On Mon, Feb 15, 2016 at 02:27:27PM +0000, Mark Rutland wrote: > > > > + uncore = event_to_thunder_uncore(event); > > > > + if (!uncore) > > > > + return -ENODEV; > > > > + if (!uncore->event_valid(event->attr.config)) > > > > + return -EINVAL; > > > > + > > > > + hwc->config = event->attr.config; > > > > + hwc->idx = -1; > > > > + > > > > + /* and we don't care about CPU */ > > > > > > Actually, you do. You want the perf core to serialize accesses via the > > > same CPU, so all events _must_ be targetted at the same CPU. Otherwise > > > there are a tonne of problems you don't even want to think about. > > > > I found that perf added the events on every CPU in the system. Because > > the uncore events are not CPU related I wanted to avoid this. Setting > > cpumask to -1 did not work. Therefore I added a single CPU in the > > cpumask, see thunder_uncore_attr_show_cpumask(). > > I understand that, which is why I wrote: > > > > You _must_ ensure this kernel-side, regardless of what the perf tool > > > happens to do. > > > > > > See the arm-cci and arm-ccn drivers for an example. > > Take a look at drivers/bus/arm-cci.c; specifically, what we do in > cci_pmu_event_init and cci_pmu_cpu_notifier. > > This is the same thing that's done for x86 system PMUs. Take a look at > uncore_pmu_event_init in arch/x86/kernel/cpu/perf_event_intel_uncore.c.
I note that we still have an open TODO rather than a call to perf_pmu_migrate_context. The better example is arm_ccn_pmu_cpu_notifier in drivers/bus/arm-ccn.c. Mark.
