linux-kernel - [PATCH v4 00/14] perf cs-etm/arm-spe: Remove hard coded config fields

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Message-Id: <20251222-james-perf-config-bits-v4-0-0608438186fc@linaro.org>
Date: Mon, 22 Dec 2025 15:14:25 +0000
From: James Clark <james.clark@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
 Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>, 
 Adrian Hunter <adrian.hunter@...el.com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>, John Garry <john.g.garry@...cle.com>, 
 Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 James Clark <james.clark@...aro.org>, Leo Yan <leo.yan@....com>
Subject: [PATCH v4 00/14] perf cs-etm/arm-spe: Remove hard coded config
 fields

The specific config field that an event format attribute is in is
consistently hard coded, even though the API is supposed to be that the
driver publishes the config field name. To stop this pattern from being
copy pasted and causing problems in the future, replace them all with
calls to a new helper that returns the value that a user set.

This reveals some issues in evsel__set_config_if_unset(). It doesn't
work with sparse bitfields, which are an unused but documented feature.
And it also only writes to the attr.config field. To fix it we need to
start tracking user changes for all config fields and then use existing
helper functions that support sparse bitfields. Some other refactoring
was also required and a test was added.

---
Changes in v4:
- Constify some function args (Ian)
- Move some evsel__* functions to evsel.c and make some pmu.c functions
  public to support this (Ian)
- Drop pmu arg where it can be fetched from evsel->pmu (Ian)
- Link to v3: https://lore.kernel.org/r/20251212-james-perf-config-bits-v3-0-aa36a4846776@linaro.org

Changes in v3:
- Fix uninitialized variable warning on GCC
- Fix leak of evlist in test
- Confirm no type punning issues with ubsan (Ian)
- Link to v2: https://lore.kernel.org/r/20251208-james-perf-config-bits-v2-0-4ac0281993b0@linaro.org

Changes in v2:
- Remove macros in get_config_chgs() and some other refactoring.
- Support sparse bitfields in evsel__set_config_if_unset().
- Always track user changes instead of only when
  'pmu->perf_event_attr_init_default' is set.
- Add a test.
- Don't bail out in cs-etm.c if any format fields are missing (Leo).
- Rename 'guess' to 'synth' (Mike).
- Link to v1: https://lore.kernel.org/r/20251201-james-perf-config-bits-v1-0-22ecbbf8007c@linaro.org

---
James Clark (14):
      perf parse-events: Refactor get_config_terms() to remove macros
      perf evsel: Refactor evsel__set_config_if_unset() arguments
      perf evsel: Move evsel__* functions to evsel.c
      perf evsel: Support sparse fields in evsel__set_config_if_unset()
      perf parse-events: Track all user changed config bits
      perf evsel: apply evsel__set_config_if_unset() to all config fields
      perf evsel: Add a helper to get the value of a config field
      perf parse-events: Always track user config changes
      perf tests: Test evsel__set_config_if_unset() and config change tracking
      perf cs-etm: Make a helper to find the Coresight evsel
      perf cs-etm: Don't use hard coded config bits when setting up ETMCR
      perf cs-etm: Don't use hard coded config bits when setting up TRCCONFIGR
      perf cs-etm: Don't hard code config attribute when configuring the event
      perf arm-spe: Don't hard code config attribute

 tools/perf/arch/arm/util/cs-etm.c    | 201 +++++++++++++++-------------
 tools/perf/arch/arm64/util/arm-spe.c |  17 +--
 tools/perf/arch/x86/util/intel-pt.c  |   3 +-
 tools/perf/tests/pmu.c               |  91 +++++++++++++
 tools/perf/util/evsel.c              | 112 +++++++++++++++-
 tools/perf/util/evsel.h              |   6 +-
 tools/perf/util/evsel_config.h       |   7 +-
 tools/perf/util/parse-events.c       | 248 ++++++++++++++++++++---------------
 tools/perf/util/pmu.c                |  95 ++++----------
 tools/perf/util/pmu.h                |  34 ++++-
 10 files changed, 529 insertions(+), 285 deletions(-)
---
base-commit: cbd41c6d4c26c161a2b0e70ad411d3885ff13507
change-id: 20251112-james-perf-config-bits-bee7106f0f00

Best regards,
-- 
James Clark <james.clark@...aro.org>