Re: [PATCH v5 2/2] perf: Fujitsu: Add the Uncore PCI PMU driver

[Mark Rutland]

On Tue, Jun 17, 2025 at 12:36:18PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 17, 2025 at 07:27:50PM +0900, Koichi Okuno wrote:
> > +	pcipmu->pmu = (struct pmu) {
> > +		.parent		= dev,
> > +		.task_ctx_nr	= perf_invalid_context,
> > +
> > +		.pmu_enable	= fujitsu_pci__pmu_enable,
> > +		.pmu_disable	= fujitsu_pci__pmu_disable,
> > +		.event_init	= fujitsu_pci__event_init,
> > +		.add		= fujitsu_pci__event_add,
> > +		.del		= fujitsu_pci__event_del,
> > +		.start		= fujitsu_pci__event_start,
> > +		.stop		= fujitsu_pci__event_stop,
> > +		.read		= fujitsu_pci__event_read,
> > +
> > +		.attr_groups	= fujitsu_pci_pmu_attr_grps,
> > +		.capabilities	= PERF_PMU_CAP_NO_EXCLUDE,
> 
> Should these drivers not also have PERF_PMU_CAP_NO_INTERRUPT ? Per them
> being uncore they cannot generate samples.

These PMUs actually have an interrupt, so that might be a bit confusing.
That said, the counters seem to be 64-bit, so the interrupt doesn't seem
practically necessary today.

Either way, the fujitsu_pci__event_init() function rejects sampling
events, so it correctly rejects sampling events.

IMO, it'd be a bit nicer to do the inverse, and have the perf core
reject sampling events by default for non-CPU PMUs.

Mark.