Seven months after its previous 4.19 release, the Xen Project, an open-source type-1 hypervisor using a microkernel design, has just released its new version, 4.20, which expands hardware support for both x86 and Arm platforms while introducing several compelling new capabilities.
On the Arm side, support has been added for LLC (Last Level Cache) coloring, which should help fine-tune performance by allowing more granular control over cache allocation. Furthermore, users can now experiment with the early-stage Armv8-R support, complementing the growing list of architectures that Xen accommodates.
Xen 4.20 has also introduced support for the NXP S32G3 Processors Family and the LINFlexD UART driver, plus, it can now handle SCMI requests over SMC using Shared Memory, effectively forwarding these calls to EL3 FW if they originate from the hardware domain.
On the x86 front, Intel EPT Paging-Write capabilities have been implemented to optimize memory management tasks. AMD Zen 5 CPU support has also been added, along with mitigation strategies for the SRSO speculative vulnerability.
However, some longstanding features have been retired: Xen Project 4.20 has officially dropped support for running on Xeon Phi processors, and the ucode=allow-same command line option is no longer available.
Additionally, the xAPIC flat driver now uses physical destination mode for external interrupts, and x2APIC Cluster Mode has also been removed—though x2APIC Physical and Mixed Modes are still supported.
The release further introduces several convenience enhancements, such as the new wallclock command line option to select the time source, and xl suspend/resume subcommands to streamline workflows.
In addition, there are a few key changes that downstream consumers and system integrators should keep in mind. For instance, the dombuilder in libxenguest no longer decompresses secondary modules; instead, that responsibility now falls to the guest kernel in its own context.
Moreover, the xenstore library has seen reduced dependencies, which should simplify packaging and deployment for developers who prefer lightweight software footprints.
Lastly, looking ahead, the team is pushing forward with PCI-passthrough features, aiming to unveil them in subsequent releases. RISC-V support also continues to evolve: early steps toward memory management and device tree handling have already been completed, and developers can expect a fully capable Xen build alongside an AIA driver for hypervisor-level UART interrupts in the near future.
For more detailed information on all changes, visit the release notes or check out the list with the new Xen 4.20 features here.
