Intel Itanium Processor 9300 Series and 9500 Series

Introduction
Protection Keys provide a method to restrict permission by tagging each virtual page
with a unique protection domain identifier. The Protection Key Registers (PKR)
represent a register cache of all protection keys required by a process. The operating
system is responsible for management and replacement polices of the protection key
cache. Before a memory access (including IA-32) is permitted, the processor compares
a translation’s key value against all keys contained in the PKRs. If a matching key is not
found, the processor raises a Key Miss fault. If a matching Key is found, access to the
page is qualified by additional read, write and execute protection checks specified by
the matching protection key register. If these checks fail, a Key Permission fault is
raised. Upon receipt of a Key Miss or Key Permission fault, software can implement the
desired security policy for the protection domain. Some processor models may
implement additional protection key registers and protection key bits. Unimplemented
bits and registers are reserved. Please see the processor-specific documentation for
further information on the number of protection key registers and protection key bits
implemented on the processor.
Figure 1-3.
Intel ® Itanium ® Processor 9500 Series Firmware Diagram
18 Intel ® Itanium ® Processor 9300 Series and 9500 Series Datasheet