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

[David Gibson]

On Wed, Aug 07, 2019 at 02:52:56PM -0300, 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.

That's certainly the intention.  If there are cases where it doesn't
behave that way, it's a bug - although possible one we have to
maintainer for machine compatibility.

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

I don't believe there is, no.

> 
> > 
> > >      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);
> > 
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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