Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf

[Markus Trippelsdorf]

On 2017.09.08 at 09:12 -0700, Andy Lutomirski wrote:
> On Fri, Sep 8, 2017 at 4:30 AM, Markus Trippelsdorf
> <markus@xxxxxxxxxxxxxxx> wrote:
> > On 2017.09.08 at 12:39 +0200, Markus Trippelsdorf wrote:
> >> On 2017.09.08 at 12:35 +0200, Ingo Molnar wrote:
> >> >
> >> > * Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx> wrote:
> >> >
> >> > > On 2017.09.08 at 11:16 +0200, Borislav Petkov wrote:
> >> > > > On Fri, Sep 08, 2017 at 10:05:36AM +0200, Borislav Petkov wrote:
> >> > > > > On Fri, Sep 08, 2017 at 08:26:44AM +0200, Thomas Gleixner wrote:
> >> > > > > > On Fri, 8 Sep 2017, Markus Trippelsdorf wrote:
> >> > > > > >
> >> > > > > > CC+ Borislav. He might have access to such a beast
> >> > > > >
> >> > > > > Can I have /proc/cpuinfo and dmesg pls, in order to see whether I have
> >> > > > > something similar?
> >> > > > >
> >> > > > > Private mail's fine too.
> >> > > >
> >> > > > So I don't have exactly your model - mine is model 2, stepping 3 but I see
> >> > > > something strange too, in dmesg:
> >> > >
> >> > > I'm pretty sure the bug is in the merged 'x86-mm-for-linus' branch:
> >> > > Either Andy's "PCID optimized TLB flushing" (would be my guess) or
> >> > > 'encrypted memory' support by Tom Lendacky.
> >> > >
> >> > > (Bisecting is hard, because sometimes I can compile stuff for over 15
> >> > > minutes without hitting the bug. At other times the machine locks up
> >> > > hard when starting X11 already.)
> >> >
> >> > Do you have the 72c0098d92ce fix?
> >>
> >> Yes. The bug still happens on the current git tree (which has the fix
> >> already):
> >
> > The bug is definitely caused by Andy Lutomirski's PCID optimized TLB
> > flushing" patches. Tom is off the hook.
> 
> I'm pretty sure it can't be PCID per se, since these CPUs are way too
> old and are very unlikely to have PCID.

Yes, the CPU doesn't support PCID (,but it does support PGE).

> It could plausibly be the lazy TLB flushing changes.

Yes, I've narrowed it down to:

commit 94b1b03b519b81c494900cb112aa00ed205cc2d9
Author: Andy Lutomirski <luto@xxxxxxxxxx>
Date:   Thu Jun 29 08:53:17 2017 -0700

    x86/mm: Rework lazy TLB mode and TLB freshness tracking


Theoretically you guys should be able to reproduce the issue by using
the "nopcid" boot option. 

-- 
Markus