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Date: Mon, 2 Mar 2009 11:41:25 +0000
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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Subject: Re: [Qemu-devel] Citrix VHD implementation
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To: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

Philipp Schmid wrote:

> Hi,
> 
> as some of you might know, citrix has open sourced the library they  
> use to read and write to VHD disk images.
> 
> I'm trying to implementing a block-vhd driver on top of libvhd, but my  
> C knowledge is very limited as I haven't written any code in C for a  
> long time.
> 
> What I already have is a git repo with the libvhd code extracted from  
> the xen-unstable tree with the blocktap2 patches applied.
> libvhd also comes with vhd-util, a utility to create and modify vhd  
> images.
> I have only tried to compile it on ubuntu 8.10, so it might not work  
> on your system.
> 
> The git repo is hosted on github: http://github.com/schmidp/libvhd/tree/master
> 
> Are there any docs about how to implement a block driver for qemu?
> As far as I have seen from the qemu code, block_int.h defines the  
> interface and you register your driver in block.c, but that is all  
> I've found out so far.
> 
> I will try to implement a synchrones driver first as it seems more  
> simple...

Why don't you just use blktap2 to create a raw device from the vhd file
and then open the raw device in qemu?