Virtual Machine World Switch State Register Dirty Bit Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current virtualization technologies in data processing devices face inefficiencies in world switch times due to the need to save and restore processor state information, which can be extensive and time-consuming, especially when switching between virtual machines and guest programs.
Innovation Solution
Implementing state registers with dirty and clean bits to selectively save and load only modified state information during world switches, and using shadow registers to maintain state information during virtual machine execution, thereby reducing the amount of data transferred during these switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all processor state information is saved and restored during world switches, then complete state preservation is achieved, but world switch time increases significantly
Solution Approach 1:
The patent extracts only the modified state information from the complete processor state using dirty bits as markers. Instead of saving all state registers, the system identifies and saves only those registers whose dirty bits are set, thereby reducing the amount of data transferred during world switches while maintaining complete preservation of all necessary state changes.
Solution Approach 2:
The patent applies partial action by saving only a portion of the processor state information - specifically, only the modified portions indicated by dirty bits - rather than performing a complete save of all state registers. This partial saving approach reduces world switch time while still achieving the necessary state preservation for correct operation.
2Loss of information
If complete processor state is saved during world switches, then state accuracy is maintained, but the amount of data transferred increases
Solution Approach 1:
The patent extracts only the modified state information from the complete processor state using dirty bits as markers. Instead of saving all state registers, the system identifies and saves only those registers whose dirty bits are set, thereby reducing the amount of data transferred during world switches while maintaining complete preservation of all necessary state changes.
Solution Approach 2:
The patent changes the parameter of data transfer volume by introducing dirty bits that track which state registers have been modified. This parameter change allows the system to dynamically determine the actual amount of state information that needs to be saved, reducing the average data transfer volume while ensuring all necessary state changes are captured.
3Reliability
If all state registers are saved and restored, then complete state restoration is achieved, but world switch performance decreases
Solution Approach 1:
The patent extracts only the modified state information from the complete processor state using dirty bits as markers. Instead of saving all state registers, the system identifies and saves only those registers whose dirty bits are set, thereby reducing the amount of data transferred during world switches while maintaining complete preservation of all necessary state changes.
Solution Approach 2:
The patent applies partial action by saving only a portion of the processor state information - specifically, only the modified portions indicated by dirty bits - rather than performing a complete save of all state registers. This partial saving approach reduces world switch time while still achieving the necessary state preservation for correct operation.
Data Source
AI summary
A data processing device includes one or more state registers to store state information associated with an execution core of the device. Each state register includes an associated “dirty” bit. When a guest program is executed at the execution core, a dirty bit is set in response to a change in the state information at the associated state register. In response to a world switch from the guest program to a VMM, the state information at each state register is stored to memory only if the associated dirty bit is set. In addition, if the VMM changes any stored state information, it clears a “clean” bit associated with the changed information. In response to a world switch from the VMM to a guest, the state information associated with cleared clean bits is retrieved from memory.