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Date: Tue, 22 Oct 2013 20:07:53 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: J David <j.david.lists@gmail.com>,
 Konstantin Belousov <kostikbel@gmail.com>
Subject: Re: 9.2 + ZFS + i386 = panic: pmap_enter: attempted pmap_enter on
 4MB page
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Cc: "freebsd-fs@freebsd.org" <freebsd-fs@FreeBSD.org>, alc@FreeBSD.org,
 Alan Cox <alc@rice.edu>
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on 22/10/2013 15:46 J David said the following:
> On Sun, Oct 20, 2013 at 9:02 AM, J David <j.david.lists@gmail.com> wrote:
>> The "attempted pmap_enter on 4MB page" panic occurred again.
> 
> Since a machine that crashes 3-4x a day is not useful, we have
> captured a few viable core images for this panic and have now set it
> to vm.pmap.pg_ps_enabled=0 in the hopes of stopping the crashes.
> 
> If there is anything else we can do to aid the debugging, please let us know.

Both panics you posted actually happened because of bad pointer dereference in ZFS.

It appears that for some reason trap_pfault does not just call panic right there
as it should, but instead attempts to "fault in" a corresponding page.

All in all, these look like a memory corruption of some sort (or use after free).

-- 
Andriy Gapon