## v6.4.0 unreleased

# New features

# Improvements

# Bug fixes

## v6.3.0 2020-05-05

# New features

qemu: support disabling hotplug/unplug of PCIe devices
libvirt can now set the "hotplug" option for pcie-root-ports and pcie-switch-downstream-ports, which can be used to disable hotplug/unplug of devices from these ports (default behavior is for these controllers to accept all hotplug/unplug attempts, but this is often undesireable).
vbox: added support for version 6.0 and 6.1 APIs
libvirt can now support use of the VirtualBox 6.0 and 6.1 APIs. This is compile tested only, so we are looking for feedback from users on how well it works in practice.
xen: Add support for 'e820_host' hypervisor feature
e820_host
is a Xen-specific option only available for PV guests. When enabled it provides the guest with a virtual e820 memory map based on the host one. It must be enabled to allow hotplugging PCI devices to PV guests, particularly when memory ballooning is enabled.
xen: Add support for 'passthrough' hypervisor feature
passthrough
is a Xen-specific option new to Xen 4.13 that enables PCI passthrough for guests. It must be enabled to allow hotplugging PCI devices.
qemu: support async IO mode 'io_uring'
Linux 5.1 introduces a fast and efficient async IO interface io_uring, then qemu implements that in version 5.0. It could be used in file, host device and host cdrom backend by `io='io_uring'` of disk XML.
Lease time option included for network DHCP settings
Users can now configure expiry time for leases for networks where libvirt manages DHCP. The time can be specified for whole range and/or fine tuned per individual host.
qemu: Implement pSeries Spectre mitigation features
Users can now setup the following capabilities of pSeries guests: CFPC (Cache Flush on Privilege Change), SBBC (Speculation Barrier Bounds Checking) and IBS (Indirect Branch Speculation).

# Improvements

qemu: Allow checkpoint redefine for offline VMs
Skip the liveness and capability checks when redefining checkpoints as we don't need QEMU interactions to update the metadata.
daemons: Improve timeout handling
Daemons now support `--timeout 0` which suppresses daemon killing after given time of inactivity.
qemu: Add support for 'multidevs' option
This option prevents misbehaviours on guest if a QEMU 9pfs export contains multiple devices, due to the potential file ID collisions this otherwise may cause.

# Bug fixes

qemu: Various embed driver fixes
When using shared resources from embed driver (e.g. hugepages, machined, etc.) libvirt now generates an unique handler that is not conflicting with other embed drivers or system or session daemons.
cpu: Distinguish Cascadelake-Server from Skylake-Server
Libvirt now properly detects Cascadelake-Server and Skylake-Server processors which differ only in stepping.
qemu: Fix domain restore from a block device
When using namespaces, libvirt was unable to restore a domain from a block device because libvirt tried to relabel the device inside the namespace while QEMU was given FD to the block device in the host.
node_device_udev: Handle move events
Libvirt now handles `move` event which is emitted on a NIC rename.
qemu: Fix capabilities probing with TCG
Libvirt no long assumes TCG is always available. It now detects whether QEMU supports TCG and reports it accordingly.

# Removed features

vbox: removed support for version 5.0 and 5.1 APIs
libvirt no longer supports use of VirtualBox 5.0 and 5.1 since these versions reached their end of life on 2017/05 and 2018/04 respectively.

## v6.2.0 2020-04-02

# New features

qemu: NVDIMM support for pSeries guests
QEMU 5.0 implements NVDIMM memory support for pSeries guests. This is done by adding an 'uuid' element in the memory XML, which can either be provided in the XML or, if omitted, generated automatically.
qemu: Add virtiofs support
This feature, introduced in QEMU 4.2, is a more modern alternative to virtio-9p, which is exposed through the same `<filesystem/>` element.
admin: Support reloading TLS certificates
After renewing TLS certificates, it was usually necessary to restart libvirtd for the new ones to be loaded: now the same result can be obtained without restarting the daemon by using `virt-admin server-update-tls`.

# Removed features

Removed support for INI style of comments
With switching of our internal code to GLib, parsing of client authentication config files is handed over to GLib which does not support `INI` style of comments starting with a semicolon (`;`). Use number sign (`#`) instead.

# Improvements

qemu: Don't compare local and remote hostnames on migration
This check was introduced to prevent same-host migration, but did not work as expected when multiple libvirtd instances were running on the same host but in different containers. With this release, the host UUID (which should be unique to the container) is checked instead.
qemu: Use per-VM event loops
Instead of using a single even loop to process communication with the QEMU monitor and guest agent, create a separate one for each VM. This helps with scalability and prevents scenarios where a single malfunctioning VM could affect all those running on the same host.
qemu: Support migration with SLIRP helper interface
With QEMU 5.0, a new D-Bus backend allows migration of external processes. When needed, libvirt will start a per-vm D-Bus bus, and migrate the slirp-helper along with QEMU.

# Bug fixes

qemu: Open backing chain late for shallow block copy reusing external images
With introduction of -blockdev for QEMU storage configuration in libvirt-5.10 we've started opening the backing chain of the destination/mirror of a virDomainBlockcopy started with VIR_DOMAIN_BLOCK_COPY_REUSE_EXT | VIR_DOMAIN_BLOCK_COPY_SHALLOW flags when starting the job rather than when virDomainBlockJobAbort with VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT is issued. For users depending on this undocumented quirky pre-blockdev behaviour this caused a regression as the backing chain could not be modified while the copy of the top image was progressing due to QEMU image locking. Note that this fix also requires qemu-5.0 while -blockdev is used starting from QEMU-4.2.
Don't generate machine names containing dots
Even though the guest name containing dots is not a problem for libvirt itself, we need to strip them out when registering with machined because of the latter's requirements.

## v6.1.0 2020-03-03

# New features

qemu: new rng backend type: builtin
It implements qemu builtin rng backend. That uses getrandom syscall to generate random, no external rng source needed. Available since QEMU 4.2.
support for virtio+hostdev NIC <teaming>
QEMU 4.2.0 and later, combined with a sufficiently recent guest virtio-net driver (e.g. the driver included in Linux kernel 4.18 and later), supports setting up a simple network bond device comprised of one virtio emulated NIC and one hostdev NIC (which must be an SRIOV VF). (in QEMU, this is known as the "virtio failover" feature). The allure of this setup is that the bond will always favor the hostdev device, providing better performance, until the guest is migrated - at that time QEMU will automatically unplug the hostdev NIC and the bond will send all traffic via the virtio NIC until migration is completed, then QEMU on the destination side will hotplug a new hostdev NIC and the bond will switch back to using the hostdev for network traffic. The result is that guests desiring the extra performance of a hostdev NIC are now migratable without network downtime (performance is just degraded during migration) and without requiring a complicated bonding configuration in the guest OS network config and complicated unplug/replug logic in the management application on the host - it can instead all be accomplished in libvirt with the interface <teaming> subelement "type" and "persistent" attributes.
support BR_ISOLATED flag for guest interfaces attached to a Linux host bridge
Since Linux kernel 4.18, the Linux host bridge has had a flag BR_ISOLATED that can be applied to individual ports. When this flag is set for a port, traffic is blocked between that port and any other port that also has the BR_ISOLATED flag set. libvirt domain interface config now supports setting this flag via the <port isolated='yes'/> setting. It can also be set for all connections to a particular libvirt network by setting the same option in the network config - since the port for the host itself does not have BR_ISOLATED set, the guests can communicate with the host and the outside world, but guests on that network can't communicate with each other. This feature works for QEMU and LXC guests with interfaces attached to a Linux host bridge.
qemu: Introduce the 'armvtimer' timer type
QEMU 5.0 introduces the ability to control the behavior of the virtual timer for KVM ARM/virt guests, and this new timer type exposes the same capability to libvirt users.
qemu: Storage configuration improvements
Libvirt now accepts `<backingStore type='volume'>` and allows specifying the offset and size of the image format container inside the storage source via the `<slices>` subelement.
qemu: Introduce the 'tpm-spapr' TPM model
This device, available starting from QEMU 5.0, is limited to pSeries guests.

# Improvements

qemu: Image format probing is allowed in certain cases
To resolve regressions when users didn't specify the backing image format in the overlay, libvirt now probes the format in certain secure scenarios which fixes a few common existing cases. Additionally the knowledge base was extended to provide more information on how to rectify the problem.
qemu: Support "dies" in CPU topology
This CPU topology concept, new in QEMU 4.1.0, sits between the existing "socket" and "core".
libxl: Add support for Credit2 scheduler parameters
lxc: Add support LXC 3 network configuration format

# Bug fixes

conf: Do not generate machine names ending with a dash
Recent systemd versions do not allow them.

# Packaging changes

use of gnulib has been completely eliminated
Historically libvirt has embedded gnulib to provide fixes for various platform portability problems. This usage has now been eliminated and alternative approaches for platform portability problems adopted where required. This has been validated on the set of platforms covered by automated CI build testing. Other modern Linux distros using glibc are expected to work. Linux distros using non-glibc packages, and other non-Linux platforms may encounter regressions when building this release. Please report any build problems encountered back to the project maintainers for evaluation.

## v6.0.0 2020-01-15

# Packaging changes

support for python2 is removed
Libvirt is no longer able to be built using the Python 2 binary. Python 3 must be used instead.
docs: the python docutils toolset is now required
The use of rst2html has been introduced for the website build process since docs are now being written in the RST as an alternative to HTML.

# New features

new PCI hostdev address type: unassigned
A new PCI hostdev address type 'unassigned' is introduced. An unassigned PCI hostdev behaves like any regular PCI hostdev inside Libvirt, but it is not usable by the guest. This gives the user a new option to manage the binding of PCI devices via Libvirt, declaring PCI hostdevs in the domain XML but allowing just a subset of them to be assigned to the guest.
Provide init scripts for sub-deaemons
So far libvirt shipped systemd unit files for sub-daemons. With this release, init scripts are available too. Package maintainers can choose which one to install via `--with-init-script` configure option.
qemu: Support cold-unplug of sound devices
qemu: Implement VIR_MIGRATE_PARAM_TLS_DESTINATION
This flag, which can be enabled using `virsh`'s `--tls-destination` option, allows migration to succeed in situations where there is a mismatch between the destination's hostname and the information stored in its TLS certificate.
qemu: Support reporting memory bandwidth usage stats
Implement Intel RDT-MBM in libvirt. The stats can be obtained via `virsh domstats --memory`.
qemu: Allow accessing NVMe disks directly
Before this release there were two ways to configure a NVMe disk for a domain. The first was using <disk/> with the <source/> pointing to the `/dev/nvmeXXXX`. The other was using PCI assignment via <hostdev/> element. Both have their disadvantages: the former adds latency of file system and block layers of the host kernel, the latter prohibits domain migration. In this release the third way of configuring NVMe disk is added which combines the advantages and drops disadvantages of the previous two ways. It's accessible via <disk type='nvme'/>.

# Removed features

'phyp' Power Hypervisor driver removed
The 'phyp' Power Hypervisor driver has not seen active development since 2011 and does not seem to have any real world usage. It has now been removed.

# Improvements

qemu: xz save image compression is faster
When using the xz format to compressed virtual machine saved state images, the "-3" compression level preset is now used. This results in slightly larger files, but with a massively reduced time to compress. The xz format offers the best compression level for saved state images, albeit still with the slowest running time. For the fastest possible running time, at cost of the larest compressed size, lzop should be used.
domain: Improve job stat handling
It is now possible to retrieve stats for completed and failed jobs.
qemu: Don't hold monitor and agent job at the same time
Before this change, a malicious (or buggy) `qemu-guest-agent` running in the guest could make other libvirt APIs unavailable for an unbounded amount of time.

# Bug fixes

qemu: Report error if backing image format is not specified explicitly
For a long time libvirt was assuming that a backing file is RAW when the format was not specified. This didn't pose a problem until blockdev support was enabled in last release. Libvirt now requires that the format is specified in the image metadata or domain XML and the VM will refuse to start otherwise. Additionally the error message now links to the knowledge base which summarizes how to fix the images.
qemu: Fix non-shared storage migration over NBD
qemu: Generate a single MAC address for hotplugged network devices
Since libvirt 4.6.0, when hotplugging a network device that didn't have a MAC address already assigned by the user, two separate addresses would be generated: one for the live configuration, which would show up immediately, and one for the inactive configuration, which would show up after the first reboot. This situation was clearly undesirable, so a single MAC address is now generated and used both for the live configuration and the inactive one.

## v5.10.0 2019-12-02

# New features

qemu: Introduce support for ARM CPU features
The only features supported at the moment are SVE vector lengths, which were introduced in QEMU 4.2.0.
qemu: Support boot display for GPU mediated devices
Until now, GPU mediated devices generally did not show any output until the guest OS had initialized the vGPU. By specifying the `ramfb` attribute, QEMU can be configured to use ramfb as a boot display for the device: this allows for display of firmware messages, boot loader menu, and other output before the guest OS has initialized the vGPU.
Add API to change the response timeout for guest agent commands
By default, when a command is sent to the guest agent, libvirt waits forever for a response from the guest agent. If the guest is unresponsive for any reason, this can block the calling thread indefinitely. By setting a custom timeout using `virDomainAgentSetResponseTimeout()`, API users can change this behavior.

# Improvements

Devices CGroup v2 support
Libvirt supported all controllers of CGroup v2 but the devices controller which is implemented in this release.
Cold plug of sound device
The QEMU driver now can handle cold plug of `<sound/>` devices.
Probe for default CPU types
With QEMU 4.2.0 we can probe for the default CPU model used by QEMU for a particular machine type and store it in the domain XML. This way the chosen CPU model is more visible to users and libvirt will make sure the guest will see the exact same CPU after migration.
Adaptation to qemu's blockdev
QEMU introduced a new way of specifying disks on the command line which enables fine-grained control over the block stack. Libvirt has adapted to this.

# Refactors

More GLib integration
More patches were merged that replace our internal functions with GLib ones. Also some effort was invested in replacing gnulib modules with GLib functions.
Rewrite of Perl scripts into Python
Libvirt used Perl scripts to check for coding style, generate some code and things like that. To bring the number of languages used down, these scripts were rewritten into Python.

# Bug fixes

Warn verbosely if using old loader:nvram pairs
Some distributions still use `--with-loader-nvram` or `nvram` variable in qemu.conf. This is now discouraged in favour of FW descriptors. However, instead of silently ignoring user's config, libvirt warns if outdated config is detected.
Drop pconfig from Icelake-Server CPU model
The pconfig feature was enabled in QEMU by accident in 3.1.0. All other newer versions do not support it and it was removed from the Icelake-Server CPU model in QEMU.
Wait longer for device removal confirmation on PPC64
After sending device hot unplug request to QEMU, libvirt waits up to 5 seconds for qemu to confirm the device removal. On some architectures (like PPC64) this can take longer time and libvirt now reflects that.
Forcibly create nodes in domain's namespace
The QEMU driver starts a domain in a namepsace with private `/dev` and creates only those nodes there which the domain is configured to have. However, it may have happened that if a node changed its minor number this change wasn't propagated to the namespace.
Various AppArmor bugfixes
The AppArmor driver now knows how to handle `<shmem/>` devices and also snapshotting more disks at once.
Improved video model autoselection
If a graphics device was added to XML that had no video device, libvirt automatically added a video device which was always of type 'cirrus' on x86_64, even if the underlying qemu didn't support cirrus. Libvirt now bases the decision on qemu's capabilities.

## v5.9.0 2019-11-05

# Packaging changes

Start linking against GLib and using its features
Up until now, libvirt has been dealing with platform portability and the lack of certain features in libc by using gnulib and implementing its own functions and data structures respectively; going forward, it will prefer the facilities offered by GLib instead.
Stop distributing generated documentation
Most downstreams already patch the libvirt source to some extent, so this change will probably not affect them.
Rewrite several Perl scripts in Python
Phasing out Perl usage is part of the project strategy.

# New features

qemu: Introduce a new video model of type 'ramfb'
Introduce a new video model type to the domain XML that supports the `ramfb` standalone device in qemu.
qemu: Implement the ccf-assist pSeries feature
Users can now decide whether ccf-assist (Count Cache Flush Assist) support should be available to pSeries guests.
Xen: Support specifying ACPI firmware path
The libxl driver now supports specifying an ACPI firmware path using the `acpi` element.
qemu: Support specifying resolution for video devices

# Removed features

logging: Drop support for including stack traces
This feature was intended to aid debugging, but in practice it resulted in logs that were too verbose to be useful and also resulted in a significant performance penalty.

# Improvements

qemu: Implement CPU comparison/baseline on s390x
This functionality has been historically limited to x86_64, but it's now available on s390x too.

# Bug fixes

lib: autostart objects exactly once
If libvirtd or any of the sub-daemons is started with socket activation then objects might be autostarted more than once. For instance, if a domain under `qemu:///session` URI is mark as autostarted and the session daemon is started then the domain is started with it. If user shuts the domain down and the session daemon is started again, the user's wish to keep the domain shut off is ignored and the domain is autostarted again. This is now fixed.
qemu: Properly advertise bochs-display availability
Support for `bochs-display` was introduced in libvirt 5.6.0, but until now the model was not listed in the domain capabilities.
security: Don't remember labels for TPM devices
Due to the way they're implemented in the kernel, trying to remember labels for TPM devices makes it impossible to use them.
security: Properly rollback after failure in a stacked driver
When multiple security drivers are involved, failure in one of them would result in only the corresponding changes being rolled back, leaving the ones performed by drivers that had been activated earlier in place. All changes are rolled back now.
Fix build with musl libc
Improve compatibility with non-bash shells

## v5.8.0 2019-10-05

# New features

qemu: Support use of precreated tap/macvtap devices by unprivileged libvirtd
It is now possible for an unprivileged libvirtd to make use of tap and macvtap devices that were previously created by some other entity. This is done by setting `managed='no'` along with the device name in the `target` subelement of `<interface type='ethernet'>`.
qemu: Support vhost-user-gpu
Support for running virtio GPUs in separate processes with vhost-user backend. It requires QEMU newer than 4.1.
Introduce virConnectSetIdentity API
When split daemons are in use, this API is used to forward uid, gid and SELinux info from `virproxyd` to other driver daemons such as `virtqemud`.

# Improvements

qemu: Support running SLIRP networking in a separate process
User can configure the slirp-helper path in `qemu.conf`. It will start a slirp-helper process to provide SLIRP networking when the VM is started with network interface "user". That will allow stricter security policies for QEMU SLIRP network.

# Removed features

Remove xenapi driver
The xenapi driver is removed since it has not received any significant development since its initial contribution nine years ago and has no known user base.

## v5.7.0 2019-09-03

# New features

qemu: Support Direct Mode for Hyper-V Synthetic timers
The QEMU driver now supports Direct Mode for Hyper-V Synthetic timers for Hyper-V guests.
lib: Add virDomainGetGuestInfo()
This API is intended to aggregate several guest agent information queries and is inspired by stats API `virDomainListGetStats()`. It is anticipated that this information will be provided by a guest agent running within the domain. It's exposed as `virsh guestinfo`.
Experimental split of libvirtd into separate daemons
The big monolithic libvirtd daemon can now be replaced by smaller per-driver daemons. The new split daemons are considered experimental at this time and distributions are encouraged to continue using the traditional libvirtd by default.
qemu: Support kvm-hint-dedicated performance hint
With `<hint-dedicated state='on'/>` and `<cpu mode='host-passthrough'/>`, it allows a guest to enable optimizations when running on dedicated vCPUs. QEMU newer than 2.12.0 and kernel newer than 4.17 are required.

# Removed features

Remove KVM assignment support
The KVM style of PCI device assignment was removed from the kernel in version 4.12.0 after being deprecated since 4.2.0. Libvirt defaults to VFIO for a long time. Remove support for KVM device assignment from libvirt too.
libxml: min required libxml is now 2.9.1
Support for building with libxml versions older than 2.9.1 has been dropped.

# Improvements

virsh: Support setting bandwidth in migrate subcommand
In addition to postcopy bandwidth, the `virsh migrate` subcommand now supports specifying precopy bandwidth with the `--bandwidth` parameter.
libxl: Implement domain metadata getter/setter
The libxl driver now supports `virDomainGetMetadata()` and `virDomainSetMetadata()` APIs.
test driver: Expand API coverage
Additional APIs have been implemented in the test driver.
Report RNG device in domain capabilities XML
Libvirt now reports if RNG devices are supported by the underlying hypervisor in the domain capabilities XML.
Stop linking NSS plugins with libvirt.so
This reduces the amount of code and 3rd party libraries are that loaded into all processes.
Split the setuid virt-login-shell binary into two pieces
The setuid virt-login-shell binary is now a tiny shim that sanitizes the process execution environment variables and arguments, before launching the trusted virt-login-shell-helper binary.
qemu: Allow migration with disk cache on
When QEMU supports flushing caches at the end of migration, we can safely allow migration even if `disk/driver/@cache` is neither `none` nor `directsync`.

# Bug fixes

Various security label remembering fixes
In the previous release libvirt introduced remembering of original owners and SELinux labels on files. However, the feature did not work properly with snapshots, on migrations or on network filesystems. This is now fixed.
Allow greater PCI domain numbers
Libvirt used to require PCI domain number to be not greater than 0xFFFF. The code was changed to allow 32 bits long numbers.
Various D-Bus fixes
When D-Bus is not available, libvirt was reporting random errors. These are now gone.
Prefer read-only opening of PCI config files
When enumerating PCI bus, libvirt opens config files under `sysfs` mount and parses them to learn various aspects of the device (e.g. its capabilities). Only in a very limited number of cases it is actually writing into the file. However, it used to open the file also for writing even if it was only reading from it.
Fix AppArmor profile
Since the `5.6.0` release, libvirt uses `procfs` to learn the list of opened file descriptors when spawning a command. However, our AppArmor profile was not allowing such access.
Don't block storage driver when starting or building a pool
Starting or building a storage pool can take a long time to finish. During this time the storage driver was blocked and thus no other API involving the storage driver could run. This is now fixed.

## v5.6.0 2019-08-05

# New features

qemu: Introduce a new video model of type 'bochs'
Introduce a new video model type that supports the `bochs-display` device that was added in qemu version 3.0.
api: new virDomainCheckpoint APIs
Introduce several new APIs for creating and managing checkpoints in the test and qemu drivers (the latter requires qcow2 images). Checkpoints serve as a way to tell which portions of a disk have changed since a point in time.
qemu: Add support for overriding max threads per process limit
systemd-based systems impose a limit on the number of threads a process can spawn, which in some cases can be exceeded by QEMU processes running VMs. Add a `max_threads_per_process` option to qemu.conf to override the system default.
Remember original owners and SELinux labels of files
When a domain is starting up libvirt changes DAC and SELinux labels so that domain can access it. However, it never remembered the original labels and therefore the file was returned back to `root:root`. With this release, the original labels are remembered and restored properly.
network: Allow passing arbitrary options to dnsmasq
This works similarly to the existing support for passing arbitary options to QEMU, and just like that feature it comes with no support guarantees.

# Removed features

xen: Remove sxpr config support
Remove the sxpr style config parser and formatter a year after the xend driver was removed.

# Improvements

qemu: Allow XML validation for snapshot creation
Add flag `VIR_DOMAIN_SNAPSHOT_CREATE_VALIDATE` to validate snapshot input XML. For virsh, users can use it as `virsh snapshot-create --validate`.
Support encrypted soft TPM
A soft TPM backend could be encrypted with passphrase. Now libvirt supports using a `secret` object to hold the passphrase, and referring to it via the `encryption` element of the TPM device.
test driver: Expand API coverage
Additional APIs have been implemented in the test driver.
Implement per-driver locking
Drivers now acquire a lock when they're loaded, ensuring that there can never be two instances of the same driver active at a time.
nss: Report newer addresses first
In some cases, a guest might be assigned a new IP address by DHCP before the previous lease has expired, in which case the NSS plugin will correctly report both addresses; many applications, however, ignore all addresses but the first, and may thus end up trying to connect using a stale address. To prevent that from happening, the NSS plugin will now always report the newest address first.
util: Optimize mass closing of FDs when spawning child processes
When the limit on the number of FDs is very high, closing all unwanted FDs after calling `fork()` can take a lot of time and delay the start of the child process. libvirt will now use an optimized algorithm that minimizes such delays.

# Bug fixes

logging: Ensure virtlogd rollover takes priority over logrotate
virtlogd implements its own rollover mechanism, but until now logrotate could end up acting on the logs before virtlogd had a chance to do so itself.

## v5.5.0 2019-07-02

# Security

api: Prevent access to several APIs over read-only connections
Certain APIs give root-equivalent access to the host, and as such should be limited to privileged users. CVE-2019-10161, CVE-2019-10166, CVE-2019-10167, CVE-2019-10168.

# New features

qemu: Support SMMUv3 IOMMU
SMMUv3 is an IOMMU implementation for ARM virt guests.
network: Introduce the network port API
This new public API can be used by virtualization drivers to manage network resources associated with guests, and is a further step towards splitting libvirtd into multiple daemons.

# Removed features

qemu: Remove support for virDomainQemuAttach and virConnectDomainXMLFromNative APIs
The qemu implementations for the APIs mentioned above were removed and the APIs now return an error. The implementation was stale for a long time and did not work with modern QEMU command lines, generated from libvirt or otherwise.
Stop supporting migration of config files from pre-XDG layout
The new layout was introduced with libvirt 0.9.13 (Jul 2012).
Remove Avahi mDNS support
This feature was never used outside of virt-manager, which has itself stopped using it a while ago.

# Improvements

sysinfo: Report SMBIOS information on aarch64
While SMBIOS support has historically been limited to x86_64, modern aarch64 machines often offer access to the same information as well, and libvirt now exposes it to the user when that's the case.
test driver: Expand API coverage
Even more APIs that were missing from the test driver have now been implemented.
virt-xml-validate: Allow input to be read from stdin
qemu: Validate spapr-vio addresses as 32-bit
libvirt has always considered these addresses (used for pSeries guests) as 64-bit, but the sPAPR specification says that they're 32-bit instead.

# Bug fixes

qemu: Set process affinity correctly when using <numatune>
libvirt would mistakenly interpret the `nodeset` attribute as a list of CPUs instead of as a list of NUMA node, and the process affinity would be set incorrectly as a result; this has now been fixed.

## v5.4.0 2019-06-03

# Security

cpu: Introduce support for the md-clear CPUID bit
This bit is set when microcode provides the mechanism to invoke a flush of various exploitable CPU buffers by invoking the x86 `VERW` instruction. CVE-2018-12126, CVE-2018-12127, CVE-2018-12130, CVE-2019-11091.
Restrict user access to virt-admin, virtlogd and virtlockd
The intended users for these facilities are the `root` user and the `libvirtd` service respectively, but these restrictions were not enforced correctly. CVE-2019-10132.

# Improvements

test driver: Expand API coverage
Several APIs that were missing from the test driver have now been implemented.
Avoid unnecessary static linking
Most binaries shipped as part of libvirt, for example `virtlogd` and `libvirt_iohelper`, were embedding parts of the library even though they also linked against the `libvirt.so` dynamic library. This is no longer the case, which results in both the disk and memory footprint being reduced.
qemu: Report stat-htlb-pgalloc and stat-htlb-pgfail balloon stats
These stats have been introduced in QEMU 3.0.

# Bug fixes

qemu: Fix emulator scheduler support
Setting the scheduler for QEMU's main thread before QEMU had a chance to start up other threads was misleading as it would affect other threads (vCPU and I/O) as well. In some particular situations this could also lead to an error when the thread for vCPU #0 was being moved to its cpu,cpuacct cgroup. This was fixed so that the scheduler for the main thread is set after QEMU starts.
apparmor: Allow hotplug of vhost-scsi devices

## v5.3.0 2019-05-04

# New features

qemu: Add support for setting the emulator scheduler parameters
I/O threads and vCPU threads already support setting schedulers, but until now it was impossible to do so for the main QEMU thread (emulator thread in the libvirt naming). This is, however, requested for some very specific scenarios, for example when vCPU threads are running at such priority that could starve the main thread.

# Removed features

vbox: Drop support for VirtualBox 4.x releases
Support for all the 4.x releases was ended by VirtualBox maintainers in December 2015. Therefore, libvirt support for these releases is dropped.

# Improvements

qemu: Use PCI by default for RISC-V guests
PCI support for RISC-V guests was already available in libvirt 5.1.0, but it required the user to opt-in by manually assigning PCI addresses: with this release, RISC-V guests will use PCI automatically when running against a recent enough (4.0.0+) QEMU release.
qemu: Advertise firmware autoselection in domain capabilities
The firmware autoselection feature is now exposed in domain capabilities and management applications can query for accepted values, i.e. values that are accepted and for which libvirt found firmware descriptor files. Firmware Secure Boot support is also advertised.
Drop YAJL 1 support
YAJL 2 is widely adopted and maintaining side by side support for two versions is unnecessary.

# Bug fixes

rpc: cleanup in virNetTLSContextNew
Failed new gnutls context allocations in virNetTLSContextNew function results in double free and segfault. Occasional memory leaks may also occur.
virsh: various completers fixes
There were some possible crashers, memory leaks, etc. which are now fixed.
qemu: Make hugepages work with memfd backend
Due to a bug in command line generation libvirt did not honor hugepages setting with memfd backend.
Enforce ACL write permission for getting guest time & hostname
Getting the guest time and hostname both require use of guest agent commands. These must not be allowed for read-only users, so the permissions check must validate "write" permission not "read".

## v5.2.0 2019-04-03

# New features

Add Storage Pool Capabilities output
Add support to list an enumerated list of supported Storage Pools via the virConnectGetCapabilities API when connected via a Storage Driver. Add support to get a more detailed list XML output Storage Pool Capabilities vis the virConnectGetStoragePoolCapabilites API.
qemu: Support virtio-{non-}transitional device models
virtio-transitional
and `virtio-non-transitional` `model` values were added to the QEMU driver for the following devices: `disk`, `interface`, `filesystem`, `rng`, `vsock`, `memballoon`, `controller` type `scsi`, `controller` type `virtio-serial`, `input` bus `virtio` type `passthrough`, `hostdev` type `scsi_host`. These new models can be used to give fine grained control over what virtio device version is presented to the guest.
qemu: Enable firmware autoselection
Libvirt allows users to provide loader path for some time now. However, this puts some burden on users because they need to know what firmware meets their requirements. Now that QEMU ships firmware description files this burden can be moved onto libvirt. It is as easy as setting the `firmware` attribute in the `os` element (accepted values are `bios` and `efi`). Moreover, libvirt automatically enables domain features needed for firmware it chooses.
snapshots: Add support for topological listings
A new flag VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL is available for the various snapshot listing APIs such as virDomainListAllSnapshots(). For drivers that support the flag, the listed snapshots are guaranteed to be sorted such that parents occur before children.
Xen: Add support for max grant frames setting
Add support for Xen's max_grant_frames setting by adding a new xenbus controller type with a maxGrantFrames attribute. E.g. `<controller type='xenbus' maxGrantFrames='64'/>`
qemu: Add support for parallel migration
With QEMU 4.0.0 libvirt can enable parallel migration which causes the memory pages to be processed in parallel by several threads and sent to the destination host using several connections at the same time. This may increase migration speed in case a single thread is unable to saturate the network link.

# Removed features

Drop support for Upstart and "Red Hat" init scripts
Not a single one of the platforms we target still uses Upstart, and the Upstart project itself has been abandoned for several years now; the same is true for the "Red Hat" (really System V) init scripts, since RHEL 7 and later releases use systemd.

# Improvements

Report class information for PCI node device capability.
Split setup of IPv4 and IPv6 top level chain
The requirement resulting from private chains improvement done in `v5.1.0` was refined so that only tables from corresponding IP version are required. This means that if a network doesn't have `IPv6` enabled then those tables are not required.
Don't default to building the QEMU driver
Historically, the QEMU driver has been special in that it was enabled by default, with the option to explicitly opt-out of it; starting now, we're enabling it opportunistically if we detect that all requirements are available, just like we do with other drivers.

# Bug fixes

virt-host-validate: Fix IOMMU check on s390x
qemu: Allow creating pSeries guests with graphics and no USB mouse
It's now possible to prevent libvirt from automatically adding a USB mouse to pSeries guests by including a USB tablet in the input XML: doing so is desiderable as using a tablet results in a much better user experience when working with GUIs.
qemu: Set $HOME and XGD variables for qemu:///system guests
This avoids files being accidentally created under `/` or the guests not being able to start because they lack the necessary permissions to write to that location.

## v5.1.0 2019-03-04

# New features

bhyve: Add support for additional command-line arguments
The bhyve driver now supports passing additional command-line arguments to the bhyve process using the new `<bhyve:commandline>` element in domain configuration.
network: Support setting a firewalld "zone" for virtual network bridges
All libvirt virtual networks with bridges managed by libvirt (i.e. those with forward mode of "nat", "route", "open", or no forward mode) will now be placed in a special firewalld zone called "libvirt" by default. The zone of any network bridge can be changed using the `zone` attribute of the network's `bridge` element.
bhyve: Support for ignoring unknown MSRs reads and writes
A new <features> element <msrs unknown='ignore'/> was introduced and the bhyve driver supports it to control unknown Model Specific Registers (MSRs) reads and writes.
qemu: Add support for encrypted VNC TLS keys
Use the password stored in the secret driver under the uuid specified by the `vnc_tls_x509_secret_uuid` option in qemu.conf.
Add storage pool namespace options
Allow for adjustment of RBD configuration options via Storage Pool XML Namespace adjustments.
qemu: Add support for setting post-copy migration bandwidth
Users can now limit the bandwidth of post-copy migration, e.g. via `virsh migrate --postcopy-bandwidth`.

# Improvements

Create private chains for virtual network firewall rules
Historically firewall rules for virtual networks were added straight into the base chains. This works but has a number of bugs and design limitations. To address them, libvirt now puts firewall rules into its own chains. Note that with this change the `filter`, `nat` and `mangle` tables are required for both `IPv4` and `IPv6`.
Detect CEPH and GPFS as shared FS
When starting a migration libvirt performs some sanity checks to make sure domain will be able to run on the destination. One of the requirements is that the disk has to either be migrated too or be accessible from a network filesystem. CEPH and GPFS weren't detected as a network filesystem.
Advertise network MTU via DHCP when specified
If network MTU is set and the network has DHCP enabled, advertise the MTU in DHCP transaction too so that clients can adjust their link accordingly.
qemu: Allocate memory at the configured NUMA nodes from start
Libvirt used to just start QEMU, let it allocate memory for the guest, and then use CGroups to move the memory to configured NUMA nodes. This is suboptimal as huge chunks of memory have to be moved. Moreover, this relies on ability to move memory later which is not always true. A change was made to set process affinity correctly from the start so that memory is allocated on the configured nodes from the beginning.
Support for newer Wireshark
Adapt libvirt to use the more recent release requiring a source build configuration of libvirt `--with-wireshark` to upgrade to the more recent version.
Batch mode virsh and virt-admin parsing improvements
When parsing a single-argument command_string in batch mode, virsh and virt-admin now permit newlines in addition to semicolons for splitting commands, and backslash-newline for splitting long lines, to be more like shell parsing.

# Bug fixes

qemu: Use CAP_DAC_OVERRIDE during QEMU capabilities probing
By default, libvirt runs the QEMU process as `qemu:qemu` which could cause issues during probing as some features like AMD SEV might be inaccessible to QEMU because of file system permissions. Therefore, `CAP_DAC_OVERRIDE` is granted to overcome these for the purposes of probing.
storage: Add default mount options for fs/netfs storage pools
Altered the command line generation for fs/netfs storage pools to add some default options. For Linux based systems, the options added are "nodev, nosuid, noexec". For FreeBSD based systems, the options added are "nosuid, noexec".
qemu: Allow use of PCI for RISC-V guests
This works with QEMU 4.0.0+ only and is opt-in at the moment, since it requires users to manually assign PCI addresses, but is otherwise fully functional.
network: Fix virtual networks on systems using firewalld+nftables
Because of the transitional state of firewalld's new support for nftables, not all iptables features required by libvirt are yet available, so libvirt must continue to use iptables for its own packet filtering rules even when the firewalld backend is set to use nftables. However, due to the way iptables support is implemented in kernels using nftables (iptables rules are converted to nftables rules and processed in a separate hook from the native nftables rules), guest networking was broken on hosts with firewalld configured to use nftables as the backend. This has been fixed by putting libvirt-managed bridges in their own firewalld zone, so that guest traffic can be forwarded beyond the host and host services can be exposed to guests on the virtual network without opening up those same services to the rest of the physical network. This means that host access from virtual machines is no longer controlled by the firewalld default zone (usually "public"), but rather by the new firewalld zone called "libvirt" (unless configured otherwise using the new zone attribute of the network bridge element).
qemu: Fix i6300esb watchdog hotplug on Q35
Ensure that libvirt allocates a PCI address for the device so that QEMU did not default to an address that would not allow for device hotplug.
lxc: Don't reboot host on virDomainReboot
If the container is really a simple one (init is just bash and the whole root is passed through) then virDomainReboot and virDomainShutdown would reboot or shutdown the host. The solution is to use different method to reboot or shutdown the container in that case (e.g. signal).
rpc: Various stream fixes
One particular race was fixed, one locking problem and error reporting from streams was made better.
qemu: Fix guestfwd hotplug/hotunplug
Fixed the generation of the guestfwd hotplug/unplug command sent to QEMU to match the syntax used when creating the initial command line.
qemu: Forbid CDROMs on virtio bus
Attempting to create an empty virtio-blk drive or attempting to eject it results into an error. Forbid configurations where users would attempt to use CDROMs in virtio bus.
qemu: Use 'raw' for 'volume' disks without format
Storage pools might want to specify format of the image when translating the volume thus libvirt can't add any default format when parsing the XML. Add an explicit format when starting the VM and format is not present neither by user specifying it nor by the storage pool translation function.
qemu: Assume 'raw' default storage format also for network storage
Post parse callback adds the 'raw' type only for local files. Remote files can also have backing store (even local) so we should do this also for network backed storage.
qemu: Fix block job progress reporting and advocate for READY event
In some cases QEMU can get to 100% and still not reach the synchronised phase. Initiating a pivot in that case will fail. Therefore it is strongly advised to wait for `VIR_DOMAIN_BLOCK_JOB_READY` event which does not suffer from this problem.
qemu: Don't format image properties for empty drive
If a `-drive` has no image, then formatting attributes such as cache, readonly, etc. would cause errors to be reported from QEMU. This was fixed by not supplying the attributes for devices without an image.
External snapshot metadata redefinition is fixed
Attempting to use VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE to reinstate the metadata describing an external snapshot created earlier for an offline domain no longer fails.

## v5.0.0 2019-01-15

# New features

Xen: Add support for openvswitch
The libxl driver now supports virtual interfaces that connect to an openvswitch bridge, including interfaces with VLAN tagging and trunking configuration.
qemu: Report whether KVM nesting is available
Running nested KVM guests requires specific configuration steps to be performed on the host; libvirt will now report in the host capabilities whether KVM nesting support is available.

# Removed features

Drop UML driver
The UML driver was unmaintained and not tested for quite some time now. Worse, there is a bug that causes it to deadlock on some very basic operations (e.g. dumping domain XML). These facts make us believe no one uses it.

# Improvements

qemu: Add support for ARMv6l guests
Support more NVDIMM configuration options
Introduce more configuration options. For the source element, add the 'alignsize' and 'pmem' subelements. For the target element, add the 'readonly' subelement.
cpu: Add support for "stibp" x86_64 feature
Add cpu flag stibp (Single Thread Indirect Branch Predictors) to prevent indirect branch predictions from being controlled by the sibling Hyperthread.
libxl: Handle external domain destroy
Historically, if a domain was destroyed using `xl` rather than through libvirt APIs, libvirt would not be aware of the fact and keep considering it as running. This is no longer the case.
Start selecting the first available DRI device for OpenGL operations
If OpenGL support is needed (either with SPICE gl enabled or with egl-headless), libvirt is now able to pick the first available DRI device for the job. At the same time, this improvement is also a bugfix as it prevents permission-related issues with regards to our mount namespaces and the default DRI render node's permissions which would normally prevent QEMU from accessing such a device.
qemu: Add support for postcopy-requests migration statistics
The `virDomainJobInfo` can get number page requests received from the destination host during post-copy migration.

# Bug fixes

lxc: Don't forbid interfaces with type=direct
Such interfaces are supported by lxc and should be allowed.
qemu: Fully clean up RNG devices on detach
Some RNG device types, such as those using EGD, might need extra clean up on the host in addition to removing the guest-side device.

## v4.10.0 2018-12-03

# New features

qemu: Add Hyper-V PV IPI and Enlightened VMCS support
The QEMU driver now has support for Hyper-V PV IPI and Enlightened VMCS for Windows and Hyper-V guests.
qemu: Added support for PCI devices on S390
PCI addresses can now include the new zpci element which contains uid (user-defined identifier) and fid (PCI function identifier) attributes and makes the corresponding devices usable by S390 guests.
Support changing IOThread polling parameters for a live guest
Introduced virDomainSetIOThreadParams which allows dynamically setting the IOThread polling parameters used by QEMU to manage the thread polling interval and the algorithm for growth or shrink of the polling time. The values only affect a running guest with IOThreads. The guest's IOThread polling values can be viewed via the domain statistics.
Xen: Add support for PVH
The libxl driver now supports Xen's PVH virtual machine type. PVH machines are enabled with the new "xenpvh" OS type, e.g. `<os><type>xenpvh</type></os>`
qemu: Added support for CMT (Cache Monitoring Technology)
Introduced cache monitoring using the `monitor` element in `cachetune` for vCPU threads. Added interfaces to get and display the cache utilization statistics through the command 'virsh domstats' via the virConnectGetAllDomainStats API.
qemu: Add support for nested HV for pSeries guests
Nested HV support makes it possible to run nested (L2) guests with minimal performance penalty when compared to regular (L1) guests on ppc64 hardware.

# Bug fixes

Xen: Handle soft reset shutdown event
The pvops Linux kernel uses soft reset to handle the crash machine operation. The libxl driver now supports the soft reset shutdown event, allowing proper crash handling of pvops-based HVM domains.

## v4.9.0 2018-11-04

# New features

util: Add cgroup v2 support
cgroup v2 support has been implemented in libvirt, with both "unified" (v2 only) and "hybrid" (v2 + v1) setups being usable; existing "legacy" (v1 only) setups will keep working.
qemu: Add vfio AP support
The QEMU driver now has support to passthrough adjunct processors into QEMU guests on S390.

# Improvements

rpc: Make 'genprotocol' output reproducible
This is another step towards making libvirt builds fully reproducible.

# Bug fixes

security: Fix permissions for UNIX sockets
Since 4.5.0, libvirt is using FD passing to hand sockets over to QEMU, which in theory removes the need for them to be accessible by the user under which the QEMU process is running; however, other processes such as vdsm need to access the sockets as well, which means adjusting permissions is still necessary.
cpu_map: Add Icelake model definitions
These CPU models will be available in the upcoming 3.1.0 QEMU release.
util: Properly parse URIs with missing trailing slash
Some storage URIs were not parsed correctly, in which case libvirt ended up emitting XML that it would then refuse to parse back.

## v4.8.0 2018-10-01

# New features

Xen: Support PM Suspend and Wakeup
The libxl driver now supports the virDomainPMSuspendForDuration and virDomainPMWakeup APIs.

# Removed features

Xen: Drop support for Xen 4.4 and 4.5
Xen 4.4 and 4.5 are no longer supported by the Xen community. Drop support for these older versions and require Xen >= 4.6.
nwfilter: Disallow binding creation in session mode
Ensure that a filter binding creation is not attempted in session mode and generates a proper error message.

# Improvements

qemu: Retrieve guest hostname through QEMU Guest Agent command
QEMU is now able to retrieve the guest hostname using a new QEMU-GA command called 'guest-get-host-name'. Virsh users can execute 'domhostname' for QEMU driver for domains configured to use the Guest Agent.
virsh: Implement vsh-table in virsh and virsh-admin
The new API fixes problems with table-alignment, making the tables more readable and deals with unicode.

# Bug fixes

storage: Allow inputvol to be encrypted
When creating a storage volume based on another volume, the base input volume is allowed to be encrypted.
virsh: Require explicit --domain for domxml-to-native
The --domain option for domxml-to-native virsh command has always been documented as required, but commit v4.3.0-127-gd86531daf2 accidentally made it optional.
lxc_monitor: Avoid AB / BA lock race
A deadlock situation could occur when autostarting a LXC domain 'guest' due to two threads attempting to take opposing locks while holding opposing locks (AB BA problem).

## v4.7.0 2018-09-03

# New features

storage: add storage pool iscsi-direct
Introduce a new storage pool backend that uses libiscsi instead of iscsiadm. It support basic pool operations: checkPool and refreshPool.
Add support for MBA (Memory Bandwidth Allocation technology)
Domain vCPU threads can now have allocated some parts of host memory bandwidth by using the `memorytune` element in `cputune`.
qemu: Add support for RISC-V guests
riscv32 and riscv64 guest architectures are now supported.

# Improvements

qemu: Add ccw support for vhost-vsock
Support the vhost-vsock-ccw device on S390.
qemu: Make default machine type independent of QEMU
We can't control whether or not QEMU will change its default machine type in the future, or whether downstream distributions will decide to compile out some machine types, so our only option to provide a predictable behavior is taking care of the default ourselves; management applications and users are encouraged to explicitly pick a machine type when creating new guests.
apparmor: Various improvements
Rules have been added to deal with a number of scenarios that didn't work correctly.

# Bug fixes

esx: Truncate CPU model name
Some CPU model names are too long to be stored into the corresponding property, and should be explicitly truncated to avoid unexpected behavior in users of the `virNodeGetInfo()` API such as `virsh nodeinfo`.
utils: Remove arbitrary limit on socket_id/core_id
Both values were assumed to be smaller than 4096, but in fact they are entirely hardware-dependent and there have been reports of machines presenting much bigger values, preventing libvirt from working correctly; all such limits have now been removed.

## v4.6.0 2018-08-06

# New features

qemu: Implement the HTM pSeries feature
Users can now decide whether HTM (Hardware Transactional Memory) support should be available to the guest.
qemu: Enable VNC console for mediated devices
Host devices now support a new atribute 'display' which can be used to turn on frame buffer rendering on a vgpu mediated device instead of on an emulated GPU, like QXL.

# Improvements

qemu: Introduce a new video model of type 'none'
Introduce a new video model type that disables the automatic addition of a video device to domains with 'graphics' specified in their XML. This can be useful with GPU mediated devices which can serve as the only rendering devices within the guest.
virsh: Add --alias to attach-disk and attach-interface commands
Add option --alias to set customized device alias name when using attach-disk or attach-interface commands.
virsh: Support usb and sata address to attach-disk
Usb or sata address could be used when attach-disk with --address. For example, use usb address as usb:<bus>.<port>, use sata address as <controller>.<bus>.<unit>.

## v4.5.0 2018-07-02

# New features

qemu: Provide TPM emulator support
Support QEMU's TPM emulator based on swtpm. Each QEMU guest gets its own virtual TPM.
bhyve: Support specifying guest CPU topology
Bhyve's guest CPU topology could be specified using the `<cpu><topology ../></cpu>` element.
qemu: Add support for extended TSEG size
Support specifying extended TSEG size for SMM in QEMU.
qemu: Add support for SEV guests
SEV (Secure Encrypted Virtualization) is a feature available on AMD CPUs that encrypts the guest memory and makes it inaccessible even to the host OS.

# Removed features

Remove support for qcow/default encrypted volumes
Disallow using a qcow encrypted volume for the guest and disallow creation of the qcow or default encrypted volume from the storage driver. Support for qcow encrypted volumes has been phasing out since QEMU 2.3 and by QEMU 2.9 creation of a qcow encrypted volume via qemu-img required usage of secret objects, but that support was never added to libvirt.
Make GnuTLS mandatory
Building without GnuTLS is no longer possible.
qemu: Remove allow_disk_format_probing configuration option
The option represented a security risk when used with malicious disk images, so users were recommended against enabling it; with this release, it's been removed altogether.

# Improvements

capabilities: Provide info about host IOMMU support
Capabilities XML now provide information about host IOMMU support.
virsh: Add --all to domblkinfo command
Alter the `domblkinfo` command to add the option --all in order to display the size details of each domain block device from one command in a output table.
qemu: Allow concurrent access to monitor and guest agent
Historically libvirt prevented concurrent accesses to the qemu monitor and the guest agent. Therefore two independent calls (one querying the monitor and the other querying guest agent) would serialize which hurts performance. The code was reworked to allow two independent calls run at the same time.
qemu: Allow configuring the page size for HPT pSeries guests
For HPT pSeries guests, the size of the host pages used to back guest memory and the usable guest page sizes are connected; the new setting can be used to request that a certain page size is available in the guest.
Add support to use an raw input volume for encryption
It is now possible to provide a raw input volume as input for to generate a luks encrypted volume via either virsh vol-create-from or virStorageVolCreateXMLFrom.
qemu: Add support for vsock hot (un)plug and cold (un)plug
qemu: Add support for NBD over TLS
NBD volumes can now be accessed securely.
qemu: Implement FD passing for Unix sockets
Instead of having QEMU open the socket and then connecting to it, which is inherently racy, starting with QEMU 2.12 we can open the socket ourselves and pass it to QEMU, avoiding race conditions.
virsh: Introduce --nowait option for domstat command
When this option is specified, virsh will try to fetch the guest stats but abort instead of stalling if they can't be retrieved right away.

# Bug fixes

qemu: Fix a potential libvirtd crash on VM reconnect
Initialization of the driver worker pool needs to come before libvirtd trying to reconnect to all machines, since one of the QEMU processes migh have already emitted events which need to be handled prior to us getting to the worker pool initialization.
qemu: Fix domain resume after failed migration
Recent versions of QEMU activate block devices before the guest CPU has been started, which makes it impossible to roll back a failed migration. Use the `late-block-activate` migration capability if supported to avoid the issue.
vmx: Permit guests to have an odd number of vCPUs
An odd number of vCPUs greater than 1 was forbidden in the past, but current versions of ESXi have lifted that restriction.

## v4.4.0 2018-06-04

# New features

bhyve: Support locking guest memory
Bhyve's guest memory may be wired using the `<memoryBacking><locked/></memoryBacking>` element.
qemu: Provide VFIO channel I/O passthrough support
Support passthrough devices that use channel I/O based mechanism in a QEMU virtual machine.
qemu: Add support for migration of VMs with non-shared storage over TLS
It's now possible to use the VIR_MIGRATE_TLS flag together with VIR_MIGRATE_NON_SHARED_DISK. The connection is then secured using the TLS environment which is setup for the migration connection.
Add support for VM Generation ID
The VM Generatation ID exposes a 128-bit, cryptographically random, integer value identifier, referred to as a Globally Unique Identifier (GUID) to the guest in order to notify the guest operating system when the virtual machine is executed with a different configuration. Add a new domain XML processing and a domain capabilities feature.
Introduce virDomainDetachDeviceAlias
This new API enables users to detach device using only its alias.
Introduce new virConnectCompareHypervisorCPU and virConnectBaselineHypervisorCPU APIs
Unlike the old virConnectCompareCPU and virConnectBaselineCPU APIs, both new APIs consider capabilities of a specific hypervisor.
Introduce SCSI persistent reservations support
The QEMU driver gained support for qemu-pr-helper which enables guests to issue SCSI commands for persistent reservation.
qemu: Implement multiple screen support for virDomainScreenshot
While the virDomainScreenshot API supported multihead video cards, the implementation was missing. But now that QEMU implemented it libvirt has done as well.
qemu: add support for vhost-vsock-device
A new vsock device was introduced, allowing communication between the guest and the host via the AF_VSOCK family.

# Improvements

qemu: Add suport for OpenGL rendering with SDL
Domains using SDL as a graphics backend will now be able to use OpenGL accelerated rendering.
qemu: Add support for 'output' audio codec
Support QEMU's 'hda-output' codec advertising only a line-out for ich6 and ich9 sound devices.
virsh: Enhance event name completion
Implement event name completion for some commands (e.g. event, secret-event, pool-event and nodedev-event)

## v4.3.0 2018-05-02

# New features

qemu: Add support for the pcie-to-pci-bridge controller
Pure PCIe guests such as x86_64/q35 and aarch64/virt will now add this controller when traditional PCI devices are in use.
Xen: Support setting CPU features for host-passthrough model
The CPU model presented to Xen HVM domains is equivalent to libvirt's host-passthrough model, although individual features can be enabled and disabled via the cpuid setting. The libvirt libxl driver now supports enabling and disabling individual features of the host-passthrough CPU model.

# Removed features

Xen: Drop the legacy xend-based driver
The xm/xend toolstack was deprecated in Xen 4.2 and removed from the Xen sources in the 4.5 development cycle. The libvirt driver based on xend is now removed from the libvirt sources.

# Improvements

qemu: Support hot plug and hot unplug of mediated devices
Libvirt now allows mediated devices to be hot plugged and hot unplugged from a guest rather than reporting an error that this isn't supported. In fact, kernel has been supporting this since 4.10.

# Bug fixes

Improve handling of device mapper targets
When starting a domain with a disk backed by a device mapper volume libvirt also needs to allow the storage backing the device mapper in CGroups. In the past kernel did not care, but starting from 4.16 CGroups are consulted on each access to the device mapper target.

## v4.2.0 2018-04-01

# New features

Support building with Python 3
Python is required to build libvirt, and up until now only Python 2 could be used as an interpreter. All scripts used during build have now been made compatible with Python 3, which means both major releases of the language are fully supported.
qemu: Provide ccw address support for graphics and input devices
Support the virtio-gpu-ccw device as a video device and virtio-{keyboard, mouse, tablet}-ccw devices as input devices on S390.

# Improvements

qemu: Add logging of guest crash information on S390
On S390, when the guest crashes and QEMU exposes the guest crash information, log the relevant data to the domain log file.
qemu: use arp table of host to get the IP address of guests
Find IP address of a VM by arp table on hosts. If someone customizing IP address inside VM, it will be helpful.
Xen: Remove hard-coded scheduler weight
The libxl driver was accidentally hard-coding the per-domain scheduler weight to 1000, silently ignoring any user-provided `<shares>` in `<cputune>`. The driver now honors `<shares>`, and defers setting a default value to Xen. Note that the Xen default is 256, so any domains started after this improvement will have one fourth the shares of previously started domains. If all domains must have equal CPU shares, administrators must manually set the weight of previously started domains to 256, or restart them.

# Bug fixes

qemu: TLS migration now enforces use of TLS for the NBD connection
When the VIR_MIGRATE_TLS flag was used with the migration API libvirt did not ensure that the NBD connection was using TLS as well. The code now rejects such migration as the TLS transport for NBD is not ready yet, but prevents a false sense of security that TLS would be used. The support TLS for NBD will be added soon.

## v4.1.0 2018-03-05

# New features

Added support for CAT (Cache allocation Technology)
Domain vCPU threads can now have allocated some parts of host cache using the `cachetune` element in `cputune`.
Allow opening secondary drivers
Up until now it was possible to connect to only hypervisor drivers (e.g. qemu:///system, lxc:///, vbox:///system, and so on). The internal drivers (like network driver, node device driver, etc.) were hidden from users and users could use them only indirectly. Starting with this release new connection URIs are accepted. For instance network:///system, storage:///system and so on.
virtlogd, virtlockd: Add support for admin protocol
These two daemons now support admin protocol through which some admin info can be gathered or some configuration tweaked on the fly.

# Improvements

virsh: Enhance bash completion
Implement more bash completions so that basic libvirt objects can be auto-completed (e.g. networks, interfaces, NWFilters, and so on).
qemu: Use VIR_ERR_DEVICE_MISSING for various hotplug/detach messages
qemu: Allow showing the dump progress for memory only dump
Alter the QEMU dump-guest-memory command processing to check for and allow asynchronous completion which then allows for the virsh dump --memory-only --verbose command to display percent completion data.
conf: add support for setting Chassis SMBIOS data fields
libxl: add support for setting clock offset and adjustment
Make port allocator global
Up until now each driver had their own port allocator module. This meant that info on port usage was not shared. Starting with this release, the port allocator module is made global and therefore drivers allocate ports from global pool.
Fixed some compiler warnings that appear with GCC 8

# Bug fixes

qemu: Check for unsafe migration more thoroughly
If a domain disk is stored on local filesystem (e.g. ext4) but is not being migrated it is very likely that domain is not able to run on destination. Regardless of share/cache mode.
qemu: Fix updating device with boot order
Starting with 3.7.0 release updating any device with boot order would fail with 'boot order X is already used by another device' while in fact it was the very same device.
virlog: determine the hostname on startup CVE-2018-6764
At later point it might not be possible or even safe to use getaddrinfo(). It can in turn result in a load of NSS module which can even be loaded from unsage guest filesystem and thus escape the confinment of its container.
qemu: Rework vCPU statistics fetching
Fetching vCPU statistics was very expensive because it lead to waking up vCPU threads in QEMU and thus it degraded performance. The code was reworked so that fetching statistics does not wake up halted vCPUs.
qemu: unlink memory backing file on domain shutdown
Depending on the filesystem where domain memory is stored, some files might have been left behind. This is not a problem on hugetlbfs, but it is a problem on regular filesystems like ext4.
qemu: Fix shutting down domains in parallel
If multiple domains were being shut down in parallel, libvirtd might have deadlocked.
nodedev: Update PCI mdev capabilities dynamically
PCI devices may have other nested capabilities, like SRIOV and mdev which depend on the device being plugged into the native vendor driver. However, in case such a device is directly assigned to a guest using VFIO driver, the device will naturally lose these capabilities and libvirt needs to reflect that.

## v4.0.0 2018-01-19

# New features

tools: Provide bash completion support
Both `virsh` and `virt-admin` now implement basic bash completion support.
qemu: Refresh capabilities on host microcode update
A microcode update can cause the CPUID bits to change; therefore, the capabilities cache should be rebuilt when such an update is detected on the host.
lxc: Set hostname based on container name

# Improvements

CPU frequency reporting improvements
The CPU frequency will now be reported by `virsh nodeinfo` and other tools for s390 hosts; at the same time; CPU frequency has been disabled on aarch64 hosts because there's no way to detect it reliably.
libxl: Mark domain0 as persistent
Xen: Add support for multiple IP addresses on interface devices
qemu: Add support for hot unplugging redirdev device

# Bug fixes

qemu: Enforce vCPU hotplug granularity constraints
QEMU 2.7 and newer don't allow guests to start unless the initial vCPUs count is a multiple of the vCPU hotplug granularity, so validate it and report an error if needed.

## v3.10.0 2017-12-04

# New features

conf: Support defining distances between virtual NUMA cells
A NUMA hardware architecture supports the notion of distances between NUMA cells. This can now be specified using the `<distances>` element within the NUMA cell configuration. Drivers which support this include Xen and QEMU.
Xen: Support defining vNUMA topology
Xen now supports defining a virtual NUMA topology for VMs, including specifying distances between NUMA cells.
qemu: Add the ability to configure HPT resizing for pSeries guests
The user can now decide whether HPT (Hash Page Table) resizing should be enabled, disabled or required instead of leaving it up to hypervisor defaults and negotiation between the guest and the host.
qemu: Add vmcoreinfo feature
Starting with QEMU 2.11, the guest can save kernel debug details when this feature is enabled and the kernel supports it. It is useful to process kernel dump with KASLR enabled, and also provides various kernel details to crash tools.
conf: Move the auth and encryption definitions to disk source
Allow parsing and formatting of the `auth` and `encryption` sub-elements to be a child of the `source` element. This will allow adding an `auth` sub-element to a `backingStore` or `mirror` elements as a means to track specific authentication and/or encryption needs.

# Improvements

vbox: Add VirtualBox 5.2 support
vbox: Add support for configuring storage controllers
The VirtualBox driver now supports the `<controller>` element in the domain XML for configuring storage controllers in VBOX VMs. Additionally, libvirt's domain XML schema was updated to allow optional `model` attribute for `<controller type='ide'>` which is used by the VBOX driver to set the IDE controller model to be one of 'piix4', 'piix4' (default), or 'ich6'. Finally, with this change `dumpxml` generates `<controller>` elements that correspond to current VBOX VM storage controller configuration.
vbox: Add support for attaching empty removable disks
The VirutalBox driver now supports adding CD-ROM and floppy disk devices that do not have the disk source specified. Previously such devices were silently ignored.
vbox: Add support for attaching SAS storage controllers
In VirtualBox, SCSI and SAS are distinct controller types whereas libvirt does not make such distinction. Therefore, the VBOX driver was updated to allow attaching SAS controllers via `<controller type='scsi' model='lsisas1068'>` element. If there are both SCSI and SAS controllers present in the VBOX VM, the domain XML can associate the disk device using the `<address>` element with the `controller` attribute, and optionally, set the port via `unit` attribute.
qemu: Generate predictable paths for qemu memory backends
In some cases management applications need to know paths passed to memory-backend-file objects upfront. Libvirt now generates predictable paths so applications can prepare the files if they need to do so.
Shareable disks work properly with recent qemu
Recent qemu versions added image locking to avoid potential corruption of disk images. This broke shareable disks with libvirt since the feature was turned on by default in qemu. Libvirt now enables sharing of those disks in qemu so that the image locking is not applied in that case. Additionally libvirt now checks that shareable disks have supported format (raw) to avoid metadata corruption.
Improve serial console behavior on non-x86 architectures
ppc64, aarch64 and s390x guests were treating the <serial> and <console> elements differently from x86, in some cases presenting misleading information to the user. The behavior is now consistent across all architectures and the information reported is always accurate.

# Bug fixes

vbox: Do not ignore failures to attach disk devices when defining
The `define` now fails and reports an error if any of the `controller` or `disk` devices specified in the domain XML fail to attach to the VirtualBox VM.
vbox: Fix dumpxml to always output disk devices
The VirtualBox driver was ignoring any disk devices in `dumpxml` output if there was a SAS storage controller attached to the VM.
vbox: Fix dumpxml to always generate valid domain XML
When a VirtualBox VM has multiple disks attached, each to a different storage controller that uses 'sd' prefix for block device names e.g. one disk attached to SATA and one to SCSI controller, it no longer generates XML where both would have 'sda' device name assigned. Instead it properly assigns 'sda' and 'sdb' to those disks in the order of appearance.
Securely pass iSCSI authentication data
Rather than supplying the authentication data as part of the iSCSI URL for a disk or host device, utilize the encrypted secret object to securely pass the authentication data.

## v3.9.0 2017-11-02

# New features

Add capability to allow hot (un)plug of a domain watchdog device
Allow users to set device aliases
Users can set aliases to domain devices and thus identify them easily.
qemu: Support multiqueue for virtio-blk
Multiqueue support for `virtio-blk` has been available in QEMU ever since 2.7.0, and now libvirt guests can enable it.
Add virDomainSetLifecycleAction API
Provided a new API to allow dynamic guest lifecycle control for guest reactions to poweroff, restart, or crash type events related to the domain XML `on_poweroff`, `on_reboot`, and `on_crash` elements. The `virsh set-lifecycle-action` command was created to control the actions.
qemu: Allow cold(un)plugging and hot(un)plugging input devices
net: Implement QoS for vhostuser

# Improvements

Allow a logical volume to be create using LUKS
A logical volume may be created using an `encryption` element using "luks" format. This does require a previously created `secret` to store the passphrase used to encrypt the volume Adding the volume to a domain can then either provide the secret or allow the consumer in the guest to provide the passphrase in order to decrypt the volume.
net: Ignore auto-generated MAC address when detaching an interface
If the MAC address has not been specified by the user, libvirt will try and fill in the gaps by generating one; however, for some error paths that led to some confusing error messages, so when an auto-generated MAC address is specified the error message will not include the auto-generated MAC.
net: Enable MAC address lookup for virDomainInterfaceStats
apparmor: Several improvements
Changes include permitting access to data about USB devices and `dnsmasq` instances, allowing spaces in guest names and many more.
cpu: Use CPU information obtained from QEMU when possible
Recent QEMU versions can expose information about which CPU models are available and usable on the host; libvirt will now make use of such information whenever possible.
hyperv: Various improvements
The error reported when clients can't connect to Hyper-V has been made more descriptive, and memory limits for guests are now mapped to more appropriate libvirt equivalents.
qemu: Report QEMU error on failed migration
Instead of reporting a generic error, ask QEMU for a more detailed and thus hopefully more helpful one.
vbox: Implement autoport for RDP
libvirt will now obtain the (dynamically allocated) RDP port number from VirtualBox itself, avoiding conflicts between multiple guests wanting to use RDP at the same time.
qemu: Allow rotation of small logs
On a host where numerous unique instances are executed per day, it's quite possible that, even though each of the single log files are fairly small, collectively the quantity and volume may add tens of thousands of log files to the `/var/log/libvirt/qemu/` directory. Removing the constraints that log have to be bigger than 100 KiB before they can be rotated solves the issue.

# Bug fixes

Fix swapped interface statistics and QoS
Due to internal implementation, reported statistics for some types of interfaces were swapped (RX appeared in TX and vice versa). Similarly, QoS was set in reversed way.
Properly resize local LUKS encrypted volume
Resizing of a local LUKS encrypted volume will now use qemu-img to resize the volume. This will require configuring a secret for the LUKS encrypted volume.
qemu: Reserve PCI addresses for implicit i440fx devices
Failing to do so causes the addresses to be considered usable by libvirt, which means they could be assigned to more than one device resulting in the guest failing to start.
spec: Restart libvirtd only at the end of the upgrade process
Use `%posttrans` to make sure `libvirtd` is not restarted before all other components, such as the library itself and storage / hypervisor drivers, have already been upgraded.

# Security

qemu: Ensure TLS clients always verify the server certificate
While it's reasonable to turn off client certificate validation, as setting it up can be non-trivial, clients should always verify the server certificate to avoid MITM attacks. However, libvirt was using the same knob to control both checks, leading to CVE-2017-1000256 / LSN-2017-0002.

## v3.8.0 2017-10-04

# New features

qemu: Added support for cold-(un)plug of watchdog devices
qemu: Added support for setting IP address os usernet interfaces
qemu: Added support for Veritas Hyperscale (VxHS) block devices
storage: Added new events for pool-build and pool-delete

# Improvements

qemu: Set DAC permissions properly for spice rendernode
When a `rendernode` path is set for SPICE GL on `qemu:///system`, we now correctly set DAC permissions on the device at VM startup. This is the last remaining hurdle to let SPICE GL work for `qemu:///system` without any external host changes.
nodedev: Add switchdev offload query to NIC capabilities
Allow querying the NIC interface capabilities for the availability of switchdev offloading (also known as kernel-forward-plane-offload).
New CPU models for AMD and Intel
AMD EPYC and Intel Skylake-Server CPU models were added together with their features
Improve long waiting when saving a domain
While waiting for a write to disk to be finished, e.g. during save, even simple operations like `virsh list` would be blocking due to domain lock. This is now resolved by unlocking the domain in places where it is not needed.

# Bug fixes

Proper units are now used in virsh manpage for dom(mem)stats
Previously the documentation used multiples of 1000, but now it is fixed to use multiples of 1024.
qemu: Fix error reporting when disk attachment fails
There was a possibility for the actual error to be overridden or cleared during the rollback.
qemu: Fix assignment of graphics ports after daemon restart
This could be seen with newer kernels that have bug regarding SO_REUSEADDR. After libvirtd was restarted it could assign already used address to new guests which would make them fail to start. This is fixed by marking used ports unavailable when reconnecting to running QEMU domains.
Fix message decoding which was causing a very strange bug
When parsing an RPC message with file descriptors was interrupted and had to restart, the offset of the payload was calculated badly causing strange issues like not being able to find a domain that was not requested.

## v3.7.0 2017-09-04

# New features

qemu: Add managedsave-edit commands
Using managedsave-dumpxml, managedsave-define and managedsave-edit commands, now we can dump and edit the XML configuration of domain which has managedsave image.
qemu: Add migrate-getmaxdowntime command
Currently, the maximum tolerable downtime for a domain being migrated is write-only from libvirt, via migrate-setmaxdowntime. This implements a complementary migrate-getmaxdowntime command
bhyve: Support autoport for VNC ports
It's no longer necessary to explicitly specify VNC port for the bhyve guests. With the autoport feature it will be allocated automatically. Please refer to the bhyve driver documentation for examples.
qemu: Added support for setting heads of virtio GPU
qemu: Added support to configure reconnect timeout for chardev devices
When you have a TCP or UNIX chardev device and it's connected somewhere you can configure reconnect timeout if the connection is closed.

# Improvements

qemu: Report a clear error when dropping a VM during startup
"Failed to load config for domain 'DOMNAME'" is now reported if a VM config can't be parsed for some reason, and thus provides a clear indication for users (and devs).
apparmor: Update for QEMU 2.10 compatibility
Starting with QEMU 2.10, disk images and NVRAM files get automatically locked to prevent them from being corrupted; however, file locking needs to be explicitly allowed through `virt-aa-helper` or AppArmor will reject the requests and the guest will not be able to run.
virsh: List Unix sockets in 'domdisplay' output
VNC and SPICE graphics can use Unix sockets instead of TCP/IP sockets as connection endpoints, but such a configuration was not handled correctly by `virsh domdisplay`, causing the respective endpoints to be missing from the output.
qemu: Don't check whether offline migration is safe
Since offline migration only copies the guest definition to the destination host, data corruption is not a concern and the operation can always be performed safely.
virt-host-validate: Fix IOMMU detection on ppc64

# Bug fixes

qemu: Better support for international domain names (with wide characters)
There were some issues with multi-byte domains getting lost on daemon restart due to truncation, so the code now handles multi-byte names a bit better.
qemu: Support long domain names with namespaces
Domains with extremely long names would fail to start due to temporary namespace paths being created with the whole name. The path is now generated with shortened name instead.
qemu: Tolerate missing emulator binary during libvirtd restart
For some time libvirt required qemu capabilities being present when parsing VM configs during startup. As a side effect VM configs would fail to parse and thus vanish, if the emulator binary would be uninstalled or broken. Libvirt now tolerates when capabilities are missing during startup.
qemu: Prevent pSeries guests from disappearing in some situations
pSeries guest would disappear if any of the host devices they were configured to use was not available during libvirtd startup, which could easily happen for SR-IOV Virtual Functions. This scenario is now handled correctly.
qemu: Honor <on_reboot/> setting
The setting was accepted by the parser, but not actually implemented.
Fix --verbose option for all daemons
Since v3.0.0, the option had been ignored by all libvirt daemons (`libvirtd`, `virtlogd` and `virtlockd`); it's now working as intended once again.

## v3.6.0 2017-08-02

# New features

hyperv: Implement virDomainSetMemory and virDomainSendKey APIs
qemu: Support multiple PHBs for pSeries guests
pSeries guests can now have multiple PHBs (PCI Host Bridges), which show up as separate PCI domains in the guest. To create additional PHBs, simply add PCI controllers with model `pci-root` to the guest configuration.
qemu: Isolate hostdevs on pSeries guests
To enable better error reporting and recovery, unrelated hostdevs will now be automatically isolated on pSeries guests by placing them on separate PHBs (PCI Host Bridges).

# Improvements

qemu: platform serial devices can now use chardev features
QEMU VMs that depend on platform serial devices can now use QEMU's `-chardev` option, which enables access to advanced features like log file configuration. This applies to the default serial devices for arm, aarch64, and some ppc configurations.
Require use of GCC 4.4 or Clang compilers
We only ever test libvirt with GCC or Clang (which provides a GCC compatible compilation environment). Between them, these compilers cover every supported operating system platform, including Windows.
qemu: shared disks with directsync cache should be safe for migration
At present shared disks can be migrated with either readonly or `cache=none`. But `cache=directsync` should be safe for migration, because both `cache=directsync` and `cache=none` don't use the host page cache, and `cache=direct` write through qemu block layer cache.
Handle hotplug change on VLAN configuration using OVS
Libvirt was taught to handle VLAN change for running OVS interface.

# Bug fixes

qemu: Use vCPU 'node-id' property and pass it back to qemu
vCPU properties gathered from query-hotpluggable-cpus need to be passed back to QEMU. As QEMU did not use the node-id property until now and libvirt forgot to pass it back properly (it was parsed but not passed around) we did not honor this.
Miscellaneous stream fixes
After introducing sparse stream features there were still some known bugs left. Those are fixed in this release.
qemu: Miscellaneous domain NS fixes
Libvirt starts qemu domains in separate Linux namespaces for a while now. However, there were still some bugs lingering. For instance libvirt did not know how to handle file based bind mounts.
Various CPU driver improvements
There were some minor bugs when using 'host-model' CPU.

## v3.5.0 2017-07-04

# New features

qemu: Add support for loadparm for a boot device
Add an optional boot parameter 'loadparm' for a boot device. Loadparm is an 8 byte parameter that, when present, is queried by S390 guests via sclp or diag 308. Linux guests on S390 use it to select a boot entry.
Support controlling how video devices are exposed to the bhyve guests
The `vgaconf` attribute was added to `video`'s `driver` element. Possible values are: `on`, `off`, and `io`. It controls the way how bhyve exposes video devices to its guests; various guest OSes might require different settings to boot properly.
qemu: Add support for live updates of coalesce settings
Users can now use `virsh update-device` to change the coalesce settings of an interfaces while the domain is running.
qemu: Allow VirtIO devices to use vIOMMU
It is now possible to turn on IOTBL for the vIOMMU and have VirtIO devices use it, provided they have been configured appropriately.

# Improvements

qemu: block copy job can be used with persistent domains
Until now it was not possible to use block copy with persistent VMs. In use cases where it's not required to recover the job after VM shutdown, it's possible to specify VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB flag to start the copy job.
JSON pseudo-protocol backing store parser supports new format of qemu 2.9
QEMU 2.9 modified a few structures corresponding to the JSON format of specifying a backing store for a disk image. Libvirt now implements the new format.
Capabilities now include info about host's CAT settings
Various information about resource control from the host is gathered and presented in capabilities if available.
apparmor: Several improvements
Allow access to Ceph config, EFI firmware on both x86_64 and aarch64, device tree on ppc64 and more.
qemu: Support host-model on POWER9 machines

# Bug fixes

qemu: snapshot: retrieve image metadata from user provided files
Disk images of an external snapshot created with VIR_DOMAIN_SNAPSHOT_CREATE_REUSE_EXT flag specified would not be scanned for metadata after recent changes.

The metadata is necessary to allow keeping relative paths between images when doing a block-commit.
Parse decimal numbers in a locale-independent way
Some locales, such as `de_DE` and `pt_BR`, use comma rather than dot to separate the integer part from the fractional part of a decimal number; however, several data sources such as the kernel use a locale-independent representation and need to be treated accordingly.
Support compilation with newer compiler and libc versions
Several fixes have been included to make compilation with Clang 4.0.0, GCC 7.1 and glibc >= 2.25.90 possible.
qemu: Query name for vhost-user interfaces at runtime
This makes it possible to use `virsh` subcommands such as `domiflist` and `domifstat` on vhost-user interfaces.
qemu: Set MTU for hotplugged interfaces correctly
When hotplugging a network interface, the MTU was only set on the guest side. Set it on the host side as well.
qemu: Forbid updating MTU for interfaces of running guests
The MTU setting can't be modified while the guest is running, so any attempt to alter it at runtime will now result in an error rather than being silently ignored.
qemu: Fix specifying QXL heads with older QEMU releases
Specifying the number of QXL heads was not working correctly for QEMU releases older than 1.6.
qemu: Fix migration to older libvirt/QEMU versions
When the guest is started, libvirt updates the CPU definition to reflect the actual CPU features to enforce ABI. We need to send original and updated CPU definition in order to support migration to older libvirt/QEMU versions. Only the updated CPU definition was sent to destination.

## v3.4.0 2017-06-02

# New features

Improved streams to efficiently transfer sparseness
New extension to virStream was implemented so that virStorageVolDownload and virStorageVolUpload can preserve file sparseness.
I/O APIC type can be specified for QEMU/KVM domains
The `ioapic` tag was added to domain `features`, so the type of the I/O APIC can now be specified (e.g. putting it in userspace for KVM domains).
The reason for VM shutdown is reported, if known
QEMU 2.10 will be able to report the reason for shutting down (whether that was caused by the guest or not), and libvirt is prepared for that and reports that information in its shutdown event as well, if it is known.

# Improvements

Repository now has new README.md file
The new file uses markdown syntax, so it looks better on github and possibly other web pages, but it has also more useful information. The old README is now symlink to the new file.
qemu: Use GICv2 by default for aarch64/virt TCG guests
The emulated GICv3 has some limitations that make it unusable as a default; use GICv2 until they're sorted out. This change makes it once again possible to run aarch64/virt guests on a x86_64 host without having to tweak their configuration.
Additional capabilities for the node_device module
Introduce two new capabilities to the node_device module. The first is for CCW devices, most common on the S390 architecture. The second is for fibre channel-backed SCSI devices and exposes the fc_remote_port sub-capability to SCSI target devices.
Node devices now report Mediated device capabilities
Endpoint devices support new `mdev` capability and their parents now report the supported types in new `mdev_types` capability.
Capabilities now report information about host caches
If supported in the kernel, host capabilities will now list L3 caches. The code for other levels was added as well, but only L3 caches are reported currently.
POWER9 CPU model was added
It is now properly reported in host capabilities.
libxl: NUMA sibling distances are now reported in host capabilities
VMDK version 3 files are now properly detected
Interrupt remapping and Extended interrupt mode for IOMMU devices
These two new features can now be controlled with new `<driver intremap='on/off' eim='on/off'/>` tag for `iommu` devices.
Graphics in libxl domains now have default addresses
Even though there were default addresses before this change, they were not saved in the XML. It is now possible to see and control the listen addresses properly.
Default USB controllers are now added for devices in libxl domains
Even though they were added automatically when USB device was attached, they could've been missing in some other cases. The logic is now fixed so there are always USB controllers, even if there was none of them in the specified XML.
Limits for RPC messages were increased
Hitting the RPC limits we have is easier every day, so they were increased once again and some guessing logic was improved as well. It is now possible to get more stats than ever using the `virConnectGetAllDomainStats()` call and push through even bigger requests and replies for all APIs.

# Bug fixes

qemu: Create memory_backing_dir on startup
Libvirt's policy is that directories are created on startup if they don't exist. We've missed this one.
PCIe 4.0 cards now report proper link speeds
It could happen that the link speed for PCIe devices was not properly reported or the nodedev-dumpxml just failed. That was due to mistake in the field width, but should now work properly.
qemu: Do not report errors on shutdown
For some users, in some rare cases, it could happen that there was an error message "internal error: End of file from qemu monitor" in the logs even though no problem happened. The detection of these false positives was improved and such errors should not show any more.
User-specified UNIX socket paths for virtio channels should not be reset
It could happen, in some cases, that libvirt would mistake a user-specified path for its own generated one and thus remove it from the XML. The detection of such addresses was improved now.
Fix address reservation during RNG hot-plug
When error occurred in a specific point in time during the hot-plug of an RNG device, it could happen that an address was released even though another device was already using it, making it possible to hot-plug another device with that address, effectively having duplicated addresses in the XML.

## v3.3.0 2017-05-05

# New features

net: Add support for coalesce settings
Enabling data batching through these settings can improve network performance for guests.
qemu: Add support for guest CPU cache specification
This features allows fine-grained control of the cache behavior of the guest CPU.
qemu: Add support for the qemu-xhci USB controller

# Improvements

hyperv: Support Hyper-V 2012 and newer
Starting with Hyper-V 2012 the API has changed causing the existing driver to be unable to send and process requests properly. This has been resolved by adding abstractions to handle the differences and ease handling such breaks if they happen in the future.
libxl: Add support for nested HVM domains
Xen has supported nested HVM domains since version 4.4. The libvirt libxl driver now supports nested HVM domains by specifying the host-passthrough CPU mode when defining a domain.
qemu: Implement ACPI support for aarch64 guests
Up until this point, ACPI support was only advertised for x86_64 guests and disabling it for aarch64 guests was not possible at all.
vz: Add support for changing the number of vCPUs
qemu: Automatically choose the best USB controller for guests
The recently introduced qemu-xhci USB controller is the best choice for both ppc64 and aarch64 guests, so use it by default on those architectures if available.
daemon: Increase default task limit for libvirtd
The default number of tasks for the pids cgroup controller is 512, which libvirtd can quickly bump into when starting lots of guests. Raise the limit to a more reasonable 32768.
docs: Include man pages describing key code names and values
virsh: Report initialization errors
Sometimes virsh might be unable to start: when that happens, report useful diagnostics instead of failing silently.

# Bug fixes

nss: Don't require a network restart for libvirt_guest
Previously, the libvirt_guest NSS module would only work properly after the corresponding network had been restarted; now newly started guests will be reported correctly right away.
storage: Remove unavailable transient pools after restart
Solve an issue where transient storage pools would be stuck in an unmanageable state if the source disappeared and libvirtd was subsequently restarted.
storage: Fix capacity value for LUKS encrypted volumes
The 'capacity' value (e.g. guest logical size) for a LUKS volume is smaller than the 'physical' value of the file in the file system, so we need to account for that.
qemu: Fix regression when hyperv/vendor_id feature is used
Guests using the feature would not be started at all; it is now possible to start them as expected.
qemu: Do not crash on USB address with no port and invalid bus
crypto: Always pad data before encrypting it
If this step is not performed, when the data length matches the chunk size the decryption routines will misinterpret the last byte of data as the padding length and fail to decode it correctly.

## v3.2.0 2017-04-02

# New features

The virt-host-validate tool now supports bhyve hypervisor
Introduce NVDIMM memory model
NVDIMM is new type of memory introduced into QEMU 2.6. The idea is that we have a non-volatile memory module that keeps the data persistent across domain reboots and offers much faster data accesses. However, due to a bug in QEMU, this feature is not enabled for QEMUs older than 2.9.0.
qemu: Introduce support for generic PCIe Root Ports
For new controllers, a generic device (pcie-root-port) will be used by default instead of the Intel-specific device (ioh3420), provided the QEMU binary supports it.
qemu: Add support for checking guest CPU ABI compatibility
When migrating a domain to a different host, restoring a domain from a file or reverting a snapshot libvirt will make sure the guest CPU QEMU presents to the guest OS exactly matches the one provided on the source host (or before the domain's state was saved). This enhanced check may also be requested when starting a new domain to ensure the virtual CPU exactly matches the one specified in the XML.
qemu: Add support to migrate using TLS
Add the ability to migrate QEMU guests using TLS via a new flag VIR_MIGRATE_TLS or virsh migrate '--tls' option. Requires using at least QEMU 2.9.0 in order to work properly.
qemu: add mediated devices framework support
Recent kernel version introduced new mediated device framework, so provide an initial support of this framework for libvirt, mainly by introducing a new host device type in the XML.
qemu: Add support for setting TSC frequency
Setting TSC frequency is required to enable migration for domains with 'invtsc' CPU feature turned on.
Add support for block device threshold event
When using thin provisioning, management tools need to resize the disk in certain cases. To avoid having them to poll disk usage this version introduces an event which will be fired when a given offset of the storage is written by the hypervisor. Together with the API it allows registering thresholds for given storage backing volumes and this event will then notify management if the threshold is exceeded. Currently only the qemu driver supports this.
bhyve: Add support for UEFI boot ROM, VNC, and USB tablet
The bhyve driver now supports booting using the UEFI boot ROM, so non-FreeBSD guests that support UEFI could be booted without using an external boot loader like grub-bhyve. Video is also supported now, allowing to connect to guests via VNC and use an USB tablet as an input device. Please refer to the driver page for domain XML examples.

# Improvements

qemu: Detect host CPU model by asking QEMU on x86_64
Previously, libvirt detected the host CPU model using CPUID instruction, which caused libvirt to detect a lot of CPU features that are not supported by QEMU/KVM. Asking QEMU makes sure we don't start it with unsupported features.
perf: Add more perf statistics
Add support to get the count of cpu clock time, task clock time, page faults, context switches, cpu migrations, minor page faults, major page faults, alignment faults, emulation faults by applications running on the platform.
Write hyperv crash information into vm log
qemu's implementation of the hyperv panic notifier now reports information about the crash from the guest os. Starting with this version, libvirt logs the information to the vm log file for possible debugging.

# Bug fixes

QEMU: Use adaptive timeout for connecting to monitor
When starting qemu, libvirt waits for qemu to create the monitor socket which libvirt connects to. Historically, there was sharp 30 second timeout after which the qemu process was killed. This approach is suboptimal as in some scenarios with huge amounts of guest RAM it can take a minute or more for kernel to allocate and zero out pages for qemu. The timeout is now flexible and computed by libvirt at domain startup.
Overwrite (clear) 2 KB instead of just 512 bytes when initializing logical device
Describe the logical backend requirements better for pool-create-as

## v3.1.0 2017-03-03

# New features

storage: Add Virtuozzo storage backend storage pool
Add new storage backend to support pool and volume management within the Virtuozzo Storage environment. Virtuozzo Storage is a highly available distributed software defined storage with built-in replication and disaster recovery.
qemu: Add support for memory backing with file source
Add support in numa topology for file source inside memory backing (hugepages are not needed) Three new elements <source/>,<access/> and <allocation/> were added to <memoryBacking/> element. Also new configuration parameter `memory_backing_dir` was added to qemu.conf.
network: make openvswitch call timeout configurable
Adding the ability to specify the timeout value in seconds for openvswitch calls in the libvirtd configuration file.
bhyve: add e1000 NIC support
Add support for e1000 NIC. Previously, the only available option was `virtio-net`.
libxl: add tunneled migration support
Add tunneled migration to libxl driver, which is always capable of strong encryption and doesn't require any extra network connection other than what's required for remote access of libvirtd.
qemu: add rendernode argument
Add a new attribute 'rendernode' to <gl> spice element.
nodedev: add drm capability
Add a new 'drm' capability for Direct Rendering Manager (DRM) devices, providing device type information.
Add API for individual/specific vCPU hotplug
The new API allows selecting specific vCPUs to be added/removed from the VM. The existing APIs allowed only adding/removing from the end which did not play well with NUMA.

# Improvements

virsh: pool-list: allow both --uuid and --name in one command
Adjust the virsh-pool command to support the --uuid and/or --name options in order to print just the --name and/or --uuid of pools.
Introduce MTU to domain <interface/> and <network>
Allow setting MTU size for some types of domain interface and network.
libxl: improve support for <timer> configurations
Add support for multiple timers. Extend the tsc timer to support the emulate mode. Improve conversion of timer XML to/from xl.cfg.
storage: modularize the storage driver
Split up the storage driver backends into loadable modules so that binary distributions don't have to compromise on shipping the storage driver with all backends which may pull in too many dependencies.

# Bug fixes

nodedev: Fabric name must not be required for fc_host capability
fabric_name is one of many fc_host attributes in Linux that is optional and left to the low-level driver to decide if it is implemented. For example the zfcp device driver does not provide a fabric name for an fcp host. The requirement for the existence of a fabric name has been removed by making it optional.
bhyve: change address allocation schema for SATA disks
Previously, the bhyve driver assigned PCI addresses to SATA disks directly rather than assigning that to a controller and using SATA addresses for disks. It was implemented this way because bhyve has no notion of an explicit SATA controller. However, as this doesn't match libvirt's understanding of disk addresses, the bhyve driver was changed to follow the common schema and have PCI addresses for SATA controllers and SATA addresses for disks. If you're having issues because of this, it's recommended to edit the domain's XML and remove <address type='pci'> from the <disk> elements with <target bus='sata'/> and let libvirt regenerate it properly.
libxl: maximum memory fixes
Fix reporting of domain maximum memory. Fix setting dom0 maximum memory.
libxl: fix disk detach when <driver> not specified
libxl: fix dom0 autoballooning with Xen 4.8
qemu: Allow empty script path to <interface/>
Historically, this was always allowed. Unfortunately, due to some rework done for 1.3.2 release a bug was dragged in which suddenly stop allowing domain with such configuration to start.

## v3.0.0 2017-01-17

# New features

Domain events for metadata content changes
The domain events framework has a new event ID that can be used to get notifications when domain metadata content changes.
Event notifications for the secret object
The secret object now supports event notifications, covering lifcycle changes and secret value changes.
New localPtr attribute for "ip" element in network XML
qemu: Support QEMU group I/O throttling
Add the capability to allow group I/O throttling via a new domain <disk> <iotune> subelement "group_name" to allow sharing I/O throttling quota between multiple drives.
nss: Introduce libvirt_guest
New `libvirt_guest` nss module that translates libvirt guest names into IP addresses.
daemon: Add support for runtime logging settings adjustment
Logging-related settings like log outputs and filters can now be adjusted during runtime using the admin interface without the necessity of the daemon's restart.
storage: Add virStorageVolInfoFlags API
Add the API to support using the VIR_STORAGE_VOL_GET_PHYSICAL flag in order to return the host physical size in bytes of the image container in the allocation field of the _virStorageVolInfo structure. The --physical flag has been added to the virsh vol-info command to access the data.
libxl: Implement virDomainGetMaxVcpus API
storage: Add overwrite flag checking for logical pool
Add support for the OVERWRITE flags for the logical storage backend including checking for existing data on the target volumes when building a new logical pool on target volume(s).
qemu: Add support for guest CPU configuration on s390(x)

# Improvements

perf: Add more perf statistics
Add support to get the count of branch instructions executed, branch misses, bus cycles, stalled frontend cpu cycles, stalled backend cpu cycles, and ref cpu cycles by applications running on the platform.
conf: Display <physical> for volume xml
Add a display of the <physical> size of a disk volume in the output of the volume XML.
qemu: Use virtio-pci by default for aarch64 mach-virt guests
virtio-pci provides several advantages over virtio-mmio, such as the ability to hotplug devices and improved performance. While opting in to virtio-pci has been possible for a while, newly-defined guests will now use it automatically.
vbox: remove support for VirtualBox 3.x and older
Those old VirtualBox versions have been unsupported by upstream for a long time and the API of 4.0 and newer has diverged enough to require code abstractions to handle differences. Removing support for those old versions drops lots of code from the driver and simplifies the logic to ease implementation of new features going forward.
virsh: pool-info: introduce option --bytes
Add option --bytes to virsh pool-info in order ti allow display of units in bytes rather than default of human readable output.
scsi: Add parent wwnn/wwpn or fabric capability for createVport
Improve the algorithm searching for the parent scsi_host device for vHBA/NPIV scsi_host creation. Rather than supplying the "parent" by name, it's now possible to define the parent by it's wwnn/wwpn or fabric_wwn in the node device create XML or the storage pool XML.
qemu: aggregate pcie-root-ports onto multiple functions of a slot
When pcie-root-ports are added to pcie-root in order to provide a place to connect PCI Express endpoint devices, libvirt now aggregates multiple root ports together onto the same slot (up to 8 per slot) in order to conserve slots. Using this method, it's possible to connect more than 200 endpoint devices to a guest that uses PCIe without requiring setup of any PCIe switches.

# Bug fixes

lxc: fix accidental killing of containers during libvirtd restart
The libvirt_lxc process was previously not moved into the container scope. As a result, if systemd reloads its config after a container is started, when libvirtd is later restarted it will accidentally kill the containers.
qemu: Correct GetBlockInfo values
For an active domain, correct the physical value provided for a raw sparse file backed storage and the allocation value provided for a qcow2 file backed storage that hasn't yet been opened on the domain.
qemu: Make virtio console usable on ppc64 guests
The chardev detection code has been improved and can now handle this configuration properly.
qemu: Enable mount namespace
To avoid funny races with udev relabelling devices under our hands and to enhance security, libvirt now spawns each qemu process with its own `/dev`.
storage: Fix implementation of no-overwrite for file system backend
Fix file system storage backend implementation of the OVERWRITE flags to be consistent between code and documentation. Add checks to ensure that when building a new file system on a target volume that there is not something already on the disk in a format that libvirt can recognize.
qemu: Create hugepage path on per domain basis
Historically, all hugepage enabled domains shared the same path under hugetlbfs. This left libvirt unable to correctly set security labels on it. With this release, however, each domain is put into a separate path which is also correctly labeled.
conf: Reject domains with duplicate drive addresses
Reject duplicate drive addresses for disks and hostdevs at domain definition.
libxl: reverse defaults on HVM net device attach
Fixes network interface attach for HVM domains when no model is specified. Emulated hotplug isn't yet supported and hence we should default to the general working scenario.
libxl: always enable pae for x86_64 HVM
By default pae is disabled in libxl. Without an explicit <pae/> setting in the domain <features> configuration, an x86_64 HVM domain would be get an i686 environment. pae should always be enabled for x86_64 HVM domains.
qemu: Fix XML dump of autogenerated websocket
As a result autogenerated websocket port is regenerated on domain restore, migration and such as it should be.

## v2.5.0 2016-12-04

# New features

shmem: Add support for additional models
The shmem device can now utilize QEMU's ivshmem-plain and ivshmem-doorbell, more modern versions of ivshmem.
vbox: Add VirtualBox 5.1 support
libssh: New transport
The new libssh transport allows one to connect to a running libvirtd via SSH, using the libssh library; for example: `qemu+libssh://server/system`.
vhost-scsi: Add support scsi_host hostdev passthrough
Add the capability to pass through a scsi_host HBA and the associated LUNs to the guest.
Allow debugging of gluster volumes in qemu
Users can now enable debug logging for native gluster volumes in qemu using the "gluster_debug_level" option in qemu.conf
Pre-allocate memory slots for memory hotplug
Slot numbers for memory devices are now automatically allocated and thus persistent. In addition slot numbers can be specified without providing a base address, which simplifies user configuration
qemu: Express devices will be placed on PCIe bus by default
For machine types that use a PCI Express root bus (e.g. x86_64/Q35 and aarch64/virt), any unaddressed PCI device that is an Express device (all virtio-1.0 devices, e1000e, nec-xhci, vfio assigned devices) will be placed on an Express controller (i.e. a pcie-root-port) instead of a legacy PCI controller (i.e. pci-bridge) with the root ports added as needed.

# Improvements

docs: Better documentation for migration APIs and flags
vbox: Address thread safety issues
virsh: Add support for passing an alternative persistent XML to migrate command
vhostuser: Allow hotplug of multiqueue devices
NEWS: Switch to an improved format
List user-visible changes instead of single commits for a better high-level overview of differences between libvirt releases.
website: Modernize layout and branding
The libvirt website looked very cluttered and outdated; it has now been completely overhauled, resulting in a design that's better organized and more pleasant to look at.

# Bug fixes

vz: Fix migration in P2P mode
Forbid newline character in names of some libvirt objects
Fix compilation on macOS