Comment 3 for bug 1602299

Here's my recreate:

On Power8 system with Xenial, KVM enabled.

1. sudo apt-get install uvtool uvtool-libvirt
2. wget http://people.canonical.com/~rharper/bugs/lp_1602299/lp_1602299.tgz
3. tar xzvf lp_1602299.tgz
4. cd lp_1602299
5. uvt-simplestreams-libvirt sync --source http://cloud-images.ubuntu.com/daily "release~(xenial|yakkety)" "arch=ppc64el"
6. uvt-kvm create --template ppc64le-template.xml --cpu 1 --disk 5 rharper-vm1 release=xenial
7. virsh destroy rharper-vm1
8. sudo qemu-img create -f raw /var/lib/uvtool/libvirt/images/rharper-vm1-disk2.raw 5G
9. virsh edit rharper-vm1
10. Add to the xml under the vdb disk element:

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/uvtool/libvirt/images/rharper-vm1-disk2.raw'/>
      <target dev='vdc' bus='virtio'/>
      <serial>bcache</serial>
    </disk>

11. virsh start rharper-vm1
12. uvt-kvm ssh --insecure rharper-vm1

# in guest
1. wget http://people.canonical.com/~rharper/bugs/lp_1602299/lp_1602299.tgz
2. tar xzvf lp_1602299.tgz
3. cd lp_1602299
4. sudo ./mkbcache.sh /dev/disk/by-id/virtio-bcache
5. sudo ./break-backing.sh /dev/disk/by-id/virtio-bcache
6. sudo ./break-cache.sh /dev/disk/by-id/virtio-bcache

The break-* scripts emit PASS or FAIL as appropriate.