Re: [PATCH 7/7] cpu: Add `machine` parameter to query-cpu-definitions

From: Eduardo Habkost <ehabkost@redhat.com>
To: Markus Armbruster <armbru@redhat.com>,
	Jiri Denemark <jdenemar@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
	libvir-list@redhat.com, David Hildenbrand <david@redhat.com>,
	Aleksandar Rikalo <arikalo@wavecomp.com>,
	Cornelia Huck <cohuck@redhat.com>,
	qemu-devel@nongnu.org, Halil Pasic <pasic@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	qemu-s390x@nongnu.org, qemu-arm@nongnu.org, qemu-ppc@nongnu.org,
	Aleksandar Markovic <amarkovic@wavecomp.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Igor Mammedov <imammedo@redhat.com>,
	Richard Henderson <rth@twiddle.net>,
	Aurelien Jarno <aurelien@aurel32.net>,
	David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH 7/7] cpu: Add `machine` parameter to query-cpu-definitions
Date: Fri, 25 Oct 2019 10:22:15 -0300	[thread overview]
Message-ID: <20191025132215.GC6744@habkost.net> (raw)
In-Reply-To: <8736fhmius.fsf@dusky.pond.sub.org>

CCing libvir-list.

On Fri, Oct 25, 2019 at 08:36:59AM +0200, Markus Armbruster wrote:
> Eduardo Habkost <ehabkost@redhat.com> writes:
> > The new parameter can be used by management software to query for
> > CPU model alias information for multiple machines without
> > restarting QEMU.
[...]
> > @@ -317,9 +321,17 @@
>    ##
>    # @query-cpu-definitions:
> >  #
> >  # Return a list of supported virtual CPU definitions
> >  #
> > +# @machine: Name of machine type.  The command returns some data
> > +#           that machine-specific.  This overrides the machine type
> 
> "that is machine-specific"
> 
> > +#           used to look up that information.  This can be used,
> > +#           for example, to query machine-specific CPU model aliases
> > +#           without restarting QEMU (since 4.2)
> > +#
> >  # Returns: a list of CpuDefInfo
> >  #
> >  # Since: 1.2.0
> >  ##
> > -{ 'command': 'query-cpu-definitions', 'returns': ['CpuDefinitionInfo'],
> > +{ 'command': 'query-cpu-definitions',
> > +  'data': { '*machine': 'str' },
> > +  'returns': ['CpuDefinitionInfo'],
> >    'if': 'defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_I386) || defined(TARGET_S390X) || defined(TARGET_MIPS)' }
> 
> I'm afraid the doc comment is less than clear.  Before I can suggest
> improvements, I have questions.
> 
> Looks like @alias-of is the only part of the return value that changes
> when I re-run query-cpu-definitions with another @machine argument.
> Correct?

Yes.

> 
> How is this going to be used?  Will management software run
> query-cpu-definitions for each machine type returned by query-machines?
> Or just for a few of them?

I don't know.  I'll let Jiri and other libvirt developers answer
that.

-- 
Eduardo