lkml.org 
[lkml]   [2017]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 00/18] Entry stack switching

* Andy Lutomirski <luto@kernel.org> wrote:

> On Tue, Nov 21, 2017 at 10:22 PM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Andy Lutomirski <luto@kernel.org> wrote:
> >
> >> This sets up stack switching, including for SYSCALL. I think it's
> >> in decent shape.
> >>
> >> Known issues:
> >> - I think we're going to want a way to turn the stack switching on and
> >> off either at boot time or at runtime. It should be fairly straightforward
> >> to make it work.
> >>
> >> - I think the ORC unwinder isn't so good at dealing with stack overflows.
> >> It bails too early (I think), resulting in lots of ? entries. This
> >> isn't a regression with this series -- it's just something that could
> >> be improved.
> >>
> >> Ingo, patch 1 may be tip/urgent material. It fixes what I think is
> >> a bug in Xen. I'm having a hard time testing because it's being
> >> masked by a bigger unrelated bug that's keeping Xen from booting
> >> when configured to hit the bug I'm fixing. (The latter bug goes at
> >> least back to v4.13, I think I know roughtly what's wrong, and I've
> >> reported it to the maintainers.)
> >
> > Hm, with this series the previous IRQ vector bug appears again:
> >
> > [ 51.156370] do_IRQ: 16.34 No irq handler for vector
> > [ 57.511030] do_IRQ: 16.34 No irq handler for vector
> > [ 57.528335] do_IRQ: 16.34 No irq handler for vector
> > [ 57.533256] do_IRQ: 16.34 No irq handler for vector
> > [ 63.991913] do_IRQ: 16.34 No irq handler for vector
> > [ 63.996810] do_IRQ: 16.34 No irq handler for vector
> >
> > I've attached the reproducer config. Note that the system appears to be working to
> > a certain extent (I could ssh to it and extract its config), but produces these
> > warnings sporadically.
>
> I'll try to reproduce this, but this is weird. This is vector 34,
> which is, or could be, a genuine IRQ vector. The only way I can think
> of that my series would have caused this is if I very severely broke
> common_interrupt, but I don't see how that could have happened without
> breaking everything. It's also weird that you're seeing this only on
> CPU 16. Maybe it's worth adding a WARN_ON to that warning to get a
> stack trace just in case.
>
> Thomas, any insight here?
>
> > but don't get the IRQ vector warnings.
>
> Ingo, are you saying that you only get the IRQ vector warnings with
> the SYSCALL hwframe fix applied? That's bizarre.

Correct. I assume it's because lockdep is working fine with that fix applied,
but that also means that different irq-tracing code paths are taken.

The lockdep error disables lockdep globally and immediately.

> Anyway, I booted your config (more or less -- I munged it through
> virtme-configkernel --update first) with 17 vCPUs and it seems fine.
> Is the issue reliable enough to bisect?

Ok, it should be bisectable, will try to bisect it.

I think it's a key aspect that the CPU is AMD - a similar config on Intel seems to
be working fine (modulo the unwinder warning).

Thanks,

Ingo

\
 
 \ /
  Last update: 2017-11-23 07:22    [W:0.071 / U:2.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site