Store-to-load forwarding conditioned on translation context updates
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Solution Overview
Problem
Side channel attacks (SCAs) exploit speculative store-to-load forwarding in processors, allowing unauthorized access to secret data by misusing microarchitectural speculation, particularly in scenarios where the translation context (TC) of a load instruction differs from that of a store instruction, leading to potential security breaches across virtual machines and hypervisor boundaries.
Innovation Solution
Implementing a method that conditions store-to-load forwarding based on updates or changes in the translation context (TC), which involves recording and detecting TC updates, and using this information to suspend or abort load instructions until all prior instructions have completed execution or until the store data is committed, thereby preventing unauthorized data forwarding across TC boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If speculative store-to-load forwarding is enabled to improve processor performance, then productivity increases, but security reliability deteriorates due to side channel attacks
Solution Approach 1:
The patent introduces translation context (TC) as an intermediary mechanism that mediates between store and load instructions. The TC acts as a mediator that verifies whether a load instruction is authorized to access store data by comparing translation contexts, thereby enabling secure speculative forwarding without compromising security. This intermediary layer prevents unauthorized data access while maintaining performance benefits.
Solution Approach 2:
The patent changes the parameter of authorization verification by introducing translation context comparison. Instead of relying solely on traditional permission bits, the system now checks whether the translation context of the load instruction matches the translation context of the store instruction. This parameter change enables more precise control over speculative forwarding, allowing performance optimization while preventing side channel attacks.
2Speed
If store data is forwarded before store instruction commitment to improve execution speed, then speed increases, but security deteriorates due to unauthorized access across translation context boundaries
Solution Approach 1:
The patent applies preliminary action by performing translation context verification before executing the speculative forward operation. The system checks whether the load instruction's translation context matches the store instruction's translation context before allowing data forwarding. This preliminary check prevents unauthorized access while enabling safe speculative execution, thus maintaining execution speed without compromising security.
Solution Approach 2:
The patent converts the potential harm of speculative forwarding (security vulnerabilities) into a benefit by using translation context as a security mechanism. The same speculative forwarding mechanism that could enable side channel attacks is now secured by requiring translation context matching. This transforms the vulnerability into a security feature, allowing fast execution while preventing unauthorized access.
3Reliability
If translation context verification is added to store-to-load forwarding logic, then security reliability improves, but device complexity increases
Solution Approach 1:
The patent applies universality by making the translation context field serve multiple functions. The same translation context that is used for address translation is also used for security verification in store-to-load forwarding. This multi-functionality avoids adding separate security context fields or mechanisms, thereby improving security reliability without significantly increasing device complexity.
Solution Approach 2:
The patent applies self-service by having the existing translation context infrastructure serve the security verification function. The translation context information is already present in the processor's address translation mechanism, so no additional external security module is needed. The system uses its own existing resources (translation context) to provide the security verification function, minimizing the increase in device complexity.
Data Source
AI summary
A processor is disclosed that mitigates side channel attacks that exploit speculative store-to-load forwarding. The processor includes logic that conditions store-to-load forwarding of uncommitted store data in the store queue from an uncommitted store instruction to the load instruction upon circumstances associated with a translation context (TC) change or update. The TC comprises an address space identifier (ASID), a virtual machine identifier (VMID), a privilege mode (PM) or a combination of two or more of the ASID, VMID and PM or a derivative thereof. The logic is embedded or associated with any of several structures, such as a store queue (SQ), a memory dependence predictor (MDP), or a reorder buffer (ROB).