Messages in this thread | | | From | Raphael Gault <> | Subject | [RFC 0/6] arm64: Enable access to pmu registers by user-space | Date | Thu, 16 May 2019 14:21:42 +0100 |
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The perf user-space tool relies on the PMU to monitor events. It offers an abstraction layer over the hardware counters since the underlying implementation is cpu-dependent. We want to allow userspace tools to have access to the registers storing the hardware counters' values directly. This targets specifically self-monitoring tasks in order to reduce the overhead by directly accessing the registers without having to go through the kernel. In order to do this we need to setup the pmu so that it exposes its registers to userspace access.
The first patch enables the tests for arm64 architecture in the perf tool to be compiled systematically.
The second patch add a test to the perf tool so that we can test that the access to the registers works correctly from userspace.
The third patch focuses on the armv8 pmuv3 PMU support and makes sure that the access to the pmu registers is enable and that the userspace have access to the relevent information in order to use them.
The fourth patch adds a hook to handle faulting access to the pmu registers. This is necessary in order to have a coherent behaviour on big.LITTLE environment.
The fifth patch put in place callbacks to enable access to the hardware counters from userspace when a compatible event is opened using the perf API.
Note: This series is applied on top of this patch (already acked): https://patchwork.kernel.org/patch/10896407/
*** BLURB HERE ***
Raphael Gault (6): perf: arm64: Compile tests unconditionally perf: arm64: Add test to check userspace access to hardware counters. arm64: pmu: Add function implementation to update event index in userpage. arm64: pmu: Add hook to handle pmu-related undefined instructions arm64: perf: Enable pmu counter direct access for perf event on armv8 Documentation: arm64: Document PMU counters access from userspace
.../arm64/pmu_counter_user_access.txt | 42 +++ arch/arm64/include/asm/mmu.h | 6 + arch/arm64/include/asm/mmu_context.h | 2 + arch/arm64/include/asm/perf_event.h | 14 + arch/arm64/kernel/perf_event.c | 72 +++++ drivers/perf/arm_pmu.c | 48 ++++ include/linux/perf/arm_pmu.h | 2 + tools/perf/arch/arm64/Build | 2 +- tools/perf/arch/arm64/include/arch-tests.h | 6 + tools/perf/arch/arm64/tests/Build | 3 +- tools/perf/arch/arm64/tests/arch-tests.c | 4 + tools/perf/arch/arm64/tests/user-events.c | 255 ++++++++++++++++++ 12 files changed, 454 insertions(+), 2 deletions(-) create mode 100644 Documentation/arm64/pmu_counter_user_access.txt create mode 100644 tools/perf/arch/arm64/tests/user-events.c
-- 2.17.1
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