Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types

[Michael S. Tsirkin]

On Wed, Aug 29, 2012 at 07:03:34AM -0300, Marcelo Tosatti wrote:
> On Wed, Aug 29, 2012 at 06:59:03AM -0300, Marcelo Tosatti wrote:
> > > I don't understand. What is the problem with the proposal?
> > > What will not work with our protocol?
> > > Can you give an example please?
> > > 
> > > 
> > > > > Too late for 1.2?
> > > > 
> > > > Absolutely (in my opinion).
> > 
> > My concern here is that you are introducing infrastructure by using
> > _one example_, claiming it to solve a general problem, without the
> > appropriate amount of energy spent in this solution.
> > 
> > Using old machines is supposed to be supported on older guests.
> > 
> > Michael, not migrating the PVEOI MSR actually crashes the guest?
> 
> Which is irrelevant since it won't be able to migrate to an older 
> qemu.
> 

With this patch, -M pc-1.1 migrates fine to an older qemu
and no crash.

Without, PV EOI bit in CPUID is set on source so
we have a problem.


-- 
MST