How to configure SR-IOV ports

Current approach of SR-IOV relies on sriov-device-plugin 2. While creating pods with SR-IOV, sriov-device-plugin should be turned on on all nodes. To use a SR-IOV port on a baremetal installation the 3 following steps should be done:

1. Create OpenStack network and subnet for SR-IOV. Following steps should be done with admin rights.

neutron net-create vlan-sriov-net --shared --provider:physical_network physnet10_4 --provider:network_type vlan --provider:segmentation_id 3501
neutron subnet-create vlan-sriov-net 203.0.114.0/24 --name vlan-sriov-subnet --gateway 203.0.114.1

Subnet id <UUID of vlan-sriov-net> will be used later in NetworkAttachmentDefinition.

  1. Add sriov section into kuryr.conf.

[sriov]
physical_device_mappings = physnet1:ens4f0
default_physnet_subnets = physnet1:<UUID of vlan-sriov-net>

This mapping is required for ability to find appropriate PF/VF functions at binding phase. physnet1 is just an identifier for subnet <UUID of vlan-sriov-net>. Such kind of transition is necessary to support many-to-many relation.

3. Prepare NetworkAttachmentDefinition object. Apply NetworkAttachmentDefinition with “sriov” driverType inside, as described in 1.

apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
    name: "sriov-net1"
    annotations:
        openstack.org/kuryr-config: '{
        "subnetId": "UUID of vlan-sriov-net",
        "driverType": "sriov"
        }'

Then add k8s.v1.cni.cncf.io/networks and request/limits for SR-IOV into the pod’s yaml.

kind: Pod
metadata:
  name: my-pod
  namespace: my-namespace
  annotations:
    k8s.v1.cni.cncf.io/networks: sriov-net1,sriov-net2
spec:
  containers:
  - name: containerName
    image: containerImage
    imagePullPolicy: IfNotPresent
    command: ["tail", "-f", "/dev/null"]
    resources:
      requests:
        intel.com/sriov: '2'
      limits:
        intel.com/sriov: '2'

In the above example two SR-IOV devices will be attached to pod. First one is described in sriov-net1 NetworkAttachmentDefinition, second one in sriov-net2. They may have different subnetId.

  1. Specify resource names

The resource name intel.com/sriov, which used in the above example is the default resource name. This name was used in SR-IOV network device plugin in version 1 (release-v1 branch). But since latest version the device plugin can use any arbitrary name of the resources 3. This name should match “^[a-zA-Z0-9_]+$” regular expression. To be able to work with arbitrary resource names physnet_resource_mappings and device_plugin_resource_prefix in [sriov] section of kuryr-controller configuration file should be filled. The default value for device_plugin_resource_prefix is intel.com, the same as in SR-IOV network device plugin, in case of SR-IOV network device plugin was started with value of -resource-prefix option different from intel.com, than value should be set to device_plugin_resource_prefix, otherwise kuryr-kubernetes will not work with resource.

Assume we have following SR-IOV network device plugin (defined by -config-file option)

{
    "resourceList":
        [
           {
              "resourceName": "numa0",
              "rootDevices": ["0000:02:00.0"],
              "sriovMode": true,
              "deviceType": "netdevice"
           }
        ]
}

We defined numa0 resource name, also assume we started sriovdp with -resource-prefix samsung.com value. The PCI address of ens4f0 interface is “0000:02:00.0”. If we assigned 8 VF to ens4f0 and launch SR-IOV network device plugin, we can see following state of kubernetes

$ kubectl get node node1 -o json | jq '.status.allocatable'
{
  "cpu": "4",
  "ephemeral-storage": "269986638772",
  "hugepages-1Gi": "8Gi",
  "hugepages-2Mi": "0Gi",
  "samsung.com/numa0": "8",
  "memory": "7880620Ki",
  "pods": "1k"
}

We have to add to the sriov section following mapping:

[sriov]
device_plugin_resource_prefix = samsung.com
physnet_resource_mappings = physnet1:numa0

  1. Enable Kubelet Pod Resources feature

To use SR-IOV functionality properly it is necessary to enable Kubelet Pod Resources feature. Pod Resources is a service provided by Kubelet via gRPC server that allows to request list of resources allocated for each pod and container on the node. These resources are devices allocated by k8s device plugins. Service was implemented mainly for monitoring purposes, but it also suitable for SR-IOV binding driver allowing it to know which VF was allocated for particular container.

To enable Pod Resources service it is needed to add --feature-gates KubeletPodResources=true into /etc/sysconfig/kubelet. This file could look like:

KUBELET_EXTRA_ARGS="--feature-gates KubeletPodResources=true"

Note that it is important to set right value for parameter kubelet_root_dir in kuryr.conf. By default it is /var/lib/kubelet. In case of using containerized CNI it is necessary to mount 'kubelet_root_dir'/pod-resources directory into CNI container.

To use this feature add enable_pod_resource_service into kuryr.conf.

[sriov]
enable_pod_resource_service = True

  1. Use privileged user

To make neutron ports active kuryr-k8s makes requests to neutron API to update ports with binding:profile information. Due to this it is necessary to make actions with privileged user with admin rights.