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

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Date:   Sun, 25 Apr 2021 15:18:56 +0800
From:   Huang Rui <ray.huang@....com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Jason Bagavatsingham <jason.bagavatsingham@...il.com>,
        "Pierre-Loup A . Griffais" <pgriffais@...vesoftware.com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Borislav Petkov <bp@...e.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Stable <stable@...r.kernel.org>
Subject: Re: [PATCH v2] x86, sched: Fix the AMD CPPC maximum perf on some
 specific generations

On Fri, Apr 23, 2021 at 11:19:46PM +0800, Rafael J. Wysocki wrote:
> On Wed, Apr 21, 2021 at 4:38 AM Huang Rui <ray.huang@....com> 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:
> >
> > ~ .$B"*.(B 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@...il.com>
> > Tested-by: Jason Bagavatsingham <jason.bagavatsingham@...il.com>
> > Bugzilla: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.kernel.org%2Fshow_bug.cgi%3Fid%3D211791&amp;data=04%7C01%7Cray.huang%40amd.com%7C5069cfd46dfe4f0c504208d9066b41be%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637547880005034494%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=YSgziLlmyJlAxMQceGlx%2FB1EgN50h512ai1F4ypXoD8%3D&amp;reserved=0
> > Signed-off-by: Huang Rui <ray.huang@....com>
> > Cc: Alex Deucher <alexander.deucher@....com>
> > Cc: Nathan Fontenot <nathan.fontenot@....com>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Cc: Borislav Petkov <bp@...e.de>
> > Cc: x86@...nel.org
> > Cc: stable@...r.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;
> 
> The extra local variable is redundant.
> 
> > +
> > +       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;
> 
> Also it would be cleaner to write this as
> 
> if (c->x86 == 0x17 && ((c->x86_model >= 0x30 && c->x86_model < 0x40) ||
>     (c->x86_model >= 0x70 && c->x86_model < 0x80))
>         return 166;
> 
> And analogously below.
> 
> > +       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;
> 
> And here
> 
> return 225;
> 
> > +}
> > +EXPORT_SYMBOL_GPL(amd_get_highest_perf);
> > 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;
> > +}
> 
> The function above is not necessary if I'm not mistaken.
> 

Yes, right.

> > +
> >  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;
> 
> The above can be written as
> 
> if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
>         highest_perf = amd_get_highest_perf();
> else
>         highest_perf = perf_caps.highest_perf;
> 

Thanks to simplify the implementation. Will update it in V4.

Best Regards,
Ray