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

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Message-ID: <CAJZ5v0jLez+WcqMs4hWeTKdeSbBbAShWvbvGHVj--foZLQ_u6w@mail.gmail.com>
Date: Wed, 6 Nov 2024 21:33:50 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Mario Limonciello <superm1@...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 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!