IP Redirect Table for Virtual Machine Instruction Fetching
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Solution Overview
Problem
Existing virtualization technologies in computer systems face inefficiencies in handling intercepted instructions, often requiring a guest to exit to a Virtual Machine Monitor (VMM) for processing, which can lead to performance bottlenecks and increased complexity.
Innovation Solution
The implementation of an IP redirect table that allows the processor to detect and redirect intercepted instructions to predefined or dynamically-generated routines within the guest, avoiding the need for a guest exit to the VMM by matching the instruction pointer with an entry in the table, thereby enabling in-guest processing of certain intercepts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If instructions are intercepted and the guest exits to the VMM for processing, then security and control are maintained, but performance deteriorates due to increased context switches and processing delays
Solution Approach 1:
The patent segments intercept processing into two categories: those requiring VMM intervention (security-critical) and those that can be handled by in-guest routines (performance-critical). This segmentation allows the system to maintain security for essential intercepts while improving performance by handling routine intercepts within the guest context, eliminating unnecessary context switches.
Solution Approach 2:
The patent introduces an intermediary mechanism (the IP redirect table and in-guest routine) between the intercepted instruction and the VMM. This intermediary allows certain intercepts to be processed within the guest without immediately transitioning to the VMM, thereby maintaining security while reducing the performance penalty of frequent context switches.
2Extent of automation
If the VMM processes all intercepted instructions, then centralized control is maintained, but device complexity increases due to the overhead of continuous context switching
Solution Approach 1:
The patent applies partial action by having the VMM handle only the subset of intercepts that require centralized control, while allowing the guest to handle routine intercepts independently through in-guest routines. This partial delegation reduces the VMM's processing burden and eliminates unnecessary context switches without sacrificing centralized control for security-critical operations.
Solution Approach 2:
The patent implements preliminary action by pre-defining in-guest routines that can handle specific intercept types before the VMM is invoked. These routines are prepared in advance and can be executed immediately when certain intercepts occur, eliminating the need for context switching and reducing overall system complexity.
3Reliability
If frequent intercepts are handled by exiting to the VMM, then security monitoring is maintained, but processing time increases due to repeated context switches
Solution Approach 1:
The patent segments intercept handling based on frequency and security implications. Frequent, routine intercepts are routed to in-guest routines that execute without context switches, while less frequent, security-critical intercepts continue to invoke the VMM. This segmentation dramatically reduces processing time for frequent intercepts while maintaining security monitoring for essential operations.
Solution Approach 2:
The patent enables the guest to serve itself by implementing in-guest routines that can handle intercepts independently without VMM intervention. This self-service capability allows the guest to process routine intercepts locally, eliminating the time loss associated with repeated context switches while the VMM maintains security monitoring through selective intercept handling.
Data Source
AI summary
In one embodiment, a processor comprises a redirect unit configured to detect a match of an instruction pointer (IP) in an IP redirect table, the IP corresponding to a guest instruction that the processor has intercepted, wherein the guest is executed under control of a virtual machine monitor (VMM), and wherein the redirect unit is configured to redirect instruction fetching by the processor to a routine identified in the IP redirect table instead of exiting to the VMM in response to the intercept of the guest instruction.