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| author | Palmer Dabbelt <palmer@rivosinc.com> | 2023-08-16 07:28:26 -0700 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2023-08-23 09:07:28 -0700 |
| commit | 7aa7d502e4d5a42353325cb4bf2aa880b10168e9 (patch) | |
| tree | be8c3acd23298081b6a3085c0a7e1b2b36a48656 /Documentation | |
| parent | 9f944d2e0ab39296bfadb29167dc333815ba9f48 (diff) | |
| parent | 26ba042414a35cb1fd7c31fae63841956ce7cecb (diff) | |
Merge patch series "riscv: Allow userspace to directly access perf counters"
Alexandre Ghiti <alexghiti@rivosinc.com> says:
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.
**Important**: The default mode is now user access through perf only, not
the legacy so some applications will break. However, we introduce a sysctl
perf_user_access like arm64 does, which will allow to switch to the legacy
mode described above.
This version needs openSBI v1.3 *and* a kernel fix that went upstream lately
(https://lore.kernel.org/lkml/20230616114831.3186980-1-maz@kernel.org/T/).
* b4-shazam-merge:
perf: tests: Adapt mmap-basic.c for riscv
tools: lib: perf: Implement riscv mmap support
Documentation: admin-guide: Add riscv sysctl_perf_user_access
drivers: perf: Implement perf event mmap support in the SBI backend
drivers: perf: Implement perf event mmap support in the legacy backend
riscv: Prepare for user-space perf event mmap support
drivers: perf: Rename riscv pmu sbi driver
riscv: Make legacy counter enum match the HW numbering
include: riscv: Fix wrong include guard in riscv_pmu.h
perf: Fix wrong comment about default event_idx
Link: https://lore.kernel.org/r/20230802080328.1213905-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/sysctl/kernel.rst | 27 |
1 files changed, 23 insertions, 4 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 3800fab1619b..8019103aac10 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -941,16 +941,35 @@ enabled, otherwise writing to this file will return ``-EBUSY``. The default value is 8. -perf_user_access (arm64 only) -================================= +perf_user_access (arm64 and riscv only) +======================================= + +Controls user space access for reading perf event counters. -Controls user space access for reading perf event counters. When set to 1, -user space can read performance monitor counter registers directly. +arm64 +===== The default value is 0 (access disabled). +When set to 1, user space can read performance monitor counter registers +directly. + See Documentation/arch/arm64/perf.rst for more information. +riscv +===== + +When set to 0, user space access is disabled. + +The default value is 1, user space can read performance monitor counter +registers through perf, any direct access without perf intervention will trigger +an illegal instruction. + +When set to 2, which enables legacy mode (user space has direct access to cycle +and insret CSRs only). Note that this legacy value is deprecated and will be +removed once all user space applications are fixed. + +Note that the time CSR is always directly accessible to all modes. pid_max ======= |