Release: Xen Hypervisor version 4.2.0
The first version of the product was developed by The University of Cambridge Computer Laboratory and it has been maintained as free software, licensed under the GNU General Public License (GPL). Xen is currently available for the IA-32, x86-64 and ARM computer architectures. It is used by many public cloud and hosting services.
Xen 4.2.0 is the result of 18 months of work on 300K lines of code of development effort, by 124 individuals from 43 organizations.
Among the new Features:
XL is now the default toolstack: Significant effort has gone in to the XL tool toolstack in this release and it is now feature complete and robust enough that we have made it the default. This toolstack can now replace xend in the majority of deployments, see XL vs Xend Feature Comparison. As well as improving XL the underlying libxl library has been significantly improved and supports the majority of the most common toolstack features. In addition the API has been declared stable which should make it even easier for external toolstack such as libvirt and XCP’s xapi to make full use of this functionality in the future.Large Systems: Following on from the improvements made in 4.1 Xen now supports even larger systems, with up to 4095 host CPUs and up to 512 guest CPUs. In addition toolstack feature like the ability to automatically create a CPUPOOL per NUMA node and more intelligent placement of guest VCPUs on NUMA nodes have further improved the Xen experience on large systems. Other new features, such as multiple PCI segment support have also made a positive impact on such systems.Improved security: The XSM/Flask subsystem has seen several enhancements, including improved support for disaggregated systems and a rewritten example policy which is clearer and simpler to modify to suit local requirements.Documentation: The Xen documentation has been much improved, both the wiki. This is in no small part down to the success of the Xen Document Days so thanks to all who have taken part.