VMM Handler Code Placement in Guest Pages for I/O Virtualization
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Solution Overview
Problem
Current virtualization technologies face challenges in efficiently managing input/output (I/O) and interrupt events across multiple privileged programs executing on the same physical machine, leading to potential interference and performance issues.
Innovation Solution
The method involves obtaining pages in the guest virtual and physical address space, storing handler code to process I/O or interrupt events, and redirecting these events from guest handler code to VMM handler code, which is stored in allocated pages, thereby controlling and processing events without guest exits, enhancing performance by avoiding unnecessary virtualization overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If guest handler code is used to process I/O or interrupt events, then the guest program can directly handle events, but the guest may interfere with other privileged programs and cause performance issues
Solution Approach 1:
The patent introduces a shadow interrupt descriptor table as an intermediary layer between the guest interrupt descriptor table and the actual interrupt handling. This shadow table redirects interrupt events to VMM handler code while maintaining the appearance of direct guest handling, thus achieving both fast event processing and proper isolation through the VMM mediator.
2Reliability
If VMM handler code is used to process all I/O or interrupt events, then isolation between privileged programs is maintained, but additional virtualization overhead is introduced
Solution Approach 1:
The patent applies local quality by making the interrupt handling approach selective rather than uniform. The shadow interrupt descriptor table allows certain interrupts to be redirected to VMM handlers while others can be handled directly by guest code, optimizing performance for specific event types while maintaining isolation where needed.
3Loss of time
If guest handler code processes events directly, then virtualization overhead is reduced, but interference between privileged programs occurs
Solution Approach 1:
The shadow interrupt descriptor table serves as a mediator that sits between guest code and the physical interrupt handling. It allows guest handler code to execute quickly for isolated events while the VMM maintains control through the shadow table, preventing interference without requiring full VMM mediation for every event.
Data Source
AI summary
In one embodiment, a method comprises: obtaining use of one or more pages in a guest physical address space of a guest; storing handler code to process one or more input/output (I/O) and/or interrupt events in the one or more pages; and redirecting a first event of the one or more I/O events from guest handler code that would process the first event to the handler code in the one or more pages. Also contemplated is a computer accessible medium comprising a plurality of instructions, which, when executed by a computer, implement the method.