Memory Address Translation Management for Virtual Machine Security
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Solution Overview
Problem
Current data processing systems face challenges in managing the translation of virtual addresses to physical addresses, particularly in ensuring secure and accurate access to memory regions, especially when dealing with virtual machine private regions and device memory regions, where unauthorized remapping or lack of translation data can compromise security and lead to translation faults.
Innovation Solution
The memory management circuitry employs first and second stage translation data to manage virtual to physical address translations, with private-device region management ensuring that intermediate physical addresses remain unchanged for virtual machine private and device memory regions, and returning fault indications when unauthorized access or missing translations occur, thereby maintaining security and integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If second stage translation is suspended to reduce power consumption, then power consumption is reduced, but translation functionality is lost when hypervisor is disabled
Solution Approach 1:
The patent implements dynamic control of the second stage translation unit (STLU) by selectively enabling or disabling it based on the operational state of the hypervisor. When the hypervisor is disabled, the STLU is also disabled to save power. When the hypervisor is enabled, the STLU is activated to provide translation services. This dynamic adaptation resolves the contradiction by making the system's translation capability match its actual operational needs.
Solution Approach 2:
The patent employs feedback mechanisms where the system monitors the hypervisor's operational state and adjusts the STLU accordingly. The management logic receives feedback about whether the hypervisor is enabled or disabled and automatically configures the translation units to maintain appropriate functionality while optimizing power consumption based on current system requirements.
2Adaptability or versatility
If intermediate physical addresses are allowed to differ from physical addresses, then translation flexibility is improved, but security is compromised for device memory regions
Solution Approach 1:
The patent applies different translation policies to different memory regions. For device memory regions, the system enforces a strict one-to-one mapping where intermediate physical addresses must equal physical addresses, ensuring security. For other memory regions, the system allows flexible translation where intermediate and physical addresses can differ. This local differentiation resolves the contradiction by applying appropriate translation rules to each region based on its security requirements.
Solution Approach 2:
The patent segments the memory address space into different regions (device memory regions versus other regions) and applies distinct translation rules to each segment. By dividing the address space and implementing region-specific translation policies, the system maintains security for device regions while preserving translation flexibility for other regions, thus resolving the contradiction between security and adaptability.
3Device complexity
If first stage translation data is cleared when hypervisor is disabled, then memory management is simplified, but translation data is lost requiring reconfiguration
Solution Approach 1:
The patent extracts and preserves only the essential first stage translation data that is needed for maintaining translation functionality when the hypervisor is re-enabled. Instead of clearing all translation data, the system selectively retains critical mappings, thereby simplifying memory management by removing unnecessary data while avoiding complete loss of translation information that would require full reconfiguration.
Data Source
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AI summary
A data processing apparatus (2) includes memory management circuitry (18) for managing a two-stage address translation from a virtual address VA to an intermediate physical address IPA and then from the intermediate physical address IPA to a physical address PA. The first stage of the translation is performed using first stage translation data (22) controlled by a virtual machine program executing within a virtual machine execution environment provided by a hypervisor program which manages second stage translation data (24) for performing a second stage translation. If a region of memory is designated as a virtual machine private region accessible to a given virtual machine, but inaccessible to the hypervisor program, and also as a device region, then the memory management circuitry (18) performs private-device region management in respect of that region (i.e. the intermediate physical address may not be altered by the second stage translation). If a region is not both a virtual machine private region and a device region, then the memory management circuitry (18) performs non-private device management thereon.