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v42.0

This release has been tracked in our roadmap project as iteration v42.0. The following user visible changes have been made:

SVE/SVE2 Support on AArch64

The SVE and SVE2 feature bits are now propagated through to the guest on AArch64. (#6678, #6691)

Notable Bug Fixes

  • Reduce latency notification when rate limited (#6672)
  • Fix virtio-console resizing (#6704)
  • Fix resizing when console uses TTY (#6754)
  • Avoid deadlock in PCI BAR reprogramming that can occur when adding a new virtio device to a VM that has been restored (#6775)
  • Fix console resizing after VM restore (#6748)
  • Fix memory resize error due to incorrect bounds checks (#6736)

Sponsorships

During this release cycle a new VFIO CI worker has been provided by Crusoe Energy and a new ARM64 CI worker has been provided by Ubicloud.

Contributors

Many thanks to everyone who has contributed to our release:

v41.0

This release has been tracked in our roadmap project as iteration v41.0. The following user visible changes have been made:

Experimental "Pvmemcontrol" Support

VMM support has been added for this experimental functionality (requires currently out of tree Linux kernel patches) to allow guests to control its physical memory properties to allow optimisations and security features. (#6318, #6467)

Sandboxing With Landlock Support

Support for restricting the VMM process using the Linux kernel "Landlock" API has been added - this can be used to restrict the files (and the read/write permissions) that the VMM process can access. This adds another layer of security alongside the existing sycall filters (seccomp) - this can be enabled with --landlock and fully documentated. (#5170)

Notable Performance Improvements

  • Reduced heap allocations in virtio-net via the use of a cache of Iovec structures (#6636)
  • Notification suppression ("EVENT_IDX") support has been added to virtio-block giving a 60% improvement in single queue block throughput and IOPs performance (#6580)
  • Correct size used for status field in virtio-block state (#6586)

Notable Bug Fixes

  • Avoid panic on out-of-bounds PCI MSI-X access (#6657)
  • Fix undefined behaviour on AArch64 leading to wrong optimisation on KVM API access (#6647)
  • Rust v1.80.0 added use of fcntl syscall on debug assertions so this is now included in the virtio-device seccomp filters for tests that use this (#6648)
  • Short reads are now handled correctly in the virtio-vsock device (#6621)
  • Fix undefined behaviour on TTY ioctl leading to wrong optimisation (#6568)

Contributors

Many thanks to everyone who has contributed to our release:

v40.0

This release has been tracked in our roadmap project as iteration v40.0. The following user visible changes have been made:

Support for Restoring File Descriptor Backed Network Devices

It is now possible to pass file descriptors over the HTTP API (and using ch-remote) when restoring to update the file descriptors for network devices. This enables snapshot & restore functionality for guests using macvtap or other file descriptor backed network devices. (#6286)

Notable Bug Fixes

  • Default values have been removed from required fields in the OpenAPI metadata (#6495)
  • The help syntax of ch-remote remove-device has been improved (#6456)
  • A double close of file descriptors has been fixed when using --serial (#6486)
  • To prevent loops a limit on the nesting level for QCOW2 backing files has been introduced (#6482)
  • Boot time performance has been improved with multiple cores by avoiding cpuid instructions and by seeding the in kernel file descriptor table (#6498, #6478)
  • L1 cache details are more likely to be propagated into the guest (#6523)
  • The default topology for guests now uses multiple cores rather than sockets (#6504)

Contributors

Many thanks to everyone who has contributed to our release:

v39.0

This release has been tracked in our roadmap project as iteration v39.0. The following user visible changes have been made:

Variable Sizing of PCI Apertures for Segments

It is now possible to use --pci-segment to adjust the aperture size that devices 32-bit and 64-bit PCI device BARs will be allocated from. Previously the address space was equally distributed across all the segments which may leave insufficient space for devices that require a large 32-bit space. With this change the weighting per segment can be adjusted. (#6387)

Direct Booting with bzImages

Support for directly booting Linux from bzImages has been added.(#6200)

Support for NVIDIA GPUDirect P2P Support

The x_nv_gpudirect_clique option was added to --device to allow the configuration of device P2P support with NVIDIA GPUs. (#6235)

Guest NMI Injection Support

A new API endpoint and ch-remote option added for injecting an NMI into the guest. (#6047)

Notable Bug Fixes

  • Workaround for kernel bug affecting guest IRQ masking on AMD (#6353)
  • Correctly cleanup sigwinch_listener process (#6208)
  • Graceful shutdown of HTTP API thread (#6248, #6247)
  • Fix queue_affinity option in OpenAPI metadata (#6268)
  • Fix documentation to indicate only stream mode is supported by virtio-vsock (#6306)
  • Fix virtio-fs tag validation (#6358, #6359)
  • Add missing pvpanic device to OpenAPI metadata (#6372)
  • Fixes for nested virtualization with VFIO devices (#6110, #6298, #6297, #6319)
  • Fix for backing file for virtio-mem regions with snapshot/restore (#6337, #6338)
  • Explicitly mark FDs used for network devices as invalid across snapshot/restore (#6332, #6286)
  • Improve event-monitor events around reboot (#6277, #6274)
  • Fix potential deadlock around paused devices during live migration (#6293)
  • Fix panic when running ch-remote with no subcommand (#6230)
  • Fix hotplug of virtio devices after snapshot/restore and live migration (#6326, #6265)

Contributors

Many thanks to everyone who has contributed to our release:

v38.0

This release has been tracked in our roadmap project as iteration v38.0. The following user visible changes have been made:

Group Rate Limiter on Block Devices

Users now can throttle a group of block devices with the new --rate-limiter-group option. Details can be found from the I/O Throttling documentation

CPU Pinning Support for Block Device Worker Thread

Users now have the option to pin virt-queue threads for block devices to specific host cpus.

Optimized Boot Time with Parallel Memory Prefault

The boot time with prefault option enabled is optimized via parallel memory prefault.

New 'debug-console' Device

A 'debug-console' device is added to provide a user-configurable debug port for logging guest information. Details can be found from the Debug IO Ports documentation.

Improved VFIO Device Support

All non-emulated MMIO regions of VFIO devices are now mapped to the VFIO container, allowing PCIe P2P between all VFIO devices on the same VM. This is required for a wide variety of multi-GPU workloads involving GPUDirect P2P (DMA between two GPUs), GPUDirect RDMA (DMA between a GPU and an IB device).

Extended CPU Affinity Support

Users now can set the vcpu affinity to a host CPU with index larger than 255.

Notable Bug Fixes

  • Enable HTT flag to avoid crashing cpu topology enumeration software such as hwloc in the guest (#6146)
  • Fix several security advisories from dependencies (#6134, #6141)
  • Handle non-power-of-two CPU topology properly (#6062)
  • Various bug fixes around virtio-vsock(#6080, #6091, #6095)
  • Enable nested virtualization on AMD if supported (#6106)
  • Align VFIO devices PCI BARs naturally (#6196)

Contributors

Many thanks to everyone who has contributed to our release:

v37.0

This release has been tracked in our roadmap project as iteration v37.0. The following user visible changes have been made:

Long Term Support (LTS) Release

This release is a LTS release. Point releases for bug fixes will be made for the next 18 months; live migration and live upgrade will be supported between the point releases of the LTS.

Multiple PCI segments Support for 32-bit VFIO devices

Now VFIO devices with 32-bit memory BARs can be attached to non-zero PCI segments on the guest, allowing users to have more 32-bit devices and assign such devices to appropriate NUMA nodes for better performance.

Configurable Named TAP Devices

Named TAP devices now accepts IP configuration from users, such as IP and MAC address, as long as the named TAP device is created by Cloud Hypervisor (e.g. not existing TAP devices).

TTY Output from Both Serial Device and Virtio Console

Now legacy serial device and virtio console can be set as TTY mode as the same time. This allows users to capture early boot logs with the legacy serial device without losing performance benefits of using virtio-console, when appropriate kernel configuration is used (such as using kernel command-line console=hvc0 earlyprintk=ttyS0 on x86).

Faster VM Restoration from Snapshots

The speed of VM restoration from snapshots is improved with a better implementation of deserializing JSON files.

Notable Bug Fixes

  • Fix aio backend behavior for block devices when writeback cache disabled (#5930)
  • Fix PvPanic device PCI BAR alignment (#5956)
  • Bug fix to OpenAPI specification file (#5967)
  • Error out early for live migration when TDX is enabled (#6025)

Contributors

Many thanks to everyone who has contributed to our release:

v36.0

This release has been tracked in our roadmap project as iteration v36.0. The following user visible changes have been made:

Command Line Changes

We switched back to use the clap crate to create our command line, since the argh crate is barely maintained. There were several syntax changes:

  • All --option value commands now are --option=value.
  • The --disk DISK1 --disk DISK2 command now is --disk DISK1 DISK2.
  • The -v -v -vcommand now is -vvv.

Note: the released binary size increased around 0.3M due to this change.

Enabled Features Reported via API Endpoint and CLI

Now the enabled (Cargo) features of the running Cloud Hypervisor instance can be queried via API endpoint (/vmm.ping) and CLI (--version -v).

NUMA Support for PCI segments

The --numa command is augmented with a new option pci_segment=, so that users can define the relationship between PCI segments and NUMA nodes. Examples can be found from the memory documentation

CPU Topology Support on AMD Platforms

Now the CPU topology on x86_64 platforms supports multiple vendors.

Unix Socket Backend for Serial Port

The --serial command is augmented with a new option socket=, allowing users to access the serial port using a Unix socket.

AIO Backend for Block Devices

An AIO backend is added for virtio-block devices to improve block device performance when the io_uring feature is not supported by the host Operating System.

Documentation Improvements

  • New documentation for collecting coverage data
  • Various typo fixes

Notable Bug Fixes

  • Fix a deadlock when TDX is enabled (#5845)
  • Only advertise AMX feature bits to guest when the AMX cpu feature is enabled (#5834)
  • Correct default value for vCPU topology on AArch64 (#5893)

Contributors

Many thanks to everyone who has contributed to our release:

v35.0

This release has been tracked in our roadmap project as iteration v35.0. The following user visible changes have been made:

virtio-vsock Support for Linux Guest Kernel v6.3+

Since kernel v6.3, a vsock packet can be included in a single descriptor, instead of being split over two descriptors. Our virtio-vsock implementation now support both situations.

User Specified Serial Number for virtio-block

A new option serial is added to the --block command that allows users to specify a serial number for block devices which will be guest visible.

vCPU TSC Frequency Included in Migration State

This ensures migration works correctly between hosts that have different TSC frequencies if the guest is running with TSC as the source of timekeeping.

Notable Bug Fixes

  • Disallow concurrent CPU resizing (#5668)
  • Handle APIC EOI message for MSHV (#5681)
  • Use wrapping add for memory offset from instruction emulator (#5719)
  • Add global spell check via the 'typos' GitHub action (#5720)
  • Ensure probing reads are block size aligned (#5727)
  • Multiple bug fixes around the latency counter for block devices (#5712, #5750, #5762, #5763)
  • Replace unsound static mut with once_cell (#5772)

Contributors

Many thanks to everyone who has contributed to our release:

v34.0

This release has been tracked in our roadmap project as iteration v34.0. The following user visible changes have been made:

Paravirtualised Panic Device Support

A new device has been added that can communicate when the guest kernel has panicked and share those details with the VMM. This is controlled with a new --pvpanic command line option and JSON API change equivalent. (#5526)

Improvements to VM Core Dump

Requesting to dump the guest memory as core dump will now transparently pause the VM if required; returning to the original state after. (#5604)

QCOW2 Support for Backing Files

The support for QCOW2 files has been enhanced to include support for using backing files. (#5573)

Minimum Host Kernel Bump

The minimum supported host kernel is now 5.13 in order to incorporate a bug fix for KVM_FEATURE_ASYNC_PF_INT functionality. (#5626)

Notable Bug Fixes

  • The x86 emulator is only compiled in if MSHV is compiled in (the kernel carries out this job with KVM) (#5561).
  • A regression has been fixed in VFIO support for devices that use MSI rather than MSI-X (#5658).
  • When triggering a VM shutdown or reset via I/O the vCPU thread will be blocked until that asynchronous event has been received (#5645).
  • Pausing a VM is now a synchronous action with the request only completing when all vCPUs are paused (#5611).
  • Event monitor support now correctly supports concurrent access (#5633).
  • Bug fixes for the QCOW2 file support (#5573).

Contributors

Many thanks to everyone who has contributed to our release:

v33.0

This release has been tracked in our roadmap project as iteration v33.0. The following user visible changes have been made:

D-Bus based API

A D-Bus based API has been added as an alternative to the existing REST API. This feature is gated by the dbus_api feature. Details can be found in the API documentation.

Expose Host CPU Cache Details for AArch64

Now the CPU cache information on the host is properly exposed to the guest on AArch64.

Notable Bug Fixes

  • Report errors explicitly to users when VM failed to boot (#5453)
  • Fix VFIO on platforms with non-4k page size (#5450, #5469)
  • Fix TDX initialization (#5454)
  • Ensure all guest memory regions are page-size aligned (#5496)
  • Fix seccomp filter lists related to virtio-console, serial and pty (#5506, #5524)
  • Populate APIC ID properly (#5512)
  • Ignore and warn TAP FDs in more situations (#5522)

Contributors

Many thanks to everyone who has contributed to our release:

v32.0

This release has been tracked in our roadmap project as iteration v32.0. The following user visible changes have been made:

Increased PCI Segment Limit

The maximum number of PCI segments that can be used is now 96 (up from 16).

API Changes

  • The VmmPingResponse now includes the PID as well as the build details. (#5348)

Notable Bug Fixes

  • Ignore and warn TAP FDs sent via the HTTP request body (#5350)
  • Properly preserve and close valid FDs for TAP devices (#5373)
  • Only use KVM_ARM_VCPU_PMU_V3 if available (#5360)
  • Only touch the tty flags if it's being used (#5343)
  • Fix seccomp filter lists for vhost-user devices (#5361)
  • The number of vCPUs is capped at the hypervisor maximum (#5357)
  • Fixes for TTY reset (#5414)
  • CPU topology fixes on MSHV (#5325)
  • Seccomp fixes for older distributions (#5397)

Contributors

Many thanks to everyone who has contributed to our release:

v31.1

This is a bug fix release. The following issues have been addressed:

  • Ignore and warn TAP FDs sent via the HTTP request body (#5350)
  • Properly preserve and close valid FDs for TAP devices (#5373)
  • Only use KVM_ARM_VCPU_PMU_V3 if available (#5360)
  • Only touch the tty flags if it's being used (#5343)
  • Fix seccomp filter lists for vhost-user devices (#5361)

v31.0

This release has been tracked in our roadmap project as iteration v31.0. The following user visible changes have been made:

Update to Latest acpi_tables

Adapted to the latest acpi_tables. There has been significant API changes in the crate.

Update Reference Kernel to 6.2

Updated the recommended guest kernel version from 6.1.6 to 6.2.

Improvements on Console SIGWINCH Handler

A separate thread had been created to capture the SIGWINCH signal and resize the guest console. Now the thread is skipped if the console is not resizable.

Two completely different code paths existed for handling console resizing, one for tty and the other for pty. That makes the understanding of the console handling code unnecessarily complicated. Now the code paths are unified. Both tty and pty are supported in single SIGWINCH handler. And the new handler can works with kernel versions earlier than v5.5.

Remove Directory Support from MemoryZoneConfig::file

Setting a directory to MemoryZoneConfig::file is no longer supported.

Before this change, user can set a directory to file of the --memory-zone option. In that case, a temporary file will be created as the backing file for the mmap(2) operation. This functionality has been unnecessary since we had the native support for hugepages and allocating anonymous shared memory.

Documentation Improvements

  • Various improvements in API document
  • Improvements in Doc comments
  • Updated Slack channel information in README

Notable Bug Fixes

  • Fixed the offset setting while removing the entire mapping of vhost-user FS client.
  • Fixed the ShutdownVmm and Shutdown commands to call the correct API endpoint.

Contributors

Many thanks to everyone who has contributed to our release:

v30.0

This release has been tracked in our roadmap project as iteration v30.0. The following user visible changes have been made:

Command Line Changes for Reduced Binary Size

The clap crate was replaced by the argh crate to create our command line, which reduced our release binary size from 3.6MB to 3.3MB. There were several syntax changes:

  • All --option=value commands now are --option value.
  • The --disk DISK1 DISK2 command now is --disk DISK1 --disk DISK2.
  • The -vvv command now is -v -v -v

Basic vfio-user Server Support

Our vfio-user crate is extended to provide basic server side support with an example of gpio vfio-user device. This crate now is moved to its own repository under the rust-vmm organization.

Heap Profiling Support

A new building target is added for profiling purposes with examples of heap profiling using dhat gated by the dhat-heap feature.

Documentation Improvements

The documentation on Intel TDX is expanded with details of the building and using TD-Shim, references to TDX Tools, and version information of guest/host kernel/TDVF/TDShim being tested. Also, a new 'heap profiling' documentation is added with improvements on the existing 'profiling' documentation.

Notable Bug Fixes

  • Close FDs for TAP devices that are provided to VM (#5199, #5206)
  • Set vcpu thread status properly and signal exit_evt upon thread exit (#5211)
  • Populate CPUID leaf 0x4000_0010 (TSC frequency) (#5178, #5179)
  • Inform the TPM guest driver upon failed TPM requests on the host (#5151)
  • Bug fix to OpenAPI specification file (#5186)

Contributors

Many thanks to everyone who has contributed to our release:

v28.2

This is a bug fix release. The following issues have been addressed:

  • Fix QCOW2 refcount table size (#5034)
  • Fix unpause support on MSHV in dual binary (#5037)
  • Threads inside virtio devices are now shutdown on reboot (#5095)

v29.0

This release has been tracked in our roadmap project as iteration v29.0. The following user visible changes have been made:

Release Binary Supports Both MSHV and KVM

On x86-64 the binary included in releases supports both the KVM and MSHV hypervisor with runtime detection to identify the correct hypervisor to use.

Snapshot/Restore and Live Migration Improvements

Improvements have been made to the data structures used for both live migration and snapshot/restore. Unfortunately this has broken compatibility with older versions (support for migrating between major versions is not yet officially supported but has worked for some versions.)

Heap Allocation Improvements

Improvements have been made to the volume of heap allocations when running with virtio-block devices along with a reduction in the peak heap size.

ch-remote Improvements

Support for "pinging" the VMM and shutting the VMM down have been added to ch-remote.

AArch64 Documentation Integration

The documentation for AArch64 support has been integrated into the main README.

virtio-block Counters Enhancement

The counters for the virtio-block device has extended to include min/mean/max latency counters.

TCP Offload Control

The virtio-net device has gained support for controlling the enabling of checksum and offloading. This allows the device to be used in environments where the hardware lacks support for the offloading.

Notable Bug Fixes

  • Update dependencies including a version of linux-loader that addresses an infinite loop issue (details)
  • Fix bugs related to virtio-net including an integer overflow issue (#4924, #4949)
  • Use host cpuid information for L2 cache for older KVM on x86 (#4920)
  • Memory mapped into the guest is now marked as non-dumpable which prevents large core files (#5016)
  • Fix QCOW2 refcount table size (#5034)
  • Fix unpause support on MSHV in dual binary (#5037)
  • Threads inside virtio devices are now shutdown on reboot (#5095)

Removals

No functionality has been removed in this release.

Deprecations

  • Support for specifying a directory with MemoryZoneConfig::file or MemoryConfig::file has been deprecated. This was originally used for supporting huge pages or shared memory backing which is now natively supported (#5085)

Contributors

Many thanks to everyone who has contributed to our release:

v28.1

This is a bug fix release. The following issues have been addressed:

  • Update dependencies including a version of linux-loader that addresses an infinite loop issue (details)
  • Fix bugs related to virtio-net including an integer overflow issue (#4924, #4949)
  • Use host cpuid information for L2 cache for older KVM on x86 (#4920)
  • Improve README and documentation

v28.0

This release has been tracked in our new roadmap project as iteration v28.0.

Community Engagement (Reminder)

Just a reminder that we have a new mailing list to support broader community discussions. Please consider subscribing. We plan to use this to announce a regular meeting for those interested in talking about Cloud Hypervisor development.

Long Term Support (LTS) Release

This is the first version of Cloud Hypervisor to be released under the LTS release process. Point releases for bug fixes will be made for the next 18 months; live migration and live upgrade will be supported between the point releases of the LTS.

Virtualised TPM Support

Support for adding an emulated CRB TPM has been added. This has its own TPM documentation.

Transparent Huge Page Support

By default, but controllable through --memory thp=off if it possible to back the guest memory with Transparent Huge Pages (no file backing/shared=off) then this will be used resulting in improved boot performance.

README Quick Start Improved

The README has been refreshed with the quick start guide updated to reflect the different firmware options and to recommend the use of pre-built binaries.

Notable Bug Fixes

  • Inappropriate Copy-on-Write of pinned pages (e.g. VFIO) leading to higher memory consumption (#4835)
  • Multiple virtio device bug fixes found through fuzzing (#4859, #4799)
  • Large QCOW files (> 4TiB) are now supported (#4767)
  • Support for > 31 vCPUS on aarch64 (#4863)
  • Multiple fixes to OpenAPI specification file (#4720, #4811)
  • Programming of the MSI-X table has been optimised leading to faster boot on newer Linux kernels (#4744)
  • Error on reboot from race to close TAP devices (#4871)
  • Non-spec compliant virtio-block read-only support (#4888)

Removals

The following functionality has been removed:

  • Support for non-PVH firmware booting has been removed (#4511)
  • I/O ports used for older versions of firmware have been removed (#3926)
  • Deprecated API options for kernel/cmdline/initramfs have been removed (#4737)

Contributors

Many thanks to everyone who has contributed to our release:

v27.0

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)

Deprecations

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.

Contributors

Many thanks to everyone who has contributed to our release:

v26.0

This release has been tracked through the v26.0 project.

SMBIOS Improvements via --platform

--platform and the appropriate API structure has gained support for supplying OEM strings (primarily used to communicate metadata to systemd in the guest) (#4319, #4446) and support for specifying the UUID (#4389.)

Unified Binary MSHV and KVM Support

Support for both the MSHV and KVM hypervisors can be compiled into the same binary with the detection of the hypervisor to use made at runtime.

Notable Bug Fixes

  • The prefetchable flag is preserved on BARs for VFIO devices (#4353, #4454)
  • PCI Express capabilities for functionality we do not support are now filtered out (#4456)
  • GDB breakpoint support is more reliable (#4354, #4363)
  • SIGINT and SIGTERM signals are now handled before the VM has booted (#4269, #4293)
  • Multiple API event loop handling bug fixes (#4309, #4362)
  • Incorrect assumptions in virtio queue numbering were addressed, allowing thevirtio-fs driver in OVMF to be used (#4341, #4314)
  • VHDX file format header fix (#4291)
  • The same VFIO device cannot be added twice (#4453, #4463)
  • SMBIOS tables were being incorrectly generated (#4442)

Deprecations

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

  • The top-level kernel and initramfs members on the VmConfig have been moved inside a PayloadConfig as the payload member. The OpenAPI document has been updated to reflect the change and the old API members continue to function and are mapped to the new version. The expectation is that these old versions will be removed in the v28.0 release.

Removals

The following functionality has been removed:

  • The unused poll_queue parameter has been removed from --disk and equivalent. This was residual from the removal of the vhost-user-block spawning feature (#4402.)

Contributors

Many thanks to everyone who has contributed to our release:

v25.0

This release has been tracked through the v25.0 project.

ch-remote Improvements

The ch-remote command has gained support for creating the VM from a JSON config and support for booting and deleting the VM from the VMM.

VM "Coredump" Support

Under the guest_debug feature flag it is now possible to extract the memory of the guest for use in debugging with e.g. the crash utility. (#4012)

Notable Bug Fixes

  • Always restore console mode on exit (#4249, #4248)
  • Restore vCPUs in numerical order which fixes aarch64 snapshot/restore (#4244)
  • Don't try and configure IFF_RUNNING on TAP devices (#4279)
  • Propagate configured queue size through to vhost-user backend (#4286)
  • Always Program vCPU CPUID before running the vCPU to fix running on Linux 5.16 (#4156)
  • Enable ACPI MADT "Online Capable" flag for hotpluggable vCPUs to fix newer Linux guest

Removals

The following functionality has been removed:

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

Contributors

Many thanks to everyone who has contributed to our release:

v24.0

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)

Deprecations

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.

Contributors

Many thanks to everyone who has contributed to our release:

v23.1

This is a bug fix release. The following issues have been addressed:

  • Add some missing seccomp rules
  • Remove virtio-fs filesystem entries from config on removal
  • Do not delete API socket on API server start (#4026)
  • Reject virtio-mem resize if the guest doesn't activate the device
  • Fix OpenAPI naming of I/O throttling knobs

v23.0

This release has been tracked through the v23.0 project.

vDPA Support

A vDPA device has a datapath that complies with the virtio specification but with a vendor specific control path. The addition of --vdpa and the REST API equivalent allows the use of these devices with Cloud Hypervisor.

Updated OS Support list

The list of officially supported and tested OS versions has been updated to include Ubuntu "jammy" 22.04 and EOLed versions removed.

AArch64 Memory Map Improvements

The memory map when running on AArch64 has been improved for the handling of the UEFI region which means that the booted guest OS now has full access to its allocated RAM. (#3938)

AMX Support

Under a compile time gate of amx it is possible compile in support for the AMX instruction set extension for guest use. This also requires runtime enabling with --cpu features=amx.

Notable Bug Fixes

  • Generate error when incorrect HTTP method used for some API endpoints (#3887)
  • CMOS based reset is now available to support rebooting on "jammy" (#3914)
  • ACPI tables are not produced for memory hotplug when running with virtio-mem (#3883)
  • virtio-iommu backed PCI segments are now comprehensively placed behind the vIOMMU (#3870)
  • Seccomp rules have been extended for virtio-fs to support direct access (#3848)

Deprecations

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)

Contributors

Many thanks to everyone who has contributed to our release:

v22.1

This is a bug fix release. The following issues have been addressed:

  • VFIO ioctl reordering to fix MSI on AMD platforms (#3827)
  • Fix virtio-net control queue (#3829)

v22.0

This release has been tracked through the v22.0 project.

GDB Debug Stub Support

Cloud Hypervisor can now be used as debug target with GDB. This is controlled by the gdb compile time feature and details of how to use it can be found in the gdb documentation.

virtio-iommu Backed Segments

In order to facilitate hotplug devices that require being behind an IOMMU (e.g. QAT) there is a new option --platform iommu_segments=<list_of_segments> that will place all the specified segments behind the IOMMU.

Before Boot Configuration Changes

It is now possible to change the VM configuration (e.g. add or remove devices, resize) before the VM is booted.

virtio-balloon Free Page Reporting

If --balloon free_page_reporting=on is used then the guest can report pages that is it not using to the VMM. The VMM will then notify the host OS that those pages are no longer in use and can be freed. This can result in improved memory density.

Support for Direct Kernel Booting with TDX

Through the use of TD-Shim lightweight firmware it is now possible to directly boot into the kernel with TDX. The TDX documentation has been updated for this usage.

PMU Support for AArch64

A PMU is now available on AArch64 for guest performance profiling. This will be exposed automatically if available from the host.

Documentation Under CC-BY-4.0 License

The documentation is now licensed under the "Creative Commons Attribution 4.0 International" license which is aligned with the project charter under the Linux Foundation.

Deprecation of "Classic" virtiofsd

The use of the Rust based virtiofsd is now recommended and we are no longer testing against the C based "classic" version.

Notable Bug Fixes

  • Can now be used on kernels without AF_INET support (#3785)
  • virtio-balloon size is now validated against guest RAM size (#3689)
  • Ensure that I/O related KVM VM Exits are correctly handled (#3677)
  • Multiple TAP file descriptors can be used for virtio-net device hotplug (#3607)
  • Minor API improvements and fixes (#3756, #3766, #3647, #3578)
  • Fix sporadic seccomp violation from glibc memory freeing (#3610, #3609)
  • Fix Windows 11 on AArch64 due to wider MSI-X register accesses (#3714, #3720)
  • Ensure vhost-user features are correct across migration (#3737)
  • Improved vCPU topology on AArch64 (#3735, #3733)

Contributors

Many thanks to everyone who has contributed to our release:

v21.0

This release has been tracked through the v21.0 project.

Efficient Local Live Migration (for Live Upgrade)

In order to support fast live upgrade of the VMM an optimised path has been added in which the memory for the VM is not compared from source to destination. This is activated by passing --local to the ch-remote send-migration command. This means that the live upgrade can complete in the order of 50ms vs 3s. (#3566)

Recommended Kernel is Now 5.15

Due to an issue in the virtio-net code in 5.14 the recommended Linux kernel is now 5.15. (#3530)

Notable Bug fixes

  • Multiple fixes were made to the OpenAPI YAML file to match the implementation (#3555,#3562)
  • Avoid live migration deadlock when triggered during the kernel boot (#3585)
  • Support live migration within firmware (#3586)
  • Validate the virtio-net descriptor chain (#3548)
  • direct=on (O_DIRECT) can now be used with a guest that makes unaligned accesses (e.g. firmware) (#3587)

Contributors

Many thanks to everyone who has contributed to our release:

v20.2

This is a bug fix release. The following issues have been addressed:

  • Don't error out when setting up the SIGWINCH handler (for console resize) when this fails due to older kernel (#3456)
  • Seccomp rules were refined to remove syscalls that are now unused
  • Fix reboot on older host kernels when SIGWINCH handler was not initialised (#3496)
  • Fix virtio-vsock blocking issue (#3497)

v20.1

This is a bug fix release. The following issues have been addressed:

  • Networking performance regression with virtio-net (#3450)
  • Limit file descriptors sent in vfio-user support (#3401)
  • Fully advertise PCI MMIO config regions in ACPI tables (#3432)
  • Set the TSS and KVM identity maps so they don't overlap with firmware RAM
  • Correctly update the DeviceTree on restore

v20.0

This release has been tracked through the v20.0 project.

Multiple PCI segments support

Cloud Hypervisor is no longer limited to 31 PCI devices. For both x86_64 and aarch64 architectures, it is now possible to create up to 16 PCI segments, increasing the total amount of supported PCI devices to 496.

CPU pinning

For each vCPU, the user can define a limited set of host CPUs on which it is allowed to run. This can be useful when assigning a 1:1 mapping between host and guest resources, or when running a VM on a specific NUMA node.

Improved VFIO support

Based on VFIO region capabilities, all regions can be memory mapped, limiting the amount of triggered VM exits, and therefore increasing the performance of the passthrough device.

Safer code

Several sections containing unsafe Rust code have been replaced with safe alternatives, and multiple comments have been added to clarify why the remaining unsafe sections are safe to use.

Extended documentation

The documentation related to VFIO has been updated while some new documents have been introduced to cover the usage of --cpus parameter as well as how to run Cloud Hypervisor on Intel TDX.

Notable bug fixes

  • Naturally align PCI BARs on relocation (#3244)
  • Fix panic in SIGWINCH listener thread when no seccomp filter set (#3338)
  • Use the tty raw mode implementation from libc (#3344)
  • Fix the emulation of register D for CMOS/RTC device (#3393)

Contributors

Many thanks to everyone who has contributed to our release:

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.

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 its 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.