Re: [PATCH v2 3/4] perf: add arm64 smmuv3 pmu driver

[Will Deacon <will.deacon@arm.com>]

On Mon, Sep 17, 2018 at 06:10:05PM +0100, John Garry wrote:
> 
> >>+
> >>+#define SMMU_EVENT_ATTR(_name, _id)                      \
> >>+    (&((struct perf_pmu_events_attr[]) {                  \
> >>+        { .attr = __ATTR(_name, 0444, smmu_pmu_event_show, NULL), \
> >>+          .id = _id, }                          \
> >>+    })[0].attr.attr)
> >>+
> >>+static struct attribute *smmu_pmu_events[] = {
> >>+    SMMU_EVENT_ATTR(cycles, SMMU_PMU_CYCLES),
> >>+    SMMU_EVENT_ATTR(transaction, SMMU_PMU_TRANSACTION),
> >>+    SMMU_EVENT_ATTR(tlb_miss, SMMU_PMU_TLB_MISS),
> >>+    SMMU_EVENT_ATTR(config_cache_miss, SMMU_PMU_CONFIG_CACHE_MISS),
> >>+    SMMU_EVENT_ATTR(trans_table_walk, SMMU_PMU_TRANS_TABLE_WALK),
> >>+    SMMU_EVENT_ATTR(config_struct_access,
> >>SMMU_PMU_CONFIG_STRUCT_ACCESS),
> >>+    SMMU_EVENT_ATTR(pcie_ats_trans_rq, SMMU_PMU_PCIE_ATS_TRANS_RQ),
> >>+    SMMU_EVENT_ATTR(pcie_ats_trans_passed,
> >>SMMU_PMU_PCIE_ATS_TRANS_PASSED),
> >>+    NULL
> >>+};
> >>+
> >>+static umode_t smmu_pmu_event_is_visible(struct kobject *kobj,
> >>+                     struct attribute *attr, int unused)
> >>+{
> >>+    struct device *dev = kobj_to_dev(kobj);
> >>+    struct smmu_pmu *smmu_pmu = to_smmu_pmu(dev_get_drvdata(dev));
> >>+    struct perf_pmu_events_attr *pmu_attr;
> >>+
> >>+    pmu_attr = container_of(attr, struct perf_pmu_events_attr,
> >>attr.attr);
> >>+
> >>+    if (test_bit(pmu_attr->id, smmu_pmu->supported_events))
> >>+        return attr->mode;
> >>+
> >>+    return 0;
> >>+}
> >>+static struct attribute_group smmu_pmu_events_group = {
> >>+    .name = "events",
> >>+    .attrs = smmu_pmu_events,
> >>+    .is_visible = smmu_pmu_event_is_visible,
> >>+};
> >>+
> >>+/* Formats */
> >>+PMU_FORMAT_ATTR(event,           "config:0-15");
> >>+PMU_FORMAT_ATTR(filter_stream_id,  "config1:0-31");
> >>+PMU_FORMAT_ATTR(filter_span,       "config1:32");
> >>+PMU_FORMAT_ATTR(filter_enable,       "config1:33");
> >>+
> >>+static struct attribute *smmu_pmu_formats[] = {
> >>+    &format_attr_event.attr,
> >>+    &format_attr_filter_stream_id.attr,
> >>+    &format_attr_filter_span.attr,
> >>+    &format_attr_filter_enable.attr,
> >>+    NULL
> >>+};
> >>+
> >>+static struct attribute_group smmu_pmu_format_group = {
> >>+    .name = "format",
> >>+    .attrs = smmu_pmu_formats,
> >>+};
> >>+
> >>+static const struct attribute_group *smmu_pmu_attr_grps[] = {
> >>+    &smmu_pmu_cpumask_group,
> >>+    &smmu_pmu_events_group,
> >>+    &smmu_pmu_format_group,
> >>+    NULL,
> >>+};
> >>+
> 
> 
> Question: If we wanted to add proper named event support for the
> IMPLEMENTATION DEFINED events, how to add (if at all)?
> 
> So currently the driver only supports the Architected events, which is fine.
> And we support raw events for the IMPLEMENTATION DEFINED events
> (0x80-0xFFFF).
> 
> But to add named event support for the IMP DEF events, I assume we would
> want to do something similar to arm64 CPU PMU events - that is, common
> architected events in kernel pmu driver, and implementation defined events
> defined in perf tool. However I don't know if it's even feasible considering
> there does not seem to be a mandatory/standard PMCG ID register to detect
> the implementation.

I guess we'd need something from firmware to identify the SMMU/PMU
implementation, so that we could probe the driver correctly. Once we have
that, it seems like it's just a matter of exposing a different name to
userspace, like we do for the CPU PMU.

Will