Cloud Hypervisor v24.0 Released!

Posted May 27, 2022 by Cloud Hypervisor Team ‐ 2 min read

This release has been tracked through the v24.0 project.

Bypass Mode for virtio-iommu

virtio-iommu specification describes how a device can be attached by default to a bypass domain. This feature is particularly helpful for booting a VM with guest software which doesn’t support virtio-iommu but still need to access the device. Now that Cloud Hypervisor supports this feature, it can boot a VM with Rust Hypervisor Firmware or OVMF even if the virtio-block device exposing the disk image is placed behind a virtual IOMMU.

Ensure Identifiers Uniqueness

Multiple checks have been added to the code to prevent devices with identical identifiers from being created, and therefore avoid unexpected behaviors at boot or whenever a device was hot plugged into the VM.

Sparse Mmap support

Sparse mmap support has been added to both VFIO and vfio-user devices. This allows the device regions that are not fully mappable to be partially mapped. And the more a device region can be mapped into the guest address space, the fewer VM exits will be generated when this device is accessed. This directly impacts the performance related to this device.

Expose Platform Serial Number

A new serial_number option has been added to --platform, allowing a user to set a specific serial number for the platform. This number is exposed to the guest through the SMBIOS.

Notable Bug Fixes

  • Fix loading RAW firmware (#4072)
  • Reject compressed QCOW images (#4055)
  • Reject virtio-mem resize if device is not activated (#4003)
  • Fix potential mmap leaks from VFIO/vfio-user MMIO regions (#4069)
  • Fix algorithm finding HOB memory resources (#3983)

Notable Improvements

  • Refactor interrupt handling (#4083)
  • Load kernel asynchronously (#4022)
  • Only create ACPI memory manager DSDT when resizable (#4013)


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

  • The mergeable option from the virtio-pmem support has been deprecated (#3968)
  • The dax option from the virtio-fs support has been deprecated (#3889)

New on the Website

A new blog post Achieving Bare Metal Performance Within a Virtual Machine has been added to the Cloud Hypervisor website.


Many thanks to everyone who has contributed to our release:


See the GitHub Release for the release assets.