Re: [PATCH v2] x86, sched: Fix the AMD CPPC maximum perf on some specific generations

["Fontenot, Nathan" <Nathan.Fontenot@amd.com>]

On 4/20/2021 9:38 PM, Huang Rui wrote:
> Some AMD Ryzen generations has different calculation method on maximum
> perf. 255 is not for all asics, some specific generations should use 166
> as the maximum perf. Otherwise, it will report incorrect frequency value
> like below:
> 
> ~ → lscpu | grep MHz
> CPU MHz:                         3400.000
> CPU max MHz:                     7228.3198
> CPU min MHz:                     2200.0000
> 
> Fixes: 41ea667227ba ("x86, sched: Calculate frequency invariance for AMD systems")
> Fixes: 3c55e94c0ade ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies")
> 
> Reported-by: Jason Bagavatsingham <jason.bagavatsingham@gmail.com>
> Tested-by: Jason Bagavatsingham <jason.bagavatsingham@gmail.com>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211791
> Signed-off-by: Huang Rui <ray.huang@amd.com>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Nathan Fontenot <nathan.fontenot@amd.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: x86@kernel.org
> Cc: stable@vger.kernel.org
> ---
> 
> Changes from V1 -> V2:
> - Enhance the commit message.
> - Move amd_get_highest_perf() into amd.c.
> - Refine the implementation of switch-case.
> - Cc stable mail list.
> 
> ---
>  arch/x86/include/asm/processor.h |  2 ++
>  arch/x86/kernel/cpu/amd.c        | 22 ++++++++++++++++++++++
>  arch/x86/kernel/smpboot.c        |  2 +-
>  drivers/cpufreq/acpi-cpufreq.c   | 19 +++++++++++++++++++
>  4 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index f1b9ed5efaa9..908bcaea1361 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -804,8 +804,10 @@ DECLARE_PER_CPU(u64, msr_misc_features_shadow);
>  
>  #ifdef CONFIG_CPU_SUP_AMD
>  extern u32 amd_get_nodes_per_socket(void);
> +extern u32 amd_get_highest_perf(void);
>  #else
>  static inline u32 amd_get_nodes_per_socket(void)	{ return 0; }
> +static inline u32 amd_get_highest_perf(void)		{ return 0; }
>  #endif
>  
>  static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 347a956f71ca..aadb691d9357 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -1170,3 +1170,25 @@ void set_dr_addr_mask(unsigned long mask, int dr)
>  		break;
>  	}
>  }
> +
> +u32 amd_get_highest_perf(void)
> +{
> +	struct cpuinfo_x86 *c = &boot_cpu_data;
> +	u32 cppc_max_perf = 225;
> +
> +	switch (c->x86) {
> +	case 0x17:
> +		if ((c->x86_model >= 0x30 && c->x86_model < 0x40) ||
> +		    (c->x86_model >= 0x70 && c->x86_model < 0x80))
> +			cppc_max_perf = 166;
> +		break;
> +	case 0x19:
> +		if ((c->x86_model >= 0x20 && c->x86_model < 0x30) ||
> +		    (c->x86_model >= 0x40 && c->x86_model < 0x70))
> +			cppc_max_perf = 166;
> +		break;
> +	}
> +
> +	return cppc_max_perf;
> +}
> +EXPORT_SYMBOL_GPL(amd_get_highest_perf);

Should this be an update to cpp_get_perf_caps()?

This approach would ensure that all callers have the correct value
and remove the need to fix up individual callers to use this new
routine to get the correct value.

-Nathan

> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 02813a7f3a7c..7bec57d04a87 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -2046,7 +2046,7 @@ static bool amd_set_max_freq_ratio(void)
>  		return false;
>  	}
>  
> -	highest_perf = perf_caps.highest_perf;
> +	highest_perf = amd_get_highest_perf();
>  	nominal_perf = perf_caps.nominal_perf;
>  
>  	if (!highest_perf || !nominal_perf) {
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index d1bbc16fba4b..3f0a19dd658c 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -630,6 +630,22 @@ static int acpi_cpufreq_blacklist(struct cpuinfo_x86 *c)
>  #endif
>  
>  #ifdef CONFIG_ACPI_CPPC_LIB
> +
> +static u64 get_amd_max_boost_ratio(unsigned int cpu, u64 nominal_perf)
> +{
> +	u64 boost_ratio, cppc_max_perf;
> +
> +	if (!nominal_perf)
> +		return 0;
> +
> +	cppc_max_perf = amd_get_highest_perf();
> +
> +	boost_ratio = div_u64(cppc_max_perf << SCHED_CAPACITY_SHIFT,
> +			      nominal_perf);
> +
> +	return boost_ratio;
> +}
> +
>  static u64 get_max_boost_ratio(unsigned int cpu)
>  {
>  	struct cppc_perf_caps perf_caps;
> @@ -646,6 +662,9 @@ static u64 get_max_boost_ratio(unsigned int cpu)
>  		return 0;
>  	}
>  
> +	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
> +		return get_amd_max_boost_ratio(cpu, perf_caps.nominal_perf);
> +
>  	highest_perf = perf_caps.highest_perf;
>  	nominal_perf = perf_caps.nominal_perf;
>  
> -- 
> 2.25.1
>