Xen Project Release Features

Note that we will add complete information related to Xen Project 4.9, in the week after the 4.9 release. Apologies, I have not been able to do this in time for the 4.9 release due to travel. I will do as much as I can, before the release, but it may not be fully complete.

Legend:

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

Overview

	Xen 4.4	Xen 4.5	Xen 4.6	Xen 4.7	Xen 4.8	Xen 4.9
Initial Release	10 March 2014	15 Jan 2015	13 Oct 2015	20 June 2016	5 Dec 2016	28 June 2017
Supported until	Sept 2015	July 2016	April 2017	Dec 2017	June 2018	Jan 2019
Security support until	March 2017	Jan 2018	Oct 2018	June 2019	Dec 2019	July 2020
Feature List	FL 4.4	FL 4.5	FL 4.6	FL 4.7	FL 4.8	FL 4.9
Release Notes	RN 4.4	RN 4.5	RN 4.6	RN 4.7	RN 4.8	RN 4.9
Supported Mainline Architectures for the hypervisor (Host)
X86-64	✓	✓	✓	✓	✓	✓
ARM v7 + Virtualization Extensions	✓	✓ ^{[ 8 ]}	✓ ^{[ 14 ]}	✓ ^{[ 26 ]}	✓ ^{[ 26 ]}	✓ ^{[ 26 ]}
ARM v8	✓	✓ ^{[ 8 ]}	✓ ^{[ 15 ]}	✓ ^{[ 15 ]}	✓ ^{[ 15 ]}	✓ ^{[ 15 ]}
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}	✓	✓	✓	✓	✓	✓
PVH Guest	✓preview	✓preview added PVH Dom0	✓preview	✓preview	✓preview started implementing PVHv2	✓preview removed PVHv1
For ARM Architectures
ARM Guest^{Optimal combination of full virtualization and PV extensions}	✓	✓	✓	✓	✓	✓

Limits

	Xen 4.4	Xen 4.5	Xen 4.6	Xen 4.7	Xen 4.8	Xen 4.9
Host Limits
For X86 Architectures
Physical CPUs	4095	4095	4095	4095	4095	4095
Physical RAM	16TB	16TB	16TB	16TB	16TB	16TB
For ARM Architectures
Physical CPUs	8	8	8 for 32bit; 128 for 64bit	8 for 32bit; 128 for 64bit	8 for 32bit; 128 for 64bit	8 for 32bit; 128 for 64bit
Physical RAM	16GB	16GB for 32bit, 5TB for 64bit	16GB for 32bit, 5TB for 64bit	16GB for 32bit, 5TB for 64bit	16GB for 32bit, 5TB for 64bit	16GB for 32bit, 5TB for 64bit
Guest Limits
X86 PV Guest Limits
Virtual CPUs	512	512	512	512	512	512
Virtual RAM	512GB	512GB	512GB	> 1TB	> 1TB	> 1TB
X86 HVM Guest Limits
Virtual CPUs	128	128	128	128	128	128
Virtual RAM	1TB	1TB	1TB	1TB	1TB	1TB
ARM Guest Limits
Virtual CPUs	8	8	8 for 32bit; 128 for 64bit	8 for 32bit; 128 for 64bit	8 for 32bit; 128 for 64bit	8 for 32bit; 128 for 64bit
Virtual RAM	16GB	1TB ^{[ 7 ]}	1TB ^{[ 7 ]}	1TB ^{[ 7 ]}	1TB ^{[ 7 ]}	1TB ^{[ 7 ]}
Number of event channels
Event Channels	131072	131072	131072	131072	131072	131072

Toolstack and Tools

	Xen 4.4	Xen 4.5	Xen 4.6	Xen 4.7	Xen 4.8	Xen 4.9
Toolstack
Built-in
xend / xm	✓deprecated	✗removed
XL	✓	✓	✓	✓	✓	✓
Qemu based disk backend (qdisk) for XL	✓ ^{[ 5 ]}	✓ ^{[ 5 ]}	✓ ^{[ 5 ]}	✓ ^{[ 5 ]}	✓ ^{[ 5 ]}	✓ ^{[ 5 ]}
XL Open vSwitch integration	✓	✓	✓	✓	✓	✓
systemd support		✓	✓	✓	✓	✓
JSON support		✓infrastructure only, no tools support	✓infrastructure only, no tools support	✓infrastructure only, no tools support	✓infrastructure only, no tools support	✓infrastructure only, no tools support
AHCI support			✓	✓	✓	✓
PVUSB				✓	✓	✓
HVM USB passthrough					✓	✓
QEMU backend hotplugging				✓	✓	✓
Soft-Reset				✓	✓	✓
3rd Party
libvirt driver for XL	✓^{[ 29 ]}	✓^{[ 29 ]}	✓^{[ 16 ] [ 29 ]}	✓^{[ 16 ] [ 29 ]}	✓^{[ 16 ] [ 29 ]}	✓^{[ 16 ] [ 29 ]}
Tooling
gdbsx debugger to debug ELF guests	✓	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}
vPMU Virtual Performance Management Unit for HVM guests	✓ ^{[ 4 ]}	✓ ^{[ 4 ]}^{[ 12 ]}	✓ ^{[ 4 ]}^{[ 12 ]}	✓ ^{[ 4 ]}^{[ 12 ]}	✓ ^{[ 4 ]}^{[ 12 ]}	✓ ^{[ 4 ]}^{[ 12 ]}
Serial console	✓	✓Add Oxford PCIe, and Broadcom TrueManage support	✓	✓	✓	✓
xentrace performance analysis	✓	✓^{[ 12 ]}	✓Added Xenalyze	✓	✓	✓

Features

	Xen 4.4	Xen 4.5	Xen 4.6	Xen 4.7	Xen 4.8	Xen 4.9
Advanced Memory Management
Memory Ballooning	✓	✓	✓	✓	✓	✓
Memory Sharing allow sharing of identical pages between HVM guests	✓preview ^{[ 3 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}
Memory Paging allow pages belonging to HVM guests to be paged to disk	✓preview ^{[ 3 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}	✓preview ^{[ 3 ]}^{[ 12 ]}
TMEM - Transcendent Memory	✓experimental ^{[ 2 ]}	✓experimental ^{[ 2 ]}^{[ 12 ]}	✓experimental ^{[ 2 ]}^{[ 12 ]}	✓experimental ^{[ 2 ]}^{[ 12 ]}	✓experimental ^{[ 2 ]}^{[ 12 ]}	✓experimental ^{[ 2 ]}^{[ 12 ]}
Resource Management
Cpupool advanced partitioning		✓	✓	✓	✓	✓
Credit 2 Scheduler designed for latency-sensitive workloads and very large systems.		✓experimental	✓experimental	✓experimental (significant additions)	✓	✓
RTDS Based Scheduler Real-time CPU scheduler built to provide guaranteed CPU capacity to guest VMs on SMP hosts.		✓experimental	✓experimental	✓experimental (significant additions)	✓experimental	✓experimental
NUMA scheduler affinity	✓	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}
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	✓	✓ ^{[ 12 ]}	✓ ^{[ 18 ]} Migration v2	✓ ^{[ 23 ]}	✓ ^{[ 23 ]}	✓ ^{[ 23 ]}
Remus Fault Tolerance	✓	✓ improvements for COLO ^{[ 10 ]}^{[ 12 ]}	✓ Remus ported to Migration v2	✓	✓	✓
COLO Manager				✓ experimental ^{[ 24 ]}	✓ experimental ^{[ 24 ]}	✓ experimental ^{[ 24 ]}
X86 vMCE Forward Machine Check Exceptions to Appropriate guests	✓	✓	✓	✓	✓	✓
Network and Storage
✓	✓	✓	✓	✓	✓	✓
Online resize of virtual disks	✓	✓	✓	✓	✓	✓
Security (also see this presentation or this document)
Driver Domains	✓	✓	✓	✓	✓	✓
Device Model Stub Domains	✓	✓^{[ 12 ]}	✓^{[ 12 ]}^{[ 17 ]}	✓^{[ 12 ]}^{[ 17 ]}	✓^{[ 12 ]}^{[ 17 ]}	✓^{[ 12 ]}^{[ 17 ]}
Kconfig				✓ experimental	✓ experimental	✓ experimental
Live Patching				✓ preview ^{[ 22 ]}	✓ preview (added ARM support)	✓ ^{[ 27 ]}
Virtual Machine Introspection (Memaccess and VM Event APIs) enabling integration of 3rd party security solutions into Xen virtualized environments	✓	✓ improvements^{[ 12 ]}	✓ ^{[ 19 ]} reworked with ARM support, added VM Event APIs	✓ improvements	✓	✓
XSM & FLASK mandatory access control policy providing fine-grained controls over Xen domains, similar to SELinux	✓	✓	✓ ^{[ 17 ]}	✓ ^{[ 17 ]}	✓ ^{[ 17 ]}	✓ ^{[ 17 ]}
XSM & FLASK support for IS_PRIV	✓	✓	✓ ^{[ 17 ]}	✓ ^{[ 17 ]}	✓ ^{[ 17 ]}	✓ ^{[ 17 ]}
vTPM Support	✓	✓	✓ vTPM 2.0	✓	✓	✓

Interoperability / Hardware Support

	Xen 4.4	Xen 4.5	Xen 4.6	Xen 4.7	Xen 4.8	Xen 4.9
X86
X86 Nested Virtualisation Running a hypervisor inside an HVM guest	✓preview	✓preview ^{[ 11 ]}	✓preview ^{[ 11 ]}	✓preview ^{[ 11 ]}	✓preview ^{[ 11 ]}	✓preview, fixes ^{[ 11 ]}
HVM PXE Stack (x86)	gPXE	iPXE	iPXE	iPXE	iPXE	iPXE
Physical CPU Hotplug	✓	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}
Physical Memory Hotplug	✓	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}
Support for PV kernels in bzImage format	✓	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}	✓^{[ 12 ]}
PCI Passthrough	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}^{[ 13 ]}	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}	✓ ^{[ 12 ]}
X86 Advanced Vector eXtension (AVX)	✓	✓	✓	✓	✓ AVX-512	✓
Intel Platform QoS Technologies		✓ preview: CMT	✓ preview: CAT, MBM	✓ preview: CDP	✓ preview: CDP	✓ preview: CDP
Other Intel® Xeon® Features				✓ ^{[ 25 ]}	✓ ^{[ 25 ]}	✓ ^{[ 25 ]}
ARM
64K Guest Pages			✓	✓	✓	✓
ACPI / SBBR Compliance				✓ experimental; ACPI 6.0+	✓ experimental	✓ experimental
ACPI guest support					✓ with UEFI	✓ with UEFI
PCSI Compatibility		✓ v0.1 & 0.2	✓	✓ v1.0	✓ v1.0	✓ v1.0
ARM® Interrupt Virtualization		✓ GiC v2	✓ GiC v2m/GiC v3	✓ improvements to v2/v3	✓	✓
Wallclock support				✓	✓	✓

Device Models and Virtual Firmware

	Xen 4.4	Xen 4.5	Xen 4.6	Xen 4.7	Xen 4.8	Xen 4.9
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	✓default, unless stubdomains are used	✓default, unless stubdomains are used	✓default, unless stubdomains are used	✓default, unless stubdomains are used	✓default, unless stubdomains are used	✓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 ]}	✓experimental ^{[ 4 ] + ARM support}	✓experimental ^{[ 4 ] + ARM support}	✓experimental ^{[ 4 ] + ARM support}	✓experimental ^{[ 4 ] + ARM support}
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	✓	✓	✓	✓	✓	✓

PV Protocols and Drivers

	Xen 4.4	Xen 4.5	Xen 4.6	Xen 4.7	Xen 4.8	Xen 4.9
Common net, block, console, keyboard=kbd, mouse, USB, framebuffer=fb	✓	✓	✓	✓	✓	✓ ^{[ 28 ]}
pvcalls POSIX function call forwarding						✓ ^{TBD: experimental or preview [ 28 ]}
9pfs share a filesystem between VMs (a requirement for adding Xen support to many container engines)						✓ ^{TBD: experimental or preview [ 28 ]}
sndif (sound device) used in automotive/embedded						✓ ^{TBD: experimental or preview [ 28 ]}
displif (display) used in automotive/embedded						✓ ^{TBD: experimental or preview [ 28 ]}

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
^{[ 7 ]} Limited by supported host memory
^{[ 8 ]} Tested on Broadcom 7445D0 A15, Midway (Calxeda), Odroid-XU, OMAP5, OMAP6, DRA7 (Texas Instrument), Exynos5 (Samsung), SunXI (AllWinner) aka A20/A21, CubieTruck, CubieBoard
^{[ 9 ]} Tested on Vexpress (ARM Ltd.), Seattle (AMD), Mustang (Applied Micro-X-Gene), McDivitt aka HP Moonshot cartridge (Applied Micro X-Gene)
^{[ 10 ]} Remus has been ported to XL and has been tested with COLO which is currently outside the Xen tree, but planned to be included in Xen 4.6. Also see Remus Toolkit Differences explaining differences between Remus with XM (not supported in Xen 4.5) and XL
^{[ 11 ]} There are a number of reported crashes that have not yet been fixed and some known limitations
^{[ 12 ]} Not yet supported on ARM; for a more detailed update on what is supported on ARM see here and here
^{[ 13 ]} The PCI passthrough features did not make it on time for Xen 4.5, but doing passthrough of MMIO regions did. In the ARM world it is quite common to have no PCIe devices and to only access devices using MMIO regions. As such this feature allows us to have driver domains be in charge of network or storage devices.
^{[ 14 ]} Added the following platforms to ^{[ 8 ]}: Renesas R-Car Gen2, Huawei hip04-d04
^{[ 15 ]} Added the following platforms to ^{[ 9 ]}: Thunder X (partial), Xilinx ZynqMP SoC
^{[ 16 ]} Now tested as part of Xen Project Test Lab and OpenStack CI Loop
^{[ 17 ]} Now tested as part of Xen Project Test Lab
^{[ 18 ]} Migration v2: see [1] and [2]. VM migration using libvirt between two hosts is now tested. Live Migration between hosts of different Xen versions is now tested.
^{[ 19 ]} The memory event subsystem has been reworked and extended to a new VM event subsystem. The new VM event subsystems supports both the ARM and x86 architectures.
^{[ 20 ]} Passthrough for non-PCI devices allows users to passthrough devices via partial device trees.
^{[ 21 ]} Dates for historical releases have not be researched.
^{[ 22 ]} The code for hypervisor live patching is NOT enabled by default. When compiling the hypervisor one must change the config to build it. Note that Live Patching is currently only supported on x86. For more information on live patching, see LivePatch.
^{[ 23 ]} CPU ID Levelling enables migration of VM’s between a larger range of non-identical hosts than previously supported.
^{[ 24 ]} The COLO Manager has been fully integrated as an experimental feature into Xen 4.7. Note that the COLO Block Replication and COLO Proxy components, both of which are QEMU components, are currently still reviewed by the QEMU community. Both components are available as out-of-tree add-ons to the Xen Project Hypervisor, until fully integrated into QEMU.
^{[ 25 ]} Added experimental support for VT-d Posted Interrupts, VMX TSC Scaling, Memory Protection Keys
^{[ 26 ]} Removed support for Huawei hip04-d04
^{[ 27 ]} See xen-devel discussion "livepatch: Declare live patching as a supported feature"
^{[ 28 ]} See xen-devel discussion "Updating https://wiki.xenproject.org/wiki/Xen_Project_Release_Features to reflect support status of new features"
^{[ 29 ]} Security support via libvirt.org/securityprocess

Xen Project Release Features

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Overview

Limits

Toolstack and Tools

Features

Interoperability / Hardware Support

Device Models and Virtual Firmware

PV Protocols and Drivers

Notes

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