Re: [Xen-devel] Xen Hypervisor porting on Raspberry Pi 3B+/4

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 23/07/2019 18:55, Roman Shaposhnik wrote:
> It would be great to have Xen running on RPi, but I have to wonder: is
> it now possible to workaround RPi limitations of how GPU boots?
>     https://www.raspberrypi.org/forums/viewtopic.php?t=187086#p1206487
>
> I thought that this is completely locked, proprietary bcm2837 code
> that Xen can't do much of anything about.
That's not really a problem. People have managed to get other hypervisor running 
on RPI. The major issue is going to be the interrupt controller, the RPI3 does 
not have a GIC which is a requirement for using Xen.
If you want to get Xen working on RPI3, then you would at least need to provide 
driver for the interrupt controller and emulate it for the guests. Alternatively 
you could provide a PV interface as x86 use to do. Both cases are going to 
require a fair amount of work and very unlikely to be accepted upstream. I would 
like to keep Xen small and simple.
Anyway, Rasberry PI foundation just release RPI4 which now contain a GIC. So 
this should make easier to get Xen working on the platform.
Andre (in CC) has been working on porting Arm Trusted Firmware to the RPI4 and 
manage to get Xen booting up to the stage of bringing-up secondary CPUs (see [1].
I also bought a RPI4 so I will have a go at Xen when I have some spare time.

Cheers,

[1] https://lists.xenproject.org/archives/html/xen-users/2019-07/msg00032.html

--
Julien Grall

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