Virtual IOMMU Zero-Copy VM Communication

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current virtual machine memory management in virtualized systems lacks effective mechanisms for secure, direct communication between virtual machines while preventing unauthorized access and managing memory mappings efficiently, leading to security breaches and high overhead in maintenance and performance.

Innovation Solution

The method involves exposing a virtual IOMMU and a virtual device to a first virtual machine, allowing it to modify memory access, and a shared memory device to a second virtual machine, where the hypervisor maps memory pages based on received base addresses, enhancing security and flexibility by using existing guest OS code for access permissions and memory management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional memory management mechanisms are used for virtual machine communication, then security control is simplified, but access breaches cannot be contained to specific memory regions and overhead is high

Engineering Contradiction:

ImprovesecurityVSAvoidmemory management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments memory access control by implementing granular permissions at the memory page level rather than treating memory as a unified resource. Each memory page can have independent read/write/execute permissions configured through the IOMMU, allowing security breaches to be contained to specific memory regions while maintaining overall system security. This segmentation resolves the contradiction by providing fine-grained security control without requiring complex centralized management mechanisms.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The IOMMU acts as an intermediary layer between virtual machines and physical memory, handling all memory access requests and enforcing security policies. This intermediary automatically manages the complex permissions and mappings without requiring direct intervention from the hypervisor or guest OS, reducing overhead while maintaining strong security controls. The IOMMU mediates access requests, translating virtual addresses to physical addresses while enforcing granular permissions.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If granular memory access control is implemented, then security is enhanced by containing breaches to specific regions, but maintenance overhead increases

Engineering Contradiction:

ImprovesecurityVSAvoidmaintenance overhead

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system enables self-service by allowing guest operating systems to autonomously configure their own memory permissions and mappings through the IOMMU interface. The guest OS can program the IOMMU with its required memory access patterns and permissions without requiring hypervisor intervention for each configuration change. This self-service capability dramatically reduces maintenance overhead while maintaining granular security controls, as the system configures itself without external management.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Memory permissions and mappings are configured in advance during system initialization and virtual machine setup, rather than being managed dynamically during runtime. The IOMMU is pre-programmed with the necessary permissions and address translations before the virtual machine begins operation. This preliminary configuration reduces ongoing maintenance overhead, as changes only require updating the pre-configured IOMMU structures rather than dynamic intervention during execution.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If complex grant tables are used for memory management, then security control is comprehensive, but system performance and maintenance efficiency decrease

Engineering Contradiction:

Improvesecurity controlVSAvoidperformance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces the software-based grant table mechanism with a hardware-based IOMMU that performs memory management functions directly in hardware. The IOMMU is a dedicated hardware device that handles address translation and permission enforcement without requiring software interpretation of grant tables. This substitution eliminates the performance overhead associated with software-based memory management while maintaining comprehensive security control, as the hardware IOMMU can enforce permissions at line rate without software intervention.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9875132B2Input output memory management unit based zero copy virtual machine to virtual machine communication

Publication Date: 2018.01.23 RED HAT ISRAEL

AI summary

In an example embodiment, a hypervisor exposes a virtual input-output memory management unit (IOMMU) to a first virtual machine. The first virtual machine includes a first guest operating system (OS). The hypervisor exposes a first virtual device to the first virtual machine. The hypervisor exposes a shared memory device to a second virtual machine. The second virtual machine includes a second guest OS. The hypervisor detects that the first guest OS modified the virtual IOMMU to provide access to a memory page of the first virtual machine. The hypervisor receives a base address from the second virtual machine. The base address is programmed into the shared memory device by the second virtual machine. The hypervisor maps the memory page into the second virtual machine at a page address, which is determined from the base address and a bus address.