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

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


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
          an alternative to device tree on ARM64.


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?


Julien Grall



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