Arm Limited

Martin Weidmann

Jason Parker

Matthew Lucien Evans

Gareth Rhys Stockwell

Timothy Nicholas Hay

Andrew Brookfield Swaine

Andrew John Turner

Michael Alexander Kennedy

Yuval Elad

Marc Zyngier

Address translation circuitry () translates a virtual address specified by a memory access request issued by requester circuitry into a target physical address (PA). Requester-side filtering circuitry () performs a granule protection lookup based on the target PA and a selected physical address space (PAS) associated with the memory access request, to determine whether to allow the memory access request to be passed to a cache or interconnect. In the granule protection lookup, the requester-side filtering circuitry obtains granule protection information corresponding to a target granule of physical addresses including the target PA, which indicates at least one allowed PAS associated with the target granule, and blocks the memory access request when the granule protection information indicates that the selected PAS is not an allowed PAS.

Apparatus and method using plurality of physical address spaces

There is provided a data processing apparatus that includes processing circuitry for executing instructions relating to an active virtual processor in a plurality of virtual processors. Exception control circuitry receives an external exception associated with a target virtual processor in the plurality of virtual processors and when the target virtual processor is other than the active virtual processor, it issues a doorbell exception to cause a scheduling operation to schedule the target virtual processor to be the active virtual processor. Storage circuitry stores an indication of a set of masked virtual processors and the scheduling operation is adapted to disregard doorbell exceptions in respect of the set of masked virtual processors.

External exception handling

A realm management unit (RMU) manages ownership of memory regions by realms, each realm corresponding to at least a portion of a software process executed by processing circuitry. Memory access circuitry enforces ownership rights for the regions, with the owner realm having a right to exclude other realms from accessing data stored within its owned region. The memory access circuitry permits execution, from within a current realm, of program code stored in a target memory region having an owner realm other than the current realm, when the target memory region is owned by a code realm and a code realm authorisation tablestored in at least one memory region owned by the current realm indicates that execution of program code from the target memory region is permitted by the current realm.

Code realms

An interrupt controller comprises issue circuitry to issue interrupt requests to a processing element and control circuitry to detect presence of a race condition in association with at least one pending interrupt request to be issued, and to set a barrier indicator when the race condition has been resolved. In response to the race condition being present, the issue circuitry is configured to select one of the at least one pending interrupt requests, to issue to the processing element the selected pending interrupt request followed by a dummy request over a path that ensures that the processing element receives the selected pending interrupt request prior to receiving the dummy request. On receiving an acknowledgement indicating that the processing element has received the dummy request, the control circuitry is then configured to set the barrier indicator.

Interrupt controller

Memory access circuitry enforces ownership rights for memory regions. A given memory region is associated with an owner realm specified from multiple realms, each realm corresponding to a portion of at least one software process executed by processing circuitry. A realm management unit initialises the realms. The realm management unit is configured to initialise realms including a full realm which corresponds to a given software process and a sub-realm corresponding to a given address range within the given software process.

Sub-realms

Memory access circuitry enforces ownership rights for memory regions. A given memory region is associated with an owner realm specified from multiple realms, each realm corresponding to a portion of at least one software process executed by processing circuitry. In response to a first variant of an exception return instruction the processing circuitry returns from processing of an exception while staying within the same realm. In response to a second variant of the exception return instruction the processing circuitry switches processing from a current realm to a destination realm.

Exception return instruction variants for realm-based switching

A realm management unit (RMU) maintains an ownership table specifying ownership entries for corresponding memory regions defining ownership attributes specifying, from among a plurality of realms, an owner realm of the corresponding region. Each realm corresponds to at least a portion of at least one software process. The owner realm has a right to exclude other realms from accessing data stored in the corresponding region. Memory access is controlled based on the ownership table. In response to a region fuse command specifying a fuse target address indicative contiguous regions of memory to be fused into a fused group of regions, a region fuse operation updates the ownership table to indicate that the ownership attributes for the fused group of regions are represented by a single ownership entry. This provides architectural support for enabling improvement of TLB performance.

Managing fusion of memory regions and ownership attributes for fused memory regions

Memory access circuitry () enforces ownership rights for memory regions. A given memory region is associated with an owner realm specified from multiple realms, each realm corresponding to a portion of at least one software process executed by processing circuitry (). The owner realm has a right to exclude other realms from accessing data within the memory region. Realm management circuitry () accesses a realm management tree storing realm management data for at least two realms in a tree structure having a variable number of levels. The realms are identified using a realm identifier which has a variable number of variable length bit portions each providing an index into a given level of the realm management tree.

Realm identifiers for realms for memory access control

An apparatus has a translation cache () comprising a number of entries for specifying address translation data. Each entry () also specifies a translation context identifier () associated with the address translation data and a realm identifier () identifying one of a number of realms. Each realm corresponds to at least a portion of at least one software process executed by processing circuitry (). In response to a memory access a lookup of the translation cache () is triggered. When the lookup misses in the cache (), control circuitry () prevents allocation of address translation data to the cache when the current realm is excluded from accessing the target memory region by an owner realm specified for the target memory region. In the lookup, whether a given entry () matches the memory access depends on both a translation context identifier comparison and a realm identifier comparison.

Realm identifier comparison for translation cache lookup

Processing circuitry () processes software processes at one of a plurality of exception levels and in one of a plurality of realms, each realm corresponding to a portion of at least one software process and being associated with a boundary exception level indicating a most privileged exception level at which the realm can be processed by the processing circuitry (). In response to a realm exiting exception condition during processing of a given realm, where the exception condition is to be handled by an exception handler at a more privileged exception level than the boundary exception level of the given realm, the processing circuitry () performs state masking to make inaccessible, to software processes processed at a more privileged exception level than the boundary exception level, architectural state of a subset of registers selected depending on the boundary exception level of the given realm.

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Haverhill, United Kingdom

Martin Weidmann