Libguestfs - Feb 2023 - [V2V PATCH 0/5] Bring support for virtio-scsi back to Windows

On Wed, Feb 22, 2023 at 08:20:43PM +0200, Andrey Drobyshev
wrote:
> Since commits b28cd1dc ("Remove requested_guestcaps / rcaps"),
f0afc439
> ("Remove guestcaps_block_type Virtio_SCSI") support for
installing
> virtio-scsi driver is missing in virt-v2v.  AFAIU plans and demands for
> bringing this feature back have been out there for a while.  E.g. I've
> found a corresponding issue which is still open [1].
> 
> The code in b28cd1dc, f0afc439 was removed due to removing the old in-place
> support.  However, having the new in-place support present and bringing
> this same code (partially) back with several additions and improvements,
> I'm able to successfully convert and boot a Win guest with a
virtio-scsi
> disk controller.  So please consider the following implementation of
> this feature.
> 
> [1] https://github.com/libguestfs/virt-v2v/issues/12
So you're right that we ended up removing virtio-scsi support because
in-place conversion was temporarily removed, and it wasn't restored
when the new virt-v2v-in-place tool was added.

I looked at the patches, and I don't have any objection to 1-4.

Patch 5 is the tricky one because it changes the default, but we
(Red Hat) are likely to stick with virtio-blk for better or worse.

Could we make this configurable?  We've traditionally shied away from
adding virt-v2v command line options which are purely for fine-tuning
conversions.  The reason for this is that when you're doing bulk
conversions of hundreds of VMs from VMware, you want virt-v2v to do
"the best it can", and it's not really feasible to hand configure
every conversion.  (There are some historical exceptions to this, like
--root, but don't look at those!)  I know the bulk conversion case
doesn't apply to Virtuozzo, but it does matter for us.

It could be argued that this isn't the same, because if we're bulk
converting, you're not fine-tuning virtio-scsi vs virtio-blk per VM,
but per target hypervisor.  So a command line option would be OK in
this case.

BTW previously we "configured" this preference through the input
libvirt XML.  That was a terrible idea, so I'd prefer to avoid it this
time around.

Anyway if you can think of a better version of patch 5 then I think we
can accept this.

Thanks,

Rich.
> 
> v2v:
> 
> Andrey Drobyshev (2):
>   Revert "Remove guestcaps_block_type Virtio_SCSI"
>   convert_windows: add Inject_virtio_win.Virtio_SCSI as a possible block
>     type
> 
>  convert/convert.ml                   | 2 +-
>  convert/convert_linux.ml             | 9 +++++++--
>  convert/convert_windows.ml           | 1 +
>  convert/target_bus_assignment.ml     | 1 +
>  lib/create_ovf.ml                    | 1 +
>  lib/types.ml                         | 3 ++-
>  lib/types.mli                        | 2 +-
>  output/openstack_image_properties.ml | 7 +++++++
>  9 files changed, 22 insertions(+), 6 deletions(-)
> 
> common:
> 
> Andrey Drobyshev (2):
>   inject_virtio_win: add Virtio_SCSI to block_type
>   inject_virtio_win: make virtio-scsi the default block driver
> 
> Roman Kagan (1):
>   inject_virtio_win: match only vendor/device
> 
>  mlcustomize/inject_virtio_win.ml  | 25 ++++++++++++++++---------
>  mlcustomize/inject_virtio_win.mli |  2 +-
>  2 files changed, 17 insertions(+), 10 deletions(-)
> 
> --
> 2.31.1
-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
nbdkit - Flexible, fast NBD server with plugins
https://gitlab.com/nbdkit/nbdkit

On 2/28/23 14:01, Richard W.M. Jones wrote:
> On Wed, Feb 22, 2023 at 08:20:43PM +0200, Andrey Drobyshev wrote:
>> Since commits b28cd1dc ("Remove requested_guestcaps /
rcaps"), f0afc439
>> ("Remove guestcaps_block_type Virtio_SCSI") support for
installing
>> virtio-scsi driver is missing in virt-v2v.  AFAIU plans and demands for
>> bringing this feature back have been out there for a while.  E.g.
I've
>> found a corresponding issue which is still open [1].
>>
>> The code in b28cd1dc, f0afc439 was removed due to removing the old
in-place
>> support.  However, having the new in-place support present and bringing
>> this same code (partially) back with several additions and
improvements,
>> I'm able to successfully convert and boot a Win guest with a
virtio-scsi
>> disk controller.  So please consider the following implementation of
>> this feature.
>>
>> [1] https://github.com/libguestfs/virt-v2v/issues/12
> 
> So you're right that we ended up removing virtio-scsi support because
> in-place conversion was temporarily removed, and it wasn't restored
> when the new virt-v2v-in-place tool was added.
> 
> I looked at the patches, and I don't have any objection to 1-4.
> 
> Patch 5 is the tricky one because it changes the default, but we
> (Red Hat) are likely to stick with virtio-blk for better or worse.
> 
> Could we make this configurable?  We've traditionally shied away from
> adding virt-v2v command line options which are purely for fine-tuning
> conversions.  The reason for this is that when you're doing bulk
> conversions of hundreds of VMs from VMware, you want virt-v2v to do
> "the best it can", and it's not really feasible to hand
configure
> every conversion.  (There are some historical exceptions to this, like
> --root, but don't look at those!)  I know the bulk conversion case
> doesn't apply to Virtuozzo, but it does matter for us.
> 
> It could be argued that this isn't the same, because if we're bulk
> converting, you're not fine-tuning virtio-scsi vs virtio-blk per VM,
> but per target hypervisor.  So a command line option would be OK in
> this case.
> 
> BTW previously we "configured" this preference through the input
> libvirt XML.  That was a terrible idea, so I'd prefer to avoid it this
> time around.
Ah, that's new information to me. I thought the "rcaps" (requested
caps,
derived from the input XML) was exactly what was missing here. Not
because of the particular reason(s) that may have motivated rcaps in the
past, but because in the use case at hand, the tweaking of the domain
XML precedes the conversion (more like, the injection of the desired
virtio drivers).

Why was it a terrible idea?
> Anyway if you can think of a better version of patch 5 then I think we
> can accept this.
ITYM "if you *cannot* think of a better version"...

But anyway, if a command line option is acceptable to you, I'm perfectly
fine with it as well. I'd like to avoid changing the default. I quite
foresee tens of QE test runs breaking, resulting in as many bug reports,
and then us eventually reverting the change-of-the-default downstream.
I'd rather favor an experimental command line switch.

Laszlo