linux-kernel - Re: [PATCH v4] ACPI: processor: Move arch_init_invariance

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Message-ID: <4b2d9200-cee9-484c-87c1-39542ccce8a5@kernel.org>
Date: Wed, 6 Nov 2024 14:44:36 -0600
From: Mario Limonciello <superm1@...nel.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
 "H . Peter Anvin" <hpa@...or.com>, Len Brown <lenb@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Mario Limonciello <mario.limonciello@....com>,
 "Gautham R . Shenoy" <gautham.shenoy@....com>,
 "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
 <linux-kernel@...r.kernel.org>, "open list:ACPI"
 <linux-acpi@...r.kernel.org>, Ivan Shapovalov <intelfx@...elfx.name>,
 Oleksandr Natalenko <oleksandr@...alenko.name>
Subject: Re: [PATCH v4] ACPI: processor: Move arch_init_invariance_cppc() call
 later

On 11/6/2024 14:33, Rafael J. Wysocki wrote:
> On Tue, Nov 5, 2024 at 9:17 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>>
>> On Mon, Nov 4, 2024 at 11:29 PM Mario Limonciello <superm1@...nel.org> wrote:
>>>
>>> From: Mario Limonciello <mario.limonciello@....com>
>>>
>>> arch_init_invariance_cppc() is called at the end of
>>> acpi_cppc_processor_probe() in order to configure frequency invariance
>>> based upon the values from _CPC.
>>>
>>> This however doesn't work on AMD CPPC shared memory designs that have
>>> AMD preferred cores enabled because _CPC needs to be analyzed from all
>>> cores to judge if preferred cores are enabled.
>>>
>>> This issue manifests to users as a warning since commit 21fb59ab4b97
>>> ("ACPI: CPPC: Adjust debug messages in amd_set_max_freq_ratio() to warn"):
>>> ```
>>> Could not retrieve highest performance (-19)
>>> ```
>>>
>>> However the warning isn't the cause of this, it was actually
>>> commit 279f838a61f9 ("x86/amd: Detect preferred cores in
>>> amd_get_boost_ratio_numerator()") which exposed the issue.
>>>
>>> To fix this problem, change arch_init_invariance_cppc() into a new weak
>>> symbol that is called at the end of acpi_processor_driver_init().
>>> Each architecture that supports it can declare the symbol to override
>>> the weak one.
>>
>> "Define it for x86, in arch/x86/kernel/acpi/cppc.c, and for all of the
>> architectures using the generic arch_topology.c code."
> 
> I've added this to the patch changelog and queued it up as a 6.12 fix.
> 
> Thanks!

Thanks!