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 libvirt 0.10.2 that have code paths that don't correctly > validate for version 2 files? And if we ever really did hit a situation > of having 31 or more incompatible features, I could envision using bit > 31 as an incompatible_feature witness that tells new enough qemu to look > at some other offset for remaining feature bits (thankfully, the > semantics of the incompatible_feature field mean that older qemu that > honors version 3 formats will reject a file with incompatible_feature > bit 31 set), so this is no real loss in the number of potential > incompatible features being added. I don't think qcow2 changes are necessary, just make a libvirt 0.10.x stable release that verifies the qcow2 version. Stefan -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list