Re: [Qemu-devel] backing file support for vpc/vhd ?

[Kevin Wolf]

Am 19.06.2013 um 16:02 hat Philipp Hahn geschrieben:
> Hello,
> 
> while working on a Xen-VM I noticed that qemu-img does not support the 
> backing file mechanism of vpc/vhd files, but Xens blktap2 does; it has a 
> libvhd and some tools to create and modify vpc/vhd files:
> [...]
> 
> Is the lack of support for backing files in vpc/vjd in qemu just a question 
> of time / interest, are there technical problems, or are there some political 
> issues?

Nobody wrote the code, that's all.

Read-only support should be almost trivial, and for read-write we'd have
to add some real code to deal with the block bitmaps (without backing
files we get away with what is mostly a slow fake implementation).

Kevin