Re: [Qemu-devel] [libvirt] [RFC PATCH 0/2] ARM: add QMP command to query GIC version

[Andrea Bolognani]

On Tue, 2016-02-16 at 12:15 +0000, Daniel P. Berrange wrote:
> On Tue, Feb 16, 2016 at 01:05:45PM +0100, Andrea Bolognani wrote:
> > On Tue, 2016-02-16 at 10:15 +0000, Daniel P. Berrange wrote:
> > > > Back to GIV.  Recognized values of gic-version are fixed at compile
> > > > time: 2, 3, host.  Once again, QOM does things in code rather than data:
> > > > the set of values is defined in the setter function
> > > > virt_set_gic_version().
> > > >  
> > > > Some values are accepted only together with other configuration: 3
> > > > requires accel=kvm (for now), host requires -cpu host.  Static
> > > > introspection can't show such constraints.
> > > >  
> > > > Would the proposed query-gic-capability show them?  How?
> > >  
> > > Also bear in mind that libvirt probes capabilities using '-m none' so
> > > you're not going to have any 'virt' machine type instantiated when
> > > probing is done.
> > 
> > The idea is to add this information to domain capabilities, which
> > already have virtualization type, architecture and machine type as
> > inputs.
> 
> Regardless of the way it is exposed in libvirt API, when libvirt probes
> for capabilities it will *always* use '-m none'.

Domain capabilities are currently derived almost entirely from data
taken from virQEMUCaps, but is there anything stopping us from
calling QEMU with the appropriate machine type from
qemuConnectGetDomainCapabilities() to query for machine type
dependent domain capabilities such as supported values for the
gic-version property?

Cheers.

-- 
Andrea Bolognani
Software Engineer - Virtualization Team