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and you can copy the resulting image to your emulated system and install it. Make sure you haven’t installed any of the disto bits. You may need to run update-grub manually to add the Xen entries.

While you probably don’t want to touch most of the tooling stuff you may well want to build your own QEMU so you can have the latest Xen enabling bits. We shall strip down the config as building inside QEMU will be slower than native:

Code Block
../../configure --disable-docs --disable-tools --disable-user --disable-tcg --disable-kvm
ninja

And finally tweak /etc/default/xencommons to point at it

Code Block
# qemu path
QEMU_XEN=/root/lsrc/qemu.git/builds/xen/qemu-system-i386

And you you can systemctl restart xencommons.service or reboot and you should be able to list Xen domains:

Code Block
18:43:39 [root@debian-arm64:~/l/q/b/xen] + systemctl restart xencommons.service
18:43:45 [root@debian-arm64:~/l/q/b/xen] + systemctl status xencommons.service
● xencommons.service - LSB: Start/stop xenstored and xenconsoled
     Loaded: loaded (/etc/init.d/xencommons; generated)                               
     Active: active (running) since Mon 2023-12-18 18:43:45 GMT; 6s ago
       Docs: man:systemd-sysv-generator(8)
    Process: 15117 ExecStart=/etc/init.d/xencommons start (code=exited, status=0/SUCCESS)
      Tasks: 9 (limit: 4659)
     Memory: 33.0M                                                                    
        CPU: 501ms                                                                    
     CGroup: /system.slice/xencommons.service
             ├─ 1135 /usr/local/sbin/xenstored --pid-file /var/run/xen/xenstored.pid
             ├─ 1141 /usr/local/sbin/xenconsoled --pid-file=/var/run/xen/xenconsoled.pid
             ├─15140 /usr/local/sbin/xenconsoled --pid-file=/var/run/xen/xenconsoled.pid
             └─15146 /root/lsrc/qemu.git/builds/xen/qemu-system-i386 -xen-domid 0 -xen-attach -name dom0 -nographic -M xenpv -daemonize -monitor /dev/null -serial /dev/null>
                                                                                      
Dec 18 18:43:44 debian-arm64 systemd[1]: Starting xencommons.service - LSB: Start/stop xenstored and xenconsoled...
Dec 18 18:43:45 debian-arm64 xencommons[15117]: Setting domain 0 name, domid and JSON config...
Dec 18 18:43:45 debian-arm64 xencommons[15137]: Dom0 is already set up   
Dec 18 18:43:45 debian-arm64 xencommons[15117]: Starting xenconsoled...     
Dec 18 18:43:45 debian-arm64 xencommons[15117]: Starting QEMU as disk backend for dom0 
Dec 18 18:43:45 debian-arm64 systemd[1]: Started xencommons.service - LSB: Start/stop xenstored and xenconsoled.
18:44:02 [root@debian-arm64:~/l/q/b/xen] 1 + xl list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0  4096     8     r-----    6753.8       

Booting Xen Directly

Once you have the user space tooling installed you can now boot the hypervisor directly and manually load the dom0 kernel. Please note you’ll want to skip the UEFI bios for this, also we downgrade the CPU as Xen doesn’t support SVE+ out of the box.

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