Xen Project Release Features

Legend: ✓: Feature ✓: Partial

	Xen 4.0	Xen 4.1	Xen 4.2	Xen 4.3
Initial Release	7 April 2010	25 March 2011	17 September 2012	TBD
Supported Mainline Architectures
IA-A32	✓	✓	✓	✓
X86-64	✓	✓	✓	✓
Itanium	✓	✓deprecated in this release	✓deprecated
ARM v7 + Virtualization Extensions				✓tech preview [ 6 ]
ARM v8				✓tech preview [ 6 ]
Guest Types
For X86 Architectures
Paravirtualised Traditional Xen 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				✓tech preview [ 6 ]
Host Limits
For X86 Architectures
Physical CPUs	128 [ 0 ]	>255	4095	4095
Physical RAM	1TB	5TB	5TB	16TB
For ARM Architectures
Physical CPUs				TBA
Physical RAM				TBA
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	256	256
Virtual RAM	1TB	1TB	1TB	1TB
ARM Guest Limits
Virtual CPUs				TBA
Virtual RAM				TBA
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 openvswitch toostack integration				✓tech preview [ 7 ]
XL Spice support				✓tech preview [ 7 ]
3rd Party
libvirt driver for XL		✓	✓	✓
Features
Live Migration, Save & Restore	✓	✓	✓	✓
Memory ballooning	✓	✓	✓	✓
Blktap2	✓	✓	✓	✓
PCI Passthrough	✓	✓	✓	✓
TMEM -- Transcendent Memory	✓ [ 2 ]	✓ [ 2 ]	✓ [ 2 ]	✓ [ 2 ]
gdbsx debugger to debug ELF guests	✓	✓	✓	✓
Memory Sharing allow sharing of identical pages between HVM guests	✓tech preview	✓tech preview	✓tech preview [ 3 ]	✓tech preview [ 3 ]
Memory Paging allow pages belonging to HVM guests to be paged to disk	✓tech preview	✓tech preview	✓tech preview [ 3 ]	✓tech preview [ 3 ]
Online resize of virtual disks	✓	✓	✓	✓
Remus Fault Tolerance	✓	✓	✓	✓
Physical CPU Hotplug	✓	✓	✓	✓
Physical Memory Hotplug	✓	✓	✓	✓
Support for PV kernels in bzImage format	✓	✓	✓	✓
Credit 2 Scheduler designed for latency-sensitive workloads and very large systems.		✓prototype	✓prototype	✓experimental
1GB/2MB super page support		✓	✓	✓
x86 Advanced Vector eXtension (AVX)		✓ [ 4 ]	✓ [ 4 ]	✓ [ 4 ]
cpupool advanced partitioning		✓	✓	✓
memaccess API enabling integration of 3rd party security solutions into Xen virtualized environments		✓	✓	✓
Deliver events to PVHVM guests using Xen event channels		✓	✓	✓
HVM PXE Stack	gPXE	iPXE	iPXE	iPXE
xentrace performance analysis	✓	✓	✓	✓
qemu based disk backend (qdisk) for XL		✓ [ 5 ]	✓ [ 5 ]	✓ [ 5 ]
FLASK mandatory access control policy providing fine-grained controls over Xen domains, similar to SELinux	✓	✓	✓	✓ Support for IS_PRIV checks
vPMU Virtual Power Management Unit for HVM guests	✓	✓	✓	✓
vMCE Forward Machine Check Exceptions to Appropriate guests	?	?	✓	✓
Nested Virtualisation Running a hypervisor inside an HVM guest			✓experimental	✓experimental
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			✓tech 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			✓	✓
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			✓	✓

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^{[ 0 ]} Compile time limit, can be increased
^{[ 1 ]} Requires hardware virtualisation support
^{[ 2 ]} Ddisabled 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
^{[ 7 ]} tech preview, depending on test coverage in Xen Test Days