Realm Management Unit Fusion for Memory Ownership

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Solution Overview

Problem

Current memory access control techniques fail to effectively enforce ownership rights across different privilege levels, leading to insecure data access and management in multi-process environments, particularly in systems with hypervisors and guest operating systems.

Innovation Solution

The implementation of a realm management unit that maintains an ownership table to specify ownership attributes for memory regions, allowing each realm to control access and perform operations like region fusion and shattering, ensuring exclusive access rights based on a hierarchical realm structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional memory access control techniques based on privilege level are used, then simple implementation is achieved, but effective enforcement of ownership rights across different privilege levels cannot be ensured

Engineering Contradiction:

Improveownership rights enforcementVSAvoidmemory access control structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The memory address space is segmented into multiple memory regions, each with its own ownership attributes. The ownership table divides memory management into discrete controllable units (memory regions), allowing independent ownership enforcement for each region. This segmentation enables reliable ownership rights enforcement by breaking down the complex memory control problem into manageable region-specific units.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A realm management unit is introduced as an intermediary between processing circuitry and memory access control. This intermediary component maintains the ownership table and enforces ownership attributes, acting as a mediator that ensures reliable ownership rights enforcement without requiring complex modifications to the existing processing circuitry or memory subsystem.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If multiple ownership entries are maintained for contiguous memory regions, then fine-grained access control is achieved, but memory access efficiency deteriorates due to multiple table lookups

Engineering Contradiction:

Improvememory access efficiencyVSAvoidaccess control precision

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Multiple contiguous memory regions with identical ownership attributes are merged into a single unified ownership entry. The ownership table stores one entry representing a group of contiguous regions, eliminating the need for multiple separate lookups. This merging maintains access control precision by preserving ownership attributes while significantly improving memory access efficiency through reduced table lookup operations.

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If memory regions are frequently split and merged, then flexible memory management is achieved, but system stability deteriorates due to repeated ownership table updates

Engineering Contradiction:

Improvememory region management flexibilityVSAvoidownership table consistency

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The ownership table is pre-configured with ownership attributes for memory regions before runtime operations. Region fusion and splitting operations are designed to work with this pre-established structure, allowing flexible memory management while maintaining ownership table consistency. The preliminary establishment of ownership attributes reduces the need for frequent updates during runtime, thereby maintaining system stability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11263155B2Managing fusion of memory regions and ownership attributes for fused memory regions

Publication Date: 2022.03.01 ARM LTD

AI summary

A realm management unit (RMU) maintains an ownership table specifying ownership entries for corresponding memory regions defining ownership attributes specifying, from among a plurality of realms, an owner realm of the corresponding region. Each realm corresponds to at least a portion of at least one software process. The owner realm has a right to exclude other realms from accessing data stored in the corresponding region. Memory access is controlled based on the ownership table. In response to a region fuse command specifying a fuse target address indicative contiguous regions of memory to be fused into a fused group of regions, a region fuse operation updates the ownership table to indicate that the ownership attributes for the fused group of regions are represented by a single ownership entry. This provides architectural support for enabling improvement of TLB performance.