Libguestfs - Feb 2010 - Order of list-devices changes when libguestfs uses virtio

Output from guestfish after upgrading to rawhide libguestfs, compiled
with virtio:
><fs> add_drive "/dev/Guests/RHEL52PV32"
><fs> add_cdrom "/var/lib/virt-v2v/transfer.iso"
><fs> launch
><fs> list-devices
/dev/sr0
/dev/vda

Note that the order has swapped. If these aren't consistent we don't
have a good way to determine which host devices map to which guest devices.

Matt
-- 
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

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On Mon, Feb 08, 2010 at 05:15:27PM +0000, Matthew Booth
wrote:
> Output from guestfish after upgrading to rawhide libguestfs, compiled
> with virtio:
> 
> ><fs> add_drive "/dev/Guests/RHEL52PV32"
> ><fs> add_cdrom "/var/lib/virt-v2v/transfer.iso"
> ><fs> launch
> ><fs> list-devices
> /dev/sr0
> /dev/vda
> 
> Note that the order has swapped. If these aren't consistent we
don't
> have a good way to determine which host devices map to which guest devices.
This is not good.

Ideas?

qemu -drive has a serial=... option.  I'm not clear what it does, but
if there is a way to assign a UUID to the device on the host side, and
read that from the guest then we should be able to restore the
ordering.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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On Mon, Feb 08, 2010 at 05:15:27PM +0000, Matthew Booth
wrote:
> Output from guestfish after upgrading to rawhide libguestfs, compiled
> with virtio:
> 
> ><fs> add_drive "/dev/Guests/RHEL52PV32"
> ><fs> add_cdrom "/var/lib/virt-v2v/transfer.iso"
> ><fs> launch
> ><fs> list-devices
> /dev/sr0
> /dev/vda
BTW, while still acknowledging that this is a serious bug, you can
work around it easily by adding the ISO image using 'add_drive'.

There is no real need to use 'add_cdrom' in any libguestfs client code
that I'm aware of, certainly not for adding ISO images which work just
as well if they are presented as ordinary drives.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/