Hi Mark,
Thank you for the thorough review. I will post an updated patchset which addresses
all of your comments. There is just one outstanding comment which I have a question about:
On 9/1/2016 12:30 PM, Mark Rutland wrote:
> On Tue, Aug 30, 2016 at 01:01:33PM -0400, Neil Leeder wrote:
>> +static int l2_cache__event_init(struct perf_event *event)
>> +{
>> + struct hw_perf_event *hwc = &event->hw;
>> + struct hml2_pmu *slice;
>> + struct perf_event *sibling;
>> + struct l2cache_pmu *l2cache_pmu = to_l2cache_pmu(event->pmu);
>> +
>> + if (event->attr.type != l2cache_pmu->pmu.type)
>> + return -ENOENT;
>> +
>> + if (hwc->sample_period) {
>> + dev_warn(&l2cache_pmu->pdev->dev, "Sampling not supported\n");
>> + return -EOPNOTSUPP;
>> + }
>> +
>> + if (event->cpu < 0) {
>> + dev_warn(&l2cache_pmu->pdev->dev, "Per-task mode not supported\n");
>> + return -EOPNOTSUPP;
>> + }
>> +
>> + /* We cannot filter accurately so we just don't allow it. */
>> + if (event->attr.exclude_user || event->attr.exclude_kernel ||
>> + event->attr.exclude_hv || event->attr.exclude_idle) {
>> + dev_warn(&l2cache_pmu->pdev->dev, "Can't exclude execution levels\n");
>> + return -EOPNOTSUPP;
>> + }
>> +
>> + if (((L2_EVT_GROUP(event->attr.config) > L2_EVT_GROUP_MAX) ||
>> + (L2_EVT_PREFIX(event->attr.config) != 0) ||
>> + (L2_EVT_REG(event->attr.config) != 0)) &&
>> + (event->attr.config != L2CYCLE_CTR_RAW_CODE)) {
>> + dev_warn(&l2cache_pmu->pdev->dev, "Invalid config %llx\n",
>> + event->attr.config);
>> + return -EINVAL;
>> + }
>> +
>> + /* Don't allow groups with mixed PMUs, except for s/w events */
>> + if (event->group_leader->pmu != event->pmu &&
>> + !is_software_event(event->group_leader)) {
>> + dev_warn(&l2cache_pmu->pdev->dev,
>> + "Can't create mixed PMU group\n");
>> + return -EINVAL;
>> + }
>> +
>> + list_for_each_entry(sibling, &event->group_leader->sibling_list,
>> + group_entry)
>> + if (sibling->pmu != event->pmu &&
>> + !is_software_event(sibling)) {
>> + dev_warn(&l2cache_pmu->pdev->dev,
>> + "Can't create mixed PMU group\n");
>> + return -EINVAL;
>> + }
>> +
>> + hwc->idx = -1;
>> + hwc->config_base = event->attr.config;
>> +
>> + /*
>> + * Ensure all events are on the same cpu so all events are in the
>> + * same cpu context, to avoid races on pmu_enable etc.
>> + */
>> + slice = get_hml2_pmu(event->cpu);
>> + event->cpu = slice->on_cpu;
>
> This could put an event on a different CPU to its group siblings, which
> is broken.
This is the same logic as in arm-ccn.c:arm_ccn_pmu_event_init(), where there
is a single CPU designated as the CPU to be used for all events. All
events for this slice are forced to slice->on_cpu which is the CPU set in the
cpumask for this slice.
I'm not sure how this can put an event on a different CPU to its group siblings?
Thanks,
Neil
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