Archived/Xen Project Release Features 4.0 to 4.3

Legend:

• ✓: Feature
• ✓: Partial
• ✗: Removed
• For definitions of experimental, preview, supported and deprecated see here

Overview

	Xen 4.0	Xen 4.1	Xen 4.2	Xen 4.3
Initial Release	7 April 2010	25 March 2011	17 Sept 2012	9 July 2013
Supported until	???[ 21 ]	???[ 21 ]	???[ 21 ]	Jan 2015
Security support until	???[ 21 ]	???[ 21 ]	Sept 2015	July 2016
Feature List			FL 4.2	FL 4.3
Release Notes	RN 4.0	RN 4.1	RN 4.2	RN 4.3
Supported Mainline Architectures for the hypervisor (Host)
IA-A32	✓	✓	✓	✗removed
X86-64	✓	✓	✓	✓
Itanium (ia64)	✓	✓deprecated in this release	✓deprecated	✗removed
ARM v7 + Virtualization Extensions				✓preview [ 6 ]
ARM v8				✓preview [ 6 ]
Guest Types
For X86 Architectures
Paravirtualised Traditional Xen Project PV guest	✓	✓	✓	✓
HVM Guest [ 1 ] Fully virtualised guest using hardware virtualisation extensions	✓	✓	✓	✓
PV-on-HVM Guest [ 1 ] Fully virtualised guest using PV extensions/drivers for improved performance	✓	✓	✓	✓
For ARM Architectures
ARM Guest Optimal combination of full virtualization and PV extensions				✓preview [ 6 ]

Limits

	Xen 4.0	Xen 4.1	Xen 4.2	Xen 4.3
Host Limits
For X86 Architectures
Physical CPUs	128 [ 0 ]	>255	4095	4095
Physical RAM	1TB	5TB	5TB	16TB
For ARM Architectures
Physical CPUs				8
Physical RAM				16GB
Guest Limits
X86 PV Guest Limits
Virtual CPUs	128	>255	512	512
Virtual RAM	512GB	512GB	512GB	512GB
X86 HVM Guest Limits
Virtual CPUs	128	128	128	128
Virtual RAM	1TB	1TB	1TB	1TB
ARM Guest Limits
Virtual CPUs				8
Virtual RAM				16GB
Number of event channels
Event Channels	1024/4096	1024/4096	1024/4096	1024/4096

Toolstack and Tools

	Xen 4.0	Xen 4.1	Xen 4.2	Xen 4.3
Toolstack
Built-in
xend / xm	✓	✓	✓deprecated in this release	✓deprecated
XL	✓initial implementation	✓preview release	✓	✓
Qemu based disk backend (qdisk) for XL		✓ [ 5 ]	✓ [ 5 ]	✓ [ 5 ]
XL Open vSwitch integration				✓preview
3rd Party
libvirt driver for XL		✓	✓	✓
Tooling
gdbsx debugger to debug ELF guests	✓	✓	✓	✓
vPMU Virtual Performance Management Unit for HVM guests	✓ [ 4 ]	✓ [ 4 ]	✓ [ 4 ]	✓ [ 4 ]
Serial console	✓	✓	✓	✓Add EHCI debug support
xentrace performance analysis	✓	✓	✓	✓

Features

	Xen 4.0	Xen 4.1	Xen 4.2	Xen 4.3
Advanced Memory Management
Memory Ballooning	✓	✓	✓	✓
Memory Sharing allow sharing of identical pages between HVM guests	✓preview	✓preview	✓preview [ 3 ]	✓preview [ 3 ]
Memory Paging allow pages belonging to HVM guests to be paged to disk	✓preview	✓preview	✓preview [ 3 ]	✓preview [ 3 ]
TMEM - Transcendent Memory	✓experimental [ 2 ]	✓experimental [ 2 ]	✓experimental [ 2 ]	✓experimental [ 2 ]
Resource Management
Cpupool advanced partitioning		✓	✓	✓
Credit 2 Scheduler designed for latency-sensitive workloads and very large systems.		✓prototype	✓prototype	✓experimental
NUMA scheduler affinity				✓
Scalability
1GB/2MB super page support		✓	✓	✓
Deliver events to PVHVM guests using Xen event channels		✓	✓	✓
Fair locks (ticket-locks)
High Availability and Fault Tolerance
Live Migration, Save & Restore	✓	✓	✓	✓
Remus Fault Tolerance	✓	✓	✓	✓
X86 vMCE Forward Machine Check Exceptions to Appropriate guests			✓	✓
Network and Storage
Blktap2	✓	✓	✓	✓
Online resize of virtual disks	✓	✓	✓	✓
Security (also see this presentation or this document)
Driver Domains	✓	✓	✓	✓
Device Model Stub Domains	✓	✓	✓	✓
Virtual Machine Introspection (Memaccess and VM Event APIs) enabling integration of 3rd party security solutions into Xen virtualized environments		✓	✓	✓
XSM & FLASK mandatory access control policy providing fine-grained controls over Xen domains, similar to SELinux	✓	✓	✓	✓
XSM & FLASK support for IS_PRIV				✓
vTPM Support	✓	✓	✓	✓ updates and new functionality

Interoperability / Hardware Support

	Xen 4.0	Xen 4.1	Xen 4.2	Xen 4.3
X86
X86 Nested Virtualisation Running a hypervisor inside an HVM guest			✓experimental	✓experimental
HVM PXE Stack (x86)	gPXE	iPXE	iPXE	iPXE
Physical CPU Hotplug	✓	✓	✓	✓
Physical Memory Hotplug	✓	✓	✓	✓
Support for PV kernels in bzImage format	✓	✓	✓	✓
PCI Passthrough	✓	✓	✓	✓ [ 12 ]
X86 Advanced Vector eXtension (AVX)		✓ [ 4 ]	✓	✓

Device Models and Virtual Firmware

	Xen 4.0	Xen 4.1	Xen 4.2	Xen 4.3
Device Models and Virtual Firmware for HVM guests
For X86 Architectures
Traditional Device Model Device emulator based on Xen fork of Qemu	✓	✓	✓	✓
Qemu Upstream Device Model Device emulator based on upstream Qemu			✓preview	✓default, unless stubdomains are used
ROMBIOS BIOS used with traditional device model only	✓	✓	✓	✓
SeaBIOS BIOS used with upstream qemu device model and XL only			✓	✓
OVMF/Tianocore UEFI Firmware used with upstream qemu device model and XL only			✓experimental [ 4 ]	✓experimental [ 4 ]
PV Bootloader support
For X86 Architectures
PyGrub support for GRUB 2	✓	✓	✓	✓
PyGrub support for /boot on ext4	✓	✓	✓	✓
pvnetboot support Bootloader supporting network boot of PV guests			✓	✓

Notes

^{[ 0 ]} Compile time limit, can be increased
^{[ 1 ]} Requires hardware virtualisation support
^{[ 2 ]} Disabled by default (enable with hypervisor command line option). Not supported in production and doesn't have full security support
^{[ 3 ]} Preview, due to limited tools support. Hypervisor side in good shape
^{[ 4 ]} Disabled by default (enable with hypervisor command line option)
^{[ 5 ]} Used as a fallback if blkback and/or blktap2 are not available
^{[ 6 ]} See Xen ARM with Virtualization Extensions; basic functionality implemented; lack of real hardware to validate against
^{[ 12 ]} Not yet supported on ARM; for a more detailed update on what is supported on ARM see here
^{[ 21 ]} Dates for historical releases have not be researched.