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.