Re: [Qemu-devel] [PATCH 28/35] kvm: x86: Introduce kvmclock device to save/restore its state

[Gerd Hoffmann]

On 01/20/11 20:39, Anthony Liguori wrote:
> On 01/20/2011 02:44 AM, Gerd Hoffmann wrote:
> > Hi,
> >
> > > For (2), you cannot use bus=X,addr=Y because it makes assumptions about
> > > the PCI topology which may change in newer -M pc's.
> >
> > Why should the PCI topology for 'pc' ever change?
> >
> > We'll probably get q35 support some day, but when this lands I expect
> > we'll see a new machine type 'q35', so '-m q35' will pick the ich9
> > chipset (which will have a different pci topology of course) and '-m
> > pc' will pick the existing piix chipset (which will continue to look
> > like it looks today).
>
> But then what's the default machine type? When I say -M pc, I really
> mean the default machine.

I'd tend to leave pc as default for a release cycle or two so we can 
hash out issues with q35, then flip the default once it got broader 
testing and runs stable.

> At some point, "qemu-system-x86_64 -device virtio-net-pci,addr=2.0"
>
> Is not going to be a reliable way to invoke qemu because there's no way
> we can guarantee that slot 2 isn't occupied by a chipset device or some
> other default device.

Indeed.  But qemu -M pc should continue to work though.  'pc' would 
better named 'piix3', but renaming it now is probably not worth the trouble.

cheers,
  Gerd