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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <4C189162.4040701@redhat.com> (Paolo Bonzini's message of "Wed,
	16 Jun 2010 10:54:58 +0200")
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Date: Wed, 16 Jun 2010 15:02:20 +0200
Message-ID: <m3aaqvnnab.fsf@trasno.mitica>
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Subject: [Qemu-devel] Re: [PATCH 5/5] ide: fix migration in the middle of a
	bmdma transfer
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org

Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 06/15/2010 03:31 PM, Juan Quintela wrote:
>> Signed-off-by: Juan Quintela<quintela@redhat.com>
>
> Sorry if this has been discussed to death before (if so I must have
> missed it...).
>
> With subsections available, what about taking advantage of the new
> protocol extension and add to the subsection info about the size of
> the subsection?

Not trivial with current infrastructure :(

> Also, with the size information, would it make sense to specify
> optional subsections that the receiver could choose to ignore?

We agreed that this was going to be forbidden.  If sender send data ->
it needs to be received.  Sender can decide to not send a subsection if
its data is not needed.

> Mandatory subsections are something such that round-trip A->B->A fail
> unless B understands the subsection, while optional subsections are
> such that A can provide a default.  IDE subsections would be optional,
> for example.

This is the whole point of the .needed() function.  if
neeeded(foo_subsection) returns false -> subsection is not needed.

If it returns true -> it is needed, destination has to understand it.

Later, Juan.