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Re: [Qemu-devel] [PATCHv2 08/11] block-migration: efficiently encode zer
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From: |
Stefan Hajnoczi |
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Subject: |
Re: [Qemu-devel] [PATCHv2 08/11] block-migration: efficiently encode zero blocks |
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Date: |
Tue, 2 Jul 2013 09:40:38 +0200 |
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User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Jul 01, 2013 at 05:55:15PM +0200, Peter Lieven wrote:
>
> Am 01.07.2013 um 16:13 schrieb Stefan Hajnoczi <address@hidden>:
>
> > 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.
CCed Juan Quintela for advice on migration.
Stefan