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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCHv3 03/13] qemu: add routines to manage PCI
	capabilities
Date: Wed, 10 Jun 2009 16:24:28 +0100
References: <cover.1244192535.git.mst@redhat.com>
	<20090610145540.GI19375@poweredge.glommer>
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To: qemu-devel@nongnu.org
Cc: Carsten Otte <cotte@de.ibm.com>, kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>, Glauber Costa <glommer@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>, virtualization@lists.linux-foundation.org, Blue Swirl <blauwirbel@gmail.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Avi Kivity <avi@redhat.com>

> > caps can be anywhere, but we don't expect it to change during machine
> > execution lifetime.
> >
> > Or I am just confused by the name "pci_device_load" ?
>
> Right. So I want to load an image and it has capability X at offset Y.
> wmask has to match. I don't want to assume that we never change Y
> for the device without breaking old images, so I clear wmask here
> and set it up again after looking up capabilities that I loaded.

We should not be loading state into a different device (or a similar device 
with a different set of capabilities).

If you want to provide backwards compatibility then you should do that by 
creating a device that is the same as the original.  As I mentioned in my 
earlier mail, loading a snapshot should never do anything that can not be 
achieved through normal operation.

Paul