Re: [Qemu-devel] [PATCH] xen: make xen-platform a default device

[Gerd Hoffmann]

On Do, 2014-05-22 at 15:35 +0300, Michael S. Tsirkin wrote:
> On Thu, May 22, 2014 at 01:11:28PM +0100, Stefano Stabellini wrote:
> > On Thu, 22 May 2014, Gerd Hoffmann wrote:
> > > Patch hooks up the xen platform device to the default device code we
> > > have in qemu.  Two effects:
> > > 
> > >   (1) The device will not be created in case -nodefaults is specified
> > >       on the command line.
> > >   (2) Autocreating the device is also turned off in case xen-platform
> > >       is added manually via -device.
> > > 
> > > With the patch applied you can move the xen-platform device to some
> > > other place with a simple 'qemu -device xen-platform,addr=$slot'.
> > > 
> > > Tested-by: Tiejun Chen <address@hidden>
> > > Signed-off-by: Gerd Hoffmann <address@hidden>
> > 
> > Given that libxl always passes -nodefaults to QEMU, this patch is going
> > to effectively disable xen_platform_pci for all Xen users. It is not a
> > good idea. With the patch applied a Xen user would have no way to enable
> > xen_platform_pci except for passing some magic command line runes via
> > device_model_args_hvm.
> > 
> 
> Yes, it's an unfortunate use of the interface.
> How about a new machine type for xenfv - that's the only one
> that's affected, right?
> It's time xen started versioning qemu hardware anyway.

That would do the trick for sure.  Question is what versioning scheme.
Might be useful for xen machine types to version after xen releases,
i.e. xenfv-4.4 would would be supposed to be compatible with the xen-4.4
toolstack etc.

cheers,
  Gerd