Re: [Qemu-devel] [PATCH RFC 0/8] cpus: make "-cpu cpux, features" global properties

[David Hildenbrand <dahi@linux.vnet.ibm.com>]

> I assume Igor explained it, already, and his suggestion sounds OK
> to you. But I will answer your questions to confirm that this is
> really the case:

Yes, this all sounds good to me, thanks for the additional explanation!
[...]

> 
> > 
> > d) has to work for us. Otherwise we will have to fallback to manual
> > property parsing.  
> 
> It will be affected by the globals, but I assume management code
> is not going to use add extra -cpu arguments when probing for CPU
> model information, right?

Yes, that's also what I figured out, this should not be a problem.

> 
> Users will need to be aware that -cpu is equivalent to -global,
> and will affect CPU information returned by query-cpu-definitions
> (or similar commands).
> 
> >   
> > > 
> > > If all you need is to parse properties, why can't you reuse the
> > > existing QOM/Device mechanisms to handle properties (the one used
> > > by -device and device_add), instead of the -cpu code?  
> > 
> > We can, if my given example works. And the global properties
> > don't interfere with cpus.  
> 
> They do, but only the model specified in -cpu.
> 
> >   
> > > 
> > > We need to use less of the infrastructure that exists for the
> > > legacy -cpu option (and use more of the generic QOM/Device
> > > mechanisms), not more of it.  
> > 
> > It is better to have one way of creating cpus that two.  
> 
> Unfortunately we already have two ways of creating CPUs: -cpu and
> device_add. We are trying to translate -cpu to something
> equivalent to generic mechanisms (-device and -global), so we
> have only one underlying mechanism.

Yes, understood. Sounds sane to me!
[...]

> I understand that this may be confusing, but that's because -smp
> and -cpu don't fit the QEMU device/object models. We are moving
> towards allowing CPU topologies to be created using only -device.
> 
> To do that, we are gradually translating -cpu to the generic
> mechanisms used by -device/-global, so command-line options could
> be easily converted to use the new mechanisms in the future.
> 
> Does that make sense?
> 

Absolutely!

David