Software Update: Xen 4.15.0

Xen is a baremetal hypervisor for the x86 and ARMv7/v8 platforms, allowing multiple operating systems to run simultaneously on a single system without drastically impacting performance. For more information about Xen and its community, see this one and this one page. Currently only Linux, NetBSD and FreeBSD are supported as host systems, but work is underway to fully support other operating systems as well. The developers have released version 4.15.0 with the following announcement:

XEN PROJECT HYPERVISOR 4.15 NOW AVAILABLE

The Xen Project, an open source hypervisor hosted at the Linux Foundation, today announced the release of Xen Project Hypervisor 4.15, which introduces a variety of features allowing for improved performance, security and device pass-through reliability. The Xen Project community continues to be active and engaged, with a wide range of developers from many companies and organizations contributing to this latest release. Additionally, community-wide initiatives, including Functional Safety, VirtIO for Xen and Xen RISC-V port, continue to make valuable progress.

Notable Features

• Arm now allows running device models in dom0 (tech preview), allowing arbitrary devices to be emulated for Arm guests. Arm also now has SMMUv3 support (also tech preview), which will improve security and reliability of device pass-through on Arm systems.
• Xen can now export Intel Processor Trace (IPT) data from guests to tools in dom0, enabling tools like VMI Kernel Fuzzer for Xen Project or DRAKVUF Sandbox.
• Xen now supports Viridian enlightenments for guests with more than 64 vcpus.
• Xenstored and oxenstored both now support LiveUpdate (tech preview), allowing security fixes to be applied without having to restart the entire host.
• “PV Shim” mode, for supporting legacy PV guests on HVM-only systems, continues to be improved; its size was reduced by further factoring out HVM-specific code. This will also help reduce the size and security of any PV-only build of the hypervisor.
• Unified boot images: It is now possible to create an image bundling together files needed for Xen to boot into a single EFI binary; making it now possible to boot a functional Xen system directly from the EFI boot manager, rather than having to go through grub multiboot. Files that can be bundled include a hypervisor, dom0 kernel, dom0 initrd, Xen KConfig, XSM configuration, and a device tree.

Community Initiative Updates

Functional Safety Update
Progress continues to be made within the Functional Safety SIG. Specifications are becoming more concrete and the group is working with other communities to establish standards. Additionally, Xen is working with other projects to converge best practices across communities.

Updates include:

• Progress on MISRA-C rules tailored for Xen in collaboration with Zephyr. MISRA-C is a set of coding guidelines for the language for safety. The SIG now has a shortlist of MISRA-C rules that apply to our project and we are currently evaluating static analyzers for each of them.
• Progress on tracking and maintaining safety requirements including collaboration with Zephyr to build a Doxygen-based infrastructure that generates safety requirements documents from in-code comments and text files. It will allow proper maintenance of safety-related artifacts next to the code under git and keep them up to date easily in the community.

Additionally, the Xen Project will be presenting, “Safety certification in the open: How the Xen project is making progress to achieve certification,” at Embedded IoT World on April 28 at 3:00 pm PT.

VirtIO drivers for Xen
Progress includes:

• Developed IOREQ server in Xen on Arm for further enablement of VirtIO protocols as a generic and standardized solution for I/O virtualization.
• Reference implementation of VirtIO block device for Xen on Arm – collaboration between Arm, EPAM and Linaro’s project STRATOS.
• Moving towards enabling PCIe virtualization support for Xen on Arm – collaboration between Xilinx, Arm, EPAM and Renesas.
• Ability to expose a VirtIO block device to a Xen on Arm guest.

“Hyper Launch”
“Dom0less” pioneered the ability to configure Xen to launch a static set of virtual machines by Xen at boot time. But configuration for these domains was very basic, and focused on embedded use cases. “Hyperlaunch” is a new initiative that intends to make this configuration far more flexible by generalizing it and introducing a “boot domain” (domB). Draft design documents have been posted, and a working group has been formed to form a plan to complete iron out the details.

RISC-V Port:
RISC-V, an open standard instruction set architecture (ISA) based on established reduced instruction set computer (RISC) principles, is a free and open ISA enabling hardware designers to design simpler chips with a royalty-free ISA. The Xen community, led by sub-project XCP.ng, is working on a RISC-V Port for Xen.

Progress includes:

• Development of host and guest virtual memory management code, one of the key components necessary for supporting guest virtualization.
• Development of the internal architecture-specific code to conform to Xen common APIs.