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Date: Wed, 19 Jun 2013 21:15:01 +0100
From: Tim Deegan <tim@xen.org>
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Subject: Re: [Qemu-devel] [Xen-devel] [PATCH] Add Xen platform PCI
	device	version 2.
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To: Matt Wilson <msw@amazon.com>
Cc: qemu-devel@nongnu.org, Paul Durrant <Paul.Durrant@citrix.com>, Ian Campbell <Ian.Campbell@citrix.com>, Alex Bligh <alex@alex.org.uk>, xen-devel@lists.xen.org

At 11:21 -0700 on 19 Jun (1371640904), Matt Wilson wrote:
> On Wed, Jun 19, 2013 at 11:42:06AM +0100, Alex Bligh wrote:
> >
> > --On 19 June 2013 10:13:17 +0000 Paul Durrant
> > <Paul.Durrant@citrix.com> wrote:
> > 
> > >>We obviously can't say to users "Are you running Windows and are you
> > >>running PV drivers >= X.Y, if so set lever A to position B, otherwise if
> > >>you are running some other OS or an earlier version of the Windows PV
> > >>driver set it to position A".
> > >
> > >Why not? The device can be chosen on a per-VM basis.
> > 
> > Not everyone knows what guest some random user will be running
> > (consider cloud platforms).
> 
> I agree. If this is really the only solution, we would need to have
> both versions presented to the guest so that old drivers continue to
> work without any intervention.

I suspect that if we expose both, both sets of drivers try to run the
same PV connections, and hilarity ensues.

Tim.