linux-kernel - Re: [PATCH v11 0/4] Support SMT control on arm64

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Message-ID: <df9784c3-c2ea-4bac-839a-2b7de0a81aac@arm.com>
Date: Fri, 28 Feb 2025 12:12:02 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Yicong Yang <yangyicong@...wei.com>, catalin.marinas@....com,
 will@...nel.org, sudeep.holla@....com, tglx@...utronix.de,
 peterz@...radead.org, mpe@...erman.id.au,
 linux-arm-kernel@...ts.infradead.org, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, pierre.gondois@....com
Cc: linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
 linux-kernel@...r.kernel.org, morten.rasmussen@....com, msuchanek@...e.de,
 gregkh@...uxfoundation.org, rafael@...nel.org, jonathan.cameron@...wei.com,
 prime.zeng@...ilicon.com, linuxarm@...wei.com, yangyicong@...ilicon.com,
 xuwei5@...wei.com, guohanjun@...wei.com, sshegde@...ux.ibm.com
Subject: Re: [PATCH v11 0/4] Support SMT control on arm64

On 18/02/2025 15:10, Yicong Yang wrote:
> From: Yicong Yang <yangyicong@...ilicon.com>
> 
> The core CPU control framework supports runtime SMT control which
> is not yet supported on arm64. Besides the general vulnerabilities
> concerns we want this runtime control on our arm64 server for:
> 
> - better single CPU performance in some cases
> - saving overall power consumption
> 
> This patchset implements it in the following aspects:
> 
> - Provides a default topology_is_primary_thread()
> - support retrieve SMT thread number on OF based system
> - support retrieve SMT thread number on ACPI based system
> - select HOTPLUG_SMT for arm64
> 
> Tests has been done on our ACPI based arm64 server and on ACPI/OF
> based QEMU VMs.

[...]

> Yicong Yang (4):
>   cpu/SMT: Provide a default topology_is_primary_thread()
>   arch_topology: Support SMT control for OF based system
>   arm64: topology: Support SMT control on ACPI based system
>   arm64: Kconfig: Enable HOTPLUG_SMT
> 
>  arch/arm64/Kconfig                  |  1 +
>  arch/arm64/kernel/topology.c        | 66 +++++++++++++++++++++++++++++
>  arch/powerpc/include/asm/topology.h |  1 +
>  arch/x86/include/asm/topology.h     |  2 +-
>  drivers/base/arch_topology.c        | 27 ++++++++++++
>  include/linux/topology.h            | 22 ++++++++++
>  6 files changed, 118 insertions(+), 1 deletion(-)

With the review comments on the individual patches [0-3]/4:

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>