On Thu, 9 Jul 2020 21:29:22 -0700 Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > +Alex, whom I completely spaced on Cc'ing. > > Alex, this is related to the dreaded VFIO memslot zapping issue from last > year. Start of thread: https://patchwork.kernel.org/patch/11640719/. > > The TL;DR of below: can you try the attached patch with your reproducer > from the original bug[*]? I honestly don't know whether it has a legitimate > chance of working, but it's the one thing in all of this that I know was > definitely a bug. I'd like to test it out if only to sate my curiosity. > Absolutely no rush. Mixed results, maybe you can provide some guidance. Running this against v5.8-rc4, I haven't reproduced the glitch. But it's been a long time since I tested this previously, so I went back to v5.3-rc5 to make sure I still have a recipe to trigger it. I can still get the failure there as the selective flush commit was reverted in rc6. Then I wondered, can I take broken v5.3-rc5 and apply this fix to prove that it works? No, v5.3-rc5 + this patch still glitches. So I thought maybe I could make v5.8-rc4 break by s/true/false/ in this patch. Nope. Then I applied the original patch from[1] to try to break it. Nope. So if anything, I think the evidence suggests this was broken elsewhere and is now fixed, or maybe it is a timing issue that I can't trigger on newer kernels. If the reproducer wasn't so touchy and time consuming, I'd try to bisect, but I don't have that sort of bandwidth. Thanks, Alex [1] https://patchwork.kernel.org/patch/10798453/
