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To: Russell King <rmk+kernel@armlinux.org.uk>, linux-pm@vger.kernel.org,
 loongarch@lists.linux.dev, linux-acpi@vger.kernel.org,
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Cc: Salil Mehta <salil.mehta@huawei.com>, Jean-Philippe Brucker
 <jean-philippe@linaro.org>, jianyong.wu@arm.com, justin.he@arm.com, James
 Morse <james.morse@arm.com>
Subject: Re: [PATCH RFC v3 21/21] cpumask: Add enabled cpumask for present
 CPUs that can be brought online
In-Reply-To: <E1rDOhX-00Dvlg-Ci@rmk-PC.armlinux.org.uk>
References: <ZXmn46ptis59F0CO@shell.armlinux.org.uk>
 <E1rDOhX-00Dvlg-Ci@rmk-PC.armlinux.org.uk>
Date: Fri, 15 Dec 2023 20:40:28 +0100
Message-ID: <87le9vmez7.ffs@tglx>
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On Wed, Dec 13 2023 at 12:50, Russell King (Oracle) wrote:
> From: James Morse <james.morse@arm.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@arm.com>
> Tested-by: Miguel Luis <miguel.luis@oracle.com>
> Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> Tested-by: Jianyong Wu <jianyong.wu@arm.com>

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