[PATCH v2 00/10] riscv: Allow userspace to directly access perf counters

From: Alexandre Ghiti
Date: Fri May 12 2023 - 04:53:59 EST

riscv used to allow direct access to cycle/time/instret counters,
bypassing the perf framework, this patchset intends to allow the user to
mmap any counter when accessed through perf. But we can't break the
existing behaviour so we introduce a sysctl perf_user_access like arm64
does, which defaults to the legacy mode described above.

*Note* that there are still ongoing discussions around which mode should
be the default mode with distro people.

base-commit-tag: v6.3

Changes in v2:
- Split into smaller patches, way better!
- Add RB from Conor
- Simplify the way we checked riscv architecture
- Fix race mmap and other thread running on other cpus
- Use hwc when available
- Set all userspace access flags in event_init, too cumbersome to handle sysctl changes
- Fix arch_perf_update_userpage for pmu other than riscv-pmu by renaming pmu driver
- Fixed kernel test robot build error
- Fixed documentation (Andrew and Bagas)
- perf testsuite passes mmap tests in all 3 modes

Alexandre Ghiti (10):
perf: Fix wrong comment about default event_idx
include: riscv: Fix wrong include guard in riscv_pmu.h
riscv: Make legacy counter enum match the HW numbering
drivers: perf: Rename riscv pmu driver
riscv: Prepare for user-space perf event mmap support
drivers: perf: Implement perf event mmap support in the legacy backend
drivers: perf: Implement perf event mmap support in the SBI backend
Documentation: admin-guide: Add riscv sysctl_perf_user_access
tools: lib: perf: Implement riscv mmap support
perf: tests: Adapt mmap-basic.c for riscv

Documentation/admin-guide/sysctl/kernel.rst | 24 ++-
arch/riscv/kernel/Makefile | 2 +-
arch/riscv/kernel/perf_event.c | 74 ++++++++
drivers/perf/riscv_pmu.c | 41 ++++
drivers/perf/riscv_pmu_legacy.c | 37 +++-
drivers/perf/riscv_pmu_sbi.c | 196 +++++++++++++++++++-
include/linux/perf/riscv_pmu.h | 10 +-
include/linux/perf_event.h | 3 +-
tools/lib/perf/mmap.c | 65 +++++++
tools/perf/tests/mmap-basic.c | 4 +-
10 files changed, 435 insertions(+), 21 deletions(-)
create mode 100644 arch/riscv/kernel/perf_event.c