Constraints on updating or usage of memory system component resource control parameters

An apparatus comprising:

• processing circuitry to process instructions from one of a plurality of software execution environments;
• and
• a memory system component to handle memory transactions issued by the processing circuitry in response to the instructions;
• in which:
• in response to a memory transaction issued by the processing circuitry specifying a partition identifier selected depending on which software execution environment caused the memory transaction to be issued, the memory system component is configured to control allocation of resources for handling the memory transaction or manage contention for said resources depending on a selected set of one or more memory system component resource control parameters, said selected set selected from among a plurality of sets of one or more memory system component resource control parameters depending on the partition identifier specified by the memory transaction;
• the memory system component comprises programmable constraint storage circuitry to store at least one resource control parameter constraint;
• based on said at least one resource control parameter constraint stored in said programmable constraint storage circuitry, the memory system component is configured to constrain at least one of:
• updating of a target memory system component resource control parameter;
• and
• usage of the target memory system component resource control parameter for controlling said allocation of resources or managing contention for said resources;
• for a given memory system component, each set of one or more memory system component resource control parameters is associated with a corresponding partition identifier and comprises a portion-based resource allocation control parameter specifying, for each of a plurality of portions of resource, whether that portion of resource is allowed to be allocated for use by a software execution environment associated with the corresponding partition identifier;
• and
• the at least one resource control parameter constraint comprises a portion-based constraint specifying, for each of a subset of portions among said plurality of portions of resource, at least one of:
• whether the portion-based resource allocation control parameter is allowed to be updated to indicate that portion of resource as being allowed to be allocated;
• and
• whether, when using the portion-based resource allocation control parameter for controlling said allocation of resources for a constrained type of memory transaction, the given memory system component should prevent that portion of resource being allocated even if the portion-based resource allocation control parameter specifies that portion of resource as being allowed to be allocated.

An apparatus comprising:

• processing circuitry to process instructions from one of a plurality of software execution environments;
• and
• a memory system component to handle memory transactions issued by the processing circuitry in response to the instructions;
• in which:
• in response to a memory transaction issued by the processing circuitry specifying a partition identifier selected depending on which software execution environment caused the memory transaction to be issued, the memory system component is configured to control allocation of resources for handling the memory transaction or manage contention for said resources depending on a selected set of one or more memory system component resource control parameters, said selected set selected from among a plurality of sets of one or more memory system component resource control parameters depending on the partition identifier specified by the memory transaction;
• the memory system component comprises programmable constraint storage circuitry to store at least one resource control parameter constraint;
• based on said at least one resource control parameter constraint stored in said programmable constraint storage circuitry, the memory system component is configured to constrain at least one of:
• updating of a target memory system component resource control parameter;
• and
• usage of the target memory system component resource control parameter for controlling said allocation of resources or managing contention for said resources;
• for a given memory system component, each set of one or more memory system component resource control parameters is associated with a corresponding partition identifier and comprises a resource allocation threshold parameter indicative of a maximum or minimum threshold for controlling allocation of resource, or management of contention for resource, for a software execution environment associated with the corresponding partition identifier;
• the at least one resource control parameter constraint comprises a threshold cap constraint indicative of a threshold cap value;
• and
• at least one of:
• in response to the parameter update request requesting an update of said resource allocation threshold parameter, the given memory system component is configured to prohibit the resource allocation threshold parameter being updated to indicate, as the maximum or minimum threshold, a threshold greater than the threshold cap value indicated by the threshold cap constraint;
• and
• in response to said memory transaction issued by the processing circuitry, when the memory transaction is a constrained type of memory transaction and the resource allocation threshold parameter breaches the threshold cap constraint, the given memory system component is configured to control allocation of resources or management of contention for resource based on a constrained threshold value less than or equal to the threshold cap value indicated by the threshold cap constraint.