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Xen Hypervisor 4.18 Released with Initial RISC-V Support

Xen is an open-source hypervisor that supports x86, x86_64, IA64, PowerPC, and other CPU architectures. It’s hosted at the Linux Foundation and is included in the Linux kernel. It allows multiple guest operating systems to run on the same computer hardware at the same time.

The Xen Project has just released version 4.18. Packed with many features and improvements, this release brings forth a few advancements catering to High-Performance Computing (HPC), Machine Learning (ML) applications, and an array of security and performance enhancements.

Here’s what’s new.

Xen 4.18: Key highlights

Arm

For the Arm architecture, the Xen 4.18 release introduces several noteworthy features. The Scalable Vector Extension (SVE) now stands proudly in the upstream Xen as a tech preview, promising extended capabilities for Arm systems. Furthermore, the Arm Firmware Framework for Arm A-profile (FF-A) framework support is now also merged as a tech preview. This adds a layer of robustness to the Xen hypervisor’s support for Arm architecture.

The memory subsystem in Xen on Arm64 has undergone improvements, making it more compliant with the Arm architecture. This is a substantial update in ensuring seamless integration and optimal performance for Arm-based systems.

x86

On the x86 front, Xen 4.18 extends its support for a variety of processors. Notably, the release ensures visibility and controllability of MSR_ARCH_CAPS on all Intel systems, offering guests access to crucial hardware details. For CPUs from 2019 onwards, this means that guest kernels can now glean insights into hardware fixes for speculative mitigations.

Support for the latest features in 4th Gen AMD EPYC Processors and Intel Sapphire Rapids CPUs has also been integrated. This includes features like CPUID_USER_DIS (CPUID Faulting), PKS (Protection Key Supervisor), VM-Notify for mitigating micro-architectural pipeline livelocks, and bus-lock detection to prevent system-wide impact from guest misuse of atomic instructions.

Intel Granite Rapids CPUs benefit from AVX512-FP16 support, the addition of Intel Hardware P-States (HWP) cpufreq driver, and enforcement of system-wide operation in Data Operand Independent Timing Mode.

RISC-V and Power (little endian)

Xen 4.18 also extends its reach to RISC-V and Power architectures. With the introduction of GitLab CI, the development process is streamlined, ensuring a robust build for Xen along with early printk messages.

Additional improvements

Security remains a top priority for Xen Project, as evidenced by the publication of 20 Xen Security Advisories (XSAs). These advisories enhance the overall security posture of the project, safeguarding against common vulnerabilities and ensuring a secure virtualization environment.

Moreover, Xen 4.18 officially adopts more MISRA-C rules. This includes an increase from four directives and 24 rules in the previous version to six directives and 65 rules in the current release.

Among other improvements, Xen 4.18 allows customization of SMBIOS strings for HVM guests through xl/libxl. On Arm, experimental support for dynamic addition/removal of Xen device tree nodes using a device tree overlay binary (.dtbo) has been introduced. Additionally, two new hypercalls have been added to map the vCPU runstate and time areas by physical rather than linear/virtual addresses, providing more flexibility to developers.

If you are looking forward to these advancements, you can read more in the official release notes.

Via release notes

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