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

On 20 August 2013 09:33, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> 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.

I will update the wiki page.

> 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).

Thanks for the hint. I will update my script.

Julien Grall

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