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Date: Wed, 10 Sep 2014 11:05:39 +0200
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Subject: Re: [Qemu-devel] [PATCH 09/10] piix: do not raise irq while loading
	vmstate
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Juan Quintela <quintela@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, Pavel Dovgaluk <Pavel.Dovgaluk@ispras.ru>, Amit Shah <amit.shah@redhat.com>

Il 10/09/2014 10:51, Peter Maydell ha scritto:
> > What is not okay (and I think it should be a rule) is to touch other
> > devices from post_load, unless you know that they are deserialized
> > first.  For example it's okay for a PCI device to talk to the parent
> > bridge in its post_load function.
> 
> I don't think it's right to talk to another device even if you do
> know it's deserialized first. Talking to it might make it change
> its state, which would be wrong (since its correct state is
> the state it's just deserialized). I would suggest the rule should
> be "never do something that can change the state of another
> device in post-load".

That's harder to do, but if it is possible to do it, it would be great
as well.

It would not surprise me to find a case where the parent device actually
_expects_ the children's post_load to inform it about something, instead
of serializing that part of state on its own.

Paolo

> (We have similar issues with reset, except worse in that we
> don't have a coherent rule to cause everything to come out
> of reset in the right state.)