Physical functions, virtual functions, and ports

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For Network Express® and RoCE Express2 and RoCE Express3, each physical adapter port is associated with one physical function (PF) while virtual functions (VF) are associated with a parent PF and thus are indirectly associated with an adapter port. On IBM Z® and LinuxONE physical functions are used for hardware-related management and for special, sensitive tasks like firmware updates.

Note:

For the RoCE Express adapters, depending on the physical slot at which the network adapter is plugged, the adapter is managed through one of the PCI resource groups.

Image of a 3 PCI network adapters accessing LPARs — Figure 1. PCI network adapters with two adapter ports

Each physical function(PF) has multiple virtual functions (VFs). The hardware administrator can make these virtual functions eligible for LPARs or DPM partitions. For the Network Express in direct mode, LPARs control the PFs to which they are assigned.

RoCE Express and Network Express in hybrid mode can only use VFs directly in Linux® on IBM Z®, therefor PFs are not accessible for these adapters. Only Network Express in direct mode can access PFs.

The maximum number of virtual functions for a physical function depends on the model of the PCI network adapter feature.

Table 1. Ports, physical functions, and virtual functions of PCI network adapter features
Feature	Physical adapter ports	Ports per PF	Maximum VFs per PF
Network Express in hybrid mode	2	1	123
Network Express in direct mode (function type NETD)	2	1	127
RoCE Express3	2	1	63
RoCE Express2.1 and RoCE Express2	2	1	63
RoCE Express (see Note)	2	2	31

Note: RoCE Express is included in Table 1 for completeness. This publication applies to Network Express, and RoCE Express2 and RoCE Express3.

As of RoCE Express2 and RoCE Express3, all PCI functions that are associated with the same physical function share one of the physical adapter ports.