Re: [Qemu-devel] core dump with drive-mirror

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Mon, Jun 30, 2014 at 05:40:16PM -0600, Eric Blake wrote:
> On 06/30/2014 05:16 PM, Eric Blake wrote:
> > I'm trying to track down a core dump with the QMP drive-mirror command.
> 
> Looks like the bug is related to a base image that is not a multiple of
> a cluster size.
> 
> > 
> > # in one terminal:
> > cd /tmp
> > rm -f base.img snap1.img snap2.img copy.img
> > 
> > # base.img <- snap1.img <- snap2.img; intentionally populating base.img
> > # with a qcow2 header, but treating it as raw data
> > qemu-img create -f qcow2 base.img 10M
> 
> If, right here, I inject:
> 
> truncate --size 262144 base.img
> 
> > qemu-img create -f qcow2 -b base.img -o backing_fmt=raw snap1.img
> > qemu-img create -f qcow2 -b snap1.img -o backing_fmt=qcow2 snap2.img
> > cp base.img copy.img
> > # Yes, this command line is derived from libvirt...
> > LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin \
> >  QEMU_AUDIO_DRV=none gdb --args  /usr/bin/qemu-system-x86_64 \
> 
> ...then everything else succeeds.  So it seems the problem is that qemu
> is doing a lousy job of handling a backing file and/or destination file
> that is not fully rounded out to a proper size.

Thanks for reporting this.  It's something we need to fix during the
QEMU 2.1 hard freeze that is starting today.

Stefan

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