Re: [PATCH v9 2/2] drivers/perf: hisi: Add driver for HiSilicon PCIe PMU

[liuqi (BA)]

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
> .