On Thu, Feb 1, 2018 at 9:22 AM, Vince Weaver vincent.weaver@maine.edu 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