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Xen and the art of hypervisor upgrades

Version 4.16 adds first look at TPM 2.0 and better big.LITTLE support

The Xen Project has delivered an upgrade to its hypervisor.

Version 4.16 was announced yesterday by developer and maintainer Ian Jackson, capping a nine-month effort that saw four release candidates emerge in November 2021 prior to launch.

The project's feature list for the release celebrates the following additions as the most notable inclusions:

  • Miscellaneous fixes to the TPM manager software in preparation for TPM 2.0 support.
  • An increased reliance on the PV shim as 32-bit PV guests will only be supported in shim mode going forward. This change reduces the attack surface in the hypervisor.
  • Increased hardware support by allowing Xen to boot on Intel devices that lack a Programmable Interval Timer.
  • Cleanup of legacy components by no longer building QEMU Traditional or PV-Grub by default.
  • Improved support for the Gitlab automated tests – 32-bit Arm builds and full system tests for x86.
  • Initial support for guest virtualized Performance Monitor Counters on Arm.
  • Improved support for dom0less mode by allowing the usage on Arm 64-bit hardware with EFI firmware.
  • Improved support for Arm 64-bit heterogeneous systems by leveling the CPU features across all to improve big.LITTLE support.

Jackson also pointed to work that has advanced Xen's efforts to achieve functional safety – a very-nice-to-have if the hypervisor is to achieve the project's goal of becoming more attractive to developers of embedded systems. He also reported "significant work has been ongoing internally in order to get dom0 booting on RISC-V hardware".

Work on VirtIO support for Arm "continued making progress" but no mention was made of when it might debut in a full release. Version 4.16 has no known issues and will be supported until June 2023. Security updates will continue until December 2024.

The release can be found here and release notes, including build instructions, await your eyeballs here. ®

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