.. role:: since

==============================
Domain capabilities XML format
==============================

.. contents::

Overview
--------

Sometimes, when a new domain is to be created it may come handy to know the
capabilities of the hypervisor so the correct combination of devices and drivers
is used. For example, when management application is considering the mode for a
host device's passthrough there are several options depending not only on host,
but on hypervisor in question too. If the hypervisor is qemu then it needs to be
more recent to support VFIO, while legacy KVM is achievable just fine with older
qemus.

The main difference between
`virConnectGetCapabilities <html/libvirt-libvirt-host.html#virConnectGetCapabilities>`__
and the emulator capabilities API is, the former one aims more on the host
capabilities (e.g. NUMA topology, security models in effect, etc.) while the
latter one specializes on the hypervisor capabilities.

While the `Driver Capabilities <formatcaps.html>`__ provides the host
capabilities (e.g NUMA topology, security models in effect, etc.), the Domain
Capabilities provides the hypervisor specific capabilities for Management
Applications to query and make decisions regarding what to utilize.

The Domain Capabilities can provide information such as the correct combination
of devices and drivers that are supported. Knowing which host and hypervisor
specific options are available or supported would allow the management
application to choose an appropriate mode for a pass-through host device as well
as which adapter to utilize.

Some XML elements may be entirely omitted from the domaincapabilities XML,
depending on what the libvirt driver has filled in. Applications should only act
on what is explicitly reported in the domaincapabilities XML. For example, if
<disk supported='yes'/> is present, you can safely assume the driver supports
<disk> devices. If <disk supported='no'/> is present, you can safely assume the
driver does NOT support <disk> devices. If the <disk> block is omitted entirely,
the driver is not indicating one way or the other whether it supports <disk>
devices, and applications should not interpret the missing block to mean any
thing in particular.

Element and attribute overview
------------------------------

A new query interface was added to the virConnect API's to retrieve the XML
listing of the set of domain capabilities ( :since:`Since 1.2.7` ):

   ``virConnectGetDomainCapabilities`` (`API docs <html/libvirt-libvirt-domain.html#virConnectGetDomainCapabilities>`__)

The root element that emulator capability XML document starts with has name
``domainCapabilities``. It contains at least four direct child elements:

::

   <domainCapabilities>
     <path>/usr/bin/qemu-system-x86_64</path>
     <domain>kvm</domain>
     <machine>pc-i440fx-2.1</machine>
     <arch>x86_64</arch>
     ...
   </domainCapabilities>

``path``
   The full path to the emulator binary. Since not every hypervisor has a
   notion of emulator binary this element might be omitted in such drivers.
``domain``
   Describes the `virtualization type <formatdomain.html#element-and-attribute-overview>`__ (or so
   called domain type).
``machine``
   The domain's `machine type <formatdomain.html#guest-firmware>`__. Since not
   every hypervisor has a sense of machine types this element might be omitted
   in such drivers.
``arch``
   The domain's `architecture <formatdomain.html#guest-firmware>`__.

CPU Allocation
~~~~~~~~~~~~~~

Before any devices capability occurs, there might be info on domain wide
capabilities, e.g. virtual CPUs:

::

   <domainCapabilities>
     ...
     <vcpu max='255'/>
     ...
   </domainCapabilities>

``vcpu``
   The maximum number of supported virtual CPUs

Guest firmware
~~~~~~~~~~~~~~

.. container::
   :name: bios-bootloader

   .. this container only exists to keep old links working

Exposes information about supported
`guest firmware <formatdomain.html#guest-firmware>`__ configurations for
domains.

::

   <domainCapabilities>
     ...
     <os supported='yes'>
       <enum name='firmware'>
         <value>bios</value>
         <value>efi</value>
       </enum>
       <firmwareFeatures supported='yes'>
         <enum name='secureBoot'>
           <value>yes</value>
           <value>no</value>
         </enum>
         <enum name='enrolledKeys'>
           <value>yes</value>
           <value>no</value>
         </enum>
       </firmwareFeatures>
       <loader supported='yes'>
         <value>/usr/share/OVMF/OVMF_CODE.fd</value>
         <enum name='type'>
           <value>rom</value>
           <value>pflash</value>
         </enum>
         <enum name='readonly'>
           <value>yes</value>
           <value>no</value>
         </enum>
         <enum name='secure'>
           <value>yes</value>
           <value>no</value>
         </enum>
       </loader>
       <varstore supported='yes'/>
     </os>
     ...
   <domainCapabilities>

The presence of the ``firmware`` enum means that libvirt can perform firmware
autoselection, and each of the values is guaranteed to be usable. In the
domain XML, firmware autoselection is enabled as follows:

::

    <os firmware='efi'>
      ...

Autoselection is the recommended mechanism for configuring the guest firmware.
Providing paths and other information manually is discouraged.

The ``<firmwareFeatures/>`` element :since:`(since 12.1.0)` contains one
enum for each of the features that can be used to fine-tune the firmware
autoselection process. For example:

::

    <firmwareFeatures supported='yes'>
      <enum name='secureBoot'>
        <value>yes</value>
      </enum>
      <enum name='enrolledKeys'>
        <value>yes</value>
        <value>no</value>
      </enum>
    </firmwareFeatures>

indicates that a domain XML such as:

::

    <os firmware='efi'>
      <firmware>
        <feature name='secure-boot' enabled='yes'/>
        <feature name='enrolled-keys' enabled='no'/>
      </firmware>
    </os>

can be used to allow unsigned operating system to run, whereas a domain XML
such as:

::

    <os firmware='efi'>
      <firmware>
        <feature name='secure-boot' enabled='no'/>
      </firmware>
    </os>

would not work, since ``no`` is not one of the valid values advertised by
the ``secureBoot`` enum.

The information contained in the ``<loader/>`` element is not relevant when
using firmware autoselection, which is the recommended approach to guest
firmware configuration, and as such can largely be ignored. Its subelements
are the following:

``value``
   One element for each known firmware binary present on the system.

   Note that a binary being present here indicates that the file exists and it
   is compatible with the architecture/machine type, but does not provide any
   insight into which mechanism (see ``type`` below) should be used to load it.
``type``
   Whether firmware can be loaded using a ``pflash`` device (UEFI only) or as
   a ``rom`` (either UEFI or BIOS).
``readonly``
   Supported values for the ``readonly`` attribute of the ``<loader/>`` element
   in the domain XML.
``secure``
   Supported values for the ``secure`` attribute of the ``<loader/>`` element
   in the domain XML.

   Note that the value ``yes`` is listed if libvirt detects a firmware
   descriptor file that points to a firmware binary that implements Secure
   Boot and is compatible with the architecture/machine type, but the UEFI
   variable store template associated with it might not have the usual set of
   Secure Boot certificates enrolled. To figure out whether it's actually
   possible to enforce Secure Boot, look at the ``enrolledKeys`` enum inside
   the ``<firmwareFeatures/>`` element instead.

The ``<varstore/>`` element :since:`(since 12.1.0)` indicates whether UEFI
variable storage backed by the ``uefi-vars`` QEMU device can be used as an
alternative to pflash-based NVRAM storage. This is the only type of variable
storage compatible with Secure Boot on non-x86 architectures, but it can be
used on x86 too.

CPU configuration
~~~~~~~~~~~~~~~~~

The ``cpu`` element exposes options usable for configuring `guest
CPUs <formatdomain.html#cpu-model-and-topology>`__.

::

   <domainCapabilities>
     ...
     <cpu>
       <mode name='host-passthrough' supported='yes'>
         <enum name='hostPassthroughMigratable'>
           <value>on</value>
           <value>off</value>
         </enum>
       </mode>
       <mode name='maximum' supported='yes'>
         <enum name='maximumMigratable'>
           <value>on</value>
           <value>off</value>
         </enum>
       </mode>
       <mode name='host-model' supported='yes'>
         <model fallback='allow'>Broadwell</model>
         <vendor>Intel</vendor>
         <maxphysaddr mode="passthrough" limit="39"/>
         <feature policy='disable' name='aes'/>
         <feature policy='require' name='vmx'/>
       </mode>
       <mode name='custom' supported='yes'>
         <model usable='no' deprecated='no' vendor='Intel' canonical='Broadwell-v1'>Broadwell</model>
         <blockers model='Broadwell'>
           <feature name='hle'/>
           <feature name='rtm'/>
         </blockers>
         <model usable='yes' deprecated='no' vendor='Intel' canonical='Broadwell-v2'>Broadwell-noTSX</model>
         <model usable='no' deprecated='no' vendor='AMD'>EPYC-Milan</model>
         <blockers model='EPYC-Milan'>
           <feature name='clzero'/>
           <feature name='cr8legacy'/>
           <feature name='fxsr_opt'/>
           <feature name='misalignsse'/>
           <feature name='mmxext'/>
           <feature name='osvw'/>
           <feature name='perfctr_core'/>
           <feature name='sse4a'/>
           <feature name='wbnoinvd'/>
           <feature name='xsaveerptr'/>
         </blockers>
         <model usable='no' deprecated='yes' vendor='Intel'>Haswell</model>
         <blockers model='Haswell'>
           <feature name='hle'/>
           <feature name='rtm'/>
         </blockers>
         ...
       </mode>
     </cpu>
     ...
   <domainCapabilities>

Each CPU mode understood by libvirt is described with a ``mode`` element which
tells whether the particular mode is supported and provides (when applicable)
more details about it:

``host-passthrough``
   The ``hostPassthroughMigratable`` enum shows possible values of the
   ``migratable`` attribute for the <cpu> element with
   ``mode='host-passthrough'`` in the domain XML.
``host-model``
   If ``host-model`` is supported by the hypervisor, the ``mode`` describes the
   guest CPU which will be used when starting a domain with ``host-model`` CPU.
   The hypervisor specifics (such as unsupported CPU models or features, machine
   type, etc.) may be accounted for in this guest CPU specification and thus the
   CPU can be different from the one shown in host capabilities XML. This is
   indicated by the ``fallback`` attribute of the ``model`` sub element:
   ``allow`` means not all specifics were accounted for and thus the CPU a guest
   will see may be different; ``forbid`` indicates that the CPU a guest will see
   should match this CPU definition. The optional ``maxphysaddr`` element
   reports physical address size of the host CPU if this value is available and
   applicable for the requested domain type. This is useful for computing
   baseline CPU definition which should be compatible with several hosts.
   Consistently with all other CPU definitions used by libvirt, features
   implicitly enabled by the selected CPU model (in ``model`` sub element) are
   not listed. Use ``--expand-cpu-features`` virsh option or the equivalent API
   flag to request all supported features to be listed in the CPU definition.
``custom``
   The ``mode`` element contains a list of supported CPU models, each described
   by a dedicated ``model`` element. The ``usable`` attribute specifies whether
   the model can be used directly on the host. A special value ``unknown``
   indicates libvirt does not have enough information to provide the usability
   data. When ``usable='no'`` the corresponding model cannot be used without
   disabling some features that the CPU of such model is expected to have.
   :since:`Since 10.9.0` each CPU model with ``usable='no'`` is followed by
   a corresponding ``blockers`` element containing a list of features blocking
   usability of the CPU model. Models marked as usable (``usable='yes'``) can
   be safely used in domain XMLs with ``check='none'`` as the hypervisor
   guarantees the model can be used on the current host and additional checks
   done by libvirt are redundant. :since:`Since 10.2.0` libvirt automatically
   detects this situation and avoids the redundant checks even when
   ``check='partial'`` is used, with older releases disabling libvirt checks
   via ``check='none'`` for such models is recommended to avoid needless issues
   with starting domains when libvirt's definition of a particular model
   differs from hypervisor's definition. The ``deprecated`` attribute reflects
   the hypervisor's policy on usage of this model :since:`(since 7.1.0)`. The
   ``vendor`` attribute :since:`(since 8.9.0)` contains the vendor of the CPU
   model for users who want to use CPU models with specific vendors only. CPU
   models with undefined vendor will be listed with ``vendor='unkwnown'``. The
   ``canonical`` attribute :since:`(since 10.10.0)` contains a canonical name of
   the CPU model if the model is actually an alias to another one.

I/O Threads
~~~~~~~~~~~

The ``iothread`` elements indicates whether or not `I/O
threads <formatdomain.html#iothreads-allocation>`__ are supported.

::

   <domainCapabilities>
     ...
     <iothread supported='yes'/>
     ...
   <domainCapabilities>

Memory Backing
~~~~~~~~~~~~~~

The ``memory backing`` element indicates whether or not `memory
backing <formatdomain.html#memory-backing>`__ is supported.

::

   <domainCapabilities>
     ...
     <memoryBacking supported='yes'>
       <enum name='sourceType'>
         <value>anonymous</value>
         <value>file</value>
         <value>memfd</value>
       </enum>
     </memoryBacking>
     ...
   <domainCapabilities>

``sourceType``
   Options for the ``type`` attribute of the <memoryBacking><source> element.

Devices
~~~~~~~

Another set of XML elements describe the supported devices and their
capabilities. All devices occur as children of the main ``devices`` element.

::

   <domainCapabilities>
     ...
     <devices>
       <disk supported='yes'>
         <enum name='diskDevice'>
           <value>disk</value>
           <value>cdrom</value>
           <value>floppy</value>
           <value>lun</value>
         </enum>
         ...
       </disk>
       <hostdev supported='no'/>
     </devices>
   </domainCapabilities>

Reported capabilities are expressed as an enumerated list of available options
for each of the element or attribute. For example, the <disk/> element has an
attribute ``device`` which can support the values ``disk``, ``cdrom``,
``floppy``, or ``lun``.

Hard drives, floppy disks, CDROMs
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Disk capabilities are exposed under the ``disk`` element. For instance:

::

   <domainCapabilities>
     ...
     <devices>
       <disk supported='yes'>
         <enum name='diskDevice'>
           <value>disk</value>
           <value>cdrom</value>
           <value>floppy</value>
           <value>lun</value>
         </enum>
         <enum name='bus'>
           <value>ide</value>
           <value>fdc</value>
           <value>scsi</value>
           <value>virtio</value>
           <value>xen</value>
           <value>usb</value>
           <value>sata</value>
           <value>sd</value>
         </enum>
       </disk>
       ...
     </devices>
   </domainCapabilities>

``diskDevice``
   Options for the ``device`` attribute of the <disk/> element.
``bus``
   Options for the ``bus`` attribute of the <target/> element for a <disk/>.

Graphical framebuffers
^^^^^^^^^^^^^^^^^^^^^^

Graphics device capabilities are exposed under the ``graphics`` element. For
instance:

::

   <domainCapabilities>
     ...
     <devices>
       <graphics supported='yes'>
         <enum name='type'>
           <value>sdl</value>
           <value>vnc</value>
           <value>spice</value>
         </enum>
       </graphics>
       ...
     </devices>
   </domainCapabilities>

``type``
   Options for the ``type`` attribute of the <graphics/> element.

Video device
^^^^^^^^^^^^

Video device capabilities are exposed under the ``video`` element. For instance:

::

   <domainCapabilities>
     ...
     <devices>
       <video supported='yes'>
         <enum name='modelType'>
           <value>vga</value>
           <value>cirrus</value>
           <value>vmvga</value>
           <value>qxl</value>
           <value>virtio</value>
         </enum>
       </video>
       ...
     </devices>
   </domainCapabilities>

``modelType``
   Options for the ``type`` attribute of the <video><model> element.

Host device assignment
^^^^^^^^^^^^^^^^^^^^^^

Some host devices can be passed through to a guest (e.g. USB, PCI and SCSI).
Well, only if the following is enabled:

::

   <domainCapabilities>
     ...
     <devices>
       <hostdev supported='yes'>
         <enum name='mode'>
           <value>subsystem</value>
           <value>capabilities</value>
         </enum>
         <enum name='startupPolicy'>
           <value>default</value>
           <value>mandatory</value>
           <value>requisite</value>
           <value>optional</value>
         </enum>
         <enum name='subsysType'>
           <value>usb</value>
           <value>pci</value>
           <value>scsi</value>
         </enum>
         <enum name='capsType'>
           <value>storage</value>
           <value>misc</value>
           <value>net</value>
         </enum>
         <enum name='pciBackend'>
           <value>default</value>
           <value>kvm</value>
           <value>vfio</value>
           <value>xen</value>
         </enum>
         <enum name='iommufd'>
           <value>yes</value>
           <value>no</value>
         </enum>
       </hostdev>
     </devices>
   </domainCapabilities>

``mode``
   Options for the ``mode`` attribute of the <hostdev/> element.
``startupPolicy``
   Options for the ``startupPolicy`` attribute of the <hostdev/> element.
``subsysType``
   Options for the ``type`` attribute of the <hostdev/> element in case of
   ``mode="subsystem"``.
``capsType``
   Options for the ``type`` attribute of the <hostdev/> element in case of
   ``mode="capabilities"``.
``pciBackend``
   Options for the ``name`` attribute of the <driver/> element.
``iommufd``
   Options for the ``iommufd`` attribute of the <driver/> element.
   :since:`Since 12.1.0`

RNG device
^^^^^^^^^^

RNG device capabilities are exposed under the ``rng`` element. For instance:

::

   <domainCapabilities>
     ...
     <devices>
       <rng supported='yes'>
         <enum name='model'>
           <value>virtio</value>
           <value>virtio-transitional</value>
           <value>virtio-non-transitional</value>
         </enum>
         <enum name='backendModel'>
           <value>random</value>
           <value>egd</value>
           <value>builtin</value>
         </enum>
       </rng>
       ...
     </devices>
   </domainCapabilities>

``model``
   Options for the ``model`` attribute of the <rng> element.
``backendModel``
   Options for the ``model`` attribute of the <rng><backend> element.

Filesystem device
^^^^^^^^^^^^^^^^^

Filesystem device capabilities are exposed under the ``filesystem`` element. For
instance:

::

   <domainCapabilities>
     ...
     <devices>
       <filesystem supported='yes'>
         <enum name='driverType'>
           <value>default</value>
           <value>path</value>
           <value>handle</value>
           <value>virtiofs</value>
         </enum>
       </filesystem>
       ...
     </devices>
   </domainCapabilities>

``driverType``
   Options for the ``type`` attribute of the <filesystem><driver> element.

TPM device
^^^^^^^^^^

TPM device capabilities are exposed under the ``tpm`` element. For instance:

::

  <domainCapabilities>
    ...
    <devices>
      <tpm supported='yes'>
        <enum name='model'>
          <value>tpm-tis</value>
          <value>tpm-crb</value>
        </enum>
        <enum name='backendModel'>
          <value>passthrough</value>
          <value>emulator</value>
        </enum>
        <enum name='backendVersion'>
          <value>1.2</value>
          <value>2.0</value>
        </enum>
      </tpm>
      ...
    </devices>
  </domainCapabilities>

``model``
   Options for the ``model`` attribute of the ``<tpm/>`` element.
``backendModel``
   Options for the ``type`` attribute of the ``<tpm><backend/>`` element.
``backendVersion``
   Options for the ``version`` attribute of the ``<tpm><backend/>`` element.

USB redirect device
^^^^^^^^^^^^^^^^^^^

USB redirdev device capabilities are exposed under the ``redirdev`` element. For instance:

::

  <domainCapabilities>
    ...
    <devices>
      <redirdev supported='yes'>
        <enum name='bus'>
          <value>usb</value>
        </enum>
      </redirdev>
      ...
    </devices>
  </domainCapabilities>

``bus``
   Options for the ``bus`` attribute of the ``<redirdev/>`` element.

Channel device
^^^^^^^^^^^^^^

Channel device capabilities are exposed under the ``channel`` element. For instance:

::

  <domainCapabilities>
    ...
    <devices>
      <channel supported='yes'>
        <enum name='type'>
          <value>pty</value>
          <value>unix</value>
          <value>spicevmc</value>
        </enum>
      </channel
      ...
    </devices>
  </domainCapabilities>

``type``
   Options for the ``type`` attribute of the ``<channel/>`` element.

Crypto device
^^^^^^^^^^^^^^

Crypto device capabilities are exposed under the ``crypto`` element. For instance:

::

  <domainCapabilities>
    ...
    <devices>
      <crypto supported='yes'>
        <enum name='model'>
          <value>virtio</value>
        </enum>
        <enum name='type'>
          <value>qemu</value>
        </enum>
        <enum name='backendModel'>
          <value>builtin</value>
          <value>lkcf</value>
        </enum>
      </crypto>
      ...
    </devices>
  </domainCapabilities>

``model``
   Options for the ``model`` attribute of the ``<crypto/>`` element.
``type``
   Options for the ``type`` attribute of the ``<crypto/>`` element.
``backendModel``
   Options for the ``backendModel`` attribute of the ``<crypto><backend/>`` element.

Interface device
^^^^^^^^^^^^^^^^

Interface device corresponds to `network interface
<formatdomain.html#network-interfaces>`__ (``<interface/>``) in domain XML.

::

  <domainCapabilities>
    ...
    <devices>
      <interface supported='yes'>
        <enum name='backendType'>
          <value>default</value>
          <value>passt</value>
        </enum>
      </interface>
      ...
    </devices>
  </domainCapabilities>

``backendType``
   Options for the ``type`` attribute of the ``<backend/>`` element

Panic device
^^^^^^^^^^^^

Interface device corresponds to `panic device
<formatdomain.html#panic-device>`__ (``<panic/>``) in domain XML.

::

  <domainCapabilities>
    ...
    <devices>
      <panic supported='yes'>
        <enum name='model'>
          <value>isa</value>
          <value>hyperv</value>
        </enum>
      </panic>
      ...
    </devices>
  </domainCapabilities>

``model``
   Options for the ``model`` attribute of the ``<panic/>`` element


Features
~~~~~~~~

One more set of XML elements describe the supported features and their
capabilities. All features occur as children of the main ``features`` element.

::

   <domainCapabilities>
     ...
     <features>
       <gic supported='yes'>
         <enum name='version'>
           <value>2</value>
           <value>3</value>
         </enum>
       </gic>
       <vmcoreinfo supported='yes'/>
       <genid supported='yes'/>
       <backingStoreInput supported='yes'/>
       <backup supported='yes'/>
       <async-teardown supported='yes'/>
       <tdx supported='yes'/>
       <sev>
         <cbitpos>47</cbitpos>
         <reduced-phys-bits>1</reduced-phys-bits>
       </sev>
       <sgx supported='yes'>
         <flc>no</flc>
         <sgx1>yes</sgx1>
         <sgx2>no</sgx2>
         <section_size unit='KiB'>524288</section_size>
         <sections>
           <section node='0' size='262144' unit='KiB'/>
           <section node='1' size='262144' unit='KiB'/>
         </sections>
       </sgx>
       <hyperv supported='yes'>
         <enum name='features'>
           <value>relaxed</value>
           <value>vapic</value>
         </enum>
       </hyperv>
     </features>
   </domainCapabilities>

Reported capabilities are expressed as an enumerated list of possible values for
each of the elements or attributes. For example, the ``gic`` element has an
attribute ``version`` which can support the values ``2`` or ``3``.

For information about the purpose of each feature, see the `relevant
section <formatdomain.html#hypervisor-features>`__ in the domain XML documentation.

GIC capabilities
^^^^^^^^^^^^^^^^

GIC capabilities are exposed under the ``gic`` element.

``version``
   Options for the ``version`` attribute of the ``gic`` element.

vmcoreinfo
^^^^^^^^^^

Reports whether the vmcoreinfo feature can be enabled.

genid
^^^^^

Reports whether the genid feature can be used by the domain.

backingStoreInput
^^^^^^^^^^^^^^^^^

Reports whether the hypervisor will obey the <backingStore> elements configured
for a <disk> when booting the guest, hotplugging the disk to a running guest, or
similar. :since:`(Since 5.10)`

backup
^^^^^^

Reports whether the hypervisor supports the backup, checkpoint, and related
features. (``virDomainBackupBegin``, ``virDomainCheckpointCreateXML`` etc). The
presence of the ``backup`` element even if ``supported='no'`` implies that the
``VIR_DOMAIN_UNDEFINE_CHECKPOINTS_METADATA`` flag for ``virDomainUndefine`` is
supported.

async-teardown
^^^^^^^^^^^^^^

Reports whether the asynchronous teardown feature can be enabled.

s390-pv capability
^^^^^^^^^^^^^^^^^^

Reports whether the hypervisor supports the Protected Virtualization. In order
to use Protected Virtualization with libvirt have a look at the `launchSecurity
element in the domain XML <formatdomain.html#launch-security>`__. For more
details on the Protected Virtualization feature please see `Protected
Virtualization on s390 <kbase/s390_protected_virt.html>`__.

ps2 capability
^^^^^^^^^^^^^^

Reports whether it is possible to disable the machine's built-in PS/2
controller.

SEV capabilities
^^^^^^^^^^^^^^^^

AMD Secure Encrypted Virtualization (SEV) capabilities are exposed under the
``sev`` element. SEV is an extension to the AMD-V architecture which supports
running virtual machines (VMs) under the control of a hypervisor. When
supported, guest owner can create a VM whose memory contents will be
transparently encrypted with a key unique to that VM.

For more details on the SEV feature, please follow resources in the AMD
developer's document store. In order to use SEV with libvirt have a look at `SEV
in domain XML <formatdomain.html#launch-security>`__

``cbitpos``
   When memory encryption is enabled, one of the physical address bits (aka the
   C-bit) is utilized to mark if a memory page is protected. The C-bit position
   is Hypervisor dependent.
``reducedPhysBits``
   When memory encryption is enabled, we lose certain bits in physical address
   space. The number of bits we lose is hypervisor dependent.
``maxGuests``
   The maximum number of SEV guests that can be launched on the host. This value
   may be configurable in the firmware for some hosts.
``maxESGuests``
   The maximum number of SEV-ES guests that can be launched on the host. This
   value may be configurable in the firmware for some hosts.

SGX capabilities
^^^^^^^^^^^^^^^^

Intel Software Guard Extensions (Intel SGX) capabilities are exposed under the
``sgx`` element.

Intel SGX helps protect data in use via unique application isolation technology.
Protect selected code and data from modification using hardened enclaves with
Intel SGX.

For more details on the SGX feature, please follow resources in the SGX developer's
document store. In order to use SGX with libvirt have a look at `SGX in domain XML
<formatdomain.html#memory-devices>`__

``flc``
   FLC (Flexible Launch Control), not strictly part of SGX2, but was not part of
   original SGX hardware either.

``sgx1``
   the sgx version 1.

``sgx2``
   The sgx version 2.

``section_size``
   The size of the SGX enclave page cache (called EPC).

``sections``
   The sections of the SGX enclave page cache (called EPC).


Hyper-V Enlightenments
^^^^^^^^^^^^^^^^^^^^^^

Report which features improving behavior of guests running Microsoft Windows
are supported. The ``features`` enum corresponds to the ``<hyperv/>`` element
(well, its children) as documented in `Hypervisor features
<formatdomain.html#hypervisor-features>`__. The ``defaults`` element then
contains child elements describing default values as reported by hypervisor,
e.g. whether direct or extended TLB flushes are available. :since:`(since
11.9.0)`

Launch security
^^^^^^^^^^^^^^^

The ``launchSecurity`` element exposes supported aspects of encrypted guests.
The ``sectype`` enum corresponds to ``type`` attribute of ``<launchSecurity/>``
element as documented in `Launch Security
<formatdomain.html#launch-security>`__.  :since:`(Since 10.5.0)` For additional
information on individual types, see sections above: `s390-pv capability`_ for
S390 PV, `SEV capabilities`_ for AMD SEV and/or AMD SEV-SNP.
