Re: [Qemu-devel] Machine config files

[David Gibson]

On Sat, Nov 15, 2008 at 12:13:03AM +0000, Paul Brook wrote:
> > > Some translation code would be required for compatibility. For example,
> > > when the DTS has 128MB of memory, and the user invokes qemu with -m 256,
> > > now you need to update the device tree in order to pass it into the
> > > guest. That's pretty easy, but once you start talking about adding PCI
> > > devices it gets a little more difficult. I seem to recall this
> > > conversation was had on qemu-devel a little while back.
> >...
> > > Of course, *some* code would still be needed *somewhere* to load the
> > > kernel, initrd, set initial register state to point to those memory
> > > locations, etc. In the case of KVM on 440, we also need to override the
> > > DTS with the real host clock frequency. (This probably isn't necessary
> > > for qemu+TCG.)
> > >
> > > But yes, replacing all the pci_nic_init(), isa_mmio_init(),
> > > cpu_register_physical_memory(), etc could be automated by walking the
> > > device tree.
> >
> > Ok.  This is starting to look interesting.  Paul, what do you think of DTS?
> 
> Things like kernel loading are easy, you just add a special device (which 
> linux will ignore) specifying the relevant parameters. IMO it should be 
> possible to use the same device tree for both linux and qemu, but it's ok to 
> require some additional information on top of what linux currently requires.

Depending on exactly what you want to pass through, it may be
appropriate to use properties in /chosen for this.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson