Re: [Xen-devel] Re: [PATCH] libxl: enabling upstream qemu as pure pv backend.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 8 Jun 2011, Ian Campbell wrote:
> > > > But if we do this we have to be careful because in the stubdom case the
> > > > libxl_device_model_info that we pass to libxl__create_xenpv_qemu is NOT
> > > > the same used to build the stubdom.
> > > > The info parameter passed to libxl__create_stubdom is the
> > > > libxl_device_model_info that describes the stub qemu-for-FV.
> > > > While the info parameter that we pass to libxl__create_xenpv_qemu is the
> > > > libxl_device_model_info that describes the qemu-for-PV in dom0.
> > > 
> > > Right, my suggestion was that they potentially _could_ be the same, with
> > > the two functions doinging the right thing internally. This would avoid
> > > the need to figure out which params need to be copied from the user
> > > supplied struct to the xenpv one -- they would simply be the same.
> > > 
> > 
> > Ideally the vnc and sdl proprieties of a vfb should be moved into
> > the corresponding fields of device_model_info, because they are not
> > specific to the vfb protocol, rather a configuration of the backend
> > (qemu).
> > This way we wouldn't need libxl__build_xenpv_qemu_args anymore.
> > 
> > I wouldn't use the same device_model_info instance for both qemu-FV and
> > qemu-PV in the stubdom case, I would rather keep them separate.
> 
> OK, then we either need a way to configure both (dupping the options) or
> one needs to be derived from the other in some useful way...

First the vfb configuration is derived from the xenfv configuration by
libxl__vfb_and_vkb_from_device_model_info.
Then from the vfb we build xenpv in libxl__create_xenpv_qemu.

device_model_into->vfb->device_model_info

If we move the sdl and vnc options away from vfb we could derive both
the xenpv configuration and the vfb configuration in
libxl__vfb_and_vkb_from_device_model_info, that would need to be
renamed.
libxl__create_stubdom would just add the vfb to xenstore and call
libxl__create_xenpv_qemu that doesn't need to do any "translation"
anymore. So I guess it would simplify the code a bit.

device_model_info-->device_model_info
                 |
                 -->vfb

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