Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 2C: Instruction Set Reference

Overview
This chapter describes the Safer Mode Extensions (SMX) for the Intel® 64 and IA-32 architectures. Safer Mode Extensions (SMX) provide a programming interface for system software to establish a measured environment within the platform to support trust decisions by end users. The measured environment includes:
• Measured launch of a system executive, referred to as a Measured Launched Environment (MLE). The system executive may be based on a Virtual Machine Monitor (VMM); a measured VMM is referred to as MVMM.
• Mechanisms to ensure the above measurement is protected and stored in a secure location in the platform.
• Protection mechanisms that allow the VMM to control attempts to modify the VMM.

The measurement and protection mechanisms used by a measured environment are supported by the capabilities of an Intel® Trusted Execution Technology (Intel® TXT) platform:
• The SMX are the processor’s programming interface in an Intel TXT platform.
• The chipset in an Intel TXT platform provides enforcement of the protection mechanisms.
• Intel® Trusted Platform Module (Intel® TPM) 1.2 in the platform provides platform configuration registers (PCRs) to store software measurement values.