Cloud Hypervisor v27.0 Released!

Posted September 29, 2022 by Cloud Hypervisor Team ‐ 3 min read

This release has been tracked in our new roadmap project as iteration v27.0.

Community Engagement

A new mailing list has been created to support broader community discussions. Please consider subscribing; an announcement of a regular meeting will be announced via this list shortly.

Prebuilt Packages

Prebuilt packages are now available. Please see this document on how to install. These packages also include packages for the different firmware options available.

Network Device MTU Exposed to Guest

The MTU for the TAP device associated with a virtio-net device is now exposed to the guest. If the user provides a MTU with --net mtu=.. then that MTU is applied to created TAP interfaces. This functionality is also exposed for vhost-user-net devices including those created with the reference backend (#4658, #4676.)

Boot Tracing

Support for generating a trace report for the boot time has been added including a script for generating an SVG from that trace (#4659.)

Simplified Build Feature Flags

The set of feature flags, for e.g. experimental features, have been simplified:

  • msvh and kvm features provide support for those specific hypervisors (with kvm enabled by default),
  • tdx provides support for Intel TDX; and although there is no MSHV support now it is now possible to compile with the mshv feature (#4696,)
  • tracing adds support for boot tracing,
  • guest_debug now covers both support for gdbing a guest (formerly gdb feature) and dumping guest memory.

The following feature flags were removed as the functionality was enabled by default: amx, fwdebug, cmos and common (#4679, #4632.)

Asynchronous Kernel Loading

AArch64 has gained support for loading the guest kernel asynchronously like x86-64. (#4538)

GDB Support for AArch64

GDB stub support (accessed through --gdb under guest_debug feature) is now available on AArch64 as well as as x86-64.

Notable Bug Fixes

  • This version incorporates a version of virtio-queue that addresses an issue where a rogue guest can potentially DoS the VMM (rust-vmm/vm-virtio#196.)
  • Improvements around PTY handling for virtio-console and serial devices (#4520, #4533, #4535.)
  • Improved error handling in virtio devices (#4626, #4605, #4509, #4631, #4697)


Deprecated features will be removed in a subsequent release and users should plan to use alternatives.

  • Booting legacy firmware (compiled without a PVH header) has been deprecated. All the firmware options (Cloud Hypervisor OVMF and Rust Hypervisor Firmware) support booting with PVH so support for loading firmware in a legacy mode is no longer needed. This functionality will be removed in the next release.


Many thanks to everyone who has contributed to our release:


See the GitHub Release for the release assets.