Il 02/07/2013 09:40, Stefan Hajnoczi ha scritto: > On Mon, Jul 01, 2013 at 05:55:15PM +0200, Peter Lieven wrote: >> >> Am 01.07.2013 um 16:13 schrieb Stefan Hajnoczi <stefa...@redhat.com>: >> >>> On Thu, Jun 27, 2013 at 03:11:32PM +0200, Peter Lieven wrote: >>> >>> This patch breaks cross-version blog migration. We need to control >>> whether or not to use the new BLK_MIG_FLAG_ZERO_BLOCK flag. >> >> you are right the upgrade way works, but downgrade not. what is the >> proposed way to fix this? > > The safest way is to add a block migration flag that toggles the zero > block. By default it would be off. > > Maybe you would also add a MigrationCapability in qapi-schema.json to > indicated that zero blocks are supported in block migration. That would > allow management tools to ask QEMU on both sides if they support zero > blocks. > > Use migrate-set-capabilities to enable the zero block feature.
Yes, a capability makes sense. Paolo
