XEN

XEN Distributions

2003	Xen Project	University of Cambridge	https://xenproject.org/	https://xenbits.xen.org/gitweb/
2007	Citrix XenServer	Citrix acquired XenSource
2010	XCP (Xen Cloud Platform)	Citrix opensource (hypervisor + management)
2018	XCP-ng	forked from XCP after citrix restrictions. Xen API (XAPI) / Xen Orchestra	https://xenproject.org/projects/xcp-ng/
2022	XenServer	Vista Equity Partners & Evergreen Coast Capital acquired Citrix	https://www.xenserver.com/story

XEN is a kernel, booted by GRUB, which can then boot a Linux kernel as Dom0. The first operating system that can control the XEN kernel and boot a privileged virtual machine as DomU. VM's are called domains, which have a name and an id. On the DomU (host), XEN can be controlled on the DomU with the command xe, xm or xl depending on the Xen version. The unprivileged vm's are named Dom0

xl info
xl create /etc/xen/win.hvm
xl list
xl destroy 2

XEN can emulate devices (HVM) or paravirtualize devices (PV). With PV you need the guest (Dom0) to be aware that it is a virtual machine and have the guest tools with the drivers involved. PV is faster than HVM.

https://wiki.xenproject.org/wiki/Understanding_the_Virtualization_Spectrum

XEN supports the fully emulated HVM network interface Intel E1000 and Realtek RTL8137C2+, which emulates the hardware, so that the default OS drivers can be used. The interface will appear as vif25.1-emu on the host.

XEN PV paravirtualized devices (VIF) that use XEN drivers to talk directly to the XEN backends (e.g. XENQEMU) will show up as vif25.0

vif = ['bridge=lan,model=e1000,rate=10Gb/s','bridge=lan,type=vif']

https://wiki.xenproject.org/wiki/Xen_Networking

https://xenbits.xen.org/docs/unstable/man/xl-network-configuration.5.html

https://xenproject.org/resources/downloads/

Boot

XEN uses SeaBios, the default QEMU BIOS, which can also run as payload of coreboot on physical hardware for the initialization of the devices.

(Default UEFI implementation is Tianocore)

https://github.com/xcp-ng/win-pv-drivers/releases

The drivers are not signed, to install them on windows the testsigning must be switch on, otherwise the driver installation will fail without error message.

bcdedit /set testsigning on

xl network-list 25
Idx BE Mac Addr.         handle state evt-ch   tx-/rx-ring-ref BE-path
0   0  00:16:3e:5b:b7:e2     0     4     -1    -1/-1          /local/domain/0/backend/vif/25/0
1   0  00:16:3e:4d:95:03     1     4     -1    -1/-1          /local/domain/0/backend/vif/25/1

Alpine Linux

Alpine Linux downloads come with a XEN ISO that can be used, but using a regulare version can also run XEN

https://wiki.alpinelinux.org/wiki/Xen_Dom0

setup-xen-dom0

apk add xen-hypervisor
apk add bridge
apk add seabios ovmf

echo "xen-netback" >> /etc/modules
echo "xen-blkback" >> /etc/modules
echo "tun" >> /etc/modules

rc-update add xenconsoled
rc-update add xendomains
rc-update add xenqemu
rc-update add xenstored

Contents of /etc/default/grub

GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=1024M,max:1024M" GRUB_DEFAULT="saved" GRUB_SAVEDEFAULT="true"

grub-mkconfig -o /boot/grub/grub.cfg
grub-set-default "$(grep ^menuentry /boot/grub/grub.cfg | grep Xen | cut -d \' -f 2 | head -1)"

efibootmgr -c -d /dev/sda -p 1 -l /EFI/boot/xen.efi -L "XEN"

efibootmgr -o 2,0,4

https://wiki.xenproject.org/wiki/Xen_EFI

https://wiki.archlinux.org/title/xen

https://xcp-ng.org/docs/architecture.html#api

PCI passthrough was indeed necessary for the software I'm using to pick up all network traffic properly (not bridging through the virtual switch). Doing so requires enabling IOMMU and using the legacy linux bridge backend networking (instead of the default Open vSwitch backend networking).

xl network-list opnsense
Idx BE Mac Addr. handle state evt-ch tx-/rx-ring-ref BE-path 
0 0 00:16:3e:3f:4f:61 0 5 -1 -1/-1 /local/domain/0/backend/vif/11/0

https://xenbits.xen.org/docs/4.15-testing/man/xl-network-configuration.5.html

https://wiki.xenproject.org/wiki/Device_Model_Stub_Domains

type=ioemu
vifspec
model=e1000
rate=10Gb/s

vif = ['bridge=lan,model=e1000,rate=10Gb/s']

device_model_stubdomain_override