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

[Luiz Capitulino <lcapitulino@redhat.com>]

On Tue, 23 Apr 2013 09:32:31 -0600
Eric Blake <eblake@redhat.com> wrote:

> On 04/23/2013 07:20 AM, Luiz Capitulino wrote:
> > On Mon, 22 Apr 2013 09:00:05 -0600
> > Eric Blake <eblake@redhat.com> wrote:
> > 
> >> 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.
> > 
> > Agreed. But as you said in another email, we need a JSON representation
> > for this command. Dumping all options as strings is just like using -help.
> > 
> > Something else that has occurred to me is that, do we want this to be
> > a QMP command or do we want this to be a command-line option? If we do this
> > as a QMP command then libvirt would have to actually start QEMU just to
> > query supported options.
> 
> A command-line option might (or might not) be useful to humans, but a
> QMP command is what libvirt wants.  Libvirt already starts a QMP session
> for lots of other queries (not the least of which is the
> 'query-commands' query which would let us know whether to even expect
> the new QMP command for command-line introspection to work).  Adding one
> more QMP query to the mix called by libvirt is easy (no additional
> processes, and the response already goes through the JSON parser that
> handles all QMP responses);

That's right.

> adding a new command line option is more
> expensive (we would have to start qemu once to use the command line
> option, then again for the QMP queries; also, it's more coding effort to
> wire up libvirt to pass the stdout from the command line call into the
> JSON parser that was normally expecting data from a Unix socket).
> 
> > 
> > Another interesting point is about full schema introspection. This patch
> > only supports command-line options. It would be desirable to be able to
> > introspect all QAPI types and QMP commands, although I'm aware that this
> > might be a lot of work to do for 1.5.
> 
> Based on the call today, getting introspection for command line
> additions in time for 1.5, and saving full QMP introspection until 1.6,
> would be reasonable; libvirt's immediate goal is to determine when it is
> safe to use new command line options while doing its one-shot QMP
> probing of a qemu binary.

Yes. All my points have been clarified in today's meeting.