Processor Core History Reset Instruction for Thread Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing processors lack an efficient mechanism to reset internal history data structures during context switches to prevent information leakage and improve security and performance across software threads.
Innovation Solution
A new instruction is introduced to explicitly request a history reset of a processor core, utilizing a model-specific register to hint at the need for a history reset without writing to it, thereby allowing the operating system to manage context switches and maintain thread isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If processor internal history data structures are not reset during context switches, then performance is maintained through cached information, but information leakage occurs between software threads and security is compromised
Solution Approach 1:
The patent extracts the history reset function from the context switch mechanism by introducing a separate HRESET instruction. This allows selective resetting of specific history data structures (branch history, load history, store history) independent of the full context switch process, preventing information leakage while maintaining performance through targeted clearing of only the necessary history structures.
Solution Approach 2:
The HRESET instruction enables preliminary resetting of history data structures before context switches or security-sensitive operations. By allowing the operating system to proactively clear history information when needed, the system prevents potential information leakage before it can occur, rather than relying on automatic resetting during context switches.
2Reliability
If history reset is performed during every context switch, then information leakage is prevented, but performance deteriorates due to repeated clearing of optimization data
Solution Approach 1:
The patent applies partial action by allowing selective resetting of specific history data structures rather than clearing all history information during every context switch. The HRESET instruction can target individual history structures (branch, load, store) based on security requirements, clearing only the necessary portions while preserving performance-critical history data for other threads.
Solution Approach 2:
The system dynamically adjusts history resetting behavior based on security needs and performance requirements. The operating system can choose when to issue HRESET instructions based on the specific context switch scenario, security policies, and performance considerations, making the history reset mechanism flexible rather than rigid.
3Productivity
If no mechanism exists to reset processor history, then performance is optimized through continuous use of cached prediction data, but thread isolation is compromised and security vulnerabilities arise
Solution Approach 1:
The HRESET instruction acts as an intermediary mechanism between the operating system and the processor's history data structures. It provides a controlled interface that allows the OS to reset specific history structures when thread isolation is required, while leaving the rest of the history mechanisms intact for performance optimization. This mediator approach balances security and performance needs.
4Reliability
If manual history reset is implemented through existing mechanisms, then security is improved, but device complexity increases and ease of operation decreases
Solution Approach 1:
The HRESET instruction is integrated into the existing processor instruction set architecture, making it a universal mechanism that works across different context switch scenarios and security requirements. Rather than creating separate complex mechanisms for different types of history resetting, the single HRESET instruction provides a unified interface for controlling history data structure resets.
Data Source
AI summary
Systems, methods, and apparatuses relating to instructions to reset software thread runtime property histories in a hardware processor are described. In one embodiment, a hardware processor includes a hardware guide scheduler comprising a plurality of software thread runtime property histories; a decoder to decode a single instruction into a decoded single instruction, the single instruction having a field that identifies a model-specific register; and an execution circuit to execute the decoded single instruction to check that an enable bit of the model-specific register is set, and when the enable bit is set, to reset the plurality of software thread runtime property histories of the hardware guide scheduler.