Re: [Qemu-devel] [PATCH] monitor: introduce query-config-schema

[Eric Blake]

On 04/22/2013 06:07 AM, Paolo Bonzini wrote:
> Il 22/04/2013 13:48, Amos Kong ha scritto:
>>>>>> Libvirt doesn't have a stable way to know option support
>>>>>> detail. This patch introdued a new qmp command to query
>>>>>> configuration schema information. hmp command isn't added.
>>>>
>>>> Can you introspect QemuOpts instead?  All new options are added there.
>>
>> It would be exact to use QemuOpts. I tried to output the vm_config_groups[]
>> in qemu-config.c, but it seems not enough. (desc list of -netdev, -drive,
>> -device are all empty)
> 
> That's expected because they are parsed otherwise, depending on the
> backend type.  -chardev is currently working but it's an implementation
> detail.

Libvirt cares most about newly added options, which should use qemuOpts
all the way.  We can understand that legacy options like -netdev might
not yet use qemuOpts, but they are also legacy options, and therefore
libvirt can already assume they exist since at least qemu 1.3 (when
libvirt switched over to QMP probing).  If we later add a new feature to
-netdev, we should also convert -netdev to qemuOpts at that time, so
that libvirt would know whether the new feature is available.

At any rate, we really DO want introspection, and having it in 1.5 is a
worthwhile goal.  Even if the introspection turns up empty on legacy
options, having it for the sake of new options is worth the effort.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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