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

[Tao Xu]

On 8/8/2019 1:52 AM, Eduardo Habkost wrote:
> On Tue, Aug 06, 2019 at 02:50:55PM +0200, Igor Mammedov wrote:
> > On Mon,  5 Aug 2019 15:13:02 +0800
> > Tao Xu <address@hidden> wrote:
> >
> > > Add MachineClass::auto_enable_numa field. When it is true, a NUMA node
> > > is expected to be created implicitly.
> > >
> > > Acked-by: David Gibson <address@hidden>
> > > Suggested-by: Igor Mammedov <address@hidden>
> > > Suggested-by: Eduardo Habkost <address@hidden>
> > > Signed-off-by: Tao Xu <address@hidden>
> [...]
> > > +    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?
Even without this patch and HMAT patch, if without numa configuration, 
global nb_numa_nodes is always existing and default is 0, so nb_nodes 
will be auto set to 1, so from my point of view, this patch will not 
change ABI.

And I would also want to listen David's opinion.
> > >       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);