Re: [Qemu-devel] [PATCHv2 2/4] pc: refactor compat code

[Michael S. Tsirkin]

On Tue, Aug 28, 2012 at 01:23:18PM -0300, Marcelo Tosatti wrote:
> On Mon, Aug 27, 2012 at 03:20:13PM +0300, Michael S. Tsirkin wrote:
> > In preparation to adding PV EOI migration for 1.2,
> > trivially refactor some some compat code
> > to make it easier to add version specific
> > cpuid tweaks.
> > 
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > ---
> >  hw/pc_piix.c | 44 ++++++++++++++++++++++++++++++++++++--------
> >  1 file changed, 36 insertions(+), 8 deletions(-)
> 
> Why can't you clear the cpuid bit in kvm paravirt leaf at hw/pc_piix.c, 
> leaving compat code isolated there?

This is not how we handle it for compat properties:
there we set flag in pc_piix and make devices look at
that flag.
And it makes sense because what you suggest does not scale: we can not
teach pc_piix about quirks of all hardware.

It will also scale better if we ever get interested about
compatibility and migration for non pc machines.
-- 
MST