Node devices XML format

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. The capability types section below describes them further.

capability types

Based on the capbility type there are further more specific attributes to a device described below.

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.

vpd

This device exposes a VPD PCI/PCIe capability. The sub-elements are summarized in vpd 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. Note that the order in which attributes are set may be important for some devices. The order that they appear in the xml definition determines the order that they will be written to the device.

uuid

This element represents the UUID of the mediated device.

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 subchannel in the Channel SubSystem (CSS) commonly found on the S390 architecture. Sub-elements include:

cssid

The channel subsystem identifier.

ssid

The subchannel-set identifier.

devno

The subchannel 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.

vpd capability

pci devices can expose a VPD capability which is optional per PCI Local Bus 2.2+ and PCIe 4.0+ specifications. If the VPD capability is present, then the parent capability element with the vpd type will contain a name element (containing a manufacturer-provided device name) and optionally one or two fields elements with an access attribute set to readonly or readwrite.

The read-only fields element may contain the following elements:

change_level

An engineering change level for this add-in card.

manufacture_id

An extension to the Vendor ID (or Subsystem Vendor ID) in the Configuration Space header which allows vendors the flexibility to identify an additional level of detail pertaining to the sourcing of a PCI device.

part_number

An extension to the Device ID (or Subsystem ID) in the Configuration Space header specifying a part number of an add-in card.

serial_number

A unique add-in card Serial Number.

vendor_field

Zero or many of those elements with an index attribute (since-character upper-case ASCII alphanumeric indexes). Contents will vary depending on a vendor.

All fields are optional and are not guaranteed to be present for a generic PCI device.

The read-write fields element may contain the following elements:

asset_tag

A system asset identifier provided by the system owner.

vendor_field

Zero or many of those elements with an index attribute (since-character upper-case ASCII alphanumeric indexes). Contents will vary depending on a vendor.

system_field

Zero or many of those elements with an index attribute (since-character upper-case ASCII alphanumeric indexes, except for letter 'A'). May store system-specific data related to a PCI device.

All fields are optional and are not guaranteed to be present for a generic PCI device. Read-write fields are not possible to alter via Libvirt at the time of writing but their content is refreshed on each invocation in case this is done by means external to Libvirt.

The device name and all fields may contain only the following characters: [0-9a-zA-F -_,.:;=]. The device name may be as large as 65535 bytes while fields are limited with 255 bytes.

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>