linux-kernel - Re: [PATCH RFC v3 21/21] cpumask: Add enabled cpumask for present CPUs that can be brought online

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Date: Fri, 15 Dec 2023 20:40:28 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Russell King <rmk+kernel@...linux.org.uk>, linux-pm@...r.kernel.org,
 loongarch@...ts.linux.dev, linux-acpi@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-riscv@...ts.infradead.org,
 kvmarm@...ts.linux.dev, x86@...nel.org,
 acpica-devel@...ts.linuxfoundation.org, linux-csky@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-ia64@...r.kernel.org,
 linux-parisc@...r.kernel.org
Cc: Salil Mehta <salil.mehta@...wei.com>, Jean-Philippe Brucker
 <jean-philippe@...aro.org>, jianyong.wu@....com, justin.he@....com, James
 Morse <james.morse@....com>
Subject: Re: [PATCH RFC v3 21/21] cpumask: Add enabled cpumask for present
 CPUs that can be brought online

On Wed, Dec 13 2023 at 12:50, Russell King (Oracle) wrote:
> From: James Morse <james.morse@....com>
>
> The 'offline' file in sysfs shows all offline CPUs, including those
> that aren't present. User-space is expected to remove not-present CPUs
> from this list to learn which CPUs could be brought online.
>
> CPUs can be present but not-enabled. These CPUs can't be brought online
> until the firmware policy changes, which comes with an ACPI notification
> that will register the CPUs.
>
> With only the offline and present files, user-space is unable to
> determine which CPUs it can try to bring online. Add a new CPU mask
> that shows this based on all the registered CPUs.
>
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Miguel Luis <miguel.luis@...cle.com>
> Tested-by: Vishnu Pajjuri <vishnu@...amperecomputing.com>
> Tested-by: Jianyong Wu <jianyong.wu@....com>

Acked-by: Thomas Gleixner <tglx@...utronix.de>