linux-kernel - Re: [RFC 2/2] platform/x86/amd: pmf: Add manual control support

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Message-ID: <a7b94f15-114f-4088-9920-8cef790fc354@kernel.org>
Date: Thu, 26 Sep 2024 13:53:54 -0500
From: Mario Limonciello <superm1@...nel.org>
To: Antheas Kapenekakis <lkml@...heas.dev>
Cc: Shyam Sundar S K <Shyam-sundar.S-k@....com>,
 "Rafael J . Wysocki" <rafael@...nel.org>, Hans de Goede
 <hdegoede@...hat.com>, Ilpo Järvinen
 <ilpo.jarvinen@...ux.intel.com>, "Luke D . Jones" <luke@...nes.dev>,
 Mark Pearson <mpearson-lenovo@...ebb.ca>,
 "open list:AMD PMF DRIVER" <platform-driver-x86@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:ACPI" <linux-acpi@...r.kernel.org>,
 "Derek J . Clark" <derekjohn.clark@...il.com>, me@...egospodneti.ch,
 Denis Benato <benato.denis96@...il.com>,
 Mario Limonciello <mario.limonciello@....com>
Subject: Re: [RFC 2/2] platform/x86/amd: pmf: Add manual control support

On 9/26/2024 03:52, Antheas Kapenekakis wrote:
> Hi Mario,
> 
> It is fine to require a module parameter for turning on custom profiles.
> 
> However, distributions such as Bazzite use per-device kernel
> parameters, which, while user accessible, will not be modified by the
> user for 95% of use-cases. In fact, the Bazzite update system manages
> the kernel parameters of devices automatically.
> 
> What this would mean in practice is that for devices where this custom
> control may be used, the module parameter will be set globally for all
> of them and taint their kernels.
> 
> Instead, only taint the kernel when entering custom mode. If combined
> with something such as `custom_mode_choices`, only taint the kernel if
> `amd-pmf-user` is selected after that.

Yeah if we continue down a variation of this direction that is a 
sensible change to push the taint down to only when in it's actually 
been used, not just when the module parameter is set.

> 
>> +{
>> +       add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
>> +       pr_crit("Manual PMF control is enabled, please disable it before "
>> +               "reporting any bugs unrelated to PMF.\n");
>> +}
> 
> "Manual PMF control is enabled. If the device supports other ways of
> thermal management, please use those before reporting any bugs
> unrelated to PMF. If not, only if setting TDP is required for testing
> (e.g., under load in specific thermal conditions), proceed with the
> understanding that this module may cause interference, especially with
> the amd-gpu driver, the suspend process, and, if the parameters are
> out of spec, general stability of the system."
> 
> Antheas