On Fri, Jan 05, 2018 at 10:15:00AM -0800, Andy Lutomirski wrote: > On Fri, Jan 5, 2018 at 9:52 AM, Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, Jan 05, 2018 at 12:48:54PM -0500, Pavel Tatashin wrote: > >> Boots successfully with "noefi" kernel parameter :) > > > > Thanks, that will help me narrow it down. I'll dig through more patches > > when I get home tonight... > > I wish you luck. The 4.4 series is "KAISER", not "KPTI", and the > relevant code is spread all over the place and is generally garbage. > See, for example, the turd called kaiser_set_shadow_pgd(). I would > not be terribly surprised if that particular turd is biting here. > > An alternative theory is that something is screwy in the EFI code. I > don't see anything directly wrong, but it's certainly a bit sketchy. > The newer kernels carefully avoid using PCID 0 for real work to avoid > corruption due to EFI and similar things. The "KAISER" code has no > such mitigation. Fortunately, it seems to use PCID=0 for kernel and > PCID=nonzero for user, so the obvious problem isn't present, but > something could still be wrong. > > Pavel, can you send your /proc/cpuinfo on a noefi boot? (Just the > first CPU worth is fine.) > > FWIW, I said before that I have very little desire to help debug > "KAISER". I stand by that. I totally understand, and do not expect your help at all. Worse case, I point people at 4.14 and tell them to upgrade, I'm not going to waste a ton of time on this for the same exact reasons you list here. And yeah, kaiser_set_shadow_pgd() is horrid, I've already gotten sucked into it for long enough... greg k-h