The Nova compute agent incorrectly identifies a GPU passthrough device as dev_type='type-PF' in the resource tracker's final view, even when the configuration explicitly sets it to type-PCI using [pci]alias.

This occurs because the libvirt driver's hardware detection logic identifies the device as a Physical Function (PF) if it is SR-IOV-capable. This hardware detection takes precedence over the operator's configuration in nova.conf. The presence of the <capability type='virt_functions'> element in the device's XML description from libvirt is what triggers this behavior.

To Reproduce Steps to reproduce the behavior:

1. Configure a compute node with a GPU that supports SR-IOV (e.g., an NVIDIA L4 or similar).
2. In nova.conf on the compute node, configure PCI passthrough for this device using device_spec/alias. Explicitly set the device_type to type-PCI.
3. Restart the nova-compute service.
4. Observe the nova-compute.log. The logs will show that the configuration is loaded correctly, but the final resource view reported by the resource tracker will show dev_type='type-PF'.

Expected behavior

• The Nova compute agent should honor the device_type specified in the [pci]alias configuration, using it to override the hardware-detected device type. If a device is configured as type-PCI, the resource tracker should report it as such, regardless of its underlying SR-IOV capabilities.
• Or at least the documentation should clarify this configuration value and autodetection logic behavior, and how the former must match the latter, or when it may be not. Upstream we state "device_type
      Type of PCI device. Valid values are: type-PCI, type-PF and type-VF. Note that "device_type": "type-PF" must be specified if you wish to passthrough a device that supports SR-IOV in its entirety."

That documentation section could have explained instead what users are not given a free choice between type-PCI, and type-PF, because that value must be matching to what libvirt and nova compute agent autodectes from HW. Or in downstream docs as well

Screenshots

• Attached Image

Device Info (please complete the following information):

Bug impact

• The incorrect dev_type prevents the Nova scheduler from correctly matching the device for instances that require a type-PCI device. This is particularly problematic for use cases like full GPU passthrough with non-GRID NVIDIA drivers, which cannot be loaded in the guest if the device is presented in SR-IOV mode.

Known workaround

• Disable SR-IOV for affected PCI devices in BIOS. Note that setting kernel args like pci=nosriov won't help with that problem.

Additional context

• • Configuration:

[pci]
alias = { "vendor_id":"10de", "product_id":"20f1", "device_type":"type-PCI", "name":"nvidia_a2" }
 

• • Logs:
    The nova-compute.log will show the device being reported incorrectly in the final resource view:

DEBUG nova.compute.resource_tracker [...] Final resource view: ... pci_stats=[PciDevicePool(...,tags=

)]