3.9 KiB
Support SRIOV interface attach and detach
https://blueprints.launchpad.net/nova/+spec/sriov-interface-attach-detach
Nova supports booting servers with SRIOV interfaces. However, attaching and detaching an SRIOV interface to an existing server is not supported as the PCI device management is missing from the attach and detach code path.
Problem description
SRIOV interfaces cannot be attached or detached from an existing nova server.
Use Cases
As an end user I need to connect my server to another neutron network via an SRIOV interface to get high throughput connectivity to that network direction.
As an end user I want to detach an existing SRIOV interface as I don't use that network access anymore and I want to free up the scarce SRIOV resource.
Proposed change
In the compute manager, during interface attach, the compute needs to
generate InstancePCIRequest
for the requested port if the
vnic_type of the port indicates an SRIOV interface. Then run a PCI claim
on the generated PCI request to check if there is a free PCI device,
claim it, and get a PciDevice
object. If this is successful
then connect the PCI request to the RequestedNetwork
object
and call Neutron as today with that RequestedNetwork
. Then
call the virt driver as of today.
If the PCI claim fails then the interface attach instance action will fail but the instance state will not be set to ERROR.
During detach, we have to recover the PCI request from the VIF being destroyed then from that, we can get the PCI device that we need to unclaim in the PCI tracker.
Note that detaching an SRIOV interface succeeds today from API user perspective. However, the detached PCI device is not freed from resource tracking and therefore leaked until the nova server is deleted or live migrated. This issue will be gone when the current spec is implemented. Also as a separate bugfix SRIOV detach will be blocked on stable branches to prevent the resource leak.
There is a separate issue with SRIOV PF detach due to the way the libvirt domain XML is generated. While the fix for that is needed for the current spec, it also needed for the existing SRIOV live migration feature because that also detaches the SRIOV interfaces during the migration. So the SRIOV PF detach issue will be fixed as an independent bugfix of the SRIOV live migration feature and the implementation of this spec will depend on that bugfix.
Alternatives
None
Data model impact
None
REST API impact
None
Security impact
None
Notifications impact
None
Other end user impact
None
Performance Impact
There will be an extra neutron call during interface attach as well
as additional DB operations. The interface_attach
RPC
method is synchronous today, so this will be an end user visible
change.
Other deployer impact
None
Developer impact
None
Upgrade impact
None
Implementation
Assignee(s)
- Primary assignee:
-
balazs-gibizer
Feature Liaison
- Feature liaison:
-
gibi
Work Items
- change the attach and detach code path
- add unit and functional tests
- add documentation
Dependencies
None
Testing
Tempest test cannot be added since the upstream CI does not have SRIOV devices. Functional tests with libvirt driver will be added instead.
Documentation Impact
- remove the limitation from the API documentation
References
None
History
Release Name | Description |
---|---|
Victoria | Introduced |