Hypervisor Memory Management Circuit Blocks DMA During VM Reboot
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Solution Overview
Problem
Existing virtualized systems face memory crashes due to direct memory access devices accessing memory regions during guest operating system reboots, leading to operation errors and data corruption.
Innovation Solution
Implement a virtualized system with a memory management circuit that includes a hypervisor to control direct memory access devices by blocking direct memory access when a target guest operating system is rebooted, using temporal isolation to prevent memory crashes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct memory access device performs direct access to memory device without passing through processor, then data transfer efficiency is improved, but memory crash occurs when guest operating system is rebooted
Solution Approach 1:
The patent introduces a memory management circuit as an intermediary between the direct memory access device and the memory device. This circuit includes a core memory management unit and a direct memory management unit that work together to intercept and control memory access requests, preventing unauthorized or erroneous direct access during guest operating system reboot while maintaining efficient data transfer during normal operation.
Solution Approach 2:
The memory management circuit is segmented into two functional units: a core memory management unit for managing processor access and a direct memory management unit for managing direct memory access device operations. This segmentation allows independent control of different access paths, enabling the system to block direct access during reboot while maintaining other memory operations.
2Reliability
If hypervisor controls memory management circuit to block direct access during guest operating system reboot, then memory crash is prevented, but access time is increased
Solution Approach 1:
The hypervisor monitors the operational state of virtual machines and guest operating systems in advance. When a guest operating system reboot is detected, the hypervisor proactively controls the memory management circuit to block direct memory access before the crash can occur, rather than reacting after the problem arises.
Solution Approach 2:
The memory management circuit periodically checks the operational state of guest operating systems through the hypervisor and adjusts direct memory access permissions accordingly. This periodic monitoring and control ensures that blocking is applied only when necessary (during reboot states) rather than continuously, minimizing access time loss.
3Measurement precision
If memory management circuit manages both core access and direct access separately, then control precision is improved, but device complexity is increased
Solution Approach 1:
The patent merges the core memory management unit and the direct memory management unit into a single integrated memory management circuit. This unified structure allows both core access and direct access to be managed within one circuit component, reducing overall device complexity while maintaining the precision benefits of separate management functions through internal unit differentiation.
Data Source
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AI summary
A virtualized system is provided. The virtualized system includes: a memory device; a processor configured to provide a virtualization environment; a direct memory access device configured to perform a function of direct memory access to the memory device; and a memory management circuit configured to manage a core access of the processor to the memory device and a direct access of the direct memory access device to the memory device. The processor is further configured to provide: a plurality of guest operating systems that run independently from each other on a plurality of virtual machines of the virtualization environment; and a hypervisor configured to control the plurality of virtual machines in the virtualization environment and control the memory management circuit to block the direct access when a target guest operating system controlling the direct memory access device, among the plurality of guest operating systems is rebooted.