Re: [Qemu-devel] [PATCH v4 15/18] target-i386: Set migratable=yes by default

[Eduardo Habkost]

On Thu, May 15, 2014 at 10:07:12PM +0200, Andreas Färber wrote:
> Am 30.04.2014 18:48, schrieb Eduardo Habkost:
> > Having only migratable flags reported by default on the "host" CPU model
> > is safer for the following reasons:
> > 
> >  * Existing users may expect "-cpu host" to be migration-safe, if they
> >    take care of always using compatible host CPUs, host kernels, and
> >    QEMU versions.
> >  * Users who don't care aboug migration and want to enable all features
> 
> "about"

Oops.

> 
> >    supported by the host kernel can simply change their setup to use
> >    migratable=no.
> > 
> > Signed-off-by: Eduardo Habkost <address@hidden>
> 
> I see no Reviewed-by or Acked-by for this change...

Paolo? Marcelo? Can you help here?

> 
> Shouldn't we at least add .compat_props if we change this behavior?

I don't believe we need it. Machine-types are about ABI stability, and
"-cpu host" has no ABI stability unless you have exactly the same host
CPU, same QEMU version and the same kernel version.

> 
> (NB at this point there are no unmigratable flags yet, but in 18/18.)

Actually, there are unmigratable flags, already: the ones supported by
the KVM kernel module but are still unknown to QEMU.

> 
> Regards,
> Andreas
> 
> > ---
> >  target-i386/cpu.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index 9c30957..9ef27fc 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -1232,7 +1232,7 @@ static int cpu_x86_fill_model_id(char *str)
> >  static X86CPUDefinition host_cpudef;
> >  
> >  static Property x86_host_cpu_properties[] = {
> > -    DEFINE_PROP_BOOL("migratable", X86CPU, migratable, false),
> > +    DEFINE_PROP_BOOL("migratable", X86CPU, migratable, true),
> >      DEFINE_PROP_END_OF_LIST()
> >  };
> >  
> 
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-- 
Eduardo