Arm Limited

Jaekyu Lee

Dam Sunwoo

Krishnendra Nathella

Yasuo Ishii

Saurabh Pijuskumar Sinha

Supreet Jeloka

Jose Alberto Joao

Lingzhe Cai

A data processing apparatus is provided that includes storage circuitry. Communication circuitry responds to an access request comprising a requested index with an access response comprising requested data. Coding circuitry performs a coding operation using a current key to: translate the requested index to an encoded index of the storage circuitry at which the requested data is stored or to translate encoded data stored at the requested index of the storage circuitry to the requested data. The current key is based on an execution environment. Update circuitry performs an update, in response to the current key being changed, of: the encoded index of the storage circuitry at which the requested data is stored or the encoded data.

Updating keys used for encryption of storage circuitry

A method for controlling hardware resource configuration for a processing system comprises obtaining performance monitoring data indicative of processing performance associated with workloads to be executed on the processing system, providing a trained machine learning model with input data depending on the performance monitoring data; and based on an inference made from the input data by the trained machine learning model, setting control information for configuring the processing system to control an amount of hardware resource allocated for use by at least one processor core. A corresponding method of training the model is provided. This is particularly useful for controlling inter-core borrowing of resource between processor cores in a multi-core processing system, where resource is borrowed between respective cores, e.g. cores on different layers of a 3D integrated circuit.

Hardware resource configuration for processing system

A data processing apparatus is provided. It includes control flow detection prediction circuitry that performs a presence prediction of whether a block of instructions contains a control flow instruction. A fetch queue stores, in association with prediction information, a queue of indications of the instructions and the prediction information comprises the presence prediction. An instruction cache stores fetched instructions that have been fetched according to the fetch queue. Post-fetch correction circuitry receives the fetched instructions prior to the fetched instructions being received by decode circuitry, the post-fetch correction circuitry includes analysis circuitry that causes the fetch queue to be at least partly flushed in dependence on a type of a given fetched instruction and the prediction information associated with the given fetched instruction.

Flushing a fetch queue using predecode circuitry and prediction information

An apparatus and method is provided, the apparatus comprising a processor pipeline to execute instructions, a cache structure to store information for reference by the processor pipeline when executing said instructions; and prefetch circuitry to issue prefetch requests to the cache structure to cause the cache structure to prefetch information into the cache structure in anticipation of a demand request for that information being issued to the cache structure by the processor pipeline. The processor pipeline is arranged to issue a trigger to the prefetch circuitry on detection of a given event that will result in a reduced level of demand requests being issued by the processor pipeline, and the prefetch circuitry is configured to control issuing of prefetch requests in dependence on reception of the trigger.

Prefetch mechanism for a cache structure

An apparatus and method are provided for controlling allocation of information into a cache storage. The apparatus has processing circuitry for executing instructions, and for allowing speculative execution of one or more of those instructions. A cache storage is also provided having a plurality of entries to store information for reference by the processing circuitry, and cache control circuitry is used to control the cache storage, the cache control circuitry comprising a speculative allocation tracker having a plurality of tracking entries. The cache control circuitry is responsive to a speculative request associated with the speculative execution, requiring identified information to be allocated into a given entry of the cache storage, to allocate a tracking entry in the speculative allocation tracker for the speculative request before allowing the identified information to be allocated into the given entry of the cache storage. The allocated tracking entry is employed to maintain restore information sufficient to enable the given entry to be restored to an original state that existed prior to the identified information being allocated into the given entry. The cache control circuitry is further responsive to a mis-speculation condition being detected in respect of the speculative request, to employ the restore information maintained in the allocated tracking entry for that speculative request in order to restore the given entry in the cache storage to the original state. Such an approach can provide robust protection against speculation-based cache timing side-channel attacks whilst alleviating the performance and/or power consumption issues associated with known techniques.

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Austin, TX, United States of America

Jaekyu Lee