Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 5 Jun 2023 08:58:16 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH V11 03/10] arm64/perf: Add branch stack support in struct arm_pmu |
| |
On Wed, May 31, 2023 at 09:34:21AM +0530, Anshuman Khandual wrote: > This updates 'struct arm_pmu' for branch stack sampling support later. This > adds a new 'features' element in the structure to track supported features, > and another 'private' element to encapsulate implementation attributes on a > given 'struct arm_pmu'. These updates here will help in tracking any branch > stack sampling support, which is being added later. This also adds a helper > arm_pmu_branch_stack_supported(). > > This also enables perf branch stack sampling event on all 'struct arm pmu', > supporting the feature but after removing the current gate that blocks such > events unconditionally in armpmu_event_init(). Instead a quick probe can be > initiated via arm_pmu_branch_stack_supported() to ascertain the support. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Tested-by: James Clark <james.clark@arm.com> > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > drivers/perf/arm_pmu.c | 3 +-- > include/linux/perf/arm_pmu.h | 12 +++++++++++- > 2 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c > index aada47e3b126..d4a4f2bd89a5 100644 > --- a/drivers/perf/arm_pmu.c > +++ b/drivers/perf/arm_pmu.c > @@ -510,8 +510,7 @@ 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)) > + if (has_branch_stack(event) && !arm_pmu_branch_stack_supported(armpmu)) > return -EOPNOTSUPP; > > return __hw_perf_event_init(event); > diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h > index f7fbd162ca4c..0da745eaf426 100644 > --- a/include/linux/perf/arm_pmu.h > +++ b/include/linux/perf/arm_pmu.h > @@ -102,7 +102,9 @@ struct arm_pmu { > int (*map_event)(struct perf_event *event); > void (*sched_task)(struct perf_event_pmu_context *pmu_ctx, bool sched_in); > int num_events; > - bool secure_access; /* 32-bit ARM only */ > + unsigned int secure_access : 1, /* 32-bit ARM only */ > + has_branch_stack: 1, /* 64-bit ARM only */ > + reserved : 30; > #define ARMV8_PMUV3_MAX_COMMON_EVENTS 0x40 > DECLARE_BITMAP(pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS); > #define ARMV8_PMUV3_EXT_COMMON_EVENT_BASE 0x4000 > @@ -118,8 +120,16 @@ struct arm_pmu { > > /* Only to be used by ACPI probing code */ > unsigned long acpi_cpuid; > + > + /* Implementation specific attributes */ > + void *private; > }; > > +static inline bool arm_pmu_branch_stack_supported(struct arm_pmu *armpmu) > +{ > + return armpmu->has_branch_stack; > +}
Since this is a trivial test, and we already access the 'secure_access' field directly, I'd prefer we removed this helper and directly accessesed arm_pmu::has_branch_stack, e.g. with the logic in armpmu_event_init() being:
if (has_branch_stack(event) && !armpmu->has_branch_stack) return -EOPNOTSUPP;
With that:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Mark.
| ![\](/images/icornerr.gif) |