# Attaching physical PCI devices to guests

The PCI passthrough feature in OpenStack allows full access and direct control of a physical PCI device in guests. This mechanism is generic for any kind of PCI device, and runs with a Network Interface Card (NIC), Graphics Processing Unit (GPU), or any other devices that can be attached to a PCI bus. Correct driver installation is the only requirement for the guest to properly use the devices.

Some PCI devices provide Single Root I/O Virtualization and Sharing (SR-IOV) capabilities. When SR-IOV is used, a physical device is virtualized and appears as multiple PCI devices. Virtual PCI devices are assigned to the same or different guests. In the case of PCI passthrough, the full physical device is assigned to only one guest and cannot be shared.

PCI devices are requested through flavor extra specs, specifically via the `pci_passthrough:alias` flavor extra spec. This guide demonstrates how to enable PCI passthrough for a type of PCI device with a vendor ID of `8086` and a product ID of `154d` - an Intel X520 Network Adapter - by mapping them to the alias `a1`. You should adjust the instructions for other devices with potentially different capabilities.

Note

For information on creating servers with SR-IOV network interfaces, refer to the Networking Guide.

Limitations

- Attaching SR-IOV ports to existing servers was not supported until the 22.0.0 Victoria release. Due to various bugs in libvirt and qemu we recommend to use at least libvirt version 6.0.0 and at least qemu version 4.2.

- Cold migration (resize) of servers with SR-IOV devices attached was not supported until the 14.0.0 Newton release, see bug 1512800 for details.

Note

Nova only supports PCI addresses where the fields are restricted to the following maximum value:

- domain - 0xFFFF

- bus - 0xFF

- slot - 0x1F

- function - 0x7

Nova will ignore PCI devices reported by the hypervisor if the address is outside of these ranges.

Changed in version 26.0.0: (Zed): PCI passthrough device inventories now can be tracked in Placement. For more information, refer to PCI tracking in Placement.

Changed in version 26.0.0: (Zed): The nova-compute service will refuse to start if both the parent PF and its children VFs are configured in `pci.device_spec`. For more information, refer to PCI tracking in Placement.

Changed in version 26.0.0: (Zed): The nova-compute service will refuse to start with `pci.device_spec` configuration that uses the `devname` field.

Changed in version 27.0.0: (2023.1 Antelope): Nova provides Placement based scheduling support for servers with flavor based PCI requests. This support is disable by default.

Changed in version 31.0.0: (2025.1 Epoxy):

- Add managed tag to define if the PCI device is managed (attached/detached from the host) by libvirt. This is required to support SR-IOV devices using the new kernel variant driver interface.

- Add a live_migratable tag to define whether a PCI device supports live migration.

- Add a live_migratable tag to alias definitions to allow requesting either a live-migratable or non-live-migratable device.

## Enabling PCI passthrough

### Configure compute host

To enable PCI passthrough on an x86, Linux-based compute node, the following are required:

- VT-d enabled in the BIOS

- IOMMU enabled on the host OS, e.g. by adding the `intel_iommu=on` or `amd_iommu=on` parameter to the kernel parameters

- Assignable PCIe devices

### Configure `nova-compute`

Once PCI passthrough has been configured for the host, nova-compute must be configured to allow the PCI device to pass through to VMs. This is done using the `pci.device_spec` option. For example, assuming our sample PCI device has a PCI address of `41:00.0` on each host:

    [pci]
    device_spec = { "address": "0000:41:00.0" }

Refer to `pci.device_spec` for syntax information.

Alternatively, to enable passthrough of all devices with the same product and vendor ID:

    [pci]
    device_spec = { "vendor_id": "8086", "product_id": "154d" }

If using vendor and product IDs, all PCI devices matching the `vendor_id` and `product_id` are added to the pool of PCI devices available for passthrough to VMs.

In addition, it is necessary to configure the `pci.alias` option, which is a JSON-style configuration option that allows you to map a given device type, identified by the standard PCI `vendor_id` and (optional) `product_id` fields, to an arbitrary name or alias. This alias can then be used to request a PCI device using the `pci_passthrough:alias` flavor extra spec, as discussed previously. For our sample device with a vendor ID of `0x8086` and a product ID of `0x154d`, this would be:

    [pci]
    alias = { "vendor_id":"8086", "product_id":"154d", "device_type":"type-PF", "name":"a1" }

It’s important to note the addition of the `device_type` field. This is necessary because this PCI device supports SR-IOV. The `nova-compute` service categorizes devices into one of three types, depending on the capabilities the devices report:

`type-PF`

  The device supports SR-IOV and is the parent or root device.

`type-VF`

  The device is a child device of a device that supports SR-IOV.

`type-PCI`

  The device does not support SR-IOV.

By default, it is only possible to attach `type-PCI` devices using PCI passthrough. If you wish to attach `type-PF` or `type-VF` devices, you must specify the `device_type` field in the config option. If the device was a device that did not support SR-IOV, the `device_type` field could be omitted.

Refer to `pci.alias` for syntax information.

Important

This option must also be configured on controller nodes. This is discussed later in this document.

Once configured, restart the nova-compute service.

#### Special Tags

When specified in `pci.device_spec` some tags have special meaning:

`physical_network`

  Associates a device with a physical network label which corresponds to the `physical_network` attribute of a network segment object in Neutron. For virtual networks such as overlays a value of `null` should be specified as follows: `"physical_network": null`. In the case of physical networks, this tag is used to supply the metadata necessary for identifying a switched fabric to which a PCI device belongs and associate the port with the correct network segment in the networking backend. Besides typical SR-IOV scenarios, this tag can be used for remote-managed devices in conjunction with the `remote_managed` tag.

Note

The use of `"physical_network": null` is only supported in single segment networks. This is due to Nova not supporting multisegment networks for SR-IOV ports. See bug 1983570 for details.

`remote_managed`

  Used to specify whether a PCI device is managed remotely or not. By default, devices are implicitly tagged as `"remote_managed": "false"` but and they must be tagged as `"remote_managed": "true"` if ports with `VNIC_TYPE_REMOTE_MANAGED` are intended to be used. Once that is done, those PCI devices will not be available for allocation for regular PCI passthrough use. Specifying `"remote_managed": "true"` is only valid for SR-IOV VFs and specifying it for PFs is prohibited.

  Important

  It is recommended that PCI VFs that are meant to be remote-managed (e.g. the ones provided by SmartNIC DPUs) are tagged as remote-managed in order to prevent them from being allocated for regular PCI passthrough since they have to be programmed accordingly at the host that has access to the NIC switch control plane. If this is not done, instances requesting regular SR-IOV ports may get a device that will not be configured correctly and will not be usable for sending network traffic.

  Important

  For the Libvirt virt driver, clearing a VLAN by programming VLAN 0 must not result in errors in the VF kernel driver at the compute host. Before v8.1.0 Libvirt clears a VLAN before passing a VF through to the guest which may result in an error depending on your driver and kernel version (see, for example, this bug which discusses a case relevant to one driver). As of Libvirt v8.1.0, EPERM errors encountered while programming a VLAN are ignored if VLAN clearing is not explicitly requested in the device XML.

`trusted`

  If a port is requested to be trusted by specifying an extra option during port creation via `--binding-profile trusted=true`, only devices tagged as `trusted: "true"` will be allocated to instances. Nova will then configure those devices as trusted by the network controller through its PF device driver. The specific set of features allowed by the trusted mode of a VF will differ depending on the network controller itself, its firmware version and what a PF device driver version allows to pass to the NIC. Common features to be affected by this tag are changing the VF MAC address, enabling promiscuous mode or multicast promiscuous mode.

  Important

  While the `trusted tag` does not directly conflict with the `remote_managed` tag, network controllers in SmartNIC DPUs may prohibit setting the `trusted` mode on a VF via a PF device driver in the first place. It is recommended to test specific devices, drivers and firmware versions before assuming this feature can be used.

`managed`

  Users must specify whether the PCI device is managed by libvirt to allow detachment from the host and assignment to the guest, or vice versa. The managed mode of a device depends on the specific device and the support provided by its driver.

  - `managed='yes'` means that nova will let libvirt to detach the device from the host before attaching it to the guest and re-attach it to the host after the guest is deleted.

  - `managed='no'` means that Nova will not request libvirt to attach or detach the device from the host. Instead, Nova assumes that the operator has pre-configured the host so that the devices are already bound to vfio-pci or an appropriate variant driver. This setup allows the devices to be directly usable by QEMU without requiring any additional operations to enable passthrough.

  Note

  If not set, the default value is managed=’yes’ to preserve the existing behavior, primarily for upgrade purposes.

  Warning

  Incorrect configuration of this parameter may result in compute node crashes.

### Configure `nova-scheduler`

The nova-scheduler service must be configured to enable the `PciPassthroughFilter`. To do this, add this filter to the list of filters specified in `filter_scheduler.enabled_filters` and set `filter_scheduler.available_filters` to the default of `nova.scheduler.filters.all_filters`. For example:

    [filter_scheduler]
    enabled_filters = ...,PciPassthroughFilter
    available_filters = nova.scheduler.filters.all_filters

Once done, restart the nova-scheduler service.

### Configure `nova-api`

It is necessary to also configure the `pci.alias` config option on the controller. This configuration should match the configuration found on the compute nodes. For example:

    [pci]
    alias = { "vendor_id":"8086", "product_id":"154d", "device_type":"type-PF", "name":"a1", "numa_policy":"preferred" }

Refer to `pci.alias` for syntax information. Refer to Affinity for `numa_policy` information.

Once configured, restart the Compute API service.

## Configuring a flavor or image

Once the alias has been configured, it can be used for an flavor extra spec. For example, to request two of the PCI devices referenced by alias `a1`, run:

    $ openstack flavor set m1.large --property "pci_passthrough:alias"="a1:2"

For more information about the syntax for `pci_passthrough:alias`, refer to the documentation.

## PCI-NUMA affinity policies

By default, the libvirt driver enforces strict NUMA affinity for PCI devices, be they PCI passthrough devices or neutron SR-IOV interfaces. This means that by default a PCI device must be allocated from the same host NUMA node as at least one of the instance’s CPUs. This isn’t always necessary, however, and you can configure this policy using the `hw:pci_numa_affinity_policy` flavor extra spec or equivalent image metadata property. There are three possible values allowed:

required

  This policy means that nova will boot instances with PCI devices only if at least one of the NUMA nodes of the instance is associated with these PCI devices. It means that if NUMA node info for some PCI devices could not be determined, those PCI devices wouldn’t be consumable by the instance. This provides maximum performance.

socket

  This policy means that the PCI device must be affined to the same host socket as at least one of the guest NUMA nodes. For example, consider a system with two sockets, each with two NUMA nodes, numbered node 0 and node 1 on socket 0, and node 2 and node 3 on socket 1. There is a PCI device affined to node 0. An PCI instance with two guest NUMA nodes and the `socket` policy can be affined to either:

  - node 0 and node 1

  - node 0 and node 2

  - node 0 and node 3

  - node 1 and node 2

  - node 1 and node 3

  The instance cannot be affined to node 2 and node 3, as neither of those are on the same socket as the PCI device. If the other nodes are consumed by other instances and only nodes 2 and 3 are available, the instance will not boot.

preferred

  This policy means that `nova-scheduler` will choose a compute host with minimal consideration for the NUMA affinity of PCI devices. `nova-compute` will attempt a best effort selection of PCI devices based on NUMA affinity, however, if this is not possible then `nova-compute` will fall back to scheduling on a NUMA node that is not associated with the PCI device.

legacy

  This is the default policy and it describes the current nova behavior. Usually we have information about association of PCI devices with NUMA nodes. However, some PCI devices do not provide such information. The `legacy` value will mean that nova will boot instances with PCI device if either:

  - The PCI device is associated with at least one NUMA nodes on which the instance will be booted

  - There is no information about PCI-NUMA affinity available

For example, to configure a flavor to use the `preferred` PCI NUMA affinity policy for any neutron SR-IOV interfaces attached by the user:

    $ openstack flavor set $FLAVOR \
        --property hw:pci_numa_affinity_policy=preferred

You can also configure this for PCI passthrough devices by specifying the policy in the alias configuration via `pci.alias`. For more information, refer to `the documentation`.

## PCI tracking in Placement

Note

The feature described below are optional and disabled by default in nova 26.0.0. (Zed). The legacy PCI tracker code path is still supported and enabled. The Placement PCI tracking can be enabled via the `pci.report_in_placement` configuration.

Warning

Please note that once it is enabled on a given compute host it cannot be disabled there any more.

Warning

If you configure more than 8 PCI devices per compute with the same product_id or resource_class then placement needs configuration tuning to keep the scheduling speed acceptable. Please read the following two release notes:

- https://github.com/openstack/placement/blob/master/releasenotes/notes/bug-2070257-allocation-candidates-generation-limit-and-strategy.yaml-e73796898163fb55.yaml

- https://github.com/openstack/placement/blob/master/releasenotes/notes/bug-2126751-optimize_for_wide_provider_trees-b50b7813fd0d9dd2.yaml

Since nova 26.0.0 (Zed) PCI passthrough device inventories are tracked in Placement. If a PCI device exists on the hypervisor and matches one of the device specifications configured via `pci.device_spec` then Placement will have a representation of the device. Each PCI device of type `type-PCI` and `type-PF` will be modeled as a Placement resource provider (RP) with the name `<hypervisor_hostname>_<pci_address>`. A devices with type `type-VF` is represented by its parent PCI device, the PF, as resource provider.

By default nova will use `CUSTOM_PCI_<vendor_id>_<product_id>` as the resource class in PCI inventories in Placement. However the name of the resource class can be customized via the `resource_class` tag in the `pci.device_spec` option. There is also a new `traits` tag in that configuration that allows specifying a list of placement traits to be added to the resource provider representing the matching PCI devices.

Note

In nova 26.0.0 (Zed) the Placement resource tracking of PCI devices does not support SR-IOV devices intended to be consumed via Neutron ports and therefore having `physical_network` tag in `pci.device_spec`. Such devices are supported via the legacy PCI tracker code path in Nova.

Note

Having different resource class or traits configuration for VFs under the same parent PF is not supported and the nova-compute service will refuse to start with such configuration.

Important

While nova supported configuring both the PF and its children VFs for PCI passthrough in the past, it only allowed consuming either the parent PF or its children VFs. Since 26.0.0. (Zed) the nova-compute service will enforce the same rule for the configuration as well and will refuse to start if both the parent PF and its VFs are configured.

Important

While nova supported configuring PCI devices by device name via the `devname` parameter in `pci.device_spec` in the past, this proved to be problematic as the netdev name of a PCI device could change for multiple reasons during hypervisor reboot. So since nova 26.0.0 (Zed) the nova-compute service will refuse to start with such configuration. It is suggested to use the PCI address of the device instead.

Important

While nova supported configuring `pci.alias` where an alias name is repeated and therefore associated to multiple alias specifications, such configuration is not supported when PCI tracking in Placement is enabled.

The nova-compute service makes sure that existing instances with PCI allocations in the nova DB will have a corresponding PCI allocation in placement. This allocation healing also acts on any new instances regardless of the status of the scheduling part of this feature to make sure that the nova DB and placement are in sync. There is one limitation of the healing logic. It assumes that there is no in-progress migration when the nova-compute service is upgraded. If there is an in-progress migration then the PCI allocation on the source host of the migration will not be healed. The placement view will be consistent after such migration is completed or reverted.

Reconfiguring the PCI devices on the hypervisor or changing the `pci.device_spec` configuration option and restarting the nova-compute service is supported in the following cases:

- new devices are added

- devices without allocation are removed

Removing a device that has allocations is not supported. If a device having any allocation is removed then the nova-compute service will keep the device and the allocation exists in the nova DB and in placement and logs a warning. If a device with any allocation is reconfigured in a way that an allocated PF is removed and VFs from the same PF is configured (or vice versa) then nova-compute will refuse to start as it would create a situation where both the PF and its VFs are made available for consumption.

Since nova 27.0.0 (2023.1 Antelope) scheduling and allocation of PCI devices in Placement can also be enabled via `filter_scheduler.pci_in_placement` config option set in the nova-api, nova-scheduler, and nova-conductor configuration. Please note that this should only be enabled after all the computes in the system is configured to report PCI inventory in Placement via enabling `pci.report_in_placement`. In Antelope flavor based PCI requests are support but Neutron port base PCI requests are not handled in Placement.

If you are upgrading from an earlier version with already existing servers with PCI usage then you must enable `pci.report_in_placement` first on all your computes having PCI allocations and then restart the nova-compute service, before you enable `filter_scheduler.pci_in_placement`. The compute service will heal the missing PCI allocation in placement during startup and will continue healing missing allocations for future servers until the scheduling support is enabled.

If a flavor requests multiple `type-VF` devices via `pci_passthrough:alias` then it is important to consider the value of `group_policy` as well. The value `none` allows nova to select VFs from the same parent PF to fulfill the request. The value `isolate` restricts nova to select each VF from a different parent PF to fulfill the request. If `group_policy` is not provided in such flavor then it will defaulted to `none`.

Symmetrically with the `resource_class` and `traits` fields of `pci.device_spec` the `pci.alias` configuration option supports requesting devices by Placement resource class name via the `resource_class` field and also support requesting traits to be present on the selected devices via the `traits` field in the alias. If the `resource_class` field is not specified in the alias then it is defaulted by nova to `CUSTOM_PCI_<vendor_id>_<product_id>`. Either the `product_id` and `vendor_id` or the `resource_class` field must be provided in each alias.

For deeper technical details please read the nova specification.

## Support for multiple types of VFs

SR-IOV devices, such as GPUs, can be configured to provide VFs with various characteristics under the same vendor ID and product ID.

To enable Nova to model this, if you configure the VFs with different resource allocations, you will need to use separate resource_classes for each.

This can be achieved by following the steps below:

- Enable PCI in Placement: This is necessary to track PCI devices with custom resource classes in the placement service.

- Define Device Specifications: Use a custom resource class to represent a specific VF type and ensure that the VFs existing on the hypervisor are matched via the VF’s PCI address.

- Specify Type-Specific Flavors: Define flavors with an alias that matches the resource class to ensure proper allocation.

Examples:

Note

The following example demonstrates device specifications and alias configurations, utilizing resource classes as part of the “PCI in placement” feature.

    [pci]
    device_spec = { "vendor_id": "10de", "product_id": "25b6", "address": "0000:25:00.4", "resource_class": "CUSTOM_A16_16A", "managed": "no" }
    device_spec = { "vendor_id": "10de", "product_id": "25b6", "address": "0000:25:00.5", "resource_class": "CUSTOM_A16_8A", "managed": "no" }
    alias = { "device_type": "type-VF", "resource_class": "CUSTOM_A16_16A", "name": "A16_16A" }
    alias = { "device_type": "type-VF", "resource_class": "CUSTOM_A16_8A", "name": "A16_8A" }

## Configuring Live Migration for PCI devices

Live migration of instances with PCI devices requires specific configuration at both the device and alias levels to ensure that the migration can succeed. This section explains how to configure PCI passthrough to support live migration.

### Configuring PCI Device Specification

Administrators must explicitly define whether a PCI device support live migration. This is done by adding the `live_migratable` attribute to the device specification in the `pci.device_spec` configuration.

Note

Of course, this requires hardware support, as well as proper system and hypervisor configuration.

Example Configuration:

    [pci]
    dev_spec = {'vendor_id': '8086', 'product_id': '1515', 'live_migratable': 'yes'}
    dev_spec = {'vendor_id': '8086', 'product_id': '1516', 'live_migratable': 'no'}

### Configuring PCI Aliases for Users

PCI devices can be requested through flavor exta_specs.. To request a live migratable PCI device, the PCI alias definition in the `pci.alias` configuration must include the `live_migratable` key.

Example Configuration:

    [pci]
    alias = {'name': 'vf_live', 'vendor_id': '8086', 'product_id': '1515', 'device_type': 'type-VF', 'live_migratable': 'yes'}
    alias = {'name': 'vf_no_migrate', 'vendor_id': '8086', 'product_id': '1516', 'device_type': 'type-VF', 'live_migratable': 'no'}

## Virtual IOMMU support

With provided `hw:viommu_model` flavor extra spec or equivalent image metadata property `hw_viommu_model` and with the guest CPU architecture and OS allows, we can enable vIOMMU in libvirt driver.

Note

Enable vIOMMU might introduce significant performance overhead. You can see performance comparison table from AMD vIOMMU session on KVM Forum 2021. For the above reason, vIOMMU should only be enabled for workflow that require it.

Here are four possible values allowed for `hw:viommu_model` (and `hw_viommu_model`):

virtio

  Supported on Libvirt since 8.3.0, for Q35 and ARM virt guests.

smmuv3

  Supported on Libvirt since 5.5.0, for ARM virt guests.

intel

  Supported for Q35 guests.

auto

  This option will translate to `virtio` if Libvirt supported, else `intel` on X86 (Q35) and `smmuv3` on AArch64.

For the viommu attributes:

- `intremap`, `caching_mode`, and `iotlb` options for viommu (These attributes are driver attributes defined in Libvirt IOMMU Domain) will directly enabled.

- `eim` will directly enabled if machine type is Q35. `eim` is driver attribute defined in Libvirt IOMMU Domain.

Note

eim(Extended Interrupt Mode) attribute (with possible values on and off) can be used to configure Extended Interrupt Mode. A q35 domain with split I/O APIC (as described in hypervisor features), and both interrupt remapping and EIM turned on for the IOMMU, will be able to use more than 255 vCPUs. Since 3.4.0 (QEMU/KVM only).

- `aw_bits` attribute can used to set the address width to allow mapping larger iova addresses in the guest. Since Qemu current supported values are 39 and 48, we directly set this to larger width (48) if Libvirt supported. `aw_bits` is driver attribute defined in Libvirt IOMMU Domain.

## Known Issues

A known issue exists where the `live_migratable` flag is ignored for devices that include the `physical_network` tag. As a result, instances using such devices do not behave as non-live migratable, and instead, they continue to migrate using the legacy VIF unplug/live migrate/VIF plug procedure.

Example configuration where the live_migratable flag is ignored:

    [pci]
    device_spec = { "vendor_id":"8086", "product_id":"10ca", "address": "0000:06:", "physical_network": "physnet2", "live_migratable": false}

A fix for this issue is planned in a follow-up for the Epoxy release. The upstream bug report is here.

## One-Time-Use Devices

Certain devices may need attention after they are released from one user and before they are attached to another. This is especially true of direct passthrough devices because the instance has full control over them while attached, and Nova doesn’t know specifics about the device itself, unlike regular more cloudy resources. Examples include:

- Securely erasing NVMe devices to ensure data residue is not passed from one user to the other unintentionally

- Reinstalling known-good firmware to the device to avoid a hijack attack

- Updating firmware to the latest release before each user

- Checking a property of the device to determine if it needs repair or replacement before giving it to another user (i.e. NVMe write-wear indicator)

- Some custom behavior, reset, etc

Nova’s scope does not cover the above, but it does support a feature that makes it easier for the operator to orchestrate tasks like this. By marking a device as “one time use” (hereafter referred to as OTU), Nova will allocate a device once, after which it will remain in a “reserved” state to avoid being allocated to another instance. After the operator’s workflow is performed and the device should be returned to the pool of available resources, the reserved flag can be dropped and Nova will consider it usable again.

Note

This feature requires PCI tracking in Placement in order to work. The compute configuration is required, but the transitional scheduler config is optional (during transition but required for safety).

A device can be marked as OTU by adding a tag in the `device_spec` like this:

    device_spec = {"address": "0000:00:1.0", "one_time_use": true}

By marking the device as such, Nova will set the `reserved` inventory value on the placement provider to fully cover the device (i.e. `reserved=total` at the point at which the instance is assigned the PCI device on the compute node. When the instance is deleted, the `used` value will return to zero but `reserved` will remain. It is the operator’s responsibility to return the `reserved` value to zero when the device is ready for re-assignment.

The best way to handle this would be to listen to Nova’s notifications for the `instance.delete.end` event so that the post-processing workflow can happen immediately. However, since notifications could be dropped or missed, regular polling should be performed. Providers that represent devices that Nova is applying the OTU behavior to will have the `HW_PCI_ONE_TIME_USE` trait, making it easier to identify them. For example:

    $ openstack resource provider list --required HW_PCI_ONE_TIME_USE
    +--------------------------------------+--------------------+------------+--------------------------------------+--------------------------------------+
    | uuid                                 | name               | generation | root_provider_uuid                   | parent_provider_uuid                 |
    +--------------------------------------+--------------------+------------+--------------------------------------+--------------------------------------+
    | b9e67d7d-43db-49c7-8ce8-803cad08e656 | jammy_0000:00:01.0 |         39 | 2ee402e8-c5c6-4586-9ac7-58e7594d27d1 | 2ee402e8-c5c6-4586-9ac7-58e7594d27d1 |
    +--------------------------------------+--------------------+------------+--------------------------------------+--------------------------------------+

Will find all such providers. For each of those, checking the inventory to find ones with `used=0` and `reserved=1` will identify devices in need of processing. To use the above example:

    $ openstack resource provider inventory list b9e67d7d-43db-49c7-8ce8-803cad08e656
    +----------------------+------------------+----------+----------+----------+-----------+-------+------+
    | resource_class       | allocation_ratio | min_unit | max_unit | reserved | step_size | total | used |
    +----------------------+------------------+----------+----------+----------+-----------+-------+------+
    | CUSTOM_PCI_1B36_0100 |              1.0 |        1 |        1 |        1 |         1 |     1 |    0 |
    +----------------------+------------------+----------+----------+----------+-----------+-------+------+

To return the above device back to the pool of allocatable resources, we can set the reserved count back to zero:

    $ openstack resource provider inventory set --amend \
        --resource CUSTOM_PCI_1B36_0100:reserved=0 \
        b9e67d7d-43db-49c7-8ce8-803cad08e656
    +----------------------+------------------+----------+----------+----------+-----------+-------+
    | resource_class       | allocation_ratio | min_unit | max_unit | reserved | step_size | total |
    +----------------------+------------------+----------+----------+----------+-----------+-------+
    | CUSTOM_PCI_1B36_0100 |              1.0 |        1 |        1 |        0 |         1 |     1 |
    +----------------------+------------------+----------+----------+----------+-----------+-------+

this page last updated: 2026-04-21 19:00:00

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