Send an IPI Communication

This section describes how a source agent sends an IPI communication message. The source agent initiates the communications.

1. Write a 32 byte request message into the appropriate destination message buffer.
2. Write a 1 in the destination trigger bit.
3. Optionally, verify that the interrupt is posted by reading the observation register.
4. Determine that the interrupt has been processed with one of the following steps. The protocol must be established between the two agents:
   1. Source agent polls its observation register until the destination status bit is cleared indicating that the destination agent has processed the interrupt.
   2. Receive another IPI interrupt from the destination agent.