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Subject[RFC] perf/x86/intel/uncore: pmu->type->single_fixed question
hi,
I'm trying to find out some documentation background for this part of uncore code:

---
static int uncore_pmu_event_init(struct perf_event *event)
{
...
if (event->attr.config == UNCORE_FIXED_EVENT) {
/* no fixed counter */
if (!pmu->type->fixed_ctl)
return -EINVAL;
/*
* if there is only one fixed counter, only the first pmu
* can access the fixed counter
*/
if (pmu->type->single_fixed && pmu->pmu_idx > 0)
return -EINVAL;
...
---

that for some uncore types (those with pmu->type->single_fixed) only
the first pmu (code_id == 0) will allow to touch the clocktick event

other cores boxes will not allow to open clocktick event, eventhough
it's announced via /sys/../events/..

I'm probably missing some HW logic of specific boxes that would explain
that, but I can't find it.

thanks for info,
jirka

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