Cloud Hypervisor v15.0 Released!

Posted April 29, 2021 by Cloud Hypervisor Team ‐ 3 min read

This release has been tracked through the v15.0 project.

Highlights for cloud-hypervisor version v15.0 include:

Version numbering and stability guarantees

This release is the first in a new version numbering scheme to represent that we believe Cloud Hypervisor is maturing and entering a period of stability. With this new release we are beginning our new stability guarantees:

  • The API (including command line options) will not be removed or changed in a breaking way without a minimum of 2 releases notice. Where possible warnings will be given about the use of deprecated functionality and the deprecations will be documented in the release notes.
  • Point releases will be made between individual releases where there are substantial bug fixes or security issues that need to be fixed.

Currently the following items are not guaranteed across updates:

  • Snapshot/restore is not supported across different versions
  • Live migration is not supported across different versions
  • The following features are considered experimental and may change substantially between releases: TDX, SGX.

Network device rate limiting

Building on our existing support for rate limiting block activity the network device also now supports rate limiting. Full details of the controls are in the IO throttling documentation.

Support for runtime control of virtio-net guest offload

The guest is now able to change the offload settings for the virtio-net device. As well as providing a useful control this mitigates an issue in the Linux kernel where the guest will attempt to reprogram the offload settings even if they are not advertised as configurable (#2528).

--api-socket supports file descriptor parameter

The --api-socket can now take an fd= parameter to specify an existing file descriptor to use. This is particularly beneficial for frameworks that need to programmatically control Cloud Hypervisor.

Bug fixes

  • A workaround has been put in place to mitigate a Linux kernel issues that results in the CPU thread spinning at 100% when using virtio-pmem (#2277).
  • PCI BARs are now correctly aligned removing the need for the guest to reprogram them (#1797,#1798)
  • Handle TAP interface not being writable within virtio-net (due to the buffer exhaustion on the host) (#2517)
  • The recommended Linux kernel is now v5.12.0 as it contains a fix that prevents snapshot & restore working (#2535)


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

  • Support for booting with the “LinuxBoot” protocol for ELF and bzImage binaries has been deprecated. When using direct boot users should configure their kernel with CONFIG_PVH=y. Will be removed in v16.0.


Many thanks to everyone who has contributed to our release including some new faces.


See the GitHub Release for the release assets.