Re: [XEN RFC PATCH 17/40] xen/arm: Introduce DEVICE_TREE_NUMA Kconfig for arm64

[Julien Grall <julien@xxxxxxx>]

On 20/08/2021 03:30, Wei Chen wrote:
> Hi Julien,
Hi Wei,

> > -----Original Message-----
> > From: Julien Grall <julien@xxxxxxx>
> > Sent: 2021年8月19日 21:38
> > To: Wei Chen <Wei.Chen@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx;
> > sstabellini@xxxxxxxxxx; jbeulich@xxxxxxxx
> > Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
> > Subject: Re: [XEN RFC PATCH 17/40] xen/arm: Introduce DEVICE_TREE_NUMA
> > Kconfig for arm64
> >
> > Hi,
> >
> > On 11/08/2021 11:24, Wei Chen wrote:
> > > We need a Kconfig option to distinguish with ACPI based
> > > NUMA. So we introduce the new Kconfig option:
> > > DEVICE_TREE_NUMA in this patch for Arm64.
> > >
> > > Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> > > ---
> > >    xen/arch/arm/Kconfig | 10 ++++++++++
> > >    1 file changed, 10 insertions(+)
> > >
> > > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> > > index ecfa6822e4..678cc98ea3 100644
> > > --- a/xen/arch/arm/Kconfig
> > > +++ b/xen/arch/arm/Kconfig
> > > @@ -33,6 +33,16 @@ config ACPI
> > >           Advanced Configuration and Power Interface (ACPI) support for Xen
> > is
> > >           an alternative to device tree on ARM64.
> > >
> > > +config DEVICE_TREE_NUMA
> > The name suggests that NUMA should only be enabled for Device-Tree...
> > But the description looks generic.
> >
> > However, I think the user should only have the choice to say whether
> > they want NUMA to be enabled or not. We should not give them the choice
> > to enable/disable the parsing for DT/ACPI.
> >
> > So we should have a generic config that will then select DT (and ACPI in
> > the future).
> How about we select DT_NUMA default on Arm64. And DT_NUMA select NUMA
> like what we have done in patch#6 in x86? And remove the description?
I would rather not make NUMA supported by default on Arm64. Instead, we 
should go throught the same process as other new features and gate it 
behind UNSUPPORTED until it is mature enough.
> If we make generic NUMA as a selectable option, and depends on
> NUMA to select DT or ACPI NUMA. It seems to be quite different from
> the existing logic?
I am a bit confused. You added just logic to select NUMA from ACPI, 
right? So are you talking about a different logic?
Cheers,

--
Julien Grall