linux-kernel - Re: [PATCH v10 17/19] arm64: Kconfig: Enable hotplug CPU on arm64 if ACPI

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Date: Mon, 1 Jul 2024 10:17:20 +1000
From: Gavin Shan <gshan@...hat.com>
To: Catalin Marinas <catalin.marinas@....com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
 linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-pm@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
 Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>,
 loongarch@...ts.linux.dev, x86@...nel.org,
 Russell King <linux@...linux.org.uk>, "Rafael J . Wysocki"
 <rafael@...nel.org>, Miguel Luis <miguel.luis@...cle.com>,
 James Morse <james.morse@....com>, Salil Mehta <salil.mehta@...wei.com>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Hanjun Guo <guohanjun@...wei.com>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 linuxarm@...wei.com, justin.he@....com, jianyong.wu@....com
Subject: Re: [PATCH v10 17/19] arm64: Kconfig: Enable hotplug CPU on arm64 if
 ACPI_PROCESSOR is enabled.

Hi Catalin,

On 6/30/24 7:26 PM, Catalin Marinas wrote:
> On Sun, Jun 30, 2024 at 10:39:04AM +1000, Gavin Shan wrote:
>> On 5/29/24 11:34 PM, Jonathan Cameron wrote:
>>> In order to move arch_register_cpu() to be called via the same path
>>> for initially present CPUs described by ACPI and hotplugged CPUs
>>> ACPI_HOTPLUG_CPU needs to be enabled.
>>>
>>> The protection against invalid IDs in acpi_map_cpu() is needed as
>>> at least one production BIOS is in the wild which reports entries
>>> in DSDT (with no _STA method, so assumed enabled and present)
>>> that don't match MADT.
>>>
>>> Tested-by: Miguel Luis <miguel.luis@...cle.com>
>>> Reviewed-by: Gavin Shan <gshan@...hat.com>
>>> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>>> ---
>>>    arch/arm64/Kconfig       |  1 +
>>>    arch/arm64/kernel/acpi.c | 22 ++++++++++++++++++++++
>>>    2 files changed, 23 insertions(+)
>>>
>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>>> index 5d91259ee7b5..e8f2ef2312db 100644
>>> --- a/arch/arm64/Kconfig
>>> +++ b/arch/arm64/Kconfig
>>> @@ -5,6 +5,7 @@ config ARM64
>>>    	select ACPI_CCA_REQUIRED if ACPI
>>>    	select ACPI_GENERIC_GSI if ACPI
>>>    	select ACPI_GTDT if ACPI
>>> +	select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR
>>
>> ACPI_HOTPLUG_CPU depends on (ACPI_PROCESSOR && HOTPLUG_CPU). It needs to be:
>>
>> 	select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU
>>
>> Otherwise, we can have compiling error with the following configurations.
>>
>> CONFIG_ACPI_PROCESSOR=y
>> CONFIG_HOTPLUG_CPU=n
>> CONFIG_ACPI_HOTPLUG_CPU=y
>>
>> arch/arm64/kernel/smp.c: In function ‘arch_unregister_cpu’:
>> arch/arm64/kernel/smp.c:563:9: error: implicit declaration of function ‘unregister_cpu’; did you mean ‘register_cpu’? [-Werror=implicit-function-declaration]
>>    563 |         unregister_cpu(c);
>>        |         ^~~~~~~~~~~~~~
>>        |         register_cpu
> 
> Ah, I thought that in addition to the warning for unmet dependencies,
> kbuild would also leave the option off. I need to add SUSPEND=n and
> HIBERNATE=n to my build scripts.
> 
> The fix matches what x86 does, so I'm ok with it.
> 

Ok, thanks for your confirm.

>> Since the series has been queued to Catalin's "for-next/vcpu-hotplug" branch, I
>> guess the easiest way would be to fix it in place with Catalin's help.
> 
> I wasn't planning to rebase the branch unless there's something major.
> Since the doesn't happen with defconfig, it's doesn't affect bisection
> that much, so my preference would be for a fix on top of this branch
> (and with a Fixes: tag since the branch is stable).
> 

Sure, I've posted a fix, applicable to branch 'for-next/vcpu-hotplug'.

https://lists.infradead.org/pipermail/linux-arm-kernel/2024-June/939690.html

Thanks,
Gavin