[Libguestfs] [PATCH] virt-v2v: Remove iface:ide parameter (RHBZ#895898)

[Richard W.M. Jones]

On Tue, Sep 03, 2013 at 11:30:07PM -0600, Mike Latimer wrote:
> On Tuesday, September 03, 2013 06:09:26 PM Mike Latimer wrote:
> > However, as mentioned in the bug, this parameter is likely no longer
> > required. Unless there is a use-case where this setting is required, it
> > seems like a good idea to remove it completely (which should work in
> > either libvirt or direct mode), rather than recommend the workaround.
> 
> As much as I hate to reply to myself... I just did some additional testing and 
> realized that if 'iface:ide' is removed, the disks could be inaccessible in 
> environments that don't have virtio_scsi (in the guestfs environment). In 
> other words, with just ata_piix, the 'iface:ide' might be required.

I'll give you a bit of background to this (mis-)feature.  The "iface"
optional argument was added so that you could use qemu's IDE interface
instead of whatever the default is (virtio-scsi, falling back to
virtio-blk).

This has no effect (only limitations) for ordinary libguestfs users,
but for virt-v2v it allows us to run the 'mkinitrd' command in the
guest and have it work for very old and buggy mkinitrd / guests that
got confused by virtio.  I think it was for RHEL 4 ...

What it does do is cause endless problems, mainly because people want
to use virt-v2v with more disks than IDE allows (just 2, once you take
into account the transfer disk and the libguestfs appliance).

So I wouldn't worry about removing iface => "ide".

> Do we know if there are any environments which are commonly missing
> the virtio stack?

Even ARM has it these days.  libguestfs doesn't work without it.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top