Troubles running Xen on Raspberry Pi 4 with 5.6.1 DomU

[Roman Shaposhnik <roman@xxxxxxxxxx>]

Hi!

I'm trying to run Xen on Raspberry Pi 4 with 5.6.1 stock,
upstream kernel. The kernel itself works perfectly well
on the board. When I try booting it as Dom0 under Xen,
it goes into a stacktrace (attached).

Looking at what nice folks over at Dornerworks have previously
done to make RPi kernels boot as Dom0 I've come across these
3 patches:
    https://github.com/dornerworks/xen-rpi4-builder/tree/master/patches/linux

The first patch seems irrelevant (unless I'm missing something
really basic here). The 2nd patch applied with no issue (but
I don't think it is related) but the 3d patch failed to apply on
account of 5.6.1 kernel no longer having:
    dev->archdata.dev_dma_ops
E.g.
    
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch/arm64/mm/dma-mapping.c?h=v5.6.1#n55

I've tried to emulate the effect of the patch by simply introducing
a static variable that would signal that we already initialized
dev->dma_ops -- but that didn't help at all.

I'm CCing Jeff Kubascik to see if the original authors of that Corey Minyard
to see if may be they have any suggestions on how this may be dealt
with.

Any advice would be greatly appreciated!

Thanks,
Roman.

Attachment: xen.rpi.txt
Description: Text document