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SubjectRe: [PATCH v5 0/9] libperf and arm64 userspace counter access support
On Wed, Jan 13, 2021 at 08:05:56PM -0600, Rob Herring wrote:
> Hi all,
>
> Another version of libperf and arm64 userspace counter access support.
> This originally resurrected Raphael's series[1] to enable userspace counter
> access on arm64. My previous versions are here[2][3][4][5]. A git branch is
> here[6].

Ping.

Will, Mark, comments on the Arm bits?

>
> Changes in v5:
> - Limit enabling/disabling access to CPUs associated with the PMU
> (supported_cpus) and with the mm_struct matching current->active_mm.
> The x86 method of using mm_cpumask doesn't work for arm64 as it is not
> updated.
> - Only set cap_user_rdpmc if event is on current cpu. See patch 2.
> - Create an mmap for every event in an evsel. This results in some changes
> to the libperf mmap API from the last version.
> - Rebase to v5.11-rc2
>
> 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/r/20190822144220.27860-1-raphael.gault@arm.com/
> [2] https://lore.kernel.org/r/20200707205333.624938-1-robh@kernel.org/
> [3] https://lore.kernel.org/r/20200828205614.3391252-1-robh@kernel.org/
> [4] https://lore.kernel.org/r/20200911215118.2887710-1-robh@kernel.org/
> [5] https://lore.kernel.org/r/20201001140116.651970-1-robh@kernel.org/
> [6] git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git user-perf-event-v5
>
>
> Raphael Gault (3):
> arm64: pmu: Add function implementation to update event index in
> userpage
> arm64: perf: Enable PMU counter direct access for perf event
> Documentation: arm64: Document PMU counters access from userspace
>
> Rob Herring (6):
> tools/include: Add an initial math64.h
> libperf: Add evsel mmap support
> 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 | 68 +++++++
> include/linux/perf/arm_pmu.h | 2 +
> tools/include/linux/math64.h | 75 +++++++
> tools/lib/perf/Documentation/libperf.txt | 2 +
> tools/lib/perf/evsel.c | 50 ++++-
> 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 | 2 +
> tools/lib/perf/mmap.c | 186 ++++++++++++++++++
> tools/lib/perf/tests/Makefile | 6 +-
> tools/lib/perf/tests/test-evsel.c | 65 ++++++
> 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, 751 insertions(+), 4 deletions(-)
> 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
>
> --
> 2.27.0

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