[libvirt] [PATCH 3/4] Fix QEMU save/restore with block devices

Daniel Veillard veillard at redhat.com
Thu Apr 22 12:12:22 UTC 2010

On Thu, Apr 22, 2010 at 02:00:56PM +0200, Daniel Veillard wrote:
> On Thu, Apr 22, 2010 at 12:43:28PM +0100, Daniel P. Berrange wrote:
> > The save process was relying on use of the shell >> append
> > operator to ensure the save data was placed after the libvirt
> > header + XML. This doesn't work for block devices though.
> > Replace this code with use of 'dd' and its 'seek' parameter.
> > This means that we need to pad the header + XML out to a
> > multiple of dd block size (in this case we choose 512).
>   err, why ? As I pointed out dd seems just fine taking byte specified
> offset, not necessarilly multiple of 512. The main problem I see with
> this is that it does break the format and a somain saved (or managed
> save) with 0.8.0 would not restore with 0.8.1.
>   I really want to understand why this is needed before going that route
> because I see this as a serious compatibility break.

  Okay fater soem out of band discussion, it proves to not be a
compatibility problem becasue the length of the xml header is updated,

  ACK to the serie,


Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel at veillard.com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/

More information about the libvir-list mailing list