Re: [Xen-devel] [RFC 00/24] Allow Xen to boot with a raw Device Tree

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-08-19 at 23:11 +0100, Julien Grall wrote:
> On 16 August 2013 22:05, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> > Hi,
> >
> > This is the first patch series to allow Xen to boot with a raw device tree, 
> > ie
> > without any specific modification for Xen.
> >
> > Few months ago, the patch series "Support multiple ARM platform in XEN", has
> > added a tree structure to handle easier the device tree. Each node can carry
> > metadata to specify if the node can be pass-through to Dom0. Therefore, this
> > patch series take advantage of the "new" Device Tree API and get a rid of
> > the FDT API that is currently used to build Dom0 dts and in some drivers.
> >
> > There is few items that was not added in this series:
> >     * Set the correct number of CPUs for Dom0 by editing CPUs node
> >     * Remove and create the GIC node
> >     * Remove and create the timer node
> >
> > I hope to add support for previous items in the next patch series.
> >
> > At the beginning of the mail, I a bit lied about Xen is able to raw DTS :).
> > The latter, still need to carry Xen and Linux command line until U-Boot/Grub
> > will support multiboot2 protocol.
> > I have noticed that U-boot has some fdt commands to change on the fly the 
> > device
> > tree. I think we can use this solution as a workaround for the beginning.
> > I will send an email later to explain the procedure.
> >
> 
> As promised, I wrote a small U-boot to remove all remaining changes in
> the Device Tree (modules and xen/dom0 bootargs). This script requires
> Andre's patch (http://osdir.com/ml/general/2013-05/msg68353.html).
> 
> http://xenbits.xensource.com/people/julieng/multiboot-fixup.scr.txt
> 
> The script creates:
>    - Xen and Dom0 bootargs
>    - the modules node with linux address correctly set up
> 
> I think, this script can be used as a workaround to avoid manual
> Device Tree modification until U-boot/Grub will support correctly
> multiboot. If people are insterested by this script, I can create a
> wiki page with all the instructions.

Yes. I think this is the way to go for now.

BTW:
        # It seems U-boot doesn't have command to retrieve the size, so the 
size is
        # set to a big value (10Mb)
u-boot sets $filesize when it loads something, so you'd just need to
stash that somewhere for use here. That places a requirement on the
script which actually does the loading (which I suppose is out of scope
of your script).

Ian.


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