panic: pmap_demote_section: No l2_bucket for wired mapping

[Pratik Singhal]

I am also able to reproduce the same bug on my Cubieboard 1 with freeBSD
11-current :-

I am pasting the stack trace and the boot log.

boot log :- http://pastie.org/10084212

stack trace :- http://pastie.org/10084214

On Mon, Mar 23, 2015 at 6:11 AM, Zbigniew Bodek <zbb at freebsd.org> wrote:

> 2015-03-22 20:45 GMT+01:00 Paul Mather <paul at gromit.dlib.vt.edu>:
> > On Mar 22, 2015, at 7:54 AM, Michael Tuexen <tuexen at freebsd.org> wrote:
> >
> >> Dear all,
> >>
> >> running head on a Raspberry Pi became unstable. When running
> >> r280329 for a while (the machine is exposed to the Internet, so
> >> ssh logins are continuously tried), the machine panics:
> >>
> >> panic: pmap_demote_section: No l2_bucket for wired mapping
> >> KDB: enter: panic
> >
> >
> > I get this panic when booting to multi-user on my newly-updated BBB
> (FreeBSD 11.0-CURRENT #0 r280350).  As pointed out later in this thread,
> setting vm.pmap.sp_enabled=0 prevents the panic (so far) and allows booting.
> >
> > Cheers,
> >
> > Paul.
> >
>
> I was able to reproduce this on my R-Pi too.
> The bug may be related to shared libraries mapping since excluding
> pmap_enter_section() (the one in the pmap_enter_object() that is
> responsible for doing the work for shared libraries mappings) results
> in normal operation even with page promotion/demotion enabled.
> I will try to find some time to look into that to ensure that this is
> not just covering the problem. If it doesn't then we may consider
> disabling pmap_enter_section() (by adding "return FALSE;") to have WA
> (without disabling superpages) until we find the real solution.
> pmap_enter_section() was being used very rarely before shared
> libraries superpage mappings were enabled so it is reasonable to think
> that the bug is somewhere around. Please let me know in case you find
> something.
>
> Best regards
> zbb
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-- 
Regards,
Pratik Singhal