Messages in this thread | | | Date | Tue, 24 Aug 2021 16:26:22 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v9 1/3] arm64: perf: Add userspace counter access disable switch |
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On Fri, Aug 06, 2021 at 04:51:21PM -0600, Rob Herring wrote: > 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 also supports writing '2' to globally enable user access. > 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: Will Deacon <will@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Arnaldo Carvalho de Melo <acme@kernel.org> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> > Cc: Jiri Olsa <jolsa@redhat.com> > Cc: Namhyung Kim <namhyung@kernel.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: linux-perf-users@vger.kernel.org > Signed-off-by: Rob Herring <robh@kernel.org> > --- > v9: > - Use sysctl instead of sysfs attr > - Default to disabled > v8: > - New patch > > --- > arch/arm64/kernel/perf_event.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c > index d07788dad388..74f77b68f5f0 100644 > --- a/arch/arm64/kernel/perf_event.c > +++ b/arch/arm64/kernel/perf_event.c > @@ -286,6 +286,21 @@ static const struct attribute_group armv8_pmuv3_events_attr_group = { > PMU_FORMAT_ATTR(event, "config:0-15"); > PMU_FORMAT_ATTR(long, "config1:0"); > > +static int sysctl_perf_user_access __read_mostly; > + > +static struct ctl_table armv8_pmu_sysctl_table[] = { > + { > + .procname = "perf_user_access", > + .data = &sysctl_perf_user_access, > + .maxlen = sizeof(unsigned int), > + .mode = 0644, > + .proc_handler = proc_dointvec_minmax, > + .extra1 = SYSCTL_ZERO, > + .extra2 = SYSCTL_ONE, > + }, > + { } > +};
This should be documented somewhere. Maybe add an entry to Documentation/admin-guide/sysctl/kernel.rst which points at the doc in patch 3, which needs updating to talk about this control?
Otherwise, looks good:
Acked-by: Will Deacon <will@kernel.org>
Will
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