Scrub-commit state for memory region

A non-transitory storage medium storing a computer program for controlling a host data processing apparatus to provide an instruction execution environment, the computer program comprising:

• processing program logic to perform data processing in response to one or more software processes;
• realm management program logic to manage ownership of a plurality of memory regions of a first memory storage area, wherein a given memory region is associated with an owner realm specified from among a plurality of realms, each realm corresponding to at least a portion of at least one of the software processes;
• and
• memory access program logic to enforce ownership rights for the plurality of memory regions of the first memory storage area, the owner realm of the given memory region having a right to exclude other realms from accessing data stored within the given memory region;
• wherein the realm management program logic is configured to control transitions of the memory regions between a plurality of region states, the plurality of region states comprising at least:
• an invalid state in which the memory region is allowed to be reallocated to a different owner realm;
• a valid state in which the memory region is allocated to an owner realm, accessible to that owner realm, and prevented from being reallocated to a different owner realm, wherein for a memory region to transition from the invalid state to the valid state, the realm management program logic is configured to require that a scrubbing process is performed to set each storage location of that memory region to a value uncorrelated with a previous value stored in the storage location;
• and
• a scrub-commit state in which the memory region is allocated to an owner realm, inaccessible to that owner realm until the scrubbing process has been performed for the memory region, and prevented from being reallocated to a different owner realm;
• wherein in response to an export command specifying an export target memory region in the valid state, the realm management program logic is configured to:
• trigger encryption of data stored in the export target memory region and writing of the encrypted data to a second memory storage area;
• and
• transition the export target memory region from the valid state to the invalid state;
• and
• wherein in response to the export command specifying an export target memory region in the scrub-commit state, the realm management program logic is configured to:
• suppress the encryption of the data stored in the export target memory region and the writing of the encrypted data to the second memory;
• generate metadata specifying that the export target memory region was in the scrub-commit state;
• and
• transition the target memory region from the scrub-commit state to the invalid state.

An apparatus comprising:

• processing circuitry to perform data processing in response to one or more software processes;
• realm management circuitry to manage ownership of a plurality of memory regions of a first memory, wherein a given memory region is associated with an owner realm specified from among a plurality of realms, each realm corresponding to at least a portion of at least one of the software processes;
• and
• memory access circuitry to enforce ownership rights for the plurality of memory regions of the first memory, the owner realm of the given memory region having a right to exclude other realms from accessing data stored within the given memory region;
• wherein the realm management circuitry is configured to control transitions of the memory regions between a plurality of region states, the plurality of region states comprising at least:
• an invalid state in which the memory region is allowed to be reallocated to a different owner realm;
• a valid state in which the memory region is allocated to an owner realm, accessible to that owner realm, and prevented from being reallocated to a different owner realm, wherein for a memory region to transition from the invalid state to the valid state, the realm management circuitry is configured to require that a scrubbing process is performed to set each storage location of that memory region to a value uncorrelated with a previous value stored in the storage location;
• and
• a scrub-commit state in which the memory region is allocated to an owner realm, inaccessible to that owner realm until the scrubbing process has been performed for the memory region, and prevented from being reallocated to a different owner realm;
• wherein in response to an export command specifying an export target memory region in the valid state, the realm management circuitry is configured to:
• trigger encryption of data stored in the export target memory region and writing of the encrypted data to a second memory;
• and
• transition the export target memory region from the valid state to the invalid state;
• and
• wherein in response to the export command, the realm management circuitry is configured to generate metadata specifying at least one characteristic of the data stored in the export target memory region, and to store the metadata to the first memory.