Re: [PATCH 3/7] perf: arm64: Use rseq to test userspace access to pmu counters

From: Raphael Gault
Date: Tue Jun 25 2019 - 09:30:01 EST

Hi Mark, Hi Will,

Now that we have a better idea what enabling this feature for heterogeneous systems would look like (both with or without using rseqs), it might be worth discussing if this is in fact a desirable thing in term of performance-complexity trade off.

Indeed, while not as scary as first thought, maybe the rseq method would still dissuade users from using this feature. It is also worth noting that if we only enable this feature on homogeneous system, the `mrs` hook/emulation would not be necessary.
If because of the complexity of the setup we need to consider whether we want to upstream this and have to maintain it afterward.


Raphael Gault