linux-kernel - [PATCH v2 0/7] perf/x86/amd/core: Add AMD PerfMonV2 support

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Message-ID: <cover.1650515382.git.sandipan.das@amd.com>
Date:   Thu, 21 Apr 2022 11:16:52 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <x86@...nel.org>
CC:     <peterz@...radead.org>, <bp@...en8.de>,
        <dave.hansen@...ux.intel.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <namhyung@...nel.org>, <jolsa@...nel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <pbonzini@...hat.com>, <jmattson@...gle.com>,
        <like.xu.linux@...il.com>, <eranian@...gle.com>,
        <ananth.narayan@....com>, <ravi.bangoria@....com>,
        <santosh.shukla@....com>, <sandipan.das@....com>
Subject: [PATCH v2 0/7] perf/x86/amd/core: Add AMD PerfMonV2 support

Add support for using AMD Performance Monitoring Version 2
(PerfMonV2) features on upcoming processors. New CPU features
are introduced for PerfMonV2 detection. New MSR definitions
are added to make use of an alternative PMC management scheme
based on the new PMC global control and status registers.

The global control register provides the ability to start and
stop multiple PMCs at the same time. This makes it possible
to enable or disable all counters with a single MSR write
instead of writing to the individual PMC control registers
iteratively under x86_pmu_{enable,disable}(). The effects
can be seen when counting the same events across multiple
PMCs.

E.g.

  $ sudo perf stat -e "{cycles,instructions,cycles,instructions}" sleep 1

Before:

   Performance counter stats for 'sleep 1':
  
             1013281      cycles
             1452859      instructions              #    1.43  insn per cycle
             1023462      cycles
             1461724      instructions              #    1.43  insn per cycle

         1.001644276 seconds time elapsed
  
         0.001948000 seconds user
         0.000000000 seconds sys

After:

   Performance counter stats for 'sleep 1':
  
              999165      cycles
             1440456      instructions              #    1.44  insn per cycle
              999165      cycles
             1440456      instructions              #    1.44  insn per cycle
  
         1.001879504 seconds time elapsed
  
         0.001817000 seconds user
         0.000000000 seconds sys

No additional failures are seen upon running the following:
  * perf built-in test suite
  * perf_event_tests suite
  * rr test suite

Previous versions can be found at:
v1: https://lore.kernel.org/all/cover.1647498015.git.sandipan.das@amd.com/

Changes in v2:
- Sort PerfCntrGlobal* register definitions based on MSR index.
- Use wrmsrl() in cpu_{starting,dead}().
- Add enum to extract bitfields from CPUID leaf 0x80000022.
- Remove static calls for counter management functions.
- Stop counters before inspecting overflow status in NMI handler.
- Save and restore PMU enabled state in NMI handler.
- Remove unused variable in NMI handler.
- Remove redundant write to APIC_LVTPC in NMI handler.
- Add comment on APIC_LVTPC mask bit behaviour during counter overflow.

Sandipan Das (7):
  x86/cpufeatures: Add PerfMonV2 feature bit
  x86/msr: Add PerfCntrGlobal* registers
  perf/x86/amd/core: Detect PerfMonV2 support
  perf/x86/amd/core: Detect available counters
  perf/x86/amd/core: Add PerfMonV2 counter control
  perf/x86/amd/core: Add PerfMonV2 overflow handling
  kvm: x86/cpuid: Fix CPUID leaf 0xA

 arch/x86/events/amd/core.c         | 227 +++++++++++++++++++++++++++--
 arch/x86/include/asm/cpufeatures.h |   2 +-
 arch/x86/include/asm/msr-index.h   |   5 +
 arch/x86/include/asm/perf_event.h  |  17 +++
 arch/x86/kernel/cpu/scattered.c    |   1 +
 arch/x86/kvm/cpuid.c               |   5 +
 6 files changed, 240 insertions(+), 17 deletions(-)

-- 
2.32.0