Re: [Qemu-devel] [Patch v1 01/29] qmp: details about CPU definitions in query-cpu-definitions

[Eduardo Habkost]

On Tue, Aug 02, 2016 at 04:27:55PM +0200, David Hildenbrand wrote:
[...]
> > > > 
> > > > I believe in this case we don't need to make it optional: just
> > > > make the field always present and set it to "false" by default.  
> > > 
> > > That is true for x86, do you know about the other architectures (arm, 
> > > ppc)?
> > > I'd like to avoid returning false information here for other 
> > > architectures.  
> > 
> > As being "static" is not a fact about the existing code, but just
> > a guarantee about what the developers are going to do in the
> > future, static=false just means that the developers didn't make
> > any promises yet (so I don't think it would ever be false
> > information).
> > 
> > In other words, I believe we can safely assume a CPU model is not
> > guaranteed to be static unless the maintainers decided to
> > explicitly document it as static (and change the data returned by
> > query-cpu-definitions).
> > 
> > (I am assuming that changing it from "false" to "true" in a new
> > QEMU version won't be a problem for anybody.)
> > 
> 
> Hmm, if "static" means, the model will never be changed, but it was changed in
> the past, this sounds somewhat strange. I would rather say then "information
> is not available" == no guarantee.

If the CPU model really changed in the past, I think it must be
always set to "false".

But if it never changed in the past and we never made an explicit
decision about future guarantees, we can set it to "false" today,
and change it to "true" later (after we made a decision).

> 
> But if nobody else sees a problem with that, I can just set it to stable=false
> on all other architectures.

I think it's OK, as long we set it to "true" only if it never
changed in the past.

-- 
Eduardo