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SubjectRe: [PATCH 09/10] drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension
On Fri, 27 Jan 2017 18:07:48 +0000
Will Deacon <will.deacon@arm.com> wrote:

> +/* Perf callbacks */
> +static int arm_spe_pmu_event_init(struct perf_event *event)
> +{
> + u64 reg;
> + struct perf_event_attr *attr = &event->attr;
> + struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu);
> +
> + /* This is, of course, deeply driver-specific */
> + if (attr->type != event->pmu->type)
> + return -ENOENT;
> +
> + if (event->cpu >= 0 &&
> + !cpumask_test_cpu(event->cpu, &spe_pmu->supported_cpus))
> + return -ENOENT;
> +
> + if (arm_spe_event_to_pmsevfr(event) & PMSEVFR_EL1_RES0)
> + return -EOPNOTSUPP;
> +
> + if (event->hw.sample_period < spe_pmu->min_period ||
> + event->hw.sample_period & PMSIRR_EL1_IVAL_MASK)
> + return -EOPNOTSUPP;
> +
> + if (attr->exclude_idle)
> + return -EOPNOTSUPP;
> +
> + /*
> + * Feedback-directed frequency throttling doesn't work when we
> + * have a buffer of samples. We'd need to manually count the
> + * samples in the buffer when it fills up and adjust the event
> + * count to reflect that. Instead, force the user to specify a
> + * sample period instead.
> + */
> + if (attr->freq)
> + return -EINVAL;
> +
> + if (is_kernel_in_hyp_mode()) {
> + if (attr->exclude_kernel != attr->exclude_hv)
> + return -EOPNOTSUPP;
> + } else if (!attr->exclude_hv) {
> + return -EOPNOTSUPP;
> + }
> +
> + reg = arm_spe_event_to_pmsfcr(event);
> + if ((reg & BIT(PMSFCR_EL1_FE_SHIFT)) &&
> + !(spe_pmu->features & SPE_PMU_FEAT_FILT_EVT))
> + return -EOPNOTSUPP;
> +
> + if ((reg & BIT(PMSFCR_EL1_FT_SHIFT)) &&
> + !(spe_pmu->features & SPE_PMU_FEAT_FILT_TYP))
> + return -EOPNOTSUPP;
> +
> + if ((reg & BIT(PMSFCR_EL1_FL_SHIFT)) &&
> + !(spe_pmu->features & SPE_PMU_FEAT_FILT_LAT))
> + return -EOPNOTSUPP;
> +
> + return 0;
> +}

Please add below messaging such as to avoid users having to do
so themselves:

diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index b4906c3..7c2635c 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -655,24 +655,33 @@ static int arm_spe_pmu_event_init(struct perf_event *event)
u64 reg;
struct perf_event_attr *attr = &event->attr;
struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu);
+ struct device *dev = &spe_pmu->pdev->dev;

/* This is, of course, deeply driver-specific */
if (attr->type != event->pmu->type)
return -ENOENT;

if (event->cpu >= 0 &&
- !cpumask_test_cpu(event->cpu, &spe_pmu->supported_cpus))
+ !cpumask_test_cpu(event->cpu, &spe_pmu->supported_cpus)) {
+ dev_err_ratelimited(dev, "CPU not supported by SPE\n");
return -ENOENT;
+ }

- if (arm_spe_event_to_pmsevfr(event) & PMSEVFR_EL1_RES0)
+ if (arm_spe_event_to_pmsevfr(event) & PMSEVFR_EL1_RES0) {
+ dev_err_ratelimited(dev, "Unsupported event filter\n");
return -EOPNOTSUPP;
+ }

if (event->hw.sample_period < spe_pmu->min_period ||
- event->hw.sample_period & PMSIRR_EL1_IVAL_MASK)
+ event->hw.sample_period & PMSIRR_EL1_IVAL_MASK) {
+ dev_err_ratelimited(dev, "Cannot set sample period below the minimum interval\n");
return -EOPNOTSUPP;
+ }

- if (attr->exclude_idle)
+ if (attr->exclude_idle) {
+ dev_err_ratelimited(dev, "Cannot exclude profiling when idle\n");
return -EOPNOTSUPP;
+ }

/*
* Feedback-directed frequency throttling doesn't work when we
@@ -681,28 +690,39 @@ static int arm_spe_pmu_event_init(struct perf_event *event)
* count to reflect that. Instead, force the user to specify a
* sample period instead.
*/
- if (attr->freq)
+ if (attr->freq) {
+ dev_err_ratelimited(dev, "a sample period must be specified\n");
return -EINVAL;
+ }

if (is_kernel_in_hyp_mode()) {
- if (attr->exclude_kernel != attr->exclude_hv)
+ if (attr->exclude_kernel != attr->exclude_hv) {
+ dev_err_ratelimited(dev, "VHE is enabled but exclude_kernel and exclude_hv do not match\n");
return -EOPNOTSUPP;
+ }
} else if (!attr->exclude_hv) {
+ dev_err_ratelimited(dev, "VHE is disabled but exclude_hv is not set\n");
return -EOPNOTSUPP;
}

reg = arm_spe_event_to_pmsfcr(event);
if ((reg & BIT(PMSFCR_EL1_FE_SHIFT)) &&
- !(spe_pmu->features & SPE_PMU_FEAT_FILT_EVT))
+ !(spe_pmu->features & SPE_PMU_FEAT_FILT_EVT)) {
+ dev_err_ratelimited(dev, "event filter feature not supported\n");
return -EOPNOTSUPP;
+ }

if ((reg & BIT(PMSFCR_EL1_FT_SHIFT)) &&
- !(spe_pmu->features & SPE_PMU_FEAT_FILT_TYP))
+ !(spe_pmu->features & SPE_PMU_FEAT_FILT_TYP)) {
+ dev_err_ratelimited(dev, "event type filter feature not supported\n");
return -EOPNOTSUPP;
+ }

if ((reg & BIT(PMSFCR_EL1_FL_SHIFT)) &&
- !(spe_pmu->features & SPE_PMU_FEAT_FILT_LAT))
+ !(spe_pmu->features & SPE_PMU_FEAT_FILT_LAT)) {
+ dev_err_ratelimited(dev, "latency filter feature not supported\n");
return -EOPNOTSUPP;
+ }

return 0;
}

Thanks,

Kim

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