Re: DMA errors in guest caused by corrupted(?) disk image

["René Pfeiffer" <lynx@luchs.at>]

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On Mar 31, 2009 at 1355 +1100, Matthew Palmer appeared and said:
> Hi,
> 
> I've just come across a somewhat strange problem that was suggested I
> report to the list.
> 
> The problem manifested itself as DMA errors and the like popping up in the
> guest, like I'd expect to see if a disk in a physical machine was dying,
> like this:
> 
>   hda: dma_timer_expiry: dma status == 0x21
> [...]

I've seen a similar effect on my KVM host server. There were I/O errors
on one partition. When I tried to reformat the partition and restore its
content from backups, mkfs was reporting I/O errors, always at the same
block number. I added a second qcow2 file and moved the partition there.

> The VM has previously been quite stable until this problem started part of
> the way through today.  Another guest on the same host machine is fine.

The KVM host runs since January very stable. The system is a Debian
Lenny with custom kernel 2.6.28.8 and kvm-84. The filesystem for images
is ext4 and the guests use ext4 in part, too.

I cannot provide the images since they are quite large (about 20 to 44
GB) and they contain sensitive data.

I plan to move to 2.6.29.x or 2.6.30.x for reasons of the ext4 patches
regarding delayed allocation and to upgrade kvm, but I can to tests with
the current system if you wish.

Best,
René.

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