Arm Limited

Richard Roy Grisenthwaite

Michael John Williams

Stuart David Biles

David Hennah Mansell

Simon John Craske

Bruce James Mathewson

David James Seal

Matthew James Horsnell

Nigel John Stephens

Andrew Christopher Rose

Jason Parker

Thomas Christopher Grocutt

Paul Kimelman

Matthew Lucien Evans

Daniel Kershaw

Christopher William Laycock

Graeme Peter Barnes

Peter Andrew Riocreux

Andrew Brookfield Swaine

Frederic Claude Marie Piry

John Michael Horley

Stephan Diestelhorst

Antony John Harris

Grigorios Magklis

Ali Ghassan Saidi

Luca Scalabrino

Edmond John Simon Ashfield

Ian Victor Devereux

Daryl Wayne Bradley

Philippe Jean-Pierre Raphalen

Sheldon James Woodhouse

Louis-Marie Vincent Mouton

Conrado Blasco Allue

Lee Douglas Smith

David John Gwilt

Anthony Jebson

Jeremy Davies

Norbert Bernard Eugéne Lataille

Gerard Richard Williams

Antony John Penton

Peter Richard Greenhalgh

Phanindra Kumar Mannava

Alex James Waugh

Ian Michael Caulfield

Klas Magnus Bruce

Michael Andrew Campbell

François Christopher Jacques Botman

Giacomo Gabrielli

Ian Field

Peter Guy Middleton

Michael Alexander Kennedy

Gilles Eric Grandou

Alexander Alfred Hornung

David John Butcher

Jocelyn Francois Orion Jaubert

Matthew Paul Elwood

Yuval Elad

David Michael Gilday

Jelena Milanovic

Bradley John Smith

Alexander Donald Charles Chadwick

Elodie Charra

Carlos Garcia-Tobin

Ruben Borisovich Ayrapetyan

Anthony John Goodacre

Harry Samuel Thomas Fearnhamm

Tan Ba Tran

Nathan Yong Seng Chong

Mélanie Emanuelle Lucie Vincent

Christopher Michael Clegg

Stewart David Biles

Phillippe Jean-Pierre Raphalen

David Aaron Rusling

Memory management circuitry () supports two-stage address translation based on a stage-1 and stage-2 translation table structures. Stage-2 access permission information specified by a stage-2 translation table entry has an encoding specifying whether a corresponding memory region has a partially-read-only permission indicating that write requests to the memory region corresponding to the target intermediate address, issued when processing circuitry () is in a predetermined execution state, are permitted for a restricted subset of write request types (including metadata-updating write requests for updating access tracking metadata in translation table entries) but prohibited for other write request types. The memory management circuitry () rejects a memory access request when the stage-2 access permission information of a corresponding stage-2 translation table entry specifies the partially-read-only permission and the memory access request is a write request, other than the restricted subset of write request types, issued in the predetermined execution state.

Two-stage address translation

An apparatus and method are provided for storing a plurality of translation entries in a cache, each translation entry corresponding to one of a plurality of page table entries and defining a translation between a first address and a second address, and encoding control information indicative of an attribute of each page table entry; returning, in response to a lookup querying a first lookup address, a corresponding second address when the first lookup address corresponds to one of the plurality of translation entries stored in the cache; modifying at least some of the control information in response to notification of a modification of the attribute in a page table entry; and retaining in the cache at least one translation entry corresponding to the page table entry for use in a subsequent address lookup querying a corresponding first lookup address in response to the notification of the modification of the attribute in the page table entry.

Data processing apparatus and method for address translation

Instruction decoder to decode processing instructions; one or more first registers; first processing circuitry to execute the decoded processing instructions in a first processing mode and configured to execute the decoded processing instructions using the one or more first registers; and control circuitry to execute the decoded processing instructions in a second processing mode using one or more second registers; the instruction decoder being configured to decode processing instructions selected from a first instruction set and a second instruction set in the second processing mode, in which one or both of the first and second instruction sets comprises at least one unique instruction set; the instruction decoder configured to decode one or more mode change instructions to change between the first and second processing mode; and the first processing circuitry configured to change the current processing mode between the first and second processing mode responding to executing mode change instruction.

Processing instructions selected from a first instruction set in a first processing mode and instructions selected from a second different instruction set in a second processing mode

An apparatus comprising translation circuitry to perform a translation operation to generate a translated second memory address within a second memory address space as a translation of a first memory address within a first memory address space, in which the translation circuitry is configured to generate the translated second memory address in dependence upon translation information stored at one or more translation information addresses; permission circuitry to perform an operation to detect permission information to indicate, for a given second memory address, whether memory access is permitted to the given second memory address; and access circuitry to allow access to data stored at the given second memory address when the permission information indicates that memory access is permitted to the given second memory address.

Apparatus and method

An apparatus comprises processing circuitry to perform data processing in response to instructions, and memory access circuitry to perform a tag-guarded memory access operation in response to a target address. The tag-guarded memory access operation comprises comparing an address tag associated with the target address with a guard tag stored in a memory system in association with a block of one or more memory locations comprising an addressed location identified by the target address, and generating an indication of whether a match is detected between the guard tag and the address tag. The memory access circuitry determines, according to a programmable mapping, a mapping of guard tag storage locations for storing guard tags for corresponding blocks of memory locations.

Programmable mapping of guard tag storage locations

Processing circuitry performs processing operations specified by program instructions, and a decoder decodes memory access instructions to generate control signals to control the processing circuitry to perform memory access operations. The memory access instructions have respective encodings specifying protected memory access instructions corresponding to protected memory access operations and less-protected memory access instructions corresponding to less-protected memory access operations. The less-protected memory access operations are associated with less restrictive memory access conditions than the protected memory access operations.

Memory access instructions

A data processing apparatus has processing circuitry with transactional memory support circuitry to support execution of a transaction using transactional memory. In response to an exception mask updating instruction which updates exception mask information to enable at least one subset of exceptions which was disabled at the start of processing of a transaction, the processing circuitry permits un-aborted processing of one or more subsequent instruction of the transaction that follow the exception mask update instruction.

Permitting unaborted processing of transaction after exception mask update instruction

An apparatus comprising memory access circuitry to perform a tag-guarded memory access in response to a received target address and methods of operation of the same are disclosed. In the tag-guarded memory access a guard-tag retrieval operation seeks to retrieve a guard tag stored in association with a block of one or more memory locations comprising an addressed location identified by the received target address, and a guard-tag check operation compares an address tag associated with the received target address with the guard tag retrieved by the guard-tag retrieval operation. When the guard-tag retrieval operation is unsuccessful in retrieving the guard tag, a substitute guard tag value is stored as the guard tag in association with the block of one or more memory locations comprising the addressed location identified by the target address.

Handling guard tag loss

A data processing system () including one or more transaction buffers () storing address translation data executes translation buffer invalidation instructions TLBI within respective address translation contexts VMID, ASID, X. Translation buffer invalidation signals generated as a consequence of execution of the translation buffer invalidation instructions are broadcast to respective translation buffers and include signals which specify the address translation context of the translation buffer invalidation instruction that was executed. This address translation context specified within the translation buffer invalidation signals is used to gate whether or not those translation buffer invalidation signals when received by translation buffers which are potential targets for the invalidation are or are not flushed. The address translation context data provided within the translation buffer invalidation signals may also be used to control whether or not local memory transactions for a local transactional memory access are or are not aborted upon receipt of the translation buffer invalidation signals.

Address translation data invalidation

An apparatus is described with support for transactional memory and load/store-exclusive instructions using an exclusive monitor indication to track exclusive access to a given address. In response to a predetermined type of load instruction specifying a load target address, which is executed within a given transaction, any exclusive monitor indication previously set for the load target address is cleared. In response to a load-exclusive instruction, an abort is triggered for a transaction for which the given address is specified as one of its working set of addresses. This helps to maintain mutual exclusion between transactional and non-transactional threads even if there is load speculation in the non-transactional thread.

Handling load-exclusive instructions in apparatus having support for transactional memory

An apparatus and method are provided for controlling memory accesses. The apparatus has memory access circuitry for performing a tag-guarded memory access operation in response to a target address, the tag-guarded memory access operation by default comprising: comparing an address tag associated with the target address with a guard tag stored in a memory system in association with a block of one or more memory locations comprising an addressed location identified by the target address; and generating an indication of whether a match is detected between the guard tag and the address tag. Further, the apparatus has control tag storage for storing, for each of a plurality of memory regions, configuration control information used to control how the tag-guarded memory access operation is performed by the memory access circuitry when the target address is within that memory region. Each memory region corresponds to multiple of the blocks. This provides a very flexible and efficient mechanism for performing tag-guarded memory access operations.

Controlling memory accesses using a tag-guarded memory access operation

Apparatus for data processing and a method of data processing are provided. Data processing operations are performed in response to data processing instructions. An error exception condition is set if a data processing operation has not been successful. It is determined if an error memory barrier condition exists and an error memory barrier procedure is performed in dependence on whether the error memory barrier condition exists. The error memory barrier procedure comprises, if the error exception condition is set and if an error mask condition is set: setting a deferred error exception condition and clearing the error exception condition.

Deferred system error exception handling in a data processing apparatus

An apparatus () comprises processing circuitry () to perform speculative execution of instructions; a main cache storage region (); a speculative cache storage region (); and cache control circuitry () to allocate an entry, for which allocation is caused by a speculative memory access triggered by the processing circuitry, to the speculative cache storage region instead of the main cache storage region while the speculative memory access remains speculative. This can help protect against potential security attacks which exploit cache timing side-channels to gain information about allocations into the cache caused by speculative memory accesses.

Speculative cache storage region

An apparatus for processing data and a method of data processing are provided. A processor core in the apparatus performs data processing operations in response to a sequence of instructions, including write operations which write data items to a non-volatile memory. A write-back cache stores local copies of the data items retrieved from the memory and written to the memory by the processor core. A storage unit is provided which stores indications of the write operations initiated by the processor core and the processor core is configured to respond to an end instruction by causing the local copies of data items which are the subject of the write operations by the processor core, and for which an indication is stored in the storage unit, to be cleaned from the write-back cache to the memory. The indications of the write operations stored in the storage unit are then cleared.

Write operations to non-volatile memory

In an apparatus with transactional memory support circuitry, for a first type of transaction started using a first type of transaction start instruction, commitment of results of instructions executed speculatively following the first type of transaction start instruction are prevented until a transaction end instruction is reached. An abort is triggered when a conflict is detected between an address of a memory access from another thread and the addresses tracked for the transaction. For a second type of transaction started using a second type of transaction start instruction, an address of the read operation is marked as trackable whilst an address of a write operation is omitted from being marked as trackable. This allows an apparatus that supports transactional memory to also be used for multi-word address watching.

Apparatus and data processing method for transactional memory

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Cambridge, United Kingdom

Richard Roy Grisenthwaite