[Xen-users] RFH: Corruption with blktap2 on Debian 2.6.32-39 + xen-4.1.2

[Philipp Hahn <hahn@xxxxxxxxxxxxx>]

Hello,

I have observed several strange blktap2(?) corruption problems using Xen-4.1.2 
on several 2.6.32-39 based amd64 Linux Systems. I run an installation of a 
domain, which use 3 blktap2 devices: 2× 20 GiB hard disk image files and 1× 
1.1 GiB DVD iso file. During installation processes start to SEGV, which 
aborts the installation.
* Not all processes in domU segfault in each 
run: "date", "bash", "grep", "wc", ...
* md5sum finds multiple files where the MD5 sum doesn't match the expected 
value after installation.
* It doesn't matter, if the domUy are PV or HV.
* If I only use one disk, I've not observed the problem.
* The problem is likely to manifest more, the more blktap2 processes are 
running.
* If I use loopback or blkback to LVM instead of blktap2, I've not observed 
the corruption.
* In one try I even had SEGVs in dom0.
* In one try the host rebooted.
* In one try the domU switched to read-only after file-system corruption.
* I tested three HW systems: On 2 of them the problem always manifests, on a 
3rd the corruption wasn't observed yet. All three have Intel i7 CPUs and 8 
GiB RAM.
This makes me wonder if this is some kind of memory corruption problem caused 
by un-synchronized parallism.

Both dom0 and domU use our UCS-2.6.32 kernel, which is equivalent to Debian 
2.6.32-5-amd64 plus some more patches for a e1000 backport and some KVM 
fixes. I actually tested the Debian as well and observed the same problem, so 
the problem should not be specific to our kernel, but Debians as well.

Has someone observed or does know about any similar problems?
Anything more I can do to narrow down that problem?

Sincerely
Philipp Hahn
-- 
Philipp Hahn           Open Source Software Engineer      hahn@xxxxxxxxxxxxx
Univention GmbH        Linux for Your Business        fon: +49 421 22 232- 0
Mary-Somerville-Str.1  D-28359 Bremen                 fax: +49 421 22 232-99
                                                   http://www.univention.de/

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