Re: [Qemu-devel] [RFC] QMP: add query-hotpluggable-cpus

[Markus Armbruster]

Igor Mammedov <address@hidden> writes:

> On Mon, 22 Feb 2016 13:54:32 +1100
> David Gibson <address@hidden> wrote:
[...]
>> This is why Eduardo suggested - and I agreed - that it's probably
>> better to implement the "1st layer" as an internal structure/interface
>> only, and implement the 2nd layer on top of that.  When/if we need to
>> we can revisit a user-accessible interface to the 1st layer.
> We are going around QOM based CPU introspecting interface for
> years now and that's exactly what 2nd layer is, just another
> implementation. I've just lost hope in this approach.
>
> What I'm suggesting in this RFC is to forget controversial
> QOM approach for now and use -device/device_add + QMP introspection,
> i.e. completely split interface from how boards internally implement
> CPU hotplug.

QMP introspection doesn't tell you anything about device_add now.
Covering device_add is hard, because introspection data is fixed at
compile-time, but device models are collected only at run time.  Worse,
non-qdev QOM properties are buried in code, which you have to run to
find them.  See also my slide 39 of my KVM Form 2015 presentation
http://events.linuxfoundation.org/sites/events/files/slides/armbru-qemu-introspection.pdf

But perhaps you means something else.