Hypervisor Memory Page Inaccessibility for VM Data Integrity

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Solution Overview

Problem

Virtualized computer systems face challenges in memory management, particularly with data integrity when hypervisors reuse memory pages without copying original content, leading to potential data modification issues due to malicious code, programming defects, or hardware errors, which conventional page poisoning techniques fail to address effectively.

Innovation Solution

Implementing mechanisms that use host page tables to mark released memory pages as inaccessible, allowing hypervisors to detect and prevent unauthorized access, thereby enhancing memory protection and management without relying on poisoning patterns.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional page poisoning techniques are used to protect memory pages, then data integrity can be verified, but the system complexity increases and performance deteriorates due to the overhead of poisoning patterns

Engineering Contradiction:

Improvedata integrityVSAvoidmemory management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the data integrity verification function from the guest operating system and relocates it to the hypervisor. The hypervisor now directly monitors memory page access and enforces accessibility constraints, eliminating the need for guest OS page poisoning mechanisms and reducing overall system complexity while maintaining reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The hypervisor acts as an intermediary between the memory management unit and the memory pages. It intercepts memory access requests, checks accessibility constraints from host page tables, and prevents unauthorized access to released memory pages, thereby ensuring data integrity without requiring complex guest OS poisoning patterns

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the hypervisor reuses memory pages without copying original content, then memory management efficiency improves, but data security deteriorates due to potential unauthorized modification

Engineering Contradiction:

Improvememory management efficiencyVSAvoidunauthorized data modification

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary action by marking memory pages as inaccessible in the host page table before the guest OS releases them. This proactive approach ensures that when memory pages are reused, any unauthorized access attempts are immediately detected and blocked, allowing efficient memory reuse while maintaining security

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The hypervisor implements feedback mechanisms by monitoring memory access requests against accessibility constraints stored in host page tables. When a violation is detected, the system provides feedback by aborting the violating instruction and logging the event, enabling continuous security verification without impacting normal memory operations

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11150929B2Enhanced memory management for virtual machines

Publication Date: 2021.10.19 RED HAT INC

AI summary

Aspects of the disclosure provide for mechanisms for memory management of virtual machines in a computer system. A method of the disclosure includes: releasing a memory page of a guest memory of a virtual machine; sending, by the virtual machine, a first notification to a hypervisor, the first notification comprising an indication that a memory page associated with the virtual machine is to be rendered inaccessible; and receiving, by the virtual machine, a second notification indicative of detection of an attempt to access the memory page.