qdev: Protect device-list-properties against broken devices

qdev: Protect device-list-properties against broken devices

Several devices don't survive object_unref(object_new(T)): they crash
or hang during cleanup, or they leave dangling pointers behind.

This breaks at least device-list-properties, because
qmp_device_list_properties() needs to create a device to find its
properties.  Broken in commit f4eb32b "qmp: show QOM properties in
device-list-properties", v2.1.  Example reproducer:

    $ qemu-system-aarch64 -nodefaults -display none -machine none -S -qmp stdio
    {"QMP": {"version": {"qemu": {"micro": 50, "minor": 4, "major": 2}, "package": ""}, "capabilities": []}}
    { "execute": "qmp_capabilities" }
    {"return": {}}
    { "execute": "device-list-properties", "arguments": { "typename": "pxa2xx-pcmcia" } }
    qemu-system-aarch64: /home/armbru/work/qemu/memory.c:1307: memory_region_finalize: Assertion `((&mr->subregions)->tqh_first == ((void *)0))' failed.
    Aborted (core dumped)
    [Exit 134 (SIGABRT)]

Unfortunately, I can't fix the problems in these devices right now.
Instead, add DeviceClass member cannot_destroy_with_object_finalize_yet
to mark them:

* Hang during cleanup (didn't debug, so I can't say why):
  "realview_pci", "versatile_pci".

* Dangling pointer in cpus: most CPUs, plus "allwinner-a10", "digic",
  "fsl,imx25", "fsl,imx31", "xlnx,zynqmp", because they create such
  CPUs

* Assert kvm_enabled(): "host-x86_64-cpu", host-i386-cpu",
  "host-powerpc64-cpu", "host-embedded-powerpc-cpu",
  "host-powerpc-cpu" (the powerpc ones can't currently reach the
  assertion, because the CPUs are only registered when KVM is enabled,
  but the assertion is arguably in the wrong place all the same)

Make qmp_device_list_properties() fail cleanly when the device is so
marked.  This improves device-list-properties from "crashes, hangs or
leaves dangling pointers behind" to "fails".  Not a complete fix, just
a better-than-nothing work-around.  In the above reproducer,
device-list-properties now fails with "Can't list properties of device
'pxa2xx-pcmcia'".

This also protects -device FOO,help, which uses the same machinery
since commit ef52358 "qdev-monitor: include QOM properties in -device
FOO, help output", v2.2.  Example reproducer:

    $ qemu-system-aarch64 -machine none -device pxa2xx-pcmcia,help

Before:

    qemu-system-aarch64: .../memory.c:1307: memory_region_finalize: Assertion `((&mr->subregions)->tqh_first == ((void *)0))' failed.

After:

    Can't list properties of device 'pxa2xx-pcmcia'

Cc: "Andreas Färber" <[email protected]>
Cc: "Edgar E. Iglesias" <[email protected]>
Cc: Alexander Graf <[email protected]>
Cc: Anthony Green <[email protected]>
Cc: Aurelien Jarno <[email protected]>
Cc: Bastian Koppelmann <[email protected]>
Cc: Blue Swirl <[email protected]>
Cc: Eduardo Habkost <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Jia Liu <[email protected]>
Cc: Leon Alrae <[email protected]>
Cc: Mark Cave-Ayland <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Walle <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Maydell <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Markus Armbruster <[email protected]>
Reviewed-by: Eduardo Habkost <[email protected]>
Message-Id: <1443689999[email protected]>