162,16 @@ static int sh_pci_host_init(PCIDevice *d)
 static void sh_pci_host_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
+    DeviceClass *dc = DEVICE_CLASS(klass);
 
     k->init = sh_pci_host_init;
     k->vendor_id = PCI_VENDOR_ID_HITACHI;
     k->device_id = PCI_DEVICE_ID_HITACHI_SH7751R;
+    /*
+     * PCI-facing part of the host bridge, not usable without the
+     * host-facing part, which can't be device_add'ed, yet.
+     */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo sh_pci_host_info = {