Re: [PATCH v4 08/10] Documentation: admin-guide: Add riscv sysctl_perf_user_access
From: Atish Patra <hidden>
Date: 2023-07-14 08:51:22
Also in:
linux-doc, linux-perf-users, linux-riscv, lkml
On Mon, Jul 3, 2023 at 5:54 AM Alexandre Ghiti [off-list ref] wrote:
quoted hunk ↗ jump to hunk
riscv now uses this sysctl so document its usage for this architecture. Signed-off-by: Alexandre Ghiti <redacted> --- Documentation/admin-guide/sysctl/kernel.rst | 27 ++++++++++++++++++--- 1 file changed, 23 insertions(+), 4 deletions(-)diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index d85d90f5d000..19b627883313 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. +
For ARM64, 1 also enables reading performance counters via perf interface only. I don't think there is any way to access the counters directly in ARM64.
See Documentation/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 ======= -- 2.39.2
-- Regards, Atish _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel