On August 31, 2022 4:06:40 PM GMT-03:00, Rob Herring [off-list ref] wrote:

On Thu, Aug 25, 2022 at 1:08 PM Rob Herring [off-list ref] wrote:

quoted

Arm SPEv1.2 adds another 64-bits of event filtering control. As the
existing perf_event_attr::configN fields are all used up for SPE PMU, an
additional field is needed. Add a new 'config3' field.

In testing this, just exposing 'config3' in the format attributes
causes the SPE PMU to be disabled. So we can't add this without
breaking existing perf. Shouldn't perf just skip any format fields it
doesn't know about?

Something it doesn't know about, even more at the main perf_event_attr level, may preclude it to grok new records.

"May" is the key word, as perf_event_hdr has a size field, maybe sometimes it's possible to do as you say.

If you're interested propose patches to make perf ignore things when possible.

- Arnaldo 

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