Setting the Parameters of a Virtual Port

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An overlying driver can change the parameters for a virtual port (VPort) on a NIC switch on a network adapter that supports single root I/O virtualization (SR-IOV). The driver issues an object identifier (OID) set request of OID_NIC_SWITCH_VPORT_PARAMETERS to change these parameters.

Before the overlying driver issues this OID set request, it must initialize an NDIS_NIC_SWITCH_VPORT_PARAMETERS structure with the parameters to be changed on the VPort. The driver then initializes an NDIS_OID_REQUEST structure for the OID request, and sets the InformationBuffer member to a pointer to the NDIS_NIC_SWITCH_VPORT_PARAMETERS structure.

Only a limited subset of configuration parameters for a VPort can be changed. The overlying driver specifies the parameter to change by setting the following members of the NDIS_NIC_SWITCH_VPORT_PARAMETERS structure:

  • The SwitchId member must be set to the identifier of the NIC switch for which parameters are to be returned.

    Note  Starting with Windows Server 2012, the SR-IOV interface supports only one NIC switch on the network adapter. This switch is known as the default NIC switch. The SwitchId member must be set to NDIS_DEFAULT_SWITCH_ID.

  • The VPortId member must be set to the identifier associated with the VPort. The overlying driver obtains the VPort identifier through one of the following ways:

  • The appropriate NDIS_NIC_SWITCH_VPORT_PARAMS_Xxx_CHANGED flags must be set in the Flags member. Members of the NDIS_NIC_SWITCH_VPORT_PARAMETERS structure can only be changed if a corresponding NDIS_NIC_SWITCH_VPORT_PARAMS_Xxx_CHANGED flag is defined in Ntddndis.h.

  • The members of the NDIS_NIC_SWITCH_VPORT_PARAMETERS structure, which correspond to the NDIS_NIC_SWITCH_VPORT_PARAMS_Xxx_CHANGED flags set in the Flags member, are set with the VPort configuration parameters that are to be changed.

Starting with Windows Server 2012, only the following members of the NDIS_NIC_SWITCH_VPORT_PARAMETERS structure can be changed through an OID set request of OID_NIC_SWITCH_VPORT_PARAMETERS:

PortName
This member contains a user-friendly description of the VPort.

InterruptModeration
This member specifies the interrupt moderation setting of the VPort.

ProcessorAffinity
This member specifies the group number and a bitmap of the CPUs that this VPort can be associated with.

The overlying driver must follow these guidelines for changing the ProcessorAffinity member for a VPort:

  • This member is valid only for the VPorts attached to the PF. This field is not valid for nondefault VPorts that are attached to a VF.

  • For nondefault VPorts that are attached to the PF, at least one processor must be specified when the VPort is created. The processor affinity associated with the nondefault VPort can be changed after VPort creation.

    Note  Nondefault VPorts are created through OID method requests of OID_NIC_SWITCH_CREATE_VPORT.

VPortState
This member specifies the current state of the VPort.

The overlying driver must follow these guidelines for changing the VPortState member for a VPort:

  • For a nondefault VPort that is attached to a VF, the VPortState member must always be set to NdisNicSwitchVPortStateActivated.

  • For a nondefault VPort that is attached to the PF, the VPortState member must be set to NdisNicSwitchVPortStateDeactivated when the VPort is created. The PF VPort is activated only after an OID set request of OID_NIC_SWITCH_VPORT_PARAMETERS is issued by the overlying drivers to change the VPortState to an activated state.

    When the nondefault VPort is activated, the PF miniport driver can allocate resources for the VPort, such as shared memory that is allocated through NdisAllocateSharedMemory. The PF miniport driver may allocate resources for VPort any time after it is activated until the driver deletes the VPort through an OID set request of OID_NIC_SWITCH_DELETE_VPORT.

  • The default VPort is always in an activated state. The value of the VPortState member must always be set to NdisNicSwitchVPortStateActivated for the default VPort.

  • When a VPort is in an activated state, it cannot be deactivated. A PF miniport driver can receive and transmit packets from a VPort only if it is in an activated state and the corresponding MAC filters are set on the VPort. However, after the VPort is deleted through an OID set request of OID_NIC_SWITCH_DELETE_VPORT, the driver must free the resources that were allocated for the VPort. The driver must also cancel all pending transmit or receive operations for packets on the VPort.

After the PF miniport driver receives the OID set request of OID_NIC_SWITCH_VPORT_PARAMETERS, the driver configures the hardware with the configuration parameters. The driver can only change those configuration parameters identified by NDIS_NIC_SWITCH_VPORT_PARAMETERS_Xxx_CHANGED flags in the Flags member of the NDIS_NIC_SWITCH_VPORT_PARAMETERS structure.