MPU Region Descriptor Globalization Logic
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Solution Overview
Problem
Existing memory protection units (MPUs) face inefficiencies and performance overhead when implementing supervisor access to user regions, as they require multiple redundant region descriptors or modifications to the process identifier (PID) values, which can be resource-intensive and constrained by mapping limitations.
Innovation Solution
The implementation of dynamic globalization logic within the MPU, which allows for masking the effective region ID of region descriptor entries, enabling supervisor access to user regions without matching the specific region ID, by temporarily forcing the region ID to a global value, thereby reducing the need for redundant descriptors and improving resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple redundant region descriptors are used to enable supervisor access to user regions, then supervisor access capability is improved, but device complexity and resource usage increase
Solution Approach 1:
The patent implements dynamic globalization logic that can temporarily mask the region ID field in region descriptors based on a globalization control signal. This allows the same region descriptor to dynamically serve both process-specific and supervisor access needs, eliminating the requirement for static redundant descriptors while maintaining adaptability for different access scenarios.
Solution Approach 2:
The region descriptor structure is enhanced with a globalization control mechanism that enables a single descriptor to fulfill multiple functions: it can enforce process-specific access control when globalization is disabled, and simultaneously enable supervisor access when globalization is activated. This multi-functionality eliminates the need for separate supervisor-specific descriptors.
2Adaptability or versatility
If process identifier (PID) value modification is used to enable supervisor access, then supervisor access to user regions is improved, but mapping constraints and performance overhead increase
Solution Approach 1:
The patent separates the access control mechanism into two independent components: the region descriptor matching logic and the process identifier. By introducing a dedicated globalization control signal that operates on the region descriptor side rather than modifying the PID, the system avoids the performance overhead of PID modification while maintaining the ability to enable supervisor access. This segmentation allows each component to operate independently without unnecessary overhead.
3Reliability
If traditional MPU region descriptor matching is used, then process-specific memory protection is improved, but supervisor access to user regions requires redundant descriptors increasing resource usage
Solution Approach 1:
The patent introduces a globalization control parameter that can dynamically change the matching behavior of region descriptors. When this parameter is activated, the region ID field is masked, allowing supervisor accesses to match user region descriptors. This parameter change enables the same descriptor to serve dual purposes without compromising the accuracy of process-specific memory protection when the parameter is inactive.
Data Source
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AI summary
Embodiments of computer processing systems and methods are provided that include a memory protection unit (MPU) (60), and a plurality of region descriptors 62 associated with the MPU. The region descriptors include address range and translation identifier values for a respective region of memory. Control logic determines whether a translation identifier control indicator is in a first state, and if the translation identifier control indicator is in the first state, the control logic allows a first process being executed by the processing system to access a memory region allocated to a second process being executed by the processing system.