Hypervisor Timeout Handling for Virtual Device Stall Prevention

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Solution Overview

Problem

Virtual devices interacting with backend elements can cause denial-of-service by stalling CPU resources due to untrusted or malicious communications, leading to potential catastrophic failures.

Innovation Solution

A hypervisor intercepts communications from virtual devices, sets a timer for responses, and disables the virtual device if no response is received within a threshold time, simulating a hard removal to prevent denial-of-service and convert the failure into a recoverable error.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the virtual device is allowed to communicate freely with the backend element, then the virtual machine can access backend resources, but the system becomes vulnerable to denial-of-service attacks and CPU stalling

Engineering Contradiction:

Improvesystem reliabilityVSAvoiddenial-of-service vulnerability

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The hypervisor acts as an intermediary between the virtual device and the backend element. It intercepts communications from the virtual machine directed to the backend element via the virtual device, sets a timer, and only allows the communication to proceed through the intermediary layer. This mediator approach prevents direct untrusted access while maintaining controlled communication channels.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary actions by setting a timer before allowing the communication to reach the backend element. The timer is configured with a threshold time, and if the backend element does not respond within this threshold, the virtual device is disabled. This preliminary timing mechanism prevents potential denial-of-service conditions before they can cause catastrophic failures.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a timer is set to intercept and monitor communications, then the system can detect unresponsive backend elements, but the complexity of the communication handling increases

Engineering Contradiction:

Improvedetection of unresponsive elementsVSAvoidcommunication handling complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The hypervisor's communication interception and timer management operates as a self-service mechanism. The system automatically monitors the timer, detects when the threshold time has elapsed without a response from the backend element, and autonomously disables the virtual device. This self-service approach simplifies the overall system by automating the detection and response process without requiring additional manual intervention or complex external monitoring systems.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20240073243A1Timeout handling for virtual devices

Publication Date: 2024.02.29 RED HAT LLC

AI summary

A virtual device can be provided to a virtual machine from a hypervisor. The virtual can correspond to a backend element accessible to the VM via communications with the virtual device. The hypervisor can intercept a communication from the VM directed to the backend element via the virtual device. The hypervisor can set a timer. The timer can track an elapsed time from the communication to a response from the backend element. The hypervisor can send the communication from the virtual machine to the backend element. The timer can then be determined to have expired without a response being received. The virtual device can then be disabled.