| Message ID | 20220929075857.158358-8-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/perf: Enable branch stack sampling | expand |
On 29/09/2022 08:58, Anshuman Khandual wrote: > Now that all the required pieces are already in place, just enable the perf > branch stack sampling support on arm64 platform, by removing the gate which > blocks it in armpmu_event_init(). > > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: linux-kernel@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > drivers/perf/arm_pmu.c | 32 +++++++++++++++++++++++++++++--- > 1 file changed, 29 insertions(+), 3 deletions(-) > > diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c > index 93b36933124f..2a9b988b53c2 100644 > --- a/drivers/perf/arm_pmu.c > +++ b/drivers/perf/arm_pmu.c > @@ -537,9 +537,35 @@ static int armpmu_event_init(struct perf_event *event) > !cpumask_test_cpu(event->cpu, &armpmu->supported_cpus)) > return -ENOENT; > > - /* does not support taken branch sampling */ > - if (has_branch_stack(event)) > - return -EOPNOTSUPP; > + if (has_branch_stack(event)) { > + /* > + * BRBE support is absent. Select CONFIG_ARM_BRBE_PMU > + * in the config, before branch stack sampling events > + * can be requested. > + */ > + if (!IS_ENABLED(CONFIG_ARM_BRBE_PMU)) { > + pr_warn_once("BRBE is disabled, select CONFIG_ARM_BRBE_PMU\n"); > + return -EOPNOTSUPP; > + } > + > + if (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_KERNEL) { > + if (!perfmon_capable()) { I'm still getting different behaviour compared to x86 when using perf_event_paranoid because of this perfmon_capable() call here. > + pr_warn_once("does not have permission for kernel branch filter\n"); Also I was under the impression that this should be more like a KERN_INFO loglevel rather than a KERN_WARNING. It's more like expected behavior rather than unexpected behavior and as far as I know anyone who sees something in dmesg might think something has gone wrong and try to follow it up. It is quite a useful message but I remember getting a review like this before and it made sense to me. > + return -EPERM; > + } > + } > + > + /* > + * Branch stack sampling event can not be supported in > + * case either the required driver itself is absent or > + * BRBE buffer, is not supported. Besides checking for > + * the callback prevents a crash in case it's absent. > + */ > + if (!armpmu->brbe_supported || !armpmu->brbe_supported(event)) { > + pr_warn_once("BRBE is not supported\n"); > + return -EOPNOTSUPP; > + } > + } > > if (armpmu->map_event(event) == -ENOENT) > return -ENOENT;
On 10/10/2022 14:55, James Clark wrote: > > > On 29/09/2022 08:58, Anshuman Khandual wrote: >> Now that all the required pieces are already in place, just enable the perf >> branch stack sampling support on arm64 platform, by removing the gate which >> blocks it in armpmu_event_init(). >> >> Cc: Mark Rutland <mark.rutland@arm.com> >> Cc: Will Deacon <will@kernel.org> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Cc: linux-kernel@vger.kernel.org >> Cc: linux-arm-kernel@lists.infradead.org >> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> >> --- >> drivers/perf/arm_pmu.c | 32 +++++++++++++++++++++++++++++--- >> 1 file changed, 29 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c >> index 93b36933124f..2a9b988b53c2 100644 >> --- a/drivers/perf/arm_pmu.c >> +++ b/drivers/perf/arm_pmu.c >> @@ -537,9 +537,35 @@ static int armpmu_event_init(struct perf_event *event) >> !cpumask_test_cpu(event->cpu, &armpmu->supported_cpus)) >> return -ENOENT; >> >> - /* does not support taken branch sampling */ >> - if (has_branch_stack(event)) >> - return -EOPNOTSUPP; >> + if (has_branch_stack(event)) { >> + /* >> + * BRBE support is absent. Select CONFIG_ARM_BRBE_PMU >> + * in the config, before branch stack sampling events >> + * can be requested. >> + */ >> + if (!IS_ENABLED(CONFIG_ARM_BRBE_PMU)) { >> + pr_warn_once("BRBE is disabled, select CONFIG_ARM_BRBE_PMU\n"); >> + return -EOPNOTSUPP; >> + } >> + >> + if (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_KERNEL) { >> + if (!perfmon_capable()) { > > I'm still getting different behaviour compared to x86 when using > perf_event_paranoid because of this perfmon_capable() call here. Given the generic events framework already checks this for any privileged branch samples (i.e., for both KERNEL and HV), the individual drivers must not add additional restrictions. > >> + pr_warn_once("does not have permission for kernel branch filter\n"); > > Also I was under the impression that this should be more like a > KERN_INFO loglevel rather than a KERN_WARNING. It's more like expected > behavior rather than unexpected behavior and as far as I know anyone who > sees something in dmesg might think something has gone wrong and try to > follow it up. It is quite a useful message but I remember getting a > review like this before and it made sense to me. +1 Suzuki
On 10/10/22 21:18, Suzuki K Poulose wrote: > On 10/10/2022 14:55, James Clark wrote: >> >> >> On 29/09/2022 08:58, Anshuman Khandual wrote: >>> Now that all the required pieces are already in place, just enable the perf >>> branch stack sampling support on arm64 platform, by removing the gate which >>> blocks it in armpmu_event_init(). >>> >>> Cc: Mark Rutland <mark.rutland@arm.com> >>> Cc: Will Deacon <will@kernel.org> >>> Cc: Catalin Marinas <catalin.marinas@arm.com> >>> Cc: linux-kernel@vger.kernel.org >>> Cc: linux-arm-kernel@lists.infradead.org >>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> >>> --- >>> drivers/perf/arm_pmu.c | 32 +++++++++++++++++++++++++++++--- >>> 1 file changed, 29 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c >>> index 93b36933124f..2a9b988b53c2 100644 >>> --- a/drivers/perf/arm_pmu.c >>> +++ b/drivers/perf/arm_pmu.c >>> @@ -537,9 +537,35 @@ static int armpmu_event_init(struct perf_event *event) >>> !cpumask_test_cpu(event->cpu, &armpmu->supported_cpus)) >>> return -ENOENT; >>> - /* does not support taken branch sampling */ >>> - if (has_branch_stack(event)) >>> - return -EOPNOTSUPP; >>> + if (has_branch_stack(event)) { >>> + /* >>> + * BRBE support is absent. Select CONFIG_ARM_BRBE_PMU >>> + * in the config, before branch stack sampling events >>> + * can be requested. >>> + */ >>> + if (!IS_ENABLED(CONFIG_ARM_BRBE_PMU)) { >>> + pr_warn_once("BRBE is disabled, select CONFIG_ARM_BRBE_PMU\n"); >>> + return -EOPNOTSUPP; >>> + } >>> + >>> + if (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_KERNEL) { >>> + if (!perfmon_capable()) { >> >> I'm still getting different behaviour compared to x86 when using >> perf_event_paranoid because of this perfmon_capable() call here. > > Given the generic events framework already checks this for any > privileged branch samples (i.e., for both KERNEL and HV), the > individual drivers must not add additional restrictions. Okay, will drop perfmon_capable() check here along with the warning. > >> >>> + pr_warn_once("does not have permission for kernel branch filter\n"); >> >> Also I was under the impression that this should be more like a >> KERN_INFO loglevel rather than a KERN_WARNING. It's more like expected >> behavior rather than unexpected behavior and as far as I know anyone who >> sees something in dmesg might think something has gone wrong and try to >> follow it up. It is quite a useful message but I remember getting a >> review like this before and it made sense to me. > > +1 Sure, will change remaining pr_warn_once() prints as pr_info() instead.
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c index 93b36933124f..2a9b988b53c2 100644 --- a/drivers/perf/arm_pmu.c +++ b/drivers/perf/arm_pmu.c @@ -537,9 +537,35 @@ static int armpmu_event_init(struct perf_event *event) !cpumask_test_cpu(event->cpu, &armpmu->supported_cpus)) return -ENOENT; - /* does not support taken branch sampling */ - if (has_branch_stack(event)) - return -EOPNOTSUPP; + if (has_branch_stack(event)) { + /* + * BRBE support is absent. Select CONFIG_ARM_BRBE_PMU + * in the config, before branch stack sampling events + * can be requested. + */ + if (!IS_ENABLED(CONFIG_ARM_BRBE_PMU)) { + pr_warn_once("BRBE is disabled, select CONFIG_ARM_BRBE_PMU\n"); + return -EOPNOTSUPP; + } + + if (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_KERNEL) { + if (!perfmon_capable()) { + pr_warn_once("does not have permission for kernel branch filter\n"); + return -EPERM; + } + } + + /* + * Branch stack sampling event can not be supported in + * case either the required driver itself is absent or + * BRBE buffer, is not supported. Besides checking for + * the callback prevents a crash in case it's absent. + */ + if (!armpmu->brbe_supported || !armpmu->brbe_supported(event)) { + pr_warn_once("BRBE is not supported\n"); + return -EOPNOTSUPP; + } + } if (armpmu->map_event(event) == -ENOENT) return -ENOENT;
Now that all the required pieces are already in place, just enable the perf branch stack sampling support on arm64 platform, by removing the gate which blocks it in armpmu_event_init(). Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> --- drivers/perf/arm_pmu.c | 32 +++++++++++++++++++++++++++++--- 1 file changed, 29 insertions(+), 3 deletions(-)