libvirt: Node devices XML format
Description: libvirt, virtualization, virtualization API

# Node devices XML format

- Node Device XML
  - mdev_types capability
- Examples

## Node Device XML

There are several libvirt functions, all with the prefix `virNodeDevice`, which deal with management of host devices that can be handed to guests via passthrough as <hostdev> elements in the domain XML. These devices are represented as a hierarchy, where a device on a bus has a parent of the bus controller device; the root of the hierarchy is the node named "computer".

When represented in XML, a node device uses the top-level `device` element, with the following elements present according to the type of device:

`name`
  The name for this device. The name will be alphanumeric, with words separated by underscore. For many devices, the name is just the bus type and address, as in "pci_0000_00_02_1" or "usb_1_5_3", but some devices are able to provide more specific names, such as "net_eth1_00_27_13_6a_fe_00". This is a read-only field that is reported by the device driver. If this element is set when defining a new device, it will be ignored.
`path`
  Fully qualified sysfs path to the device. This is a read-only field that is reported by the device driver. If this element is set when defining a new device, it will be ignored.
`parent`
  This element identifies the parent node in the device hierarchy. The value of the element will correspond with the device parent's `name` element or `computer` if the device does not have any parent.
`driver`
  This elements reports the driver in use for this device. The presence of this element in the output XML depends on whether the underlying device manager (most likely udev) exposes information about the driver.
`devnode`
  This node appears for each associated `/dev` special file. A mandatory attribute `type` specify the kind of file path, which may be either `dev` for the main name, or `link` for additional symlinks.
`capability`
  This node appears for each capability that libvirt associates with a node. A mandatory attribute `type` lists which category the device belongs to, and controls which further subelements will be present to describe the node:
  `system`
    Describes the overall host. Sub-elements include:
    `product`
      If present, a simple text string giving the product name of the system.
    `hardware`
      Describes the hardware of the system, including sub-elements for `vendor`, `version`, `serial`, and `uuid`.
    `firmware`
      Describes the firmware of the system, including sub-elements for `vendor`, `version`, and `release_date`.
  `pci`
    Describes a device on the host's PCI bus. Sub-elements include:
    `class`
      Optional element for combined class, subclass and programming interface codes as 6-digit hexadecimal number. Since 5.2.0
    `domain`
      Which domain the device belongs to.
    `bus`
      Which bus within the domain.
    `slot`
      Which slot within the bus.
    `function`
      Which function within the slot.
    `product`
      Product details from the device ROM, including an attribute `id` with the hexadecimal product id, and an optional text description of that id.
    `vendor`
      Vendor details from the device ROM, including an attribute `id` with the hexadecimal vendor id, and an optional text name of that vendor.
    `iommuGroup`
      This optional element describes the "IOMMU group" this device belongs to. If the element exists, it has a mandatory `number` attribute which tells the group number used for management of the group (all devices in group "n" will be found in "/sys/kernel/iommu_groups/n"). It will also have a list of `address` subelements, each containing the PCI address of a device in the same group. The toplevel device will itself be included in this list.
    `capability`
      This optional element can occur multiple times. If it exists, it has a mandatory `type` attribute which will be set to:
      `phys_function`
        That means there will be a single `address` subelement which contains the PCI address of the SRIOV Physical Function (PF) that is the parent of this device (and this device is, by implication, an SRIOV Virtual Function (VF)).
      `virt_functions`
        In this case this device is an SRIOV PF, and the capability element will have a list of `address` subelements, one for each VF on this PF. If the host system supports reporting it (via the "sriov_totalvfs" file in the device's sysfs directory) the capability element will also have an attribute named `maxCount` which is the maximum number of SRIOV VFs supported by this device, which could be higher than the number of VFs that are currently active since 1.3.0; in this case, even if there are currently no active VFs the virtual_functions capabililty will still be shown.
      `pci-bridge` or `cardbus-bridge`
        This shows merely that the lower 7 bits of PCI header type have either value of 1 or 2 respectively. Usually this means such device cannot be used for PCI passthrough. Since 1.3.3
      `mdev_types`
        This device is capable of creating mediated devices. The sub-elements are summarized in mdev_types capability.
    `numa`
      This optional element contains information on the PCI device with respect to NUMA. For example, the optional `node` attribute tells which NUMA node is the PCI device associated with.
    `pci-express`
      This optional element contains information on PCI Express part of the device. For example, it can contain a child element `link` which addresses the PCI Express device's link. While a device has its own capabilities (`validity='cap'`), the actual run time capabilities are negotiated on the device initialization (`validity='sta'`). The `link` element then contains three attributes: `port` which says in which port is the device plugged in, `speed` (in GigaTransfers per second) and `width` for the number of lanes used. Since the port can't be negotiated, it's not exposed in `./pci-express/link/[@validity='sta']`.
  `usb_device`
    Describes a device on the host's USB bus, based on its location within the bus. Sub-elements include:
    `bus`
      Which bus the device belongs to.
    `device`
      Which device within the bus.
    `product`
      Product details from the device ROM, including an attribute `id` with the hexadecimal product id, and an optional text description of that id.
    `vendor`
      Vendor details from the device ROM, including an attribute `id` with the hexadecimal vendor id, and an optional text name of that vendor.
  `usb`
    Describes a USB device, based on its advertised driver interface. Sub-elements include:
    `number`
      The device number.
    `class`
      The device class.
    `subclass`
      The device subclass.
    `protocol`
      The device protocol.
    `description`
      If present, a description of the device.
  `net`
    Describes a device capable for use as a network interface. Sub-elements include:
    `interface`
      The interface name tied to this device.
    `address`
      If present, the MAC address of the device.
    `link`
      Optional to reflect the status of the link. It has two optional attributes: `speed` in Mbits per second and `state` to tell the state of the link. So far, the whole element is just for output, not setting.
    `feature`
      If present, the hw offloads supported by this network interface. Possible features are:
      `rx`
        rx-checksumming
      `tx`
        tx-checksumming
      `sg`
        scatter-gather
      `tso`
        tcp-segmentation-offload
      `ufo`
        udp-fragmentation-offload
      `gso`
        generic-segmentation-offload
      `gro`
        generic-receive-offload
      `lro`
        large-receive-offload
      `rxvlan`
        rx-vlan-offload
      `txvlan`
        tx-vlan-offload
      `ntuple`
        ntuple-filters
      `rxhash`
        receive-hashing
      `rdma`
        remote-direct-memory-access
      `txudptnl`
        tx-udp-tunnel-segmentation
      `switchdev`
        kernel-forward-plane-offload
    `capability`
      A network protocol exposed by the device, where the attribute `type` can be "80203" for IEEE 802.3, or "80211" for various flavors of IEEE 802.11.
  `scsi_host`
    Describes a SCSI host device. Sub-elements include:
    `host`
      The SCSI host number.
    `unique_id`
      On input, this optionally provides the value from the 'unique_id' file found in the scsi_host's directory. To view the values of all 'unique_id' files, use `find -H /sys/class/scsi_host/host{0..9}/unique_id | xargs grep '[0-9]'`. On output, if the unique_id file exists, the value from the file will be displayed. This can be used in order to help uniquely identify the scsi_host adapter in a Storage Pool. Since 1.2.7
    `capability`
      Current capabilities include "vports_ops" (indicates vport operations are supported) and "fc_host". "vport_ops" could contain two optional sub-elements: `vports`, and `max_vports`. `vports` shows the number of vport in use. `max_vports` shows the maximum vports the HBA supports. "fc_host" implies following sub-elements: `wwnn`, `wwpn`, and optionally `fabric_wwn`.
  `scsi`
    Describes a SCSI device. Sub-elements include:
    `host`
      The SCSI host containing the device.
    `bus`
      The bus within the host.
    `target`
      The target within the bus.
    `lun`
      The lun within the target.
    `type`
      The type of SCSI device.
  `storage`
    Describes a device usable for storage. Sub-elements include:
    `block`
      A block device file name that accesses the storage present on the device.
    `bus`
      If present, the name of the bus the device is found on.
    `drive_type`
      The type of the drive, such as "disk" or "cdrom".
    `model`
      Any model information available from the device.
    `vendor`
      Any vendor information available from the device.
    `serial`
      Any serial number information available from the device.
    `size`
      For fixed-size storage, the amount of storage available.
    `capability`
      If present, an additional capability is listed via the attribute `type`. Current capabilities include "hotpluggable" and "removable", with the latter implying the following sub-elements: `media_available` (0 or 1), `media_size`, and `media_label`.
  `drm`
    Describes a Direct Rendering Manager (DRM) device. Sub-elements include:
    `type`
      The type of DRM device. Could be `primary`, `control` or `render`.
  `mdev`
    Describes a mediated device. Since 3.4.0 Sub-elements include:
    `type`
      Describes a mediated device type which acts as an abstract template defining a resource allocation for instances of this device type. The element has one attribute `id` which holds an official vendor-supplied identifier for the type.
    `iommuGroup`
      This element supports a single attribute `number` which holds the IOMMU group number to which the mediated device belongs. This is a read-only field that is reported by the device driver.
    `attr`
      This optional element can occur multiple times. It represents a vendor-specific attribute that is used to configure this mediated device. It has two required attributes: `name` and `value`.
  `ccw`
    Describes a Command Channel Word (CCW) device commonly found on the S390 architecture. Sub-elements include:
    `cssid`
      The channel subsystem identifier.
    `ssid`
      The subchannel-set identifier.
    `devno`
      The device number.
  `css`
    Describes a Channel SubSystem (CSS) device commonly found on the S390 architecture. Sub-elements include:
    `cssid`
      The channel subsystem identifier.
    `ssid`
      The subchannel-set identifier.
    `devno`
      The device number.
    `capability`
      This optional element can occur multiple times. If it exists, it has a mandatory `type` attribute which will be set to:
      `mdev_types`
        Since 6.10.0 This device is capable of creating mediated devices. The sub-elements are summarized in mdev_types capability.
  `vdpa`
    Describes a virtual datapath acceleration (vDPA) network device. Since 6.9.0. Sub-elements include:
    `chardev`
      The path to the character device that is used to access the device.
  `ap_card`
    Describes the Adjunct Processor (AP) Card device on a S390 host. Sub-elements include:
    `ap-adapter`
      AP Card identifier.
  `ap_queue`
    Describes the AP queue on a s390 host. An AP queue is an AP domain on an AP adapter which is specified by an adapter identifier and a domain identifier. Sub-elements include:
    `ap-adapter`
      The ap-adapter of an AP queue identifies the AP card to which this AP queue belongs.
    `ap-domain`
      The ap-domain of an AP queue identifies the AP domain to which this AP queue belongs.
      AP Queue identifier.
  `ap_matrix`
    Describes an AP Matrix device on a S390 architecture providing cryptographic host resources usable for virtualization. Sub-elements include:
    `capability`
      This optional element can occur multiple times. If it exists, it has a mandatory `type` attribute which will be set to:
      `mdev_types`
        Since 6.10.0 This device is capable of creating mediated devices. The sub-elements are summarized in mdev_types capability.

### mdev_types capability

PCI, CSS and AP Matrix devices can be capable of creating mediated devices. If they indeed are capable, then the parent `capability` element for `mdev_types` type will contain a list of `type` elements, which list all mdev types supported on the physical device. Since 3.4.0 Each `type` element has a single `id` attribute that holds an official vendor-supplied identifier for the type. It supports the following sub-elements:

`name`
  The `name` element holds a vendor-supplied code name for the given mediated device type. This is an optional element.
`deviceAPI`
  The value of this element describes how an instance of the given type will be presented to the guest by the VFIO framework.
`availableInstances`
  This element reports the current state of resource allocation. In other words, how many instances of the given type can still be successfully created on the physical device.

## Examples

The following are some example node device XML outputs:

    <device>
      <name>computer</name>
      <capability type='system'>
        <product>2241B36</product>
        <hardware>
          <vendor>LENOVO</vendor>
          <version>ThinkPad T500</version>
          <serial>R89055N</serial>
          <uuid>c9488981-5049-11cb-9c1c-993d0230b4cd</uuid>
        </hardware>
        <firmware>
          <vendor>LENOVO</vendor>
          <version>6FET82WW (3.12 )</version>
          <release_date>11/26/2009</release_date>
        </firmware>
      </capability>
    </device>

    <device>
      <name>net_eth1_00_27_13_6a_fe_00</name>
      <parent>pci_0000_00_19_0</parent>
      <capability type='net'>
        <interface>eth1</interface>
        <address>00:27:13:6a:fe:00</address>
        <capability type='80203'/>
      </capability>
    </device>

    <device>
      <name>pci_0000_02_00_0</name>
      <path>/sys/devices/pci0000:00/0000:00:04.0/0000:02:00.0</path>
      <parent>pci_0000_00_04_0</parent>
      <driver>
        <name>igb</name>
      </driver>
      <capability type='pci'>
        <class>0x020000</class>
        <domain>0</domain>
        <bus>2</bus>
        <slot>0</slot>
        <function>0</function>
        <product id='0x10c9'>82576 Gigabit Network Connection</product>
        <vendor id='0x8086'>Intel Corporation</vendor>
        <capability type='virt_functions'>
          <address domain='0x0000' bus='0x02' slot='0x10' function='0x0'/>
          <address domain='0x0000' bus='0x02' slot='0x10' function='0x2'/>
          <address domain='0x0000' bus='0x02' slot='0x10' function='0x4'/>
          <address domain='0x0000' bus='0x02' slot='0x10' function='0x6'/>
          <address domain='0x0000' bus='0x02' slot='0x11' function='0x0'/>
          <address domain='0x0000' bus='0x02' slot='0x11' function='0x2'/>
          <address domain='0x0000' bus='0x02' slot='0x11' function='0x4'/>
        </capability>
        <iommuGroup number='12'>
          <address domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
          <address domain='0x0000' bus='0x02' slot='0x00' function='0x1'/>
        </iommuGroup>
        <pci-express>
          <link validity='cap' port='1' speed='2.5' width='1'/>
          <link validity='sta' speed='2.5' width='1'/>
        </pci-express>
      </capability>
    </device>