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SubjectRe: [PATCH v9 2/2] drivers/perf: hisi: Add driver for HiSilicon PCIe PMU
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Hi, Will
On 2021/8/24 22:31, Will Deacon wrote:
> Hi,
>
> On Wed, Aug 18, 2021 at 01:12:46PM +0800, Qi Liu wrote:
>> PCIe PMU Root Complex Integrated End Point(RCiEP) device is supported
>> to sample bandwidth, latency, buffer occupation etc.
>>
>> Each PMU RCiEP device monitors multiple Root Ports, and each RCiEP is
>> registered as a PMU in /sys/bus/event_source/devices, so users can
>> select target PMU, and use filter to do further sets.
>>
>> Filtering options contains:
>> event - select the event.
>> port - select target Root Ports. Information of Root Ports are
>> shown under sysfs.
>> bdf - select requester_id of target EP device.
>> trig_len - set trigger condition for starting event statistics.
>> trig_mode - set trigger mode. 0 means starting to statistic when bigger
>> than trigger condition, and 1 means smaller.
>> thr_len - set threshold for statistics.
>> thr_mode - set threshold mode. 0 means count when bigger than threshold,
>> and 1 means smaller.
>
> I think this is getting there now, thanks for sticking with it. Just a
> couple of comments below..
>
>> +static bool hisi_pcie_pmu_validate_event_group(struct perf_event *event)
>> +{
>> + struct perf_event *sibling, *leader = event->group_leader;
>> + int counters = 1;
>> +
>> + if (!is_software_event(leader)) {
>> + if (leader->pmu != event->pmu)
>> + return false;
>> +
>> + if (leader != event)
>> + counters++;
>> + }
>> +
>> + for_each_sibling_event(sibling, event->group_leader) {
>> + if (is_software_event(sibling))
>> + continue;
>> +
>> + if (sibling->pmu != event->pmu)
>> + return false;
>> +
>> + counters++;
>> + }
>> +
>> + return counters <= HISI_PCIE_MAX_COUNTERS;
>> +}
>
> Given that this function doesn't look at the event numbers, doesn't this
> over-provision the counter registers? For example, if I create a group
> containing 4 of the same event, then we'll allocate four counters but only
> use one. Similarly, if I create a group containing two events, one for the
> normal counter and one for the extended counter, then we'll again allocate
> two counters instead of one.
>

Yes, we should add some check in hisi_pcie_pmu_validate_event_group()
function to avoid over-provision. I'll use a array to record events and
do this check.

Thanks for your review, I'll fix this.

> Have I misunderstood?
>
>> +static int hisi_pcie_pmu_event_init(struct perf_event *event)
>> +{
>> + struct hisi_pcie_pmu *pcie_pmu = to_pcie_pmu(event->pmu);
>> + struct hw_perf_event *hwc = &event->hw;
>> +
>> + event->cpu = pcie_pmu->on_cpu;
>> +
>> + if (EXT_COUNTER_IS_USED(hisi_pcie_get_event(event)))
>> + hwc->event_base = HISI_PCIE_EXT_CNT;
>> + else
>> + hwc->event_base = HISI_PCIE_CNT;
>> +
>> + if (event->attr.type != event->pmu->type)
>> + return -ENOENT;
>> +
>> + /* Sampling is not supported. */
>> + if (is_sampling_event(event) || event->attach_state & PERF_ATTACH_TASK)
>> + return -EOPNOTSUPP;
>> +
>> + if (!hisi_pcie_pmu_valid_filter(event, pcie_pmu)) {
>> + pci_err(pcie_pmu->pdev, "Invalid filter!\n");
>
> Please remove this message, as it's triggerable from userspace.
>
got it, will remove this.

Thanks,
Qi
> Will
> .
>

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