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Message-ID: <27e48da5-e1d0-4e4b-978e-954f1766c350@redhat.com>
Date: Wed, 1 May 2024 21:14:50 +1000
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Subject: Re: [PATCH v9 19/19] cpumask: Add enabled cpumask for present CPUs
 that can be brought online
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To: Jonathan Cameron <Jonathan.Cameron@huawei.com>,
 Thomas Gleixner <tglx@linutronix.de>, Peter Zijlstra <peterz@infradead.org>,
 linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
 linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
 kvmarm@lists.linux.dev, x86@kernel.org, Russell King
 <linux@armlinux.org.uk>, "Rafael J . Wysocki" <rafael@kernel.org>,
 Miguel Luis <miguel.luis@oracle.com>, James Morse <james.morse@arm.com>,
 Salil Mehta <salil.mehta@huawei.com>,
 Jean-Philippe Brucker <jean-philippe@linaro.org>,
 Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>,
 Marc Zyngier <maz@kernel.org>, Hanjun Guo <guohanjun@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
 Dave Hansen <dave.hansen@linux.intel.com>, linuxarm@huawei.com,
 justin.he@arm.com, jianyong.wu@arm.com
References: <20240430142434.10471-1-Jonathan.Cameron@huawei.com>
 <20240430142434.10471-20-Jonathan.Cameron@huawei.com>
From: Gavin Shan <gshan@redhat.com>
In-Reply-To: <20240430142434.10471-20-Jonathan.Cameron@huawei.com>
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On 5/1/24 00:24, Jonathan Cameron 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>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> ---
> v9: No change
> ---
>   .../ABI/testing/sysfs-devices-system-cpu      |  6 +++++
>   drivers/base/cpu.c                            | 10 ++++++++
>   include/linux/cpumask.h                       | 25 +++++++++++++++++++
>   kernel/cpu.c                                  |  3 +++
>   4 files changed, 44 insertions(+)
> 

Reviewed-by: Gavin Shan <gshan@redhat.com>