Messages in this thread | | | From | Rob Herring <> | Subject | [PATCH v4 0/9] libperf and arm64 userspace counter access support | Date | Thu, 1 Oct 2020 09:01:07 -0500 |
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This is resurrecting Raphael's series[1] to enable userspace counter access on arm64. My previous versions are here[2][3][4]. A git branch is here[5].
Changes in v4: - Dropped 'arm64: pmu: Add hook to handle pmu-related undefined instructions'. The onus is on userspace to pin itself to a homogeneous subset of CPUs and avoid any aborts on heterogeneous systems, so the hook is not needed. - Make perf_evsel__mmap() take pages rather than bytes for size - Fix building arm64 heterogeneous test.
Changes in v3: - Dropped removing x86 rdpmc test until libperf tests can run via 'perf test' - Added verbose prints for tests - Split adding perf_evsel__mmap() to separate patch
The following changes to the arm64 support have been made compared to Raphael's last version:
The major change is support for heterogeneous systems with some restrictions. Specifically, userspace must pin itself to like CPUs, open a specific PMU by type, and use h/w specific events. The tests have been reworked to demonstrate this.
Chained events are not supported. The problem with supporting chained events was there's no way to distinguish between a chained event and a native 64-bit counter. We could add some flag, but do self monitoring processes really need that? Native 64-bit counters are supported if the PMU h/w has support. As there's already an explicit ABI to request 64-bit counters, userspace can request 64-bit counters and if user access is not enabled, then it must retry with 32-bit counters.
Prior versions broke the build on arm32 (surprisingly never caught by 0-day). As a result, event_mapped and event_unmapped implementations have been moved into the arm64 code.
There was a bug in that pmc_width was not set in the user page. The tests now check for this.
The documentation has been converted to rST. I've added sections on chained events and heterogeneous.
The tests have been expanded to test the cycle counter access.
Rob
[1] https://lore.kernel.org/linux-arm-kernel/20190822144220.27860-1-raphael.gault@arm.com/ [2] https://lore.kernel.org/linux-arm-kernel/20200707205333.624938-1-robh@kernel.org/ [3] https://lore.kernel.org/linux-arm-kernel/20200828205614.3391252-1-robh@kernel.org/ [4] https://lore.kernel.org/linux-arm-kernel/20200911215118.2887710-1-robh@kernel.org/ [5] git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git user-perf-event-v4
Raphael Gault (3): arm64: pmu: Add function implementation to update event index in userpage arm64: perf: Enable pmu counter direct access for perf event on armv8 Documentation: arm64: Document PMU counters access from userspace
Rob Herring (6): tools/include: Add an initial math64.h libperf: Add libperf_evsel__mmap() libperf: tests: Add support for verbose printing libperf: Add support for user space counter access libperf: Add arm64 support to perf_mmap__read_self() perf: arm64: Add test for userspace counter access on heterogeneous systems
Documentation/arm64/index.rst | 1 + .../arm64/perf_counter_user_access.rst | 56 ++++++ arch/arm64/include/asm/mmu.h | 5 + arch/arm64/include/asm/mmu_context.h | 2 + arch/arm64/include/asm/perf_event.h | 14 ++ arch/arm64/kernel/perf_event.c | 62 ++++++ include/linux/perf/arm_pmu.h | 2 + tools/include/linux/math64.h | 75 +++++++ tools/lib/perf/Documentation/libperf.txt | 1 + tools/lib/perf/evsel.c | 34 ++++ tools/lib/perf/include/internal/evsel.h | 2 + tools/lib/perf/include/internal/mmap.h | 3 + tools/lib/perf/include/internal/tests.h | 32 +++ tools/lib/perf/include/perf/evsel.h | 2 + tools/lib/perf/libperf.map | 1 + tools/lib/perf/mmap.c | 188 ++++++++++++++++++ tools/lib/perf/tests/Makefile | 4 +- tools/lib/perf/tests/test-evsel.c | 63 ++++++ tools/perf/arch/arm64/include/arch-tests.h | 7 + tools/perf/arch/arm64/tests/Build | 1 + tools/perf/arch/arm64/tests/arch-tests.c | 4 + tools/perf/arch/arm64/tests/user-events.c | 170 ++++++++++++++++ 22 files changed, 728 insertions(+), 1 deletion(-) create mode 100644 Documentation/arm64/perf_counter_user_access.rst create mode 100644 tools/include/linux/math64.h create mode 100644 tools/perf/arch/arm64/tests/user-events.c
-- 2.25.1
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