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v19.0

This release has been tracked through the v19.0 project.

Improved PTY handling for serial and virtio-console

The PTY support for serial has been enhanced with improved buffering when the the PTY is not yet connected to. Using virtio-console with PTY now results in the console being resized if the PTY window is also resized.

PCI boot time optimisations

Multiple optimisations have been made to the PCI handling resulting in significant improvements in the boot time of the guest.

Improved TDX support

When using the latest TDVF firmware the ACPI tables created by the VMM are now exposed via the firmware to the guest.

Live migration enhancements

Live migration support has been enhanced to support migration with virtio-mem based memory hotplug and the virtio-balloon device now supports live migration.

virtio-mem support with vfio-user

The use of vfio-user userspaces devices can now be used in conjunction with virtio-mem based memory hotplug and unplug.

AArch64 for virtio-iommu

A paravirtualised IOMMU can now be used on the AArch64 platform.

Notable bug fixes

  • ACPI hotplugged memory is correctly restored after a live migration or snapshot/restore (#3165)
  • Multiple devices from the same IOMMU group can be passed through via VFIO (#3078 #3113)
  • Live migration with large blocks of memory was buggy due to an in issue in the underlying crate (#3157)

Contributors

Many thanks to everyone who has contributed to our release:

v18.0

This release has been tracked through the v18.0 project.

Experimental User Device (vfio-user) support

Experimental support for running PCI devices in userspace via vfio-user has been included. This allows the use of the SPDK NVMe vfio-user controller with Cloud Hypervisor. This is enabled by --user-device on the command line.

Migration support for vhost-user devices

Devices exposed into the VM via vhost-user can now be migrated using the live migration support. This requires support from the backend however the commonly used DPDK vhost-user backend does support this.

VHDX disk image support

Images using the VHDX disk image format can now be used with Cloud Hypervisor.

Device pass through on MSHV hypervisor

When running on the MSHV hypervisor it is possible to pass through devices from the host through to the guest (e.g with --device)

AArch64 for support virtio-mem

The reference Linux kernel we recommend for using with Cloud Hypervisor now supports virtio-mem on AArch64.

Live migration on MSHV hypervisor

Live migration is now supported when running on the MSHV hypervisor including efficient tracking of dirty pages.

AArch64 CPU topology support

The CPU topology (as configured through --cpu topology=) can now be configured on AArch64 platforms and is conveyed through either ACPI or device tree.

Power button support on AArch64

Use of the ACPI power button (e.g ch-remote --api-socket=<API socket> power-button) is now supported when running on AArch64.

Notable bug fixes

  • Using two PTY outputs e.g. --serial pty --console pty now works correctly (#3012)
  • TTY input is now always sent to the correct destination (#3005)
  • The boot is no longer blocked when using a unattached PTY on the serial console (#3004)
  • Live migration is now supported on AArch64 (#3049)
  • Ensure signal handlers are run on the correct thread (#3069)

Contributors

Many thanks to everyone who has contributed to our release:

v17.0

This release has been tracked through the v17.0 project.

ARM64 NUMA support using ACPI

The support for ACPI on ARM64 has been enhanced to include support for specifying a NUMA configuration using the existing control options.

Seccomp support for MSHV backend

The seccomp rules have now been extended to support running against the MSHV hypervisor backend.

Hotplug of macvtap devices

Hotplug of macvtap devices is now supported with the file descriptor for the network device if opened by the user and passed to the VMM. The ch-remote tool supports this functionality when adding a network device.

Improved SGX support

The SGX support has been updated to match the latest Linux kernel support and now supports SGX provisioning and associating EPC sections to NUMA nodes.

Inflight tracking for vhost-user devices

Support for handling inflight tracking of I/O requests has been added to the vhost-user devices allowing recovery after device reconnection.

Notable bug fixes

  • VFIO PCI BAR calculation code now correctly handles I/O BARs (#2821).
  • The VMM side of vhost-user devices no longer advertise the VIRTIO_F_RING_PACKED feature as they are not yet supported in the VMM (#2833).
  • On ARM64 VMs can be created with more than 16 vCPUs (#2763).

Contributors

Many thanks to everyone who has contributed to our release:

v16.0

This release has been tracked through the v16.0 project.

Improved live migration support

The live migration support inside Cloud Hypervisor has been improved with the addition of the tracking of dirty pages written by the VMM to complement the tracking of dirty pages made by the guest itself. Further the internal state of the VMM now is versioned which allows the safe migration of VMs from one version of the VMM to a newer one. However further testing is required so this should be done with care. See the live migration documentation for more details.

Improved vhost-user support

When using vhost-user to access devices implemented in different processes there is now support for reconnection of those devices in the case of a restart of the backend. In addition it is now possible to operate with the direction of the vhost-user-net connection reversed with the server in the VMM and the client in the backend. This is aligns with the default approach recommended by Open vSwitch.

ARM64 ACPI and UEFI support

Cloud Hypervisor now supports using ACPI and booting from a UEFI image on ARM64. This allows the use of stock OS images without direct kernel boot.

Notable bug fixes

  • Activating fewer virtio-net queues than advertised is now supported. This appeared when using OVMF with an MQ enabled device (#2578).
  • When using MQ with virtio devices Cloud Hypervisor now enforces a minimum vCPU count which ensures that the user will not see adverse guest performance (#2563).
  • The KVM clock is now correctly handled during live migration / snapshot & restore.

Removed functionality

The following formerly deprecated features have been removed:

  • 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.

Contributors

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

v15.0

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)

Deprecations

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.

Contributors

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

v0.14.1

Bug fix release branched off the v0.14.0 release. The following bugs were fixed in this release:

  • CPU hotplug on Windows failed due to misreported CPU state information and the lack of HyperV CPUID bit enabled (#2437, #2449, #2436)
  • A seccomp rule was missing that was triggered on CPU unplug (#2455)
  • A bounds check in VIRTIO queue validation was erroneously generating DescriptorChainTooShort errors in certain circumstances (#2450, #2424)

v0.14.0

This release has been tracked through the 0.14.0 project.

Highlights for cloud-hypervisor version 0.14.0 include:

Structured event monitoring

A new option was added to the VMM --event-monitor which reports structured events (JSON) over a file or file descriptor at key events in the lifecycle of the VM. The list of events is limited at the moment but will be further extended over subsequent releases. The events exposed form part of the Cloud Hypervisor API surface.

MSHV improvements

Basic support has been added for running Windows guests atop the MSHV hypervisor as an alternative to KVM and further improvements have been made to the MSHV support.

Improved aarch64 platform

The aarch64 platform has been enhanced with more devices exposed to the running VM including an enhanced serial UART.

Updated hotplug documentation

The documentation for the hotplug support has been updated to reflect the use of the ch-remote tool and to include details of virtio-mem based hotplug as well as documenting hotplug of paravirtualised and VFIO devices.

PTY control for serial and virtio-console

The --serial and --console parameters can now direct the console to a PTY allowing programmatic control of the console from another process through the PTY subsystem.

Block device rate limiting

The block device performance can now be constrained as part of the VM configuration allowing rate limiting. Full details of the controls are in the IO throttling documentation.

Deprecations

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.

Contributors

Many thanks to everyone who has contributed to our 0.14.0 release including some new faces.

Bo Chen chen.bo@intel.com Henry Wang Henry.Wang@arm.com Iggy Jackson iggy@theiggy.com Jiachen Zhang zhangjiachen.jaycee@bytedance.com Michael Zhao michael.zhao@arm.com Muminul Islam muislam@microsoft.com Penny Zheng Penny.Zheng@arm.com Rob Bradford robert.bradford@intel.com Sebastien Boeuf sebastien.boeuf@intel.com Vineeth Pillai viremana@linux.microsoft.com Wei Liu liuwe@microsoft.com William Douglas william.r.douglas@gmail.com Zide Chen zide.chen@intel.com

v0.13.0

This release has been tracked through the 0.13.0 project.

Highlights for cloud-hypervisor version 0.13.0 include:

Wider VFIO device support

It is now possible to use Cloud Hypervisor's VFIO support to passthrough PCI devices that do not support MSI or MSI-X and instead rely on INTx interrupts. Most notably this widens the support to most NVIDIA cards with the proprietary drivers.

Improved huge page support

Through the addition of hugepage_size on --memory it is now possible to specify the desired size of the huge pages used when allocating the guest memory. The user is required to ensure they have sufficient pages of the desired size in their pool.

MACvTAP support

It is now possible to provide file descriptors using the fd parameter to --net which point at TAP devices that have already been opened by the user. This aids integration with libvirt but also permits the use of MACvTAP support. This is documented in dedicated macvtap documentation.

VHD disk image support

It is now possible to use VHD (fixed) disk images as well as QCOWv2 and raw disk image with Cloud Hypervisor.

Improved Virtio device threading

Device threads are now derived from the main VMM thread which allows more restrictive seccomp filters to be applied to them. The threads also have a predictable name derived from the device id.

Clean shutdown support via synthetic power button

It is now possible to request that the guest VM shut itself down by triggering a synthetic ACPI power button press from the VMM. If the guest is listening for such an event (e.g. using systemd) then it will process the event and cleanly shut down. This functionality is exposed through the HTTP API and can be triggered via ch-remote --api-socket=<API socket> power-button.

Contributors

Many thanks to everyone who has contributed to our 0.13.0 release including some new faces.

v0.12.0

This release has been tracked through the 0.12.0 project.

Highlights for cloud-hypervisor version 0.12.0 include:

ARM64 enhancements

The use of --watchdog is now fully supported as is the ability to reboot the VM from within the guest when running Cloud Hypervisor on an ARM64 system.

Removal of vhost-user-net and vhost-user-block self spawning

In order to use vhost-user-net or vhost-user-block backends the user is now responsible for starting the backend and providing the socket for the VMM to use. This functionality was deprecated in the last release and how now been removed.

Migration of vhost-user-fs backend

The vhost-user-fs backend is no longer included in Cloud Hypervisor and it is instead hosted in it's own repository

Enhanced "info" API

The vm.info HTTP API endpoint has been extended to include the details of the devices used by the VM including any VFIO devices used.

Contributors

Many thanks to everyone who has contributed to our 0.12.0 release:

v0.11.0

This release has been tracked through the 0.11.0 project.

Highlights for cloud-hypervisor version 0.11.0 include:

io_uring support by default for virtio-block

Provided that the host OS supports it (Linux kernel 5.8+) then io_uring will be used for a significantly higher performance block device.

Windows Guest Support

This is the first release where we officially support Windows running as a guest. Full details of how to setup the image and run Cloud Hypervisor with a Windows guest can be found in the dedicated Windows documentation.

vhost-user "Self Spawning" Deprecation

Automatically spawning a vhost-user-net or vhost-user-block backend is now deprecated. Users of this functionality will receive a warning and should make adjustments. The functionality will be removed in the next release.

virtio-mmio Removal

Support for using the virtio-mmio transport, rather than using PCI, has been removed. This has been to simplify the code and significantly reduce the testing burden of the project.

Snapshot/Restore support for ARM64

When running on the ARM64 architecture snapshot and restore has now been implemented.

Improved Linux Boot Time

The time to boot the Linux kernel has been significantly improved by the identifying some areas of delays around PCI bus probing, IOAPIC programming and MPTABLE issues. Full details can be seen in #1728.

SIGTERM/SIGINT Interrupt Signal Handling

When the VMM process receives the SIGTERM or SIGINT signals then it will trigger the VMM process to cleanly deallocate resources before exiting. The guest VM will not be cleanly shutdown but the VMM process will clean up its resources.

Default Log Level Changed

The default logging level was changed to include warnings which should make it easier to see potential issues. New logging documentation was also added.

New --balloon Parameter Added

Control of the setup of virtio-balloon has been moved from --memory to its own dedicated parameter. This makes it easier to add more balloon specific controls without overloading --memory.

Experimental virtio-watchdog Support

Support for using a new virtio-watchdog has been added which can be used to have the VMM reboot the guest if the guest userspace fails to ping the watchdog. This is enabled with --watchdog and requires kernel support.

Notable Bug Fixes

  • MTRR bit was missing from CPUID advertised to guest
  • "Return" key could not be used under CMD.EXE under Windows SAC (#1170)
  • CPU identification string is now exposed to the guest
  • virtio-pmem withdiscard_writes=on no longer marks the guest memory as read only so avoids excessive VM exits (#1795)
  • PCI device hotplug after an unplug was fixed (#1802)
  • When using the ACPI method to resize the guest memory the full reserved size can be used (#1803)
  • Snapshot and restore followed by a second snapshot and restore now works correctly
  • Snapshot and restore of VMs with more than 2GiB in one region now work correctly

Contributors

Many thanks to everyone who has contributed to our 0.11.0 release including some new faces.

v0.10.0

This release has been tracked through the 0.10.0 project.

Highlights for cloud-hypervisor version 0.10.0 include:

virtio-block Support for Multiple Descriptors

Some virtio-block device drivers may generate requests with multiple descriptors and support has been added for those drivers.

Memory Zones

Support has been added for fine grained control of memory allocation for the guest. This includes controlling the backing of sections of guest memory, assigning to specific host NUMA nodes and assigning memory and vCPUs to specific memory nodes inside the guest. Full details of this can be found in the memory documentation.

Seccomp Sandbox Improvements

All the remaining threads and devices are now isolated within their own seccomp filters. This provides a layer of sandboxing and enhances the security model of cloud-hypervisor.

Preliminary KVM HyperV Emulation Control

A new option (kvm_hyperv) has been added to --cpus to provide an option to toggle on KVM's HyperV emulation support. This enables progress towards booting Windows without adding extra emulated devices.

Notable Bug Fixes

  • When using ch-remote to resize the VM parameter now accepts the standard sizes suffices (#1596)
  • cloud-hypervisor no longer panics when started with --memory hotplug_method=virtio-mem and no hotplug_size (#1564)
  • After a reboot memory can remove when using --memory hotplug_method=virtio-mem (#1593)
  • --version shows the version for released binaries (#1669)
  • Errors generated by worker threads for virtio devices are now printed out (#1551)

Contributors

Many thanks to everyone who has contributed to our 0.10.0 release including some new faces.

v0.9.0

This release has been tracked through the 0.9.0 project.

Highlights for cloud-hypervisor version 0.9.0 include:

io_uring Based Block Device Support

If the io_uring feature is enabled and the host kernel supports it then io_uring will be used for block devices. This results a very significant performance improvement.

Block and Network Device Statistics

Statistics for activity of the virtio network and block devices is now exposed through a new vm.counters HTTP API entry point. These take the form of simple counters which can be used to observe the activity of the VM.

HTTP API Responses

The HTTP API for adding devices now responds with the name that was assigned to the device as well the PCI BDF.

CPU Topology

A topology parameter has been added to --cpus which allows the configuration of the guest CPU topology allowing the user to specify the numbers of sockets, packages per socket, cores per package and threads per core.

Release Build Optimization

Our release build is now built with LTO (Link Time Optimization) which results in a ~20% reduction in the binary size.

Hypervisor Abstraction

A new abstraction has been introduced, in the form of a hypervisor crate so as to enable the support of additional hypervisors beyond KVM.

Snapshot/Restore Improvements

Multiple improvements have been made to the VM snapshot/restore support that was added in the last release. This includes persisting more vCPU state and in particular preserving the guest paravirtualized clock in order to avoid vCPU hangs inside the guest when running with multiple vCPUs.

Virtio Memory Ballooning Support

A virtio-balloon device has been added, controlled through the resize control, which allows the reclamation of host memory by resizing a memory balloon inside the guest.

Enhancements to ARM64 Support

The ARM64 support introduced in the last release has been further enhanced with support for using PCI for exposing devices into the guest as well as multiple bug fixes. It also now supports using an initramfs when booting.

Intel SGX Support

The guest can now use Intel SGX if the host supports it. Details can be found in the dedicated SGX documentation.

Seccomp Sandbox Improvements

The most frequently used virtio devices are now isolated with their own seccomp filters. It is also now possible to pass --seccomp=log which result in the logging of requests that would have otherwise been denied to further aid development.

Notable Bug Fixes

  • Our virtio-vsock implementation has been resynced with the implementation from Firecracker and includes multiple bug fixes.
  • CPU hotplug has been fixed so that it is now possible to add, remove, and re-add vCPUs (#1338)
  • A workaround is now in place for when KVM reports MSRs available MSRs that are in fact unreadable preventing snapshot/restore from working correctly (#1543).
  • virtio-mmio based devices are now more widely tested (#275).
  • Multiple issues have been fixed with virtio device configuration (#1217)
  • Console input was wrongly consumed by both virtio-console and the serial. (#1521)

Contributors

Many thanks to everyone who has contributed to our 0.9.0 release including some new faces.

v0.8.0

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.

Contributors

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

v0.7.0

This release has been tracked through the 0.7.0 project.

Highlights for cloud-hypervisor version 0.7.0 include:

Block, Network, Persistent Memory (PMEM), VirtioFS and Vsock hotplug

Further to our effort to support modifying a running guest we now support hotplug and unplug of the following virtio backed devices: block, network, pmem, virtio-fs and vsock. This functionality is available on the (default) PCI based transport and is exposed through the HTTP API. The ch-remote utility provides a CLI for adding or removing these device types after the VM has booted. User can use the id parameter on the devices to choose names for devices to ease their removal.

Alternative libc Support

Cloud Hypervisor can now be compiled with the musl C library and this release contains a static binary compiled using that toolchain.

Multithreaded Multi Queued vhost-user Backends

The vhost-user backends for network and block support that are shipped by Cloud Hypervisor have been enhanced to support multiple threads and queues to improve throughput. These backends are used automatically if vhost_user=true is passed when the devices are created.

Initial RamFS Support

By passing the --initramfs command line option the user can specify a file to be loaded into the guest memory to be used as the kernel initial filesystem. This is usually used to allow the loading of drivers needed to be able to access the real root filesystem but it can also be used standalone for a very minimal image.

Alternative Memory Hotplug: virtio-mem

As well as supporting ACPI based hotplug Cloud Hypervisor now supports using the virtio-mem hotplug alternative. This can be controlled by the hotplug_method parameter on the --memory command line option. It currently requires kernel patches to be able to support it.

Seccomp Sandboxing

Cloud Hypervisor now has support for restricting the system calls that the process can use via the seccomp security API. This on by default and is controlled by the --seccomp command line option.

Updated Distribution Support

With the release of Ubuntu 20.04 we have added that to the list of supported distributions and is part of our regular testing programme.

Command Line and API Changes

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

  • New id fields added for devices to allow them to be named to ease removal. If no name is specified the VMM chooses one.
  • Use --memory's shared and hugepages controls for determining backing memory instead of providing a path.
  • The --vsock parameter only takes one device as the Linux kernel only supports a single Vsock device. The REST API has removed the vector for this option and replaced it with a single optional field.
  • There is enhanced validation of the command line and API provided configurations to ensure that the provided options are compatible e.g. that shared memory is in use if any attempt is made to used a vhost-user backed device.
  • ch-remote has added add-disk, add-fs, add-net, add-pmem and add-vsock subcommands. For removal remove-device is used. The REST API has appropriate new HTTP endpoints too.
  • Specifying a size with --pmem is no longer required and instead the size will be obtained from the file. A discard_writes option has also been added to provide the equivalent of a read-only file.
  • The parameters to --block-backend have been changed to more closely align with those used by --disk.

Contributors

Many thanks to everyone who has contributed to our 0.7.0 release including some new faces.

v0.6.0

This release has been tracked through the 0.6.0 project.

Highlights for cloud-hypervisor version 0.6.0 include:

Directly Assigned Devices Hotplug

We continued our efforts around supporting dynamically changing the guest resources. After adding support for CPU and memory hotplug, Cloud Hypervisor now supports hot plugging and hot unplugging directly assigned (a.k.a. VFIO) devices into an already running guest. This closes the features gap for providing a complete Kata Containers workloads support with Cloud Hypervisor.

Shared Filesystem Improvements

We enhanced our shared filesystem support through many virtio-fs improvements. By adding support for DAX, parallel processing of multiple requests, FS_IO, LSEEK and the MMIO virtio transport layer to our vhost_user_fs daemon, we improved our filesystem sharing performance, but also made it more stable and compatible with other virtio-fs implementations.

Block and Networking IO Self Offloading

When choosing to offload the paravirtualized block and networking I/O to an external process (through the vhost-user protocol), Cloud Hypervisor now automatically spawns its default vhost-user-blk and vhost-user-net backends into their own, separate processes. This provides a seamless paravirtualized I/O user experience for those who want to run their guest I/O into separate executions contexts.

Command Line Interface

More and more Cloud Hypervisor services are exposed through the Rest API and thus only accessible via relatively cumbersome HTTP calls. In order to abstract those calls into a more user friendly tool, we created a Cloud Hypervisor Command Line Interface (CLI) called ch-remote. The ch-remote binary is created with each build and available e.g. at cloud-hypervisor/target/debug/ch-remote when doing a debug build.

Please check ch-remote --help for a complete description of all available commands.

PVH Boot

In addition to the traditional Linux boot protocol, Cloud Hypervisor now supports direct kernel booting through the PVH ABI.

Contributors

With the 0.6.0 release, we are welcoming a few new contributors. Many thanks to them and to everyone that contributed to this release:

v0.5.1

This is a bugfix release branched off v0.5.0. It contains the following fixes:

  • Update DiskConfig to contain missing disk control features (#790) - Samuel Ortiz and Sergio Lopez
  • Prevent memory overcommit via virtio-fs (#763) - Sebastien Boeuf
  • Fixed error reporting for resize command - Samuel Ortiz
  • Double reboot workaround (#783) - Rob Bradford
  • Various CI and development tooling fixes - Sebastien Boeuf, Samuel Ortiz, Rob Bradford

v0.5.0

This release has been tracked through the 0.5.0 project.

Highlights for cloud-hypervisor version 0.5.0 include:

Virtual Machine Dynamic Resizing

With 0.4.0 we added support for CPU hot plug, and 0.5.0 adds CPU hot unplug and memory hot plug as well. This allows to dynamically resize Cloud Hypervisor guests which is needed for e.g. Kubernetes related use cases. The memory hot plug implementation is based on the same framework as the CPU hot plug/unplug one, i.e. hardware-reduced ACPI notifications to the guest.

Next on our VM resizing roadmap is the PCI devices hotplug feature.

Multi-Queue, Multi-Threaded Paravirtualization

We enhanced our virtio networking and block support by having both devices use multiple I/O queues handled by multiple threads. This improves our default paravirtualized networking and block devices throughput.

New Interrupt Management Framework

We improved our interrupt management implementation by introducing an Interrupt Manager framework, based on the currently on-going rust-vmm vm-device crates discussions. This move made the code significantly cleaner, and allowed us to remove several KVM related dependencies from crates like the PCI and virtio ones.

Development Tools

In order to provide a better developer experience, we worked on improving our build, development and testing tools. Somehow similar to the excellent Firecracker's devtool, we now provide a dev_cli script.

With this new tool, our users and contributors will be able to build and test Cloud Hypervisor through a containerized environment.

Kata Containers Integration

We spent some significant time and efforts debugging and fixing our integration with the Kata Containers project. Cloud Hypervisor is now a fully supported Kata Containers hypervisor, and is integrated into the project's CI.

Contributors

Many thanks to everyone that contributed to the 0.5.0 release:

v0.4.0

This release has been tracked through the 0.4.0 project.

Highlights for cloud-hypervisor version 0.4.0 include:

Dynamic virtual CPUs addition

As a way to vertically scale Cloud-Hypervisor guests, we now support dynamically adding virtual CPUs to the guests, a mechanism also known as CPU hot plug. Through hardware-reduced ACPI notifications, Cloud Hypervisor can now add CPUs to an already running guest and the high level operations for that process are documented here

During the next release cycles we are planning to extend Cloud Hypervisor hot plug framework to other resources, namely PCI devices and memory.

Programmatic firmware tables generation

As part of the CPU hot plug feature enablement, and as a requirement for hot plugging other resources like devices or RAM, we added support for programmatically generating the needed ACPI tables. Through a dedicated acpi-tables crate, we now have a flexible and clean way of generating those tables based on the VMM device model and topology.

Filesystem and block devices vhost-user backends

Our objective of running all Cloud Hypervisor paravirtualized I/O to a vhost-user based framework is getting closer as we've added Rust based implementations for vhost-user-blk and virtiofs backends. Together with the vhost-user-net backend that came with the 0.3.0 release, this will form the default Cloud Hypervisor I/O architecture.

Guest pause and resume

As an initial requirement for enabling live migration, we added support for pausing and resuming any VMM components. As an intermediate step towards live migration, the upcoming guest snapshotting feature will be based on the pause and resume capabilities.

Userspace IOAPIC by default

As a way to simplify our device manager implementation, but also in order to stay away from privileged rings as often as possible, any device that relies on pin based interrupts will be using the userspace IOAPIC implementation by default.

PCI BAR reprogramming

In order to allow for a more flexible device model, and also support guests that would want to move PCI devices, we added support for PCI devices BAR reprogramming.

New cloud-hypervisor organization

As we wanted to be more flexible on how we manage the Cloud Hypervisor project, we decided to move it under a dedicated GitHub organization. Together with the cloud-hypervisor project, this new organization also now hosts our kernel and firmware repositories. We may also use it to host any rust-vmm that we'd need to temporarily fork. Thanks to GitHub's seamless repository redirections, the move is completely transparent to all Cloud Hypervisor contributors, users and followers.

Contributors

Many thanks to everyone that contributed to the 0.4.0 release:

v0.3.0

This release has been tracked through the 0.3.0 project.

Highlights for cloud-hypervisor version 0.3.0 include:

Block device offloading

We continue to work on offloading paravirtualized I/O to external processes, and we added support for vhost-user-blk backends. This enables cloud-hypervisor users to plug a vhost-user based block device like SPDK) into the VMM as their paravirtualized storage backend.

Network device backend

The previous release provided support for vhost-user-net backends. Now we also provide a TAP based vhost-user-net backend, implemented in Rust. Together with the vhost-user-net device implementation, this will eventually become the Cloud Hypervisor default paravirtualized networking architecture.

Virtual sockets

In order to more efficiently and securely communicate between host and guest, we added an hybrid implementation of the VSOCK socket address family over virtio. Credits go to the Firecracker project as our implementation is a copy of theirs.

HTTP based API

In anticipation of the need to support asynchronous operations to Cloud Hypervisor guests (e.g. resources hotplug and guest migration), we added a HTTP based API to the VMM. The API will be more extensively documented during the next release cycle.

Memory mapped virtio transport

In order to support potential PCI-free use cases, we added support for the virtio MMIO transport layer. This will allow us to support simple, minimal guest configurations that do not require a PCI bus emulation.

Paravirtualized IOMMU

As we want to improve our nested guests support, we added support for exposing a paravirtualized IOMMU device through virtio. This allows for a safer nested virtio and directly assigned devices support.

To add the IOMMU support, we had to make some CLI changes for Cloud Hypervisor users to be able to specify if devices had to be handled through this virtual IOMMU or not. In particular, the --disk option now expects disk paths to be prefixed with a path= string, and supports an optional iommu=[on|off] setting.

Ubuntu 19.10

With the latest hypervisor firmware, we can now support the latest Ubuntu 19.10 (Eoan Ermine) cloud images.

Large memory guests

After simplifying and changing our guest address space handling, we can now support guests with large amount of memory (more than 64GB).

v0.2.0

This release has been tracked through the 0.2.0 project.

Highlights for cloud-hypervisor version 0.2.0 include:

Network device offloading

As part of our general effort to offload paravirtualized I/O to external processes, we added support for vhost-user-net backends. This enables cloud-hypervisor users to plug a vhost-user based networking device (e.g. DPDK) into the VMM as their virtio network backend.

Minimal hardware-reduced ACPI

In order to properly implement and guest reset and shutdown, we implemented a minimal version of the hardware-reduced ACPI specification. Together with a tiny I/O port based ACPI device, this allows cloud-hypervisor guests to cleanly reboot and shutdown.

The ACPI implementation is a cloud-hypervisor build time option that is enabled by default.

Debug I/O port

Based on the Firecracker idea of using a dedicated I/O port to measure guest boot times, we added support for logging guest events through the 0x80 PC debug port. This allows, among other things, for granular guest boot time measurements. See our debug port documentation for more details.

Improved direct device assignment

We fixed a major performance issue with our initial VFIO implementation: When enabling VT-d through the KVM and VFIO APIs, our guest memory writes and reads were (in many cases) not cached. After correctly tagging the guest memory from cloud-hypervisor we're now able to reach the expected performance from directly assigned devices.

Improved shared filesystem

We added shared memory region with DAX support to our virtio-fs shared file system. This provides better shared filesystem IO performance with a smaller guest memory footprint.

Ubuntu bionic based CI

Thanks to our simple KVM firmware improvements, we are now able to boot Ubuntu bionic images. We added those to our CI pipeline.

v0.1.0

This release has been tracked through the 0.1.0 project.

Highlights for cloud-hypervisor version 0.1.0 include:

Shared filesystem

We added support for the virtio-fs shared file system, allowing for an efficient and reliable way of sharing a filesystem between the host and the cloud-hypervisor guest.

See our filesystem sharing documentation for more details on how to use virtio-fs with cloud-hypervisor.

Initial direct device assignment support

VFIO (Virtual Function I/O) is a kernel framework that exposes direct device access to userspace. cloud-hypervisor uses VFIO to directly assign host physical devices into its guest.

See our VFIO documentation for more detail on how to directly assign host devices to cloud-hypervisor guests.

Userspace IOAPIC

cloud-hypervisor supports a so-called split IRQ chip implementation by implementing support for the IOAPIC. By moving part of the IRQ chip implementation from kernel space to user space, the IRQ chip emulation does not always run in a fully privileged mode.

Virtual persistent memory

The virtio-pmem implementation emulates a virtual persistent memory device that cloud-hypervisor can e.g. boot from. Booting from a virtio-pmem device allows to bypass the guest page cache and improve the guest memory footprint.

Linux kernel bzImage

The cloud-hypervisor linux kernel loader now supports direct kernel boot from bzImage kernel images, which is usually the format that Linux distributions use to ship their kernels. For example, this allows for booting from the host distribution kernel image.

Console over virtio

cloud-hypervisor now exposes a virtio-console device to the guest. Although using this device as a guest console can potentially cut some early boot messages, it can reduce the guest boot time and provides a complete console implementation.

The virtio-console device is enabled by default for the guest console. Switching back to the legacy serial port is done by selecting --serial tty --console off from the command line.

Unit testing

We now run all unit tests from all our crates directly from our CI.

Integration tests parallelization

The CI cycle run time has been significantly reduced by refactoring our integration tests; allowing them to all be run in parallel.