ARM SPE and other tracing PMUs write records directly to perf AUX buffers. Unlike ordinary sampling PMUs, they do not necessarily generate a perf_event_overflow() callback for each record. A kernel consumer therefore needs to drain the AUX buffer directly.
Userspace allocates AUX buffers through perf_event_open() and mmap(). Kernel consumers created through perf_event_create_kernel_counter() currently lack an equivalent interface. This series adds perf-core APIs for kernel consumers to allocate and release AUX buffers, read the producer head, copy trace data, and advance the consumer tail. The APIs keep perf's internal page layout private and follow the existing non-overwrite AUX ring-buffer protocol. Setup and release serialize buffer attachment and detachment through event->mmap_mutex; consumers must quiesce before releasing the buffer. Patches 1-2 add the ownership, lifecycle, and access APIs. Patches 3-5 add KUnit tests, a userspace AUX regression test, and a selftest script. The first consumer is a DAMON ARM SPE backend, but this series is independent of DAMON and adds no consumer-specific policy to perf. Testing ======= The series builds cleanly at each step. arm64 (Kunpeng 920, 256 CPUs, SPEv1.1): built and booted the Image from this series. KUnit: pass:39 fail:0 skip:0. The arm_spe_0 userspace regression test passed, and the AUX head advanced under live SPE traffic. Selftest script: 92 passed, 0 failed, 2 skipped. perf record with arm_spe_0 captured data; dmesg showed no warnings. x86_64 (vmlinux build, qemu/kvm): KUnit pass:39 fail:0 skip:0, including KASAN and lockdep (PROVE_LOCKING); 15 repeated boots produced no splats. The Intel PT userspace regression test passed. Signed-off-by: Kunwu Chan <[email protected]> Changes since v1 [2]: - Fix double-release in KUnit error cleanup and make the coexistence test cleanup failure-safe. - Make failure-sensitive userspace test outcomes report SKIP rather than PASS, read the AUX head after event disable to observe flushed trace data, and pass the PMU name from the script to the C test. - Fix the selftest script exit-status handling, remove the /usr/src/linux fallback, and handle Intel PT event modifiers. - Remove an unnecessary smp_rmb() from the tail update path. Changes since RFC [1]: - Serialize AUX teardown under event->mmap_mutex and fix lifetime handling around ring_buffer_attach(). - Improve KUnit cleanup and concurrent-release coverage. - Extend userspace and selftest coverage. - Document AUX lifecycle, ordering, and cursor validation. [1] https://lore.kernel.org/linux-perf-users/[email protected]/ [2] https://lore.kernel.org/all/[email protected]/ Kunwu Chan (3): perf/core: add AUX buffer ownership for kernel events perf/core: add AUX ring accessors for kernel consumers selftests/perf_events: add AUX kernel API selftest script Lian Wang (2): perf/core: add KUnit tests for AUX kernel-consumer API selftests/perf_events: add userspace AUX regression test .../userspace-api/perf_ring_buffer.rst | 62 +- include/linux/perf_event.h | 18 + kernel/events/Makefile | 1 + kernel/events/aux_kernel_test.c | 1172 +++++++++++++++++ kernel/events/core.c | 164 +++ kernel/events/internal.h | 6 + kernel/events/ring_buffer.c | 212 ++- lib/Kconfig.debug | 14 + tools/testing/selftests/perf_events/Makefile | 2 + .../selftests/perf_events/aux_kernel.sh | 635 +++++++++ .../perf_events/aux_kernel_usermode.c | 645 +++++++++ tools/testing/selftests/perf_events/config | 2 + 12 files changed, 2928 insertions(+), 5 deletions(-) create mode 100644 kernel/events/aux_kernel_test.c create mode 100755 tools/testing/selftests/perf_events/aux_kernel.sh create mode 100644 tools/testing/selftests/perf_events/aux_kernel_usermode.c base-commit: 6350de8671b94afb7691d110f63bcda42f658a69 -- 2.43.0
