Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree

[Simon Glass <sjg@chromium.org>]

Hi Peter,

On Sun, 26 Sept 2021 at 12:47, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Sun, 26 Sept 2021 at 19:34, Simon Glass <sjg@chromium.org> wrote:
> >
> > At present qemu creates a device tree automatically with the 'virt' generic
> > virtual platform. This is very convenient in most cases but there is not
> > much control over what is generated.
> >
> > Add a way to provide a device tree binary file with additional properties
> > to add before booting. This provides flexibility for situations where
> > Linux needs some tweak to operate correctly. It also allows configuration
> > information to be passed to U-Boot, supporting verified boot, for example.
>
> So, I'm strongly inclined to say "nope" here. The device
> tree virt generates is supposed to entirely describe the
> virtual hardware we pass to the guest. If a guest doesn't
> work with that, then either we're generating bogus dtb info
> or the guest is not handling the dtb we pass it, and one
> or the other should be fixed.

Thanks for the response.

In the case of U-Boot at least, it uses the devicetree for
configuration (it is a boot loader, so there is no user space to
provide configuration). So the current setup is not sufficient to boot
it correctly in all cases. On the other hand, the 'virt' feature is
very useful for testing U-Boot, so it would be great to be able to
support this.

I also forgot to ask about testing, but am happy to add a test if you
can give me some pointers.

Regards,
Simon