Chapter 12. QP Verbs and QP State Machine

The Previous Chapter

The previous chapter provided a detailed discussion of how PSNs in request packets are generated by the requester QP's SQ Logic (or, in RD, the requester EEC's Send Logic) and how they are verified by the responder QP's RQ Logic (or, in RD, the responder EEC's Receive Logic). It described how the Start PSN is assigned to one QP's SQ Logic (or, in RD, one EEC's Send Logic) and the expected PSN (ePSN) is assigned to the other QP's RQ Logic (or, in RD, the other EEC's Receive Logic). It described how, when using RD, RC, and UC the PSN in each response packet is verified by the requester QP's SQ Logic (or, in RD, the requester EEC's Send Logic). The concepts of valid and invalid PSNs, as well as duplicate requests and responses, were introduced. The previous chapter concluded the introductory portion of the book (i.e., Part 1).

This Chapter

This chapter provides a detailed description of the verbs used to create a QP, modify its operational characteristics, obtain its current operational characteristics, and destroy it. It provides a detailed description of the creation of a QP and the steps required to program it. The QP state machine is described in detail.

The Next Chapter

The next chapter provides a detailed description of how Work Requests (WRs) are posted to a QP's SQ or RQ, as well as a detailed description of the WR content. Once a WR has been posted to a QP's SQ or RQ, it is referred to as a WQE (Work Queue Entry; pronounced as “wookie”). This chapter describes the ordering rules that govern:

• WQE execution order.

• WQE completion order.

• RD RQ WQE completion order. The reason why RD RQ WQEs can complete out of order is described.

• RDMA Read relaxed ordering rules.

When a message transfer request WQE completes execution, a Completion Queue Entry (CQE; pronounced as “cookie”) is created on the respective work queue's Completion Queue (CQ). This chapter provides a detailed description of the verbs used to create a CQ, resize it, obtain its current operational characteristics, and destroy it. It also covers:

• The completion event handler.

• The Set Completion Event Handler verb.

• The Poll for Completion verb.

• The Request for Completion Notification verb.

• The detailed content of a CQE.

• Solicited and unsolicited events.