From e2012600810c9ded81f6f63a8d04781be3c300ad Mon Sep 17 00:00:00 2001 From: Rob Herring Date: Wed, 8 Dec 2021 14:11:22 -0600 Subject: arm64: perf: Add userspace counter access disable switch Like x86, some users may want to disable userspace PMU counter altogether. Add a sysctl 'perf_user_access' file to control userspace counter access. The default is '0' which is disabled. Writing '1' enables access. Note that x86 supports globally enabling user access by writing '2' to /sys/bus/event_source/devices/cpu/rdpmc. As there's not existing userspace support to worry about, this shouldn't be necessary for Arm. It could be added later if the need arises. Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Namhyung Kim Cc: Catalin Marinas Cc: linux-perf-users@vger.kernel.org Acked-by: Will Deacon Reviewed-by: Mark Rutland Signed-off-by: Rob Herring Link: https://lore.kernel.org/r/20211208201124.310740-4-robh@kernel.org Signed-off-by: Will Deacon --- Documentation/admin-guide/sysctl/kernel.rst | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'Documentation/admin-guide/sysctl/kernel.rst') diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 0e486f41185e..d359bcfadd39 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -905,6 +905,17 @@ enabled, otherwise writing to this file will return ``-EBUSY``. The default value is 8. +perf_user_access (arm64 only) +================================= + +Controls user space access for reading perf event counters. When set to 1, +user space can read performance monitor counter registers directly. + +The default value is 0 (access disabled). + +See Documentation/arm64/perf.rst for more information. + + pid_max ======= -- cgit