Re: [Qemu-ppc] [Qemu-devel] [PATCH v4 6/7] qdev: Protect device-list-properties against broken devices

[Andreas Färber]

Am 28.09.2015 um 22:08 schrieb Markus Armbruster:
> 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_even_create_with_object_new_yet
> to mark them:

This name is very misleading unfortunately. You must be able to create
any QOM object with object_new(), you just can't clean them up IIUC.

What about cannot_clean_up_with_finalize_yet or irreversible_to_create?

ACK for the general approach of adding a new ugly field. ;)

Regards,
Andreas

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