Single root I/O virtualization

Single root I/O virtualization (SR-IOV) is a Peripheral component interconnect express (PCIe) standard architecture that defines extensions to PCIe specifications to enable multiple logical partitions running simultaneously within a system to share PCIe devices. The architecture defines virtual replicas of PCI functions known as virtual functions (VF). A Logical partition can connect directly to an SR-IOV adapter VF without going through a virtual intermediary (VI) such as a POWER Hypervisor or Virtual I/O Server. This ability provides for a low latency and lower CPU utilization alternative by avoiding a VI.

An SR-IOV capable adapter might be assigned to a logical partition in dedicated mode or enabled for shared mode. The management console provides an interface to enable SR-IOV shared mode. An SR-IOV capable adapter in shared mode is assigned to the POWER Hypervisor for management of the adapter and provisioning of adapter resources to logical partitions. The management console, along with the POWER Hypervisor, provides the ability to manage the adapter's physical Ethernet ports and logical ports. To connect a logical partition to an SR-IOV Ethernet adapter VF, create an SR-IOV Ethernet logical port for the logical partition. When you create an Ethernet logical port for a partition, select the adapter physical Ethernet port to connect to the logical partition and specify the resource requirements for the logical port. Each logical partition can have one or more logical ports from each SR-IOV adapter in shared mode. The number of logical ports for all configured logical partitions cannot exceed the adapter logical port limit.

To create an SR-IOV Ethernet logical port for a logical partition, use one of the following methods:
  • Create an Ethernet logical port when you create a partition.
  • Add an Ethernet logical port to a partition profile, shut down the logical partition, and reactivate the logical partition by using the partition profile.
  • Add an Ethernet logical port to a running logical partition by using dynamic partitioning.
    Note: An SR-IOV adapter does not support Live Partition Mobility unless the VF is assigned to a shared Ethernet adapter.

When you activate a logical partition, the logical ports in the partition profile are considered to be a required resource. If the physical adapter resources required by the logical port are not available, the logical partition cannot be activated. However, logical ports can be removed dynamically from other logical partition to make the required resources available to the logical partition.

For an SR-IOV adapter in shared mode, the physical port switch mode can be configured in Virtual Ethernet Bridge (VEB) or Virtual Ethernet Port Aggregator (VEPA) mode. If the switch mode is configured in VEB mode, the traffic between the logical ports is not visible to the external switch. If the switch mode is configured in VEPA mode, the traffic between logical ports must be routed back to the physical port by the external switch. Before you enable the physical port switch in VEPA mode, ensure that the switch attached to the physical port is supported and is enabled for reflective relay.

When you create an Ethernet logical port, you can select a promiscuous permission to allow the logical port to be configured as a promiscuous logical port by the logical partition. A promiscuous logical port receives all unicast traffic with a destination address that does not match the address of one of the other logical ports configured for the same physical port. The number of logical ports with promiscuous permission configured for logical partitions, active or shutdown, on a physical port is limited to minimize potential performance impact due to increased processor usage associated with promiscuous logical ports. The management console indicates the number of logical ports on the physical port that are allowed to have a promiscuous permission setting.

When bridging between virtual Ethernet adapters and a physical Ethernet adapter, an SR-IOV Ethernet logical port might be used as the physical Ethernet adapter to access the outside network. When a logical port is configured as the physical Ethernet adapter for bridging, the logical port must have the promiscuous permission enabled. For example, if you create a logical port for a Virtual I/O Server logical partition and the intent is to use the logical port as the physical adapter for the shared Ethernet adapter, you must select the promiscuous permission for the logical port.

Configuration requirements

Consider the following configuration requirements when an Ethernet logical port is used as the physical Ethernet device for shared Ethernet adapter bridging:
  • When there is a requirement to divert all network traffic to flow through an external switch, consider the following requirements:
    • The POWER Hypervisor virtual switch must be set to the VEPA switching mode and the SR-IOV Ethernet adapter physical port switch mode must also be set to the VEPA switching mode.
    • In addition, the logical port is the only logical port that is configured for the physical port.
  • When you create an Ethernet logical port you can specify a capacity value. The capacity value specifies the required capacity of the logical port as a percentage of the capability of the physical port. The capacity value determines the amount of resources assigned to the logical port from the physical port. The assigned resources determine the minimum capability of the logical port. Physical port resources not used by other logical ports might be temporarily used by the logical port when the logical port exceeds its assigned resources to allow additional capability. System or network limitations can influence the amount of throughput a logical port can actually achieve. The maximum capacity that can be assigned to a logical port is 100%. The sum of the capacity values for all the configured logical ports on a physical port must be less than or equal to 100%. To minimize the configuration effort while adding additional logical ports, you might want to reserve physical port capacity for additional logical ports.
  • When an Ethernet logical port is used as a physical adapter for bridging virtual Ethernet adapters, the parameter values such as the number of client virtual adapters and expected throughput must be considered when choosing a capacity value.
  • The Ethernet logical ports allow the logical port to run diagnostics on the adapter and physical port. Select this permission only while running the diagnostics by using the logical port.