[Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default

[Thomas Huth]

Historically we've marked all devices as hotpluggable by default. However,
most devices are not hotpluggable, and you also need a HotplugHandler to
support these devices. So if the user tries to "device_add" or "device_del"
such a non-hotpluggable device during runtime, either nothing really usable
happens, or QEMU even crashes/aborts unexpectedly (see for example commit
84ebd3e8c7d4fe955b - "Mark diag288 watchdog as non-hotpluggable").
So let's change this dangerous default behaviour and mark the devices as
non-hotpluggable by default. Certain parent devices classes which are known
as hotpluggable (e.g. PCI, USB, etc.) are marked with "hotpluggable = true",
so that devices that are derived from these classes continue to work as
expected.

Signed-off-by: Thomas Huth <address@hidden>
---
 v2: Add missing devices and dropped "RFC" status. See Eduardo's reply on
 the previous version of this patch for the rationale which devices need
 to be hotpluggable:
 https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg06128.html

 hw/char/virtio-serial-bus.c   |  1 +
 hw/core/qdev.c                | 10 ++++------
 hw/mem/nvdimm.c               |  3 +++
 hw/mem/pc-dimm.c              |  1 +
 hw/pci/pci.c                  |  1 +
 hw/ppc/spapr_cpu_core.c       |  1 +
 hw/s390x/ccw-device.c         |  1 +
 hw/scsi/scsi-bus.c            |  1 +
 hw/usb/bus.c                  |  1 +
 hw/usb/dev-smartcard-reader.c |  1 +
 hw/xen/xen_backend.c          |  1 +
 target/i386/cpu.c             |  4 ++--
 target/s390x/cpu.c            |  1 +
 13 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 17a1bb0..da26fc2 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -1097,6 +1097,7 @@ static void virtio_serial_port_class_init(ObjectClass 
*klass, void *data)
     k->realize = virtser_port_device_realize;
     k->unrealize = virtser_port_device_unrealize;
     k->props = virtser_props;
+    k->hotpluggable = true;
 }
 
 static const TypeInfo virtio_serial_port_type_info = {
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index d9ccce6..28fd92f 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -1125,13 +1125,11 @@ static void device_class_init(ObjectClass *class, void 
*data)
     dc->realize = device_realize;
     dc->unrealize = device_unrealize;
 
-    /* by default all devices were considered as hotpluggable,
-     * so with intent to check it in generic qdev_unplug() /
-     * device_set_realized() functions make every device
-     * hotpluggable. Devices that shouldn't be hotpluggable,
-     * should override it in their class_init()
+    /*
+     * All devices are considered as cold-pluggable by default. The devices
+     * that are hotpluggable should override it in their class_init().
      */
-    dc->hotpluggable = true;
+    dc->hotpluggable = false;
     dc->user_creatable = true;
 }
 
diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
index 952fce5..02be9f3 100644
--- a/hw/mem/nvdimm.c
+++ b/hw/mem/nvdimm.c
@@ -148,9 +148,12 @@ static MemoryRegion 
*nvdimm_get_vmstate_memory_region(PCDIMMDevice *dimm)
 
 static void nvdimm_class_init(ObjectClass *oc, void *data)
 {
+    DeviceClass *dc = DEVICE_CLASS(oc);
     PCDIMMDeviceClass *ddc = PC_DIMM_CLASS(oc);
     NVDIMMClass *nvc = NVDIMM_CLASS(oc);
 
+    dc->hotpluggable = true;
+
     ddc->realize = nvdimm_realize;
     ddc->get_memory_region = nvdimm_get_memory_region;
     ddc->get_vmstate_memory_region = nvdimm_get_vmstate_memory_region;
diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
index 66eace5..1f78567 100644
--- a/hw/mem/pc-dimm.c
+++ b/hw/mem/pc-dimm.c
@@ -443,6 +443,7 @@ static void pc_dimm_class_init(ObjectClass *oc, void *data)
     dc->unrealize = pc_dimm_unrealize;
     dc->props = pc_dimm_properties;
     dc->desc = "DIMM memory module";
+    dc->hotpluggable = true;
 
     ddc->get_memory_region = pc_dimm_get_memory_region;
     ddc->get_vmstate_memory_region = pc_dimm_get_vmstate_memory_region;
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 1e6fb88..8db380d 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -2534,6 +2534,7 @@ static void pci_device_class_init(ObjectClass *klass, 
void *data)
     k->unrealize = pci_qdev_unrealize;
     k->bus_type = TYPE_PCI_BUS;
     k->props = pci_props;
+    k->hotpluggable = true;
     pc->realize = pci_default_realize;
 }
 
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index c08ee75..720284e 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -325,6 +325,7 @@ void spapr_cpu_core_class_init(ObjectClass *oc, void *data)
     dc->realize = spapr_cpu_core_realize;
     dc->unrealize = spapr_cpu_core_unrealizefn;
     dc->props = spapr_cpu_core_properties;
+    dc->hotpluggable = true;
     scc->cpu_class = cpu_class_by_name(TYPE_POWERPC_CPU, data);
     g_assert(scc->cpu_class);
 }
diff --git a/hw/s390x/ccw-device.c b/hw/s390x/ccw-device.c
index f9bfa15..d1b6e6f 100644
--- a/hw/s390x/ccw-device.c
+++ b/hw/s390x/ccw-device.c
@@ -48,6 +48,7 @@ static void ccw_device_class_init(ObjectClass *klass, void 
*data)
     k->realize = ccw_device_realize;
     k->refill_ids = ccw_device_refill_ids;
     dc->props = ccw_device_properties;
+    dc->hotpluggable = true;
 }
 
 const VMStateDescription vmstate_ccw_dev = {
diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
index 977f7bc..6703b2a 100644
--- a/hw/scsi/scsi-bus.c
+++ b/hw/scsi/scsi-bus.c
@@ -1741,6 +1741,7 @@ static void scsi_device_class_init(ObjectClass *klass, 
void *data)
     k->realize   = scsi_qdev_realize;
     k->unrealize = scsi_qdev_unrealize;
     k->props     = scsi_props;
+    k->hotpluggable = true;
 }
 
 static void scsi_dev_instance_init(Object *obj)
diff --git a/hw/usb/bus.c b/hw/usb/bus.c
index d910f84..16701aa 100644
--- a/hw/usb/bus.c
+++ b/hw/usb/bus.c
@@ -793,6 +793,7 @@ static void usb_device_class_init(ObjectClass *klass, void 
*data)
     k->realize  = usb_qdev_realize;
     k->unrealize = usb_qdev_unrealize;
     k->props    = usb_props;
+    k->hotpluggable = true;
 }
 
 static const TypeInfo usb_device_type_info = {
diff --git a/hw/usb/dev-smartcard-reader.c b/hw/usb/dev-smartcard-reader.c
index bef1f03..e28d1ba 100644
--- a/hw/usb/dev-smartcard-reader.c
+++ b/hw/usb/dev-smartcard-reader.c
@@ -1499,6 +1499,7 @@ static void ccid_card_class_init(ObjectClass *klass, void 
*data)
     k->init = ccid_card_init;
     k->exit = ccid_card_exit;
     k->props = ccid_props;
+    k->hotpluggable = true;
 }
 
 static const TypeInfo ccid_card_type_info = {
diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
index c46cbb0..96621fe 100644
--- a/hw/xen/xen_backend.c
+++ b/hw/xen/xen_backend.c
@@ -620,6 +620,7 @@ static void xendev_class_init(ObjectClass *klass, void 
*data)
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
     /* xen-backend devices can be plugged/unplugged dynamically */
     dc->user_creatable = true;
+    dc->hotpluggable = true;
 }
 
 static const TypeInfo xendev_type_info = {
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 0aa28fc..122623b 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -4170,6 +4170,8 @@ static void x86_cpu_common_class_init(ObjectClass *oc, 
void *data)
     dc->realize = x86_cpu_realizefn;
     dc->unrealize = x86_cpu_unrealizefn;
     dc->props = x86_cpu_properties;
+    dc->user_creatable = true;
+    dc->hotpluggable = true;
 
     xcc->parent_reset = cc->reset;
     cc->reset = x86_cpu_reset;
@@ -4215,8 +4217,6 @@ static void x86_cpu_common_class_init(ObjectClass *oc, 
void *data)
 #endif
     cc->cpu_exec_enter = x86_cpu_exec_enter;
     cc->cpu_exec_exit = x86_cpu_exec_exit;
-
-    dc->user_creatable = true;
 }
 
 static const TypeInfo x86_cpu_type_info = {
diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
index 34538c3..ef61d19 100644
--- a/target/s390x/cpu.c
+++ b/target/s390x/cpu.c
@@ -462,6 +462,7 @@ static void s390_cpu_class_init(ObjectClass *oc, void *data)
     dc->realize = s390_cpu_realizefn;
     dc->props = s390x_cpu_properties;
     dc->user_creatable = true;
+    dc->hotpluggable = true;
 
     scc->parent_reset = cc->reset;
 #if !defined(CONFIG_USER_ONLY)
-- 
1.8.3.1