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Re: [Xen-devel] segfault in VM

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] segfault in VM
From: Chris Andrews <chris@xxxxxxxxxx>
Date: Mon, 19 Jul 2004 09:28:40 +0100
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Keir Fraser wrote:
Clearly there's some fairly random memory corruption going on, which
then causes segfaults (if the corruption hits code pages) and
filesystem corruption (if the corruption hits buffer-cache pages).
The "Bailing: not a -ve offset" and "GPF (0004):" messages are almost
certainly just symptoms of executing a corrupted block of code. i.e.,
the bug has already triggered some time ago - probably corrupted a
page of glibc or the kernel.

It would be interesting to see whether or not this is SMP-related.
It's also interesting that someone said they couldn't reproduce
corruption when using 2.6.7 for the non-privileged guest OSes.

I'm seeing this corruption on a single CPU machine, with a single 2.4 guest running but idle. I only ran one 2.6.7 guest, and I didn't give it any work, but it didn't take any load in the 2.4 guest to provoke problems.

The machine uses devicemapper, so I'm going to move some partitions around and see if I still get corruption without it. I can also build Xen with debug=y and try that, once I've got the disk sorted.


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