[ kvm-Bugs-2487340 ] Possible memory corruption when file > RAM

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2009-01-10T12:47:41Z

Bugs item #2487340, was opened at 2009-01-05 13:39
Message generated for change (Settings changed) made by amitshah
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Category: None
Group: None
>Status: Pending
Resolution: None
Priority: 5
Private: No
Submitted By: Jake Muss (jaketmuss)
Assigned to: Nobody/Anonymous (nobody)
Summary: Possible memory corruption when file > RAM

Initial Comment:
Host: Debian Lenny AMD64, Intel Q6600 , kvm-82
Guest, Debian Lenny AMD64

I've been having issues with file corruption and I've simplified the issue down to the following:

create a 1G file: dd if=/dev/urandom of=1G bs=1G count=1
md5sum the file twice and the results will be different.

I've tested this on ext2, ext3, backing device lvm,qcow2,raw

If I change the RAM to 2G, I can then correctly md5sum the original file, however if I create a new file that's 2G the issue reappears.

The only time the test has not failed was for the first few tests after the odd reboot.

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>Comment By: Amit Shah (amitshah)
Date: 2009-01-10 18:17

Message:
I can't reproduce this on a Lenny guest on an F10 host. Both are 64-bit.

Can you try reproducing this with -no-kvm and report the results?

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Comment By: Jake Muss (jaketmuss)
Date: 2009-01-09 17:48

Message:
Guest RAM.

I have also now tried using Fedora 10 as a guest and using Debian Lenny
i386 (32 bit) as a guest, still have the same issue. I ram memcheck for one
pass in fedora and that didnlt come up with anything, and also one pass on
the host. I'm not able to take the host down for long periods.

Lastly, I seem to be able to get the same md5 sum if nothing else is
causing a big change the page cache, however the md5sum is still wrong and
won't be repeated later on. So I guess it's either getting into the cache
incorrectly, or something to do with the way is accessed. I did some other
tests with a binary diff and in a 1 gig file I had about 8 bits different.

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Comment By: Amit Shah (amitshah)
Date: 2009-01-09 17:26