On Fri, Feb 02, 2018 at 12:50:14PM -0200, Eduardo Habkost wrote:
> (CCing qemu-devel)
>
> On Fri, Feb 02, 2018 at 09:21:59AM -0500, Luiz Capitulino wrote:
> > On Fri, 2 Feb 2018 14:19:38 +0000
> > Daniel P. Berrangé <berrange@xxxxxxxxxx> wrote:
> > > On Fri, Feb 02, 2018 at 12:15:54PM -0200, Eduardo Habkost wrote:
> [...]
> > > > It would be also interesting to update QEMU QMP documentation to
> > > > clarify the arch-specific semantics of "halted".
> > >
> > > Any also especially clarify the awful performance implications of running
> > > this particular query command. In general I would not expect query-xxx
> > > monitor commands to interrupt all vcpus, so we should clearly warn about
> > > this !
> >
> > Or deprecate it...
>
> We could deprecate the expensive fields on query-cpus, and move
> them to a more expensive query-cpu-state command. I believe most
> users of query-cpus are only interested in qom_path, thread_id,
> and topology info.
>
> Markus, Eric: from the QAPI point of view, is it OK to remove
> fields between QEMU versions, as long as we follow our
> deprecation policy?
I would expect that to not be OK. A fully backwards compatible way to
deal with this would just be to add a flag to the query-cpus command
eg something like
query-cpus arch-specific=false
to turn off all this arch specific state, and just report the cheap
generic info. If it defaults to arch-specific=true when omitted, then
there's no compat problems.
Regards,
Daniel
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