[PATCH V2 0/7] arm64/perf: Enable branch stack sampling

Anshuman Khandual
2022-09-08T05:11:05Z

This series enables perf branch stack sampling support on arm64 platform
via a new arch feature called Branch Record Buffer Extension (BRBE). All
relevant register definitions could be accessed here.

https://developer.arm.com/documentation/ddi0601/2021-12/AArch64-Registers

This series applies on v6.0-rc4 after the BRBE related perf ABI changes series
(V7) that was posted earlier, and a branch sample filter helper patch.

https://lore.kernel.org/all/20220824044822.70230-1-anshuman.khandual@arm.com/

https://lore.kernel.org/all/20220906084414.396220-1-anshuman.khandual@arm.com/

Following issues have been resolved

- Jame's concerns regarding permission inadequacy related to perfmon_capable()
- Jame's concerns regarding using perf_event_paranoid along with perfmon_capable()

Following issues remain inconclusive

- Rob's concerns regarding the series structure, arm_pmu callbacks based framework

Changes in V2:

- Dropped branch sample filter helpers consolidation patch from this series
- Added new hw_perf_event.flags element ARMPMU_EVT_PRIV to cache perfmon_capable()
- Use cached perfmon_capable() while configuring BRBE branch record filters

Changes in V1:

https://lore.kernel.org/linux-arm-kernel/20220613100119.684673-1-anshuman.khandual@arm.com/

- Added CONFIG_PERF_EVENTS wrapper for all branch sample filter helpers
- Process new perf branch types via PERF_BR_EXTEND_ABI

Changes in RFC V2:

https://lore.kernel.org/linux-arm-kernel/20220412115455.293119-1-anshuman.khandual@arm.com/

- Added branch_sample_priv() while consolidating other branch sample filter helpers
- Changed all SYS_BRBXXXN_EL1 register definition encodings per Marc
- Changed the BRBE driver as per proposed BRBE related perf ABI changes (V5)
- Added documentation for struct arm_pmu changes, updated commit message
- Updated commit message for BRBE detection infrastructure patch
- PERF_SAMPLE_BRANCH_KERNEL gets checked during arm event init (outside the driver)
- Branch privilege state capture mechanism has now moved inside the driver

Changes in RFC V1:

https://lore.kernel.org/all/1642998653-21377-1-git-send-email-anshuman.khandual@arm.com/

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Clark <james.clark@arm.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-perf-users@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Anshuman Khandual (7):
arm64/perf: Add register definitions for BRBE
arm64/perf: Update struct arm_pmu for BRBE
arm64/perf: Update struct pmu_hw_events for BRBE
driver/perf/arm_pmu_platform: Add support for BRBE attributes detection
arm64/perf: Drive BRBE from perf event states
arm64/perf: Add BRBE driver
arm64/perf: Enable branch stack sampling

arch/arm64/include/asm/sysreg.h | 222 ++++++++++++++++
arch/arm64/kernel/perf_event.c | 48 ++++
drivers/perf/Kconfig | 11 +
drivers/perf/Makefile | 1 +
drivers/perf/arm_pmu.c | 82 +++++-
drivers/perf/arm_pmu_brbe.c | 448 ++++++++++++++++++++++++++++++++
drivers/perf/arm_pmu_brbe.h | 259 ++++++++++++++++++
drivers/perf/arm_pmu_platform.c | 34 +++
include/linux/perf/arm_pmu.h | 67 +++++
9 files changed, 1169 insertions(+), 3 deletions(-)
create mode 100644 drivers/perf/arm_pmu_brbe.c
create mode 100644 drivers/perf/arm_pmu_brbe.h

--
2.25.1