Re: Xen on Raspberry Pi 4

[Julien Grall <julien@xxxxxxx>]

Hi Paul

Sorry for the late reply.

On 13/08/2023 18:46, Paul Leiber wrote:
> Am 11.08.2023 um 20:51 schrieb Julien Grall:
> > Hi Paul,
> >
> > On 04/08/2023 06:44, Paul Leiber wrote:
> > > 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.
> > Is Debian using 4.17.2? Did you see any output from Xen/Linux.
> xl info on a standard Debian installation gives me version 4.17.2-pre. 
> If I remember correctly, the output when booting both my self-compiled 
> Debian xen package or the self-compiled 17.1 version is identical to the 
> one above, it stops with:
> Using modules provided by bootloader in FDT
> Xen 4.17.2-pre (c/s ) EFI loader
>
> > > 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?
> > I don't remember any change related to ACPI on Arm that are in master 
> > but not 4.17. I will try to have a look in the next couple of weeks 
> > and find which patches may be missing.
> Let me know if I can help.
I finally managed to find time to try Xen 4.17.2 on the RPI4. It seems 
to work without any issue once I have ACPI enabled.
Is this still a problem for you? If so, would you be able to share your 
.config and the Linux kernel version you are using?
Do you also have any logs to share?

Cheers,

--
Julien Grall