Intel Corporation

Nvidia Corporation

Stexar Corp.

Darrell D Boggs

David J Sager

Amit A Merchant

Alan Beecher Kyker

Michael D Upton

Ross Segelken

James D Allen

David W Burns

Andrew F Glew

Guillermo Juan Rozas

Dion Rodgers

Michael A Fetterman

Paul S Serris

Magnus Ekman

Hens Vanderschoot

Rajesh Kota

Rachel Hsu

Brad Hoyt

Sridharan Ramakrishnan

Glenn J Hinton

Alexander Klaiber

Donald D Parker

Gary L Brown

James Van Zoeren

Per H Hammarlund

Scott Dion Rodgers

David B Papworth

Ronak Singhal

Robert P Colwell

Keshavan K Tiruvallur

Francis X Mckeen

Douglas M Carmean

Rohit A Vidwans

Michael M Hancock

Shlomit Weiss

Shailender Chaudhry

Hong Wang

Stephan Jourdan

Ittai Anati

David A Dunn

John Thomas Shen

James B Crossland

Bryant E Bigbee

Xiang Chris Zou

Anil Aggarwal

Doron Orenstein

Robert F Krick

Chris J Newburn

Ashwani Kumar Gupta

Chan W Lee

Bruce Holmer

John Alan Miller

Nathan Daniel Tuck

Larry O Smith

William Alexander

David W Clift

Aravindh Baktha

Christopher Scott Jones

Nick Fortino

Mike Cornaby

Denis Khartikov

Alok Mooley

Gordon Vreugdenhil

Shivanandan Kaushik

Mehul Dave

Shiaoli Mendyke

Gail M Rupnick

James Allen

An improved architectural means to address processor cache attacks based on speculative execution defines a new memory type that is both cacheable and inaccessible by speculation. Speculative execution cannot access and expose a memory location that is speculatively inaccessible. Such mechanisms can disqualify certain sensitive data from being exposed through speculative execution. Data which must be protected at a performance cost may be specifically marked. If the processor is told where secrets are stored in memory and is forbidden from speculating on those memory locations, then the processor will ensure the process trying to access those memory locations is privileged to access those locations before reading and caching them. Such countermeasure is effective against attacks that use speculative execution to leak secrets from a processor cache.

Memory type which is cacheable yet inaccessible by speculative instructions

Embodiments related to managing lazy runahead operations at a microprocessor are disclosed. For example, an embodiment of a method for operating a microprocessor described herein includes identifying a primary condition that triggers an unresolved state of the microprocessor. The example method also includes identifying a forcing condition that compels resolution of the unresolved state. The example method also includes, in response to identification of the forcing condition, causing the microprocessor to enter a runahead mode.

Lazy runahead operation for a microprocessor

Embodiments related to re-dispatching an instruction selected for re-execution from a buffer upon a microprocessor re-entering a particular execution location after runahead are provided. In one example, a microprocessor is provided. The example microprocessor includes fetch logic, one or more execution mechanisms for executing a retrieved instruction provided by the fetch logic, and scheduler logic for scheduling the retrieved instruction for execution. The example scheduler logic includes a buffer for storing the retrieved instruction and one or more additional instructions, the scheduler logic being configured, upon the microprocessor re-entering at a particular execution location after runahead, to re-dispatch, from the buffer, an instruction that has been previously dispatched to one of the execution mechanisms.

Checkpointed buffer for re-entry from runahead

Various embodiments of microprocessors and methods of operating a microprocessor during runahead operation are disclosed herein. One example method of operating a microprocessor includes identifying a runahead-triggering event associated with a runahead-triggering instruction and, responsive to identification of the runahead-triggering event, entering runahead operation and inserting the runahead-triggering instruction along with one or more additional instructions in a queue. The example method also includes resuming non-runahead operation of the microprocessor in response to resolution of the runahead-triggering event and re-dispatching the runahead-triggering instruction along with the one or more additional instructions from the queue to the execution logic.

Queued instruction re-dispatch after runahead

Embodiments related to managing potentially invalid results generated/obtained by a microprocessor during runahead are provided. In one example, a method for operating a microprocessor includes causing the microprocessor to enter runahead upon detection of a runahead event. The example method also includes, during runahead, determining that an operation associated with an instruction referencing a storage location would produce a potentially invalid result based on a value of an architectural poison bit associated with the storage location and performing a different operation in response.

Managing potentially invalid results during runahead

Various embodiments relating to executing different types of instruction code in a micro-processing system are provided. In one embodiment, a micro-processing system includes a memory/storage subsystem configured to store non-native instruction set architecture (ISA) code and native ISA code in a common address space, fetch logic configured to retrieve the non-native ISA code and native ISA code from the common address space, instruction type determining logic configured to determine, at runtime, whether fetched instruction code is non-native ISA code or native ISA code, and processing logic configured to execute the fetched instruction code via a first pipeline configuration in response to the instruction type determining logic determining that the fetched instruction code is non-native ISA code, and via a second pipeline configuration which is different than the first pipeline configuration, in response to the instruction type determining logic determining that the fetched instruction code is native ISA code.

Dynamic configuration of processing pipeline based on determined type of fetched instruction

In a multi-threaded processor, thread priority variables are set up in memory. The actual assignment of thread priority is based on the expiration of a thread precedence counter. To further augment, the effectiveness of the thread precedence counters, starting counters are associated with each thread that serve as a multiplier for the value to be used in the thread precedence counter. The value in the starting counters are manipulated so as to prevent one thread from getting undue priority to the resources of the multi-threaded processor.

Method and apparatus for assigning thread priority in a processor or the like

Method, apparatus, and system for a programmable event driven yield mechanism that may activate other threads. The yield mechanism may allow triggering of a service thread that may execute currently with a main thread upon occurrence of an architecturally-defined condition. The service thread may be activated, in response to the condition, with limited intervention of an operating system. In one embodiment, an apparatus includes execution resources to execute a plurality of instructions and a monitor to detect an architecturally-defined condition. The apparatus may include an event handler to handle a yield event generated when the architecturally-defined condition has been detected. An architectural mechanism, including processor instructions and channel registers, may be utilized to allow user-level code to enable the yield event mechanism. Other embodiments are also described and claimed.

Programmable event driven yield mechanism which may activate service threads

A method and apparatus are provided for entering and exiting multiple threads within a multithreaded processor. A state machine is maintained to indicate a respective status of an associated thread of multiple threads being executed within a multithreaded processor. A change of status for a first thread within the multithreaded processor is detected and, responsive to the change of status for the first thread within the multithreaded processor, a partitioning scheme for the functional unit is altered to service a second thread, but not the first thread, within the multithreaded processor when the change of the status of the first thread comprises a transition from an active state to an inactive state.

Alteration of functional unit partitioning scheme in multithreaded processor based upon thread statuses

A system includes a multithreaded processor, a memory to store the plurality of threads, and a bus to deliver the plurality of threads to the multithreaded processor. The multithreaded processor includes an event detector to detect a first event indication for a first thread. The event detector, responsive to the detection of the first event indication for the first thread, monitors a second thread being processed within the multithreaded processor to detect a clearing point for the second thread and, responsive to the detection of the clearing point for the second thread clears a functional unit within the multithreaded processor for at least the first thread.

Method and apparatus for processing an event occurrence within a multithreaded processor

A processor is provided that includes an execution unit for executing instructions and a replay system for replaying instructions which have not executed properly. The replay system is coupled to the execution unit and includes a checker for determining whether each instruction has executed properly and a plurality of replay queues or replay queue sections coupled to the checker for temporarily storing one or more instructions for replay. In one embodiment, thread-specific replay queue sections may each be used to store a long latency instruction for each thread until the long latency instruction is ready to be executed (e.g., data for a load instruction has been retrieved from external memory). By storing the long latency instruction and its dependents in a replay queue section for one thread which has stalled, execution resources are made available for improving the speed of execution of other threads which have not stalled.

Multi-threading techniques for a processor utilizing a replay queue

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Aloha, OR, United States of America

Darrell D Boggs