Re: [Qemu-devel] [PATCH] qcow3 - arbitrary metadata

[Anthony Liguori]

Nathaniel McCallum wrote:
> On Mon, Jul 28, 2008 at 5:17 PM, Anthony Liguori 
> <address@hidden <mailto:address@hidden>> wrote:
>
>     Nathaniel McCallum wrote:
>
>         On Mon, Jul 28, 2008 at 4:50 PM, Anthony Liguori
>         <address@hidden <mailto:address@hidden>
>         <mailto:address@hidden <mailto:address@hidden>>>
>         wrote:
>
>            Something that would be pretty interesting, but also terribly
>            hacky, would be to have an option that would allow one to use a
>            disk with an offset.  For instance:
>
>            qemu-system-x86_64 -drive file=foo.img,offset=4096,if=ide
>
>
>         I assume this technique is more "mergable"
>
>
>     Than forking the qcow format?  Definitely, although I'm not
>     convinced there isn't a better way to do it that is even less hacky.
>
>
> I'd love to know what that other option could be.   Adding an offset 
> option is going to touch a lot of files...

Actually, it wouldn't.  You just need to modify the RAW block driver to 
add an offset to any of the operations that would seek within the file.  
There's no clear way to pass individual arguments to a particular block 
format though so that would make it somewhat hairy.

Regards,

Anthony Liguori