Re: [PATCH v3 3/4] powercap: Add AMD Fam17h RAPL support

[Victor Ding]

On Wed, Nov 4, 2020 at 1:17 PM Srinivas Pandruvada
<srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote:
>
> On Wed, 2020-11-04 at 12:43 +1100, Victor Ding wrote:
> > On Wed, Nov 4, 2020 at 4:09 AM Srinivas Pandruvada
> > <srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote:
> > > On Tue, 2020-11-03 at 17:10 +1100, Victor Ding wrote:
> > > > On Mon, Nov 2, 2020 at 12:39 PM Zhang Rui <rui.zhang@xxxxxxxxx>
> > > > wrote:
> > > > > On Tue, 2020-10-27 at 07:23 +0000, Victor Ding wrote:
> > > > > > This patch enables AMD Fam17h RAPL support for the power
> > > > > > capping
> > > > > > framework. The support is as per AMD Fam17h Model31h (Zen2)
> > > > > > and
> > > > > > model 00-ffh (Zen1) PPR.
> > > > > >
> > > > > > Tested by comparing the results of following two sysfs
> > > > > > entries
> > > > > > and
> > > > > > the
> > > > > > values directly read from corresponding MSRs via
> > > > > > /dev/cpu/[x]/msr:
> > > > > >   /sys/class/powercap/intel-rapl/intel-rapl:0/energy_uj
> > > > > >   /sys/class/powercap/intel-rapl/intel-rapl:0/intel-
> > > > > > rapl:0:0/energy_uj
> > >
> > > Is this for just energy reporting? No capping of power?
> > Correct, the hardware does not support capping of power.
> I wonder if there is no capping, is this the right interface?
> Do you have specific user space, which cares about this?
We have tools that previously developed to measure energy status
on Intel via the powercap interface. Powercap is the only interface
allowing reading RAPL energy counters without requiring MSR access
privileges. We want to use these tools on AMD with minimal modifications.
I believe the powercap interface should support these counters,
regardless of the use cases, mainly for two reasons:
1. Powercap interface already supports monitoring-only power domains,
e.g. power limit is locked by BIOS or the (Intel) CPU does not expose an
MSR for certain power domains. The latter is the exact situation on AMD;
2. As AMD has partially introduced the equivalent of Intel's RAPL, we
should leverage this opportunity to reduce the divergence in the APIs. i.e.
OS as a hardware abstraction layer should allow users to use the same
set of APIs to access RAPL features if it issupported on both Intel and AMD.
In this specific case, if users can query for Intel's RAPL counters via
powercap, they should be able to do so as well for AMD's.
>
> I think these counters are already exposed via hwmon sysf.
Yes, they were introduced early this year. However, it is not the same as
the counters exposed via powercap interface: powercap exposes the
actual value of the energy counters while hwmon adds an accumulation
layer on top.
In addition, I don't think Intel's RAPL counters are exposed via hwmon;
therefore: 1. existing fine grade power monitoring tools are not based on
hwmon; 2. new tools cannot query the same set of counters via the same
API so that they have to actively maintain two sets of logic.
>
> Thanks,
> Srinivas
>
> > > Thanks,
> > > Srinivas
> > >
> > >
> > > > > > Signed-off-by: Victor Ding <victording@xxxxxxxxxx>
> > > > > > Acked-by: Kim Phillips <kim.phillips@xxxxxxx>
> > > > > >
> > > > > >
> > > > > > ---
> > > > > >
> > > > > > Changes in v3:
> > > > > > By Victor Ding <victording@xxxxxxxxxx>
> > > > > >  - Rebased to the latest code.
> > > > > >  - Created a new rapl_defaults for AMD CPUs.
> > > > > >  - Removed redundant setting to zeros.
> > > > > >  - Stopped using the fake power limit domain 1.
> > > > > >
> > > > > > Changes in v2:
> > > > > > By Kim Phillips <kim.phillips@xxxxxxx>:
> > > > > >  - Added Kim's Acked-by.
> > > > > >  - Added Daniel Lezcano to Cc.
> > > > > >  - (No code change).
> > > > > >
> > > > > >  arch/x86/include/asm/msr-index.h     |  1 +
> > > > > >  drivers/powercap/intel_rapl_common.c |  6 ++++++
> > > > > >  drivers/powercap/intel_rapl_msr.c    | 20
> > > > > > +++++++++++++++++++-
> > > > > >  3 files changed, 26 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/arch/x86/include/asm/msr-index.h
> > > > > > b/arch/x86/include/asm/msr-index.h
> > > > > > index 21917e134ad4..c36a083c8ec0 100644
> > > > > > --- a/arch/x86/include/asm/msr-index.h
> > > > > > +++ b/arch/x86/include/asm/msr-index.h
> > > > > > @@ -327,6 +327,7 @@
> > > > > >  #define MSR_PP1_POLICY                       0x00000642
> > > > > >
> > > > > >  #define MSR_AMD_RAPL_POWER_UNIT              0xc0010299
> > > > > > +#define MSR_AMD_CORE_ENERGY_STATUS           0xc001029a
> > > > > >  #define MSR_AMD_PKG_ENERGY_STATUS    0xc001029b
> > > > > >
> > > > > >  /* Config TDP MSRs */
> > > > > > diff --git a/drivers/powercap/intel_rapl_common.c
> > > > > > b/drivers/powercap/intel_rapl_common.c
> > > > > > index 0b2830efc574..bedd780bed12 100644
> > > > > > --- a/drivers/powercap/intel_rapl_common.c
> > > > > > +++ b/drivers/powercap/intel_rapl_common.c
> > > > > > @@ -1011,6 +1011,10 @@ static const struct rapl_defaults
> > > > > > rapl_defaults_cht = {
> > > > > >       .compute_time_window = rapl_compute_time_window_atom,
> > > > > >  };
> > > > > >
> > > > > > +static const struct rapl_defaults rapl_defaults_amd = {
> > > > > > +     .check_unit = rapl_check_unit_core,
> > > > > > +};
> > > > > > +
> > > > >
> > > > > why do we need power_unit and time_unit if we only want to
> > > > > expose
> > > > > the
> > > > > energy counter?
> > > > AMD's Power Unit MSR provides identical information as Intel's,
> > > > including
> > > > time units, power units, and energy status units. By reusing the
> > > > check unit
> > > > method, we could avoid code duplication as well as easing future
> > > > enhance-
> > > > ment when AMD starts to support power limits.
> > > > > Plus, in rapl_init_domains(), PL1 is enabled for every RAPL
> > > > > Domain
> > > > > blindly, I'm not sure how this is handled on the AMD CPUs.
> > > > > Is PL1 invalidated by rapl_detect_powerlimit()? or is it still
> > > > > registered as a valid constraint into powercap sysfs I/F?
> > > > AMD's CORE_ENERGY_STAT MSR is like Intel's PP0_ENERGY_STATUS;
> > > > therefore, PL1 also always exists on AMD.
> > > > rapl_detect_powerlimit()
> > > > correctly
> > > > markes the domain as monitoring-only after finding power limit
> > > > MSRs
> > > > do not
> > > > exist.
> > > > > Currently, the code makes the assumption that there is only on
> > > > > power
> > > > > limit if priv->limits[domain_id] not set, we probably need to
> > > > > change
> > > > > this if we want to support RAPL domains with no power limit.
> > > > The existing code already supports RAPL domains with no power
> > > > limit:
> > > > PL1 is
> > > > enabled when there is zero or one power limit,
> > > > rapl_detect_powerlimit() will then
> > > > mark if PL1 is monitoring-only if power limit MSRs do not exist.
> > > > Both
> > > > AMD's RAPL
> > > > domains are monitoring-only and are correctly marked and handled.
> > > > > thanks,
> > > > > rui
> > > > > >  static const struct x86_cpu_id rapl_ids[] __initconst = {
> > > > > >       X86_MATCH_INTEL_FAM6_MODEL(SANDYBRIDGE,         &rapl_d
> > > > > > efau
> > > > > > lt
> > > > > > s_core),
> > > > > >       X86_MATCH_INTEL_FAM6_MODEL(SANDYBRIDGE_X,       &rapl_d
> > > > > > efau
> > > > > > lts_core),
> > > > > > @@ -1061,6 +1065,8 @@ static const struct x86_cpu_id
> > > > > > rapl_ids[]
> > > > > > __initconst = {
> > > > > >
> > > > > >       X86_MATCH_INTEL_FAM6_MODEL(XEON_PHI_KNL,        &rapl_d
> > > > > > efau
> > > > > > lts_hsw_se
> > > > > > rver),
> > > > > >       X86_MATCH_INTEL_FAM6_MODEL(XEON_PHI_KNM,        &rapl_d
> > > > > > efau
> > > > > > lts_hsw_se
> > > > > > rver),
> > > > > > +
> > > > > > +     X86_MATCH_VENDOR_FAM(AMD, 0x17, &rapl_defaults_amd),
> > > > > >       {}
> > > > > >  };
> > > > > >  MODULE_DEVICE_TABLE(x86cpu, rapl_ids);
> > > > > > diff --git a/drivers/powercap/intel_rapl_msr.c
> > > > > > b/drivers/powercap/intel_rapl_msr.c
> > > > > > index a819b3b89b2f..78213d4b5b16 100644
> > > > > > --- a/drivers/powercap/intel_rapl_msr.c
> > > > > > +++ b/drivers/powercap/intel_rapl_msr.c
> > > > > > @@ -49,6 +49,14 @@ static struct rapl_if_priv
> > > > > > rapl_msr_priv_intel
> > > > > > = {
> > > > > >       .limits[RAPL_DOMAIN_PLATFORM] = 2,
> > > > > >  };
> > > > > >
> > > > > > +static struct rapl_if_priv rapl_msr_priv_amd = {
> > > > > > +     .reg_unit = MSR_AMD_RAPL_POWER_UNIT,
> > > > > > +     .regs[RAPL_DOMAIN_PACKAGE] = {
> > > > > > +             0, MSR_AMD_PKG_ENERGY_STATUS, 0, 0, 0 },
> > > > > > +     .regs[RAPL_DOMAIN_PP0] = {
> > > > > > +             0, MSR_AMD_CORE_ENERGY_STATUS, 0, 0, 0 },
> > > > > > +};
> > > > > > +
> > > > > >  /* Handles CPU hotplug on multi-socket systems.
> > > > > >   * If a CPU goes online as the first CPU of the physical
> > > > > > package
> > > > > >   * we add the RAPL package to the system. Similarly, when
> > > > > > the
> > > > > > last
> > > > > > @@ -138,7 +146,17 @@ static int rapl_msr_probe(struct
> > > > > > platform_device
> > > > > > *pdev)
> > > > > >       const struct x86_cpu_id *id =
> > > > > > x86_match_cpu(pl4_support_ids);
> > > > > >       int ret;
> > > > > >
> > > > > > -     rapl_msr_priv = &rapl_msr_priv_intel;
> > > > > > +     switch (boot_cpu_data.x86_vendor) {
> > > > > > +     case X86_VENDOR_INTEL:
> > > > > > +             rapl_msr_priv = &rapl_msr_priv_intel;
> > > > > > +             break;
> > > > > > +     case X86_VENDOR_AMD:
> > > > > > +             rapl_msr_priv = &rapl_msr_priv_amd;
> > > > > > +             break;
> > > > > > +     default:
> > > > > > +             pr_err("intel-rapl does not support CPU vendor
> > > > > > %d\n",
> > > > > > boot_cpu_data.x86_vendor);
> > > > > > +             return -ENODEV;
> > > > > > +     }
> > > > > >       rapl_msr_priv->read_raw = rapl_msr_read_raw;
> > > > > >       rapl_msr_priv->write_raw = rapl_msr_write_raw;
> > > > > >
> > > > Best regards,
> > > > Victor Ding
> > Best regards,
> > Victor Ding
>
Best regards,
Victor Ding