I just noticed this March-era update to the UEFI list of ACPI specs. It is a large, well-written spec, compared to some of the recent ACPI specs I’ve looked at.

I/O Virtualization Reporting Structure (IVRS)

This document describes AMD I/O Virtualization Technology. AMD I/O Virtualization Technology is embodied in the system-level function called the I/O Memory Management Unit (IOMMU). This document provides the IOMMU behavioral definition and associated design notes. It is intended for the use of system designers, chipset designers, and programmers involved in the development of low-level BIOS (basic input/output system) functions, drivers, operating system kernel modules, and virtual machine monitor (VMM) software. The intended user should have prior experience in personal computer design, microprocessor programming, and legacy x86 and AMD64 microprocessor architecture.