Re: [RFC 4/7] arm64: pmu: Add function implementation to update event index in userpage.

[Raphael Gault]

Hi Peter,

On 5/29/19 10:46 AM, Peter Zijlstra wrote:
> On Tue, May 28, 2019 at 04:03:17PM +0100, Raphael Gault wrote:
> > +static int armv8pmu_access_event_idx(struct perf_event *event)
> > +{
> > +	if (!(event->hw.flags & ARMPMU_EL0_RD_CNTR))
> > +		return 0;
> > +
> > +	/*
> > +	 * We remap the cycle counter index to 32 to
> > +	 * match the offset applied to the rest of
> > +	 * the counter indeces.
> > +	 */
> > +	if (event->hw.idx == ARMV8_IDX_CYCLE_COUNTER)
> > +		return 32;
> > +
> > +	return event->hw.idx;
>
> Is there a guarantee event->hw.idx is never 0? Or should you, just like
> x86, use +1 here?

You are right, I should use +1 here. Thanks for pointing that out.

> > +}

Thanks,

--
Raphael Gault