- Change the term System Management Mode (SMM) to Management Mode (MM)
- Provide a Management Mode infrastructure on ARM systems by using TrustZone.
- Allow initialization of Management Mode, as early as SEC or PEI. Also introduced a new class of MM drivers that launch natively within MM.
- Improved I2C support.
- Allow SEC to pass HOBs to PEI.
- New multi-processor protocol
- Updated Disk Info to support SD/MMC
- and more...
As you can see, SMM (or rather MM) was a big part of this update. I started this, but my efforts were dwarfed by others. Part of the reason was that the ARM 64-bit folks had already started down a standardization path for TrustZone and it required some diligent technical and consensus-building work to create an environment that both ARM and x86 architecture firmware could share. We didn't just include Aarch64 systems. We made IA32 and X64 systems more robust and flexible as well. A shout out to Charles Garcia-Tobin (ARM) and Vincent Zimmer (Intel) on this.