armsse: Define ARMSSEClass correctly

TYPE_ARM_SSE is a TYPE_SYS_BUS_DEVICE subclass, but
ARMSSEClass::parent_class is declared as DeviceClass.

It never caused any problems by pure luck:

We were not setting class_size for TYPE_ARM_SSE, so class_size of
TYPE_SYS_BUS_DEVICE was being used (sizeof(SysBusDeviceClass)).
This made the system allocate enough memory for TYPE_ARM_SSE
devices even though ARMSSEClass was too small for a sysbus
device.

Additionally, the ARMSSEClass::info field ended up at the same
offset as SysBusDeviceClass::explicit_ofw_unit_address.  This
would make sysbus_get_fw_dev_path() crash for the device.
Luckily, sysbus_get_fw_dev_path() never gets called for
TYPE_ARM_SSE devices, because qdev_get_fw_dev_path() is only used
by the boot device code, and TYPE_ARM_SSE devices don't appear at
the fw_boot_order list.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-id: 20200826181006.4097163-1-ehabkost@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/armsse.c

@@ -1160,6 +1160,7 @@ static const TypeInfo armsse_info = {
     .name = TYPE_ARMSSE,
     .parent = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(ARMSSE),
+    .class_size = sizeof(ARMSSEClass),
     .instance_init = armsse_init,
     .abstract = true,
     .interfaces = (InterfaceInfo[]) {

include/hw/arm/armsse.h

@@ -220,7 +220,7 @@ typedef struct ARMSSE {
 typedef struct ARMSSEInfo ARMSSEInfo;
 
 typedef struct ARMSSEClass {
-    DeviceClass parent_class;
+    SysBusDeviceClass parent_class;
     const ARMSSEInfo *info;
 } ARMSSEClass;