Re: [PATCH 1/2] image-vm: Convert vmdk/vdi/qcow2/hdddirect images to IMAGE_CMD

[Patrick Ohly <patrick.ohly@intel.com>]

On Fri, 2017-07-21 at 16:52 -0400, Tom Rini wrote:
> On Fri, Jul 21, 2017 at 03:01:33PM +0200, Patrick Ohly wrote:
> > On Fri, 2017-07-21 at 07:21 -0400, Tom Rini wrote:
> > > On Fri, Jul 21, 2017 at 09:47:21AM +0200, Patrick Ohly wrote:
> > > > On Thu, 2017-07-20 at 18:43 -0400, Tom Rini wrote:
> > > > > The support for writing vmdk/vdi/qcow2 images has not been converted to make
> > > > > use of the IMAGE_CMD infrastructure and instead relies on custom logic for
> > > > > adding tasks in the right place.  Convert these images to making use of
> > > > > IMAGE_CMD.
> > > > 
> > > > Thanks for working on this. I still have
> > > > https://bugzilla.yoctoproject.org/show_bug.cgi?id=10204 open for
> > > > enhancing vmdk/vdi/qcow2.
> > > > 
> > > > However, your patch doesn't go as far as described in that bug, does it?
> > > > Instead of allowing, for example, IMAGE_FSTYPES = "wic.vmdk", it merely
> > > > changes how IMAGE_FSTYPES = "vmdk" is implemented.
> > > > 
> > > > The current patch has its merits as it simplifies the implementation,
> > > > but I think it would be worthwhile to go all the way, even if it changes
> > > > how images are going to be named.
> > > 
> > > Ah, interesting.  I guess the first thing I would argue against is
> > > saying that hdddirect should be masked.  There are reasons to want to
> > > have a raw image created.
> > 
> > I'm not sure I understand what you mean with "hdddirect should be
> > masked" - it's been a while that I looked at the code.
> > 
> > > I will take a look into using CONVERSIONCMD for vmdk/qcow2/vdi to allow
> > > for wic.vmdk to work.  But we also must have vmdk.xz work (and fwiw with
> > > my series you can get arbitrary compression that we support done, I did
> > > vmdk.xz, qcow2.lzo and vdi.bz2 just for 'fun').
> > 
> > The same is true with CONVERSIONCMD. They can be chained multiple times.
> > 
> > > But I'm not 100% sure that I like changing the normal case from "vmdk"
> > > to "wic.vmdk" or "hdddirect.vmdk" just to get a disk image to throw at
> > > ${VM_TECHNOLOGY}.
> > 
> > Yes, that's the biggest user-visible change. Basically the internal
> > implementation (multiple conversions chained together) becomes visible
> > in the end-result.
> > 
> > That is a good and a bad thing. The good thing is that it is visible how
> > the .vmdk image was created. The bad thing is that some users might not
> > care and get confused.
> 
> So, Patrick, Ed and I talked on IRC a bit about this, and I think
> without putting too many words in their mouths, I think it can be
> summarized like this.
>
> We all agree that vmdk/qcow2/vdi are a type of conversion.  It would be
> quite handy to use these conversions on other things, such as wic.
> 
> And at least from my point of view, the contents of "hdddirect" doesn't
> matter so much as the overall functionality.
> 
> So that here's where I'm at now.  I've found out when Patrick's chaining
> compression code (so that you could do silly things like ext3.gz.bz2 or
> _useful_ things like wic.vmdk.xz) was broken, and I see the best way to
> fix that too.  So I'm going to v2 this series shortly which addresses
> the problem of chaining compression types, and then brings the VM stuff
> over to using that too.

Thanks for the good summary and working on this functionality.

I'd like to add that you pointed out that a "generic" vmdk type is what
some developers ask for when they don't care about the exact way how the
resulting image is created (hdddirect vs. wic, for example). We agreed
that this is useful.

I didn't get around to mentioning it on IRC, but what I would find it
useful is if someone (BSP and/or distro?) can define which kind of raw
image is used as input for the conversion to vmdk. Hard-coding that to
just hdddirect always felt wrong to me.

-- 
Best Regards, Patrick Ohly

The content of this message is my personal opinion only and although
I am an employee of Intel, the statements I make here in no way
represent Intel's position on the issue, nor am I authorized to speak
on behalf of Intel on this matter.