Date: Wed, 20 Aug 2008 16:29:25 -0300
From: "Luiz Fernando N. Capitulino" <lcapitulino@mandriva.com.br>
To: linux-kernel@vger.kernel.org
Cc: mathieu.desnoyers@polymtl.ca, mingo@elte.hu
Subject: 2.6.{26.2,27-rc} oops on virtualbox
Message-ID: <20080820162925.75a5e064@doriath.conectiva>
Organization: Mandriva
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 Hi there,

 Users of different Linux distros (includes Ubuntu, Mandriva, ArchLinux and
possibly Fedora) are reporting that kernel 2.6.26.2 is OOPSing in the
Virtual Box emulator[1].

 It is not clear if this is a kernel or Virtual Box bug, but as the kernel
is also OOPsing in QEMU (although with different behaivor) I have decided
to post my debug results here in case someone is interested in debugging
the kernel part further.

 I have done a bisection by hand among kernel versions and found that
the commit which triggers the oops in _Virtual Box_ was introduced in
2.6.26-rc1 and the problem also happens with latest Linus tree.

 By using git bisect I found that the commit is this:

"""
commit e587cadd8f47e202a30712e2906a65a0606d5865
Author: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date:   Thu Mar 6 08:48:49 2008 -0500

    x86: enhance DEBUG_RODATA support - alternatives

[...]

"""

 By reverting this commit I don't get the OOPS anymore. I have
tested with 2.6.26-rc1 and latest Linus tree (2.6.27-rc3).

 What puzzles me though is that a similar problem happens with
QEMU, but it also OOPSes with kernels before 2.6.26-rc1,
reverting the patch above makes no difference and it works with
current Linus tree.

 Does this look like a kernel bug?

 All my tests have been done with vanilla kernels, but I have
built .iso installation images with them and I'm not sure of
what the build script does.

[1] http://en.wikipedia.org/wiki/Virtual_box

 Thanks for reading this.

-- 
Luiz Fernando N. Capitulino
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