linux-kernel - Re: [PATCH v2] ACPI: processor: Move arch_init_invariance

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Message-ID: <CAJZ5v0h4eg0LkwYrXp7gS2Lu4=i5WQ-HHonR5hL2nmZ4EMT8ew@mail.gmail.com>
Date: Mon, 4 Nov 2024 18:43:33 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Mario Limonciello <superm1@...nel.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, 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 v2] ACPI: processor: Move arch_init_invariance_cppc() call later

On Mon, Nov 4, 2024 at 6:17 PM Mario Limonciello <superm1@...nel.org> wrote:
>
> On 11/4/2024 10:55, Rafael J. Wysocki wrote:
> > On Sat, Nov 2, 2024 at 4:24 AM 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, push the call to the arch_init_invariance_cppc()
> >> macro to the end of acpi_processor_driver_init().
> >>
> >> Fixes: 279f838a61f9 ("x86/amd: Detect preferred cores in amd_get_boost_ratio_numerator()")
> >> Reported-by: Ivan Shapovalov <intelfx@...elfx.name>
> >> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219431
> >> Tested-by: Oleksandr Natalenko <oleksandr@...alenko.name>
> >> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> >> ---
> >> v1->v2:
> >>   * Fix LKP robot issue when CONFIG_ACPI_CPPC_LIB not defined
> >> ---
> >>   arch/x86/include/asm/topology.h | 2 ++
> >>   drivers/acpi/cppc_acpi.c        | 6 ------
> >>   drivers/acpi/processor_driver.c | 1 +
> >>   3 files changed, 3 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
> >> index abe3a8f22cbd..b04c5db7e945 100644
> >> --- a/arch/x86/include/asm/topology.h
> >> +++ b/arch/x86/include/asm/topology.h
> >> @@ -295,6 +295,8 @@ extern void arch_scale_freq_tick(void);
> >>   #ifdef CONFIG_ACPI_CPPC_LIB
> >>   void init_freq_invariance_cppc(void);
> >>   #define arch_init_invariance_cppc init_freq_invariance_cppc
> >> +#else
> >> +static inline void arch_init_invariance_cppc(void) { }
> >>   #endif
> >>
> >>   #endif /* _ASM_X86_TOPOLOGY_H */
> >> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> >> index ed91dfd4fdca..9d48cd706659 100644
> >> --- a/drivers/acpi/cppc_acpi.c
> >> +++ b/drivers/acpi/cppc_acpi.c
> >> @@ -671,10 +671,6 @@ static int pcc_data_alloc(int pcc_ss_id)
> >>    *  )
> >>    */
> >>
> >> -#ifndef arch_init_invariance_cppc
> >> -static inline void arch_init_invariance_cppc(void) { }
> >> -#endif
> >> -
> >>   /**
> >>    * acpi_cppc_processor_probe - Search for per CPU _CPC objects.
> >>    * @pr: Ptr to acpi_processor containing this CPU's logical ID.
> >> @@ -905,8 +901,6 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
> >>                  goto out_free;
> >>          }
> >>
> >> -       arch_init_invariance_cppc();
> >> -
> >>          kfree(output.pointer);
> >>          return 0;
> >>
> >> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> >> index cb52dd000b95..59620e7bc664 100644
> >> --- a/drivers/acpi/processor_driver.c
> >> +++ b/drivers/acpi/processor_driver.c
> >> @@ -270,6 +270,7 @@ static int __init acpi_processor_driver_init(void)
> >>                                    NULL, acpi_soft_cpu_dead);
> >>
> >>          acpi_processor_throttling_init();
> >> +       arch_init_invariance_cppc();
> >>          return 0;
> >>   err:
> >>          driver_unregister(&acpi_processor_driver);
> >> --
> >
> > Applied as a fix for 6.12-rc7.
> >
> > However, it would be good to add a comment explaining why
> > acpi_processor_driver_init() calls arch_init_invariance_cppc() at the
> > end.  The ACPI processor driver and CPPC are not otherwise related I
> > think?
>
> Sure, I'm thinking a comment like this.
>
> /*
>   * Frequency invariance calculations on AMD platforms can't be run until
>   * _CPC has been evaluated on all processors which will only happen
>   * after probing is complete.
>   */

It would be more precise to say "after acpi_cppc_processor_probe() has
been called for all online CPUs".

Which among other things means that the ordering of this call with
respect to acpi_processor_throttling_init() does not matter.

> If that sounds good do you want to squash it in?  Or if you would prefer
> another commit tacked on that's no problem I'll do that.

IMV a separate patch for 6.13 will be fine.