linux-kernel - Re: [RFC PATCH 02/32] ACPI: Move ACPI_HOTPLUG

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Message-ID: <ZO+K9+C+RgNeZ7Nq@shell.armlinux.org.uk>
Date:   Wed, 30 Aug 2023 19:31:19 +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,
        kvmarm@...ts.linux.dev, kvm@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Borislav Petkov <bp@...en8.de>, H Peter Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Len Brown <lenb@...nel.org>,
        Rafael Wysocki <rafael@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Salil Mehta <salil.mehta@...wei.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [RFC PATCH 02/32] ACPI: Move ACPI_HOTPLUG_CPU to be enabled per
 architecture

On Fri, Feb 03, 2023 at 01:50:13PM +0000, James Morse wrote:
> --- a/arch/ia64/Kconfig
> +++ b/arch/ia64/Kconfig
> @@ -15,6 +15,7 @@ config IA64
>  	select ARCH_MIGHT_HAVE_PC_PARPORT
>  	select ARCH_MIGHT_HAVE_PC_SERIO
>  	select ACPI
> +	select ACPI_HOTPLUG_CPU if ACPI
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -5,6 +5,7 @@ config LOONGARCH
>  	select ACPI
>  	select ACPI_GENERIC_GSI if ACPI
>  	select ACPI_MCFG if ACPI
> +	select ACPI_HOTPLUG_CPU if ACPI
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -59,6 +59,7 @@ config X86
>  	#
>  	select ACPI_LEGACY_TABLES_LOOKUP	if ACPI
>  	select ACPI_SYSTEM_POWER_STATES_SUPPORT	if ACPI
> +	select ACPI_HOTPLUG_CPU			if ACPI
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -309,7 +309,6 @@ config ACPI_HOTPLUG_CPU
>  	bool
>  	depends on ACPI_PROCESSOR && HOTPLUG_CPU
>  	select ACPI_CONTAINER
> -	default y

When selecting the symbol, it's a good idea to ensure that its
dependencies are satisfied. So here, ACPI_HOTPLUG_CPU depends on
ACPI_PROCESSOR and HOTPLUG_CPU.

For x86, you're selecting ACPI_HOTPLUG_CPU if ACPI is enabled,
and ACPI can be freely enabled. HOTPLUG_CPU depends on SMP,
which is also a freely selectable option. Lastly,
ACPI_PROCESSOR depends on X86 || IA64 || ARM64 || LOONGARCH,
and is a user selectable, defaulting-y option if ACPI is
enabled.

So, shouldn't the x86 select be:

	select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU

?

I suspect similar issues exist for the other architecture Kconfig files
modified above.

This seems to also be in the latest rfc too, which is why I'm bringing
it up.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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