panic: pmap_demote_section: No l2_bucket for wired mapping

[Milan Obuch]

On Fri, 10 Apr 2015 14:39:05 +0530
Pratik Singhal <ps06756 at gmail.com> wrote:

> 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
> 

Hi,

could you try adding 'options ARM_NEW_PMAP' to your kernel configs? It
looks like it fixes this issue for me. If yoo can verify it, then I
suggest to add this into RPI-B kernel config in our source tree for
everybody, and some other kernel configs as well.

Regards,
Milan

> 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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> 
> 
>