Kernel Driver Hot Swap Through Wrapped Endpoint Switching
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Solution Overview
Problem
Updating or servicing kernel-mode drivers in an operating system often requires a system reboot or shutdown, leading to downtime and loss of productivity.
Innovation Solution
The implementation of driver hot swap technology, which uses a driver proxy component to wrap endpoints with synchronization mechanisms, allowing seamless swapping between driver instances without rebooting the system, by using wrapper functions to manage transitions and hot patching to ensure compatibility and data access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If kernel-mode drivers are updated using traditional methods, then driver functionality can be improved with bug fixes and feature additions, but system reboot or shutdown is required causing downtime and loss of productivity
Solution Approach 1:
The driver update mechanism transitions from static (requiring reboot) to dynamic (hot swap capability). The system allows driver instances to be loaded, unloaded, and swapped at runtime without system shutdown, enabling continuous operation while updating driver functionality through wrapper functions that manage transitions between driver versions.
Solution Approach 2:
Wrapper functions serve as intermediaries between the operating system and driver instances. These wrappers manage the hot swap process by intercepting calls, tracking active external calls, and coordinating the transition between driver versions, thereby enabling seamless updates without system downtime.
2Productivity
If driver updates are performed without rebooting the system, then system availability is maintained, but complex synchronization mechanisms and wrapper functions are required to manage active external calls
Solution Approach 1:
The driver update process is segmented into distinct phases: loading new driver instance, wrapping endpoints with synchronization mechanisms, tracking active external calls, and swapping driver instances. This segmentation allows complex synchronization to be managed in controlled, discrete steps rather than as a monolithic process.
Solution Approach 2:
The wrapper functions implement feedback mechanisms by tracking the count of active external calls to driver instances. This feedback information is used to determine when it is safe to swap driver instances, ensuring that synchronization only occurs when appropriate and preventing updates during critical operations.
3Reliability
If wrapper functions track all active external calls to ensure safe driver swapping, then system stability is maintained, but additional overhead is introduced in incrementing and decrementing call counts
Solution Approach 1:
The wrapper functions perform partial tracking by only monitoring the essential aspect of driver calls (the count of active external calls) rather than analyzing every detail of driver operations. This selective approach provides sufficient information for safe driver swapping while minimizing computational overhead.
Data Source
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AI summary
A method implemented in a computer system involving a processor system includes loading a first version of a driver into memory, identifying a first endpoint set within the driver, and wrapping each endpoint in the set with a wrapper. The wrappers are registered within the operating system for calling endpoints in the first endpoint set. Subsequently, a second version of the driver is loaded into memory, and the first version is swapped with the second version. The swap process involves determining if the first version has active external calls, ceasing execution if no active calls are present, configuring the wrappers to use the second endpoint set, and initiating execution of the second version of the driver.