Re: [Qemu-devel] [PATCH] numa: Introduce MachineClass::auto_enable_numa for implicit NUMA node

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Aug 06, 2019 at 02:50:55PM +0200, Igor Mammedov wrote:
> On Mon,  5 Aug 2019 15:13:02 +0800
> Tao Xu <tao3.xu@intel.com> wrote:
> 
> > Add MachineClass::auto_enable_numa field. When it is true, a NUMA node
> > is expected to be created implicitly.
> > 
> > Acked-by: David Gibson <david@gibson.dropbear.id.au>
> > Suggested-by: Igor Mammedov <imammedo@redhat.com>
> > Suggested-by: Eduardo Habkost <ehabkost@redhat.com>
> > Signed-off-by: Tao Xu <tao3.xu@intel.com>
[...]
> > +    mc->auto_enable_numa = true;
> 
> this will always create a numa node (that will affect not only RAM but
> also all other components that depends on numa state (like CPUs)),
> where as spapr_populate_memory() was only faking numa node in DT for RAM.
> It makes non-numa configuration impossible.
> Seeing David's ACK on the patch it might be fine, but I believe
> commit message should capture that and explain why the change in
> behavior is fine.

After a quick look, all spapr code seems to have the same
behavior when nb_numa_nodes==0 and nb_numa_nodes==1, but I'd like
to be sure.

David and/or Tao Xu: do you confirm there's no ABI change at all
on spapr after implicitly creating a NUMA node?

> 
> >      smc->default_caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_OFF;
> >      smc->default_caps.caps[SPAPR_CAP_VSX] = SPAPR_CAP_ON;
> > diff --git a/include/hw/boards.h b/include/hw/boards.h
> > index 2eb9a0b4e0..4a350b87d2 100644
> > --- a/include/hw/boards.h
> > +++ b/include/hw/boards.h
> > @@ -220,6 +220,7 @@ struct MachineClass {
> >      bool smbus_no_migration_support;
> >      bool nvdimm_supported;
> >      bool numa_mem_supported;
> > +    bool auto_enable_numa;
> >  
> >      HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
> >                                             DeviceState *dev);
> 

-- 
Eduardo