Re: Hand over of the Xen shared info page

[Julien Grall <julien@xxxxxxx>]

On 14/05/2021 10:50, Anastasiia Lukianenko wrote:
> Hi Julien!
Hello,

> On Thu, 2021-05-13 at 09:37 +0100, Julien Grall wrote:
> > On 13/05/2021 09:03, Anastasiia Lukianenko wrote:
> > The alternative is for U-boot to go through the DT and infer which
> > regions are free (IOW any region not described).
> Thank you for interest in the problem and advice on how to solve it.
> Could you please clarify how we could find free regions using DT in U-
> boot?
I don't know U-boot code, so I can't tell whether what I suggest would work.

In theory, the device-tree should described every region allocated in 
address space. So if you parse the device-tree and create a list (or any 
datastructure) with the regions, then any range not present in the list 
would be free region you could use.
However, I realized a few days ago that the magic pages are not 
described in the DT. We probably want to fix it by marking the page as 
"reserved" or create a specific bindings.
So you will need a specific quirk for them.

I have posted some more idea a separate thread [1] related to FreeBSD 
support for Arm.
Cheers,

[1] 
https://lore.kernel.org/xen-devel/f7360dac-5d83-733b-7ec5-c73d4dc0350d@xxxxxxx/
--
Julien Grall