Re: [Qemu-devel] hindsight on qcow2v3 format

2013-12-17 Thread Stefan Hajnoczi
On Mon, Dec 16, 2013 at 05:24:53PM -0700, Eric Blake wrote: > Is it worth tweaking docs/specs/qcow2.txt to permanently change the > incompatible_features field to be 4 bytes (76-79) and mandate that bytes > 72-75 always be 0, as a conservative way to prevent other misbehavior of > programs like lib

[Qemu-devel] hindsight on qcow2v3 format

2013-12-16 Thread Eric Blake
I spent a couple hours today debugging a bug in an older branch of libvirt (0.10.2) - one where libvirt only knew how to parse version 2 qcow2 images. Alas, that version of libvirt can be coerced into reading the header of a random file under the assumption that it is qcow2 data, and where it trie