Cache annotations to indicate specultative side-channel condition

摘要

In a circuit 2 supporting speculative processing of read micro-operations (uops) to read data from memory 20-22, a profiling circuit 40 annotates micro-operations stored in a cache 8 with annotation information 56. The annotation is based on analysis of read uops satisfying a speculative side‑channel condition indicative of a risk of information leakage if the uop is processed speculatively. Speculative side-channel mitigation measures are based on the annotation information. This provides better balance between performance and safety against speculative side channel attacks compared to mitigation measures applied to all operations which unnecessarily sacrifice performance. Annotation information is determined from previously processed uops, while the condition is based on dependencies for read uops and additional information comprising: execution operating state, memory permissions. Bounds 58 indicate limits of validity of the annotation information and specify subset of operating states of the circuit or address ranges. Read uops comprise control‑dependent producer/consumer read micro-operations.