Re: [Xen-devel] [Qemu-devel] [PATCH] Add Xen platform PCI device version 2.

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Alex Bligh [mailto:alex@xxxxxxxxxxx]
> Sent: 19 June 2013 11:42
> To: Paul Durrant; Ian Campbell
> Cc: qemu-devel@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; Alex Bligh
> Subject: Re: [Qemu-devel] [Xen-devel] [PATCH] Add Xen platform PCI device
> version 2.
> 
> 
> 
> --On 19 June 2013 10:13:17 +0000 Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> 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).
> 
> Expecting an admin to introspect the guest is not a good plan.
> Having the same set of levers that work at least reasonably with
> everything is the way to go.
> 

If I can get agreement on the need for a new device (id/revision) then it would 
be possible to create both the new and the old device. If both were present 
then the admin doesn't need to know what the guest is. For instance, linux 
PVonHVM drivers should just continue to work as is. The only visible thing in 
the guest would be a device for which there was no driver.

  Paul

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