Message-ID: <25d7112c4ca6d84e6a1289663cbf172bf7709fee.camel@intelfx.name>
Date: Tue, 05 Nov 2024 01:38:03 +0400
From: Ivan Shapovalov <intelfx@...elfx.name>
To: Mario Limonciello <superm1@...nel.org>, "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>,  Oleksandr Natalenko
 <oleksandr@...alenko.name>
Subject: Re: [PATCH v3] ACPI: processor: Move arch_init_invariance_cppc()
 call later

On 2024-11-04 at 15:14 -0600, Mario Limonciello wrote:
> On 11/4/2024 15:10, Rafael J. Wysocki wrote:
> > On Mon, Nov 4, 2024 at 9:54 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.
> > > 
> > > 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>
> > > ---
> > > v3:
> > >   * Weak symbol instead of macro to help riscv build failure
> > >   * Update commit message
> > >   * Add comment
> > > ---
> > >   arch/arm64/include/asm/topology.h | 2 +-
> > >   arch/x86/include/asm/topology.h   | 2 +-
> > >   drivers/acpi/cppc_acpi.c          | 6 ------
> > >   drivers/acpi/processor_driver.c   | 9 +++++++++
> > >   include/acpi/processor.h          | 2 ++
> > >   5 files changed, 13 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> > > index 5fc3af9f8f29b..8a1860877967e 100644
> > > --- a/arch/arm64/include/asm/topology.h
> > > +++ b/arch/arm64/include/asm/topology.h
> > > @@ -27,7 +27,7 @@ void update_freq_counters_refs(void);
> > >   #define arch_scale_freq_ref topology_get_freq_ref
> > > 
> > >   #ifdef CONFIG_ACPI_CPPC_LIB
> > > -#define arch_init_invariance_cppc topology_init_cpu_capacity_cppc
> > > +#define acpi_processor_init_invariance_cppc topology_init_cpu_capacity_cppc
> > >   #endif
> > > 
> > >   /* Replace task scheduler's default cpu-invariant accounting */
> > > diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
> > > index aef70336d6247..0fb705524aeaa 100644
> > > --- a/arch/x86/include/asm/topology.h
> > > +++ b/arch/x86/include/asm/topology.h
> > > @@ -307,7 +307,7 @@ 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
> > > +#define acpi_processor_init_invariance_cppc init_freq_invariance_cppc
> > >   #endif
> > > 
> > >   #endif /* _ASM_X86_TOPOLOGY_H */
> > > diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> > > index 1a40f0514eaa3..5c0cc7aae8726 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 cb52dd000b958..3b281bc1e73c3 100644
> > > --- a/drivers/acpi/processor_driver.c
> > > +++ b/drivers/acpi/processor_driver.c
> > > @@ -237,6 +237,9 @@ static struct notifier_block acpi_processor_notifier_block = {
> > >          .notifier_call = acpi_processor_notifier,
> > >   };
> > > 
> > > +void __weak acpi_processor_init_invariance_cppc(void)
> > > +{ }
> > 
> > Does this actually work if acpi_processor_init_invariance_cppc is a
> > macro?  How does the compiler know that it needs to use
> > init_freq_invariance_cppc() instead of this?
> > 
> > It would work if a __weak definition of init_freq_invariance_cppc() was present.
> 
> I also wasn't sure, so I explicitly added some tracing in 
> init_freq_invariance_cppc() to make sure it got called and checked it 
> (GCC 13.2.0).

Aren't C macros substituted strictly lexically, i.e. if the #define is
present by the time the function definition is parsed, it's just

void __weak acpi_processor_init_invariance_cppc(void) {}
-> void __weak init_freq_invariance_cppc(void) {}

? So it _is_ a weak definition of init_freq_invariance_cppc().

> 
> But I'll admit it's a confusing behavior.  If you think it's too 
> confusing I'll swap it around to just axe the macros.

...That said, it does look kinda confusing. Seems to be norm for that
arch/ header file though.

Anyway,

  Tested-by: Ivan Shapovalov <intelfx@...elfx.name>


> 
> > 
> > > +
> > >   /*
> > >    * We keep the driver loaded even when ACPI is not running.
> > >    * This is needed for the powernow-k8 driver, that works even without
> > > @@ -270,6 +273,12 @@ static int __init acpi_processor_driver_init(void)
> > >                                    NULL, acpi_soft_cpu_dead);
> > > 
> > >          acpi_processor_throttling_init();
> > > +
> > > +       /*
> > > +        * Frequency invariance calculations on AMD platforms can't be run until
> > > +        * after acpi_cppc_processor_probe() has been called for all online CPUs.
> > > +        */
> > > +       acpi_processor_init_invariance_cppc();
> > >          return 0;
> > >   err:
> > >          driver_unregister(&acpi_processor_driver);
> > > diff --git a/include/acpi/processor.h b/include/acpi/processor.h
> > > index e6f6074eadbf3..a17e97e634a68 100644
> > > --- a/include/acpi/processor.h
> > > +++ b/include/acpi/processor.h
> > > @@ -465,4 +465,6 @@ extern int acpi_processor_ffh_lpi_probe(unsigned int cpu);
> > >   extern int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi);
> > >   #endif
> > > 
> > > +void acpi_processor_init_invariance_cppc(void);
> > > +
> > >   #endif
> > > 
> > > base-commit: 6db936d4ac0fe281af48b4d1ebf69b1523bbac31
> > > --
> > > 2.43.0
> > > 
> 

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