linux-kernel - Re: [PATCH v4 0/4] Support SMT control on arm64

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Date:   Thu, 30 Nov 2023 14:56:33 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     <catalin.marinas@....com>, <will@...nel.org>,
        <sudeep.holla@....com>, <linux-arm-kernel@...ts.infradead.org>
CC:     <yangyicong@...ilicon.com>, <dietmar.eggemann@....com>,
        <gregkh@...uxfoundation.org>, <rafael@...nel.org>,
        <jonathan.cameron@...wei.com>, <prime.zeng@...ilicon.com>,
        <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 0/4] Support SMT control on arm64

Hi Sudeep, Catalin, Will and ARM folks,

Any comments? Appreciate for any feedbacks.

Thanks.

On 2023/11/21 17:25, 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:
> 
> - implements the basic support in arch_topology driver
> - 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 real ACPI based arm64 server and on
> ACPI/OF based QEMU VMs.
> 
> The patchset is based on v6.7-rc1.
> 
> Change since v3:
> - Fix some build and kconfig error reported by kernel test robot <lkp@...el.com>
> Link: https://lore.kernel.org/linux-arm-kernel/20231114040110.54590-1-yangyicong@huawei.com/
> 
> Change since v2:
> - Detect SMT thread number at topology build from ACPI/DT, avoid looping CPUs
> - Split patches into ACPI/OF/arch_topology path and enable the kconfig for arm64
> Link: https://lore.kernel.org/linux-arm-kernel/20231010115335.13862-1-yangyicong@huawei.com/
> 
> Yicong Yang (4):
>   arch_topology: Support basic SMT control for the driver
>   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  | 23 ++++++++++++++++++
>  drivers/base/arch_topology.c  | 45 +++++++++++++++++++++++++++++++++++
>  include/linux/arch_topology.h | 14 +++++++++++
>  4 files changed, 83 insertions(+)
>