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Date: Wed, 10 Jun 2009 18:50:00 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCHv3 03/13] qemu: add routines to manage PCI
	capabilities
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To: Paul Brook <paul@codesourcery.com>
Cc: Carsten Otte <cotte@de.ibm.com>, kvm@vger.kernel.org, Glauber Costa <glommer@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Blue Swirl <blauwirbel@gmail.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Avi Kivity <avi@redhat.com>

On Wed, Jun 10, 2009 at 04:24:28PM +0100, Paul Brook wrote:
> > > 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

Why shouldn't it? You don't load a snapshot while guest is running.

-- 
MST