On Thu, Feb 1, 2018 at 9:22 AM, Vince Weaver <vincent.weaver@xxxxxxxxx> wrote:
>
> Unless I'm misunderstanding, the fix going into 4.4 actually fixes the
> issue (BTS trying to access a VM buffer that is unmapped) using the KAISER
> infrastructure.
>
> The "fix" in 4.15 just disables BTS totally (until someone figures out how
> to fix things properly).
>
> So while in theory both are equivelant fixes ("the kernel no longer
> crashes when using perf/bts") the mechanism is completely different.
Absolutely. That's not uncommon for some "backports" where the code has changed.
What the eventual intel_bts evolution will be, I have no idea. Maybe
people won't care, and it's all simply "dead code until fixed chips"
issue.
Happily, the PTI-fixed parts *will* come fairly soon, and developers
(who are the main target of things like profiling) are more likely to
get new machines. Telling your management "I as a developer need a
newer system that supports XYZ" is easier than "we need to upgrade all
our machines".
Linus