On Thu, Jan 28, 2021 at 06:57:35PM +0100, Borislav Petkov wrote: > Crazy idea: if you still can reproduce on -rc3, you could bisect: i.e., > if you apply the patch on -rc3 and it explodes and if you apply the same > patch on -rc5 and it works, then that could be a start... Yeah, don't > have a better idea here. :-\ I tried reporoducing (applied the original patch I posted back to -rc3) and the same issue stubbornly refused to show up again. But I did hit something with the same signature (overflow bit set in bank 1) while running my futex test (which has two processes mapping the poison page). This time I *do* understand what happened. The test failed when the two processes were running on the two hyperhtreads of the same core. Seeing overflow in this case is understandable because bank 1 MSRs on my test machine are shared between the HT threads. When I run the test again using taskset(1) to only allowing running on thread 0 of each core, it keeps going for hunderds of iterations. I'm not sure I can stitch together how this overflow also happened for my single process test. Maybe a migration from one HT thread to the other at an awkward moment? -Tony
