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Date: Mon, 23 Nov 2009 16:53:57 +0200
From: Gleb Natapov <gleb@redhat.com>
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Subject: [Qemu-devel] Re: Live migration protocol, device features,
 ABIs and   other beasts
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Juan Quintela <quintela@trasno.org>, qemu-devel@nongnu.org

On Mon, Nov 23, 2009 at 08:51:17AM -0600, Anthony Liguori wrote:
> Gleb Natapov wrote:
> >>>>My problem implementing optional features/sections/... is not the
> >>>>savevm/VMState bits.  At the end, implementing that is easy.  What is
> >>>>more dificult is once that a device have 5 features, what are the valid
> >>>>combinations.  i.e. if you have pci and msix features, msix requires
> >>>>pci.  In this case, the dependency is trivial, but in others that
> >>>>hasen't to be so obvious.
> >>>It doesn't matter what device support and how it is configured. This can
> >>>be handled by each device separately. i.e if destination detects that
> >>>source had MSIX enabled for the device but destination hasn't it will
> >>>signal an error.
> >>And guess what, with current code migration is going to "suceed" on the
> >>source host and fail on the target host.
> >Then current code is buggy. It should be possible to abort migration in
> >the middle if device can't understand the data it received.
> 
> It can, post_load() can error which will terminate the migration.
> This can be used to validate fields beyond whether they fit into the
> type specified.
> 
Then I don't see why Juan claims what he claims.

--
			Gleb.