Enumerating Virtual Ports on a Network Adapter

An overlying driver or user application can obtain a list of all virtual ports (VPorts) on a NIC switch of a network adapter that supports single root I/O virtualization (SR-IOV). The driver or application issues an object identifier (OID) method request of OID_NIC_SWITCH_ENUM_VPORTS to obtain this list.

After a successful return from this OID query request, the InformationBuffer member of the NDIS_OID_REQUEST structure contains a pointer to a buffer that contains the following:

• An NDIS_NIC_SWITCH_VPORT_INFO_ARRAY structure that defines the number of elements within the array.

• An array of NDIS_NIC_SWITCH_VPORT_INFO structures. Each of these structures contains information about a VPort on the network adapter's NIC switch.

  Note  If no VPorts have been created on the network adapter, the driver sets the NumElements member of the NDIS_NIC_SWITCH_VPORT_INFO_ARRAY structure to zero and no NDIS_NIC_SWITCH_VPORT_INFO structures are returned.

Before the overlying driver or user application issues the OID_NIC_SWITCH_ENUM_VPORTS request, it must initialize an NDIS_NIC_SWITCH_VPORT_INFO_ARRAY structure that is passed along with the request. The driver or application must follow these guidelines when initializing the NDIS_NIC_SWITCH_VPORT_INFO_ARRAY structure:

• If the NDIS_NIC_SWITCH_VPORT_INFO_ARRAY_ENUM_ON_SPECIFIC_SWITCH flag is set in the Flags member, information is returned for all VPorts created on a specified NIC switch. The NIC switch is specified by the SwitchId member of that structure.

  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, and is referenced by the NDIS_DEFAULT_SWITCH_ID identifier. Regardless of the flags that are set in the Flags member, the SwitchId member must be set to NDIS_DEFAULT_SWITCH_ID.

• If the NDIS_NIC_SWITCH_VPORT_INFO_ARRAY_ENUM_ON_SPECIFIC_FUNCTION flag is set in the Flags member, information is returned for all VPorts attached to a specified PCI Express (PCIe) Physical Function (PF) or Virtual Function (VF) on the network adapter. The PF or VF is specified by the AttachedFunctionId member of that structure.

  If the AttachedFunctionId member is set to NDIS_PF_FUNCTION_ID, information is returned for all VPorts. This includes the default VPort that is attached to the PF. If the AttachedFunctionId member is set to a valid VF identifier, information is returned for all VPorts attached to the specified VF.

  Note  Starting with Windows Server 2012, only one nondefault VPort can be attached to a VF. However, multiple VPorts (including the default VPort) can be attached to the PF.

• If the Flags member is set to zero, information is returned for all VPorts attached to the PF or VF on the network adapter. In this case, the values of the SwitchId and AttachedFunctionId are ignored.

NDIS handles the OID_NIC_SWITCH_ENUM_VPORTS request for miniport drivers. NDIS returns the information from an internal cache of the data that it maintains from inspecting the following sources:

• OID method requests of OID_NIC_SWITCH_CREATE_VPORT.

• OID set requests of OID_NIC_SWITCH_VPORT_PARAMETERS.