Re: Xen on Raspberry Pi 4

[Julien Grall <julien@xxxxxxx>]

On 02/08/2023 21:42, Paul Leiber wrote:
> Hi list,
Hi Paul,

> Now that the devices are available again, I got hold of a Raspberry Pi 4 
> (8 GB) which I am currently trying to set up Xen on for using it as a 
> backup server.
> What I did was to install a standard Debian distribution booted via 
> EFI/GRUB2 (following 
> https://forums.raspberrypi.com/viewtopic.php?t=282839) and then install 
> the xen-System-arm64 package via apt. I have output on a console via 
> UART (at least when booting Debian without Xen, see hypothesis 3 below).
> Booting Debian without Xen is working fine. (Although I only see the 
> Grub selection menu via UART when no HDMI is plugged in while booting.)
> Selecting Xen in Grub leads to the following output on the console right 
> after Grub hands over:
> Loading Xen 4.17-arm64.efi ...
> Loading Linux 6.1.0-10-arm64 ...
> Loading initial ramdisk ...
> Using modules provided by bootloader in FDT
> Xen 4.17.2-pre (c/s ) EFI loader
>
> And then the output stops.
>
> I have four hypotheses (not mutually exclusive, and there are very 
> probably unknown unknowns on my side):
> 1. Booting Xen via EFI is not working, and I need to use U-Boot as 
> described in 
> https://xenproject.org/2020/09/29/xen-on-raspberry-pi-4-adventures/
> 2. The Debian package xen-system-arm64 is not suitable for this purpose 
> and I need to compile Xen from scratch
> 3. I got the console settings wrong (I currently use the settings from 
> https://xenproject.org/2020/09/29/xen-on-raspberry-pi-4-adventures/ for 
> Xen command line specified in Grub, but I also tried a lot of different 
> settings), and Xen is actually doing something, but I don't see the output.
> 4. There is something wrong with my setup and I need to change specific 
> EFI and/or other settings.
> Has anybody got a similar setup working and can give me hints?
I have been using Debian + Xen + Grub + UEFI on Rpi4. UEFI firmwares are 
mostly shipped with ACPI only (IOW no Device-Tree support) This is not 
yet a fully supported configuration on Arm64 and therefore not enabled 
by default.
Can you check the kernel log when booting Debian without Xen for 
anything referring to ACPI? If so, you will need to Xen build yourself 
to enable ACPI (this is protected by EXPERT). Alternatively you could 
use U-boot where Device-Tree boot will be available.
Cheers,

--
Julien Grall