Re: [Qemu-devel] Add support for new image type

[Kai Meyer]

On 03/01/2012 08:03 AM, Kevin Wolf wrote:
> Am 29.02.2012 22:52, schrieb Kai Meyer:
> > Is it possible to extend qemu to support a new image type? I have an
> > image type that is ready for consumption and I'm looking for the
> > integration point between qemu and the new image format.
> Which image format do you want to get integrated?
>
> Have a look at block/qcow2.c to get an idea of what a qemu block driver
> looks like. At the bottom of the file there is a struct that contains
> function pointers to all exported functions, so this is usually a good
> place to start exploring a driver.
>
> Kevin

Great, this is exactly what we're after. I work for StorageCraft, and we 
would like to figure out some way to allow qemu to directly consume our 
image-based backups. It would provide us with user-space mounting (via 
libguestfs) as well as booting VMs directly from Backup images. We 
already have a proprietary image access library that provides block-wise 
access to our image files. I have been able to scratch together a proof 
of concept already, which I am really pleased with.

I see only two roadblocks for which I don't have immediate answers for.

1) Licensing
Is it possible to license our contributions in such a way that we do not 
need to open the source code of our image access library?
2) External dependency on our image access library.
We do not want to force qemu to require our image access library to be 
present to build. Would it be better to do a conditional build 
(./configure --with-spf) or a run-time check for our image access library?