Cloud Hypervisor v0.8.0 Released!

Posted June 11, 2020 by Cloud Hypervisor Team ‐ 3 min read


This release has been tracked through the 0.8.0 project.

Highlights for cloud-hypervisor version 0.8.0 include:

Experimental Snapshot and Restore Support

This release includes the first version of the snapshot and restore feature. This allows a VM to be paused and then subsequently snapshotted. At a later point that snapshot may be restored into a new running VM identical to the original VM at the point it was paused.

This feature can be used for offline migration from one VM host to another, to allow the upgrading or rebooting of the host machine transparently to the guest or for templating the VM. This is an experimental feature and cannot be used on a VM using passthrough (VFIO) devices. Issues with SMP have also been observed (#1176).

Experimental ARM64 Support

Included in this release is experimental support for running on ARM64. Currently only virtio-mmio devices and a serial port are supported. Full details can be found in the ARM64 documentation.

Support for Using 5-level Paging in Guests

If the host supports it the guest is now enabled for 5-level paging (aka LA57). This works when booting the Linux kernel with a vmlinux, bzImage or firmware based boot. However booting an ELF kernel built with CONFIG_PVH=y does not work due to current limitations in the PVH boot process.

Virtio Device Interrupt Suppression for Network Devices

With virtio-net and vhost-user-net devices the guest can suppress interrupts from the VMM by using the VIRTIO_RING_F_EVENT_IDX feature. This can lead to an improvement in performance by reducing the number of interrupts the guest must service.

vhost_user_fs Improvements

The implementation in Cloud Hypervisor of the VirtioFS server now supports sandboxing itself with seccomp.

Notable Bug Fixes

  • VMs that have not yet been booted can now be deleted (#1110).
  • By creating the tap device ahead of creating the VM it is not required to run the cloud-hypervisor binary with CAP_NET_ADMIN (#1273).
  • Block I/O via virtio-block or vhost-user-block now correctly adheres to the specification and synchronizes to the underlying filesystem as required based on guest feature negotiation. This avoids potential data loss (#399, #1216).
  • When booting with a large number of vCPUs then the ACPI table would be overwritten by the SMP MPTABLE. When compiled with the acpi feature the MPTABLE will no longer be generated (#1132).
  • Shutting down VMs that have been paused is now supported (#816).
  • Created socket files are deleted on shutdown (#1083).
  • Trying to use passthrough devices (VFIO) will be rejected on mmio builds (#751).

Command Line and API Changes

This is non exhaustive list of HTTP API and command line changes:

  • All user visible socket parameters are now consistently called socket rather than sock in some cases.
  • The ch-remote tool now shows any error message generated by the VMM
  • The wce parameter has been removed from --disk as the feature is always offered for negotiation.
  • --net has gained a host_mac option that allows the setting of the MAC address for the tap device on the host.


Many thanks to everyone who has contributed to our 0.8.0 release including some new faces.


See the GitHub Release for the release assets.