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

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Julien,

> -----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?

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?

> > +   bool "NUMA (Non-Uniform Memory Access) Support (UNSUPPORTED)" if
> UNSUPPORTED
> > +   depends on ARM_64
> > +   select NUMA
> > +   ---help---
> > +
> > +     Non-Uniform Memory Access (NUMA) is a computer memory design used
> in
> > +     multiprocessing, where the memory access time depends on the
> memory
> > +     location relative to the processor.
> > +
> 
> Cheers,
> 
> --
> Julien Grall