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Re: [XEN RFC PATCH 17/40] xen/arm: Introduce DEVICE_TREE_NUMA Kconfig for arm64
On 20/08/2021 11:49, Wei Chen wrote:
Hi Julien,
Hi Wei,
-----Original Message-----
From: Julien Grall <julien@xxxxxxx>
Sent: 2021年8月20日 16:41
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 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.
Ok. I agree with this.
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?
No, I didn't want a different one. I thought you wanted it that way.
Obviously, I mis-understanded your comments.
Can I understand your previous comments like following:
1. We should have a generic config that will then select DT and ACPI:
Because we already have CONFIG_NUMA in common layer. So we need to
add another one for Arm like CONFIG_ARM_NUMA?
I think so.
And in this option, we can select CONFIG_DEVICE_TREE_NUMA
automatically if device tree is enabled. If CONFIG_ACPI
is enabled, we will select CONFIG_ACPI_NUMA too (in the
future)
In Xen code, DT_NUMA and ACPI_NUMA code can co-exist, Xen
Distributions should not have to build a different Xen for DT and ACPI.
So it is more they *must* co-exist.
will check the system ACPI support status to decide to use
DT_NUMA or ACPI_NUMA?
Yes. A user should only have to say "I want to use NUMA". This is Xen to
figure out whether we need to compile the support for DT and/or ACPI.
Once we have support for APCI, it doesn't make a lot of sense for the
users to say "I want to compile with DT and ACPI but I only want NUMA
when using DT".
Cheers,
--
Julien Grall
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