Browse Prior Art Database

System Management Mode Cache Line Attribute

IP.com Disclosure Number: IPCOM000013513D
Original Publication Date: 2000-Oct-25
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Abstract

Disclosed is a method to allow System Management Code to be cached and remain resident in the cache

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System Management Mode Cache Line Attribute

    Disclosed is a method to allow System Management Code to be cached and remain resident in the cache

after the microprocessor leaves System Management Mode (SMM) without allowing the contents to be

modified and executed without permission. In most existing PC systems, program code contained in the

System Management address space can't be allowed to execute or reside in the cache. In those systems

which allow the system management code to be cached, the System Management code resident in the

System Management address space must invalidate the cache and flush all valid data in the cache to

prevent access to such data prior to the processor leaving the SMM. If system management code or data is

loaded and not protected in the cache while the processor is operating in normal modes, the code and/or data

could potentially be accessed, modified or executed, thus compromising the system's integrity and basic

operations of the PC. Also, if security data is contained within the System Management address space, this

data could be inadvertently loaded in the cache and left there after leaving SMM. This leaves the data open

for viewing when the processor is not operating in SMM. A byproduct of the invention allows for

potential improvements in execution of system management code as it will be left resident in the cache

unless the cache line replacement policy removes it prior to the return of the processor to SMM.

The current state of the art caches are improved by this invention, both internal and external caches, by

adding an additional...