Re: Xen on Raspberry Pi 4

[Paul Leiber <paul@xxxxxxxxxxxxxxxx>]

Am 02.08.2023 um 23:03 schrieb Julien Grall:
> On 02/08/2023 21:42, Paul Leiber wrote:
> > Hi list,
> Hi Paul,
>
> > 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 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.
Indeed, the device is using ACPI. There is an option in the UEFI 
settings to switch to Device-Tree, but that didn't have any effect I 
could see, other than plain Debian didn't boot anymore either.
I compiled Xen with the ACPI option for Arm, and got it running. Thank 
you very much for your hint, Julien!
For reference:

To enable the ACPI option, I went to the "xen" subdirectory in the Xen 
source main directory after "git clone" and did a "make menuconfig".
Out of convience, I initially intended to only rebuild the Debian Xen 
hypervisor package with the ACPI switch on, but that didn't work 
somehow. I couldn't find out why. I then created a "Frankenxen" with a 
newly built hypervisor and standard debian tools, which booted (yay!), 
but of course the xen tools didn't work. Using the repo to check out a 
Xen 17.1 version and build the hypervisor (so I could still rely on 
Debian updates for all the other Xen packages) also didn't work, Xen 
didn't boot. I then decided to build a complete Xen version from scratch 
from the master repo, which worked well. So perhaps this approach with 
enabling ACPI only works on Xen versions > 17.1?