Re: Question about xen and Rasp 4B

[Jukka Kaartinen <jukka.kaartinen@xxxxxxxxxx>]

Hi Roman,

> > >
> > Good catch.
> > GPU works now and I can start X! Thanks! I was also able to create domU
> > that runs Raspian OS.
> This is very interesting that you were able to achieve that - congrats!
>
> Now, sorry to be a bit dense -- but since this thread went into all
> sorts of interesting
> directions all at once -- I just have a very particular question: what is exact
> combination of versions of Xen, Linux kernel and a set of patches that went
> on top that allowed you to do that? I'd love to obviously see it
> productized in Xen
> upstream, but for now -- I'd love to make available to Project EVE/Xen community
> since there seems to be a few folks interested in EVE/Xen combo being able to
> do that.
I have tried Xen Release 4.14.0, 4.14.1 and master (from week 4, 2021).

Kernel rpi-5.9.y and rpi-5.10.y branches from 
https://github.com/raspberrypi/linux
and

U-boot (master).

For the GPU to work it was enough to disable swiotlb from the kernel(s) 
as suggested in this thread.
If you use Xen master then you need to revert the 
25849c8b16f2a5b7fcd0a823e80a5f1b590291f9. Apparently v3d uses same 
resources and will not start.
I was able to get most of the combinations to work without any big efforts.
In case you use USB SSD U-boot needs a fix if you use 5.9 kernel.
The 5.10 works with the lates Xen master but then you need one small 
workaround to the xen since there is address that Xen cannot map. Some 
usb address cannot be found (address was 0 if recall correctly). I just 
by passed the error:
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index e824ba34b0..3e8a175f2e 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1409,7 +1409,7 @@ static int __init handle_device(struct domain *d, 
struct dt_device_node *dev,
         {
             printk(XENLOG_ERR "Unable to retrieve address %u for %s\n",
                    i, dt_node_full_name(dev));
-            return res;
+            continue; //return res;
         }

         res = map_range_to_domain(dev, addr, size, &mr_data);