Re: [Qemu-devel] [PATCH 6/6] qapi: discriminate CpuInfo[Fast] on SysEmuTarget, not CpuInfoArch

[Eric Blake <eblake@redhat.com>]

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On 04/27/2018 01:53 AM, Markus Armbruster wrote:

> We could perhaps still declare *all* @arch values useless in v2.12.0,
> then fix them in v2.12.1.
> 

Well, it's still useful to know that "s390" means the extra field is
available even in 2.12.0.  But your plan:

> Or we deprecate @arch right when we introduce @target, and drop it later
> in accordance with our deprecation policy (qemu-doc.texi @appendix
> Deprecated features).  That way, the rather ridiculous code to compute
> it will be temporary.  I think that's cleaner.
> 
>    @arch in     query-cpus      query-cpus-fast
>    before 2.6   nonexistent
>    2.6 - 2.11   CpuInfoArch
>    2.12         cmd deprecated  CpuInfoArch
>    2.13         cmd deprecated  memb deprecated
>    2.14         cmd gone        memb deprecated
>    2.15         cmd gone        memb gone

works well for me.  I don't think we can accelerate the deprecation by
backporting that to 2.12.1, or if the deprecation belongs only in 2.13,
but the overall plan is sane (libvirt has the deprecation timeframe to
start accessing 'target' instead of 'arch' when worrying about whether
the extra s390x information is present - if it doesn't already just read
the information when present without worrying about the value of 'arch'
in the first place).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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