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