linux-kernel - Re: [RFC PATCH v2 06/35] arm64: setup: Switch over to GENERIC_CPU_DEVICES using arch_register

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Message-ID: <ZQLYuo0J1WWunb5R@shell.armlinux.org.uk>
Date:   Thu, 14 Sep 2023 10:56:10 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     James Morse <james.morse@....com>
Cc:     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, Salil Mehta <salil.mehta@...wei.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        jianyong.wu@....com, justin.he@....com
Subject: Re: [RFC PATCH v2 06/35] arm64: setup: Switch over to
 GENERIC_CPU_DEVICES using arch_register_cpu()

On Wed, Sep 13, 2023 at 04:37:54PM +0000, James Morse wrote:
> To allow ACPI's _STA value to hide CPUs that are present, but not
> available to online right now due to VMM or firmware policy, the
> register_cpu() call needs to be made by the ACPI machinery when ACPI
> is in use. This allows it to hide CPUs that are unavailable from sysfs.
> 
> Switching to GENERIC_CPU_DEVICES is an intermediate step to allow all
> five ACPI architectures to be modified at once.
> 
> Switch over to GENERIC_CPU_DEVICES, and provide an arch_register_cpu()
> that populates the hotpluggable flag. arch_register_cpu() is also the
> interface the ACPI machinery expects.
> 
> The struct cpu in struct cpuinfo_arm64 is never used directly, remove
> it to use the one GENERIC_CPU_DEVICES provides.
> 
> This changes the CPUs visible in sysfs from possible to present, but
> on arm64 smp_prepare_cpus() ensures these are the same.
> 
> Signed-off-by: James Morse <james.morse@....com>

Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

-- 
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