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

[Eduardo Habkost]

On Tue, Aug 02, 2016 at 03:23:30PM +0200, David Hildenbrand wrote:
[...]
> > > +#
> > > +# @static: #optional whether a CPU definition is static and will not 
> > > change
> > > +#          between QEMU versions / QEMU machines. A static model is 
> > > always
> > > +#          migration-safe. If not provided, information is not 
> > > available.  
> > 
> > I assume static models don't change depending on the
> > machine-type, either. If that's case, we should document that.
> 
> That's what I meant with "QEMU machines", should that be "QEMU machine types"
> instead?

Sorry, I was reading it too quickly. You did document it. :)

We could extend it to mention the other guarantees (just like my
previous suggestion for CpuModelExpansionType::static): "will not
change depending on QEMU version, machine type, machine options,
and accelerator options".

> 
> > 
> > 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.)

-- 
Eduardo