linux-kernel - Re: [PATCH v3] ACPI: processor: Move arch_init_invariance

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Message-ID: <814adf82-99ec-44f8-83d0-6540f2cccbcb@kernel.org>
Date: Mon, 4 Nov 2024 15:14:48 -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 v3] ACPI: processor: Move arch_init_invariance_cppc() call
 later

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).

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.

> 
>> +
>>   /*
>>    * 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
>>