Systems and methods for managing content in a flash memory. Systems and methods for implementing hash tables in a flash memory are disclosed. A hash table may include a flat array or an array of buckets that are each associated with a linked list. Adding or removing entries from the hash table or from the linked list are achieved by performing an overwrite operation where possible to pointers affected by the table operation.

A memory interface for interfacing between a memory bus and a cache memory, comprising: a plurality of bus interfaces configured to transfer data between the memory bus and the cache memory; and a plurality of snoop processors configured to receive snoop requests from the memory bus; wherein each snoop processor is associated with a respective bus interface and each snoop processor is configured, on receiving a snoop request, to determine whether the snoop request relates to the bus interface associated with that snoop processor and to process the snoop request in dependence on that determination.

A cache management circuit that includes a predictive adjustment circuit configured to predictively generate cache control information based on a cache hit-miss indicator and the retention ranks of accessed cache lines to improve cache efficiency is disclosed. The predictive adjustment circuit stores the cache control information persistently, independent of whether the data remains in cache memory. The stored cache control information is indicative of prior cache access activity for data from a memory address, which is indicative of the data's “usefulness.” Based on the cache control information, the predictive adjustment circuit controls generation of retention ranks for data in the cache lines when the data is inserted, accessed, and evicted. After the data has been evicted from the cache memory and is later accessed by a subsequent memory request, the persistently stored cache control information corresponding to that memory address increases the information available for determining the usefulness of data.

A cache management circuit that includes a predictive adjustment circuit configured to predictively generate cache control information based on a cache hit-miss indicator and the retention ranks of accessed cache lines to improve cache efficiency is disclosed. The predictive adjustment circuit stores the cache control information persistently, independent of whether the data remains in cache memory. The stored cache control information is indicative of prior cache access activity for data from a memory address, which is indicative of the data's “usefulness.” Based on the cache control information, the predictive adjustment circuit controls generation of retention ranks for data in the cache lines when the data is inserted, accessed, and evicted. After the data has been evicted from the cache memory and is later accessed by a subsequent memory request, the persistently stored cache control information corresponding to that memory address increases the information available for determining the usefulness of data.

A method is provided in a data processing system having second level address translation (SLAT) controlled by a hypervisor. In the method, hashes of all memory pages accessible by a guest OS are stored (set S). Also, hashes of all memory pages previously accessed by the guest OS are stored (set T). When the guest OS attempts an access to a memory page having executable code for which it does not have permission, an exception is generated. A hash of the memory page is compared with the hashes of set T and set S. If there is not a match within set T, then the guest OS has never attempted the requested operation before and suspicious behavior is reported. If there is not a match within set S, the requested operation is reported as illegal. In another embodiment, the memory page may be encrypted to prevent the guest OS from reading the memory page.

A method is provided in a data processing system having second level address translation (SLAT) controlled by a hypervisor. In the method, hashes of all memory pages accessible by a guest OS are stored (set S). Also, hashes of all memory pages previously accessed by the guest OS are stored (set T). When the guest OS attempts an access to a memory page having executable code for which it does not have permission, an exception is generated. A hash of the memory page is compared with the hashes of set T and set S. If there is not a match within set T, then the guest OS has never attempted the requested operation before and suspicious behavior is reported. If there is not a match within set S, the requested operation is reported as illegal. In another embodiment, the memory page may be encrypted to prevent the guest OS from reading the memory page.

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 8. In response to a realm switch from a source realm to a target realm at a more privileged exception level, state masking of a subset of architectural state associated with a source realm is performed to make the state inaccessible to a target realm. In response to a flush command following the realm switch, any of the subset of architectural state data not already saved to at least one realm execution context memory region is ensured to be saved.

A data processing apparatus is provided, which includes a cache to store operations produced by decoding instructions fetched from memory. The cache is indexed by virtual addresses of the instructions in the memory. Receiving circuitry receives an incoming invalidation request that references a physical address in the memory. Invalidation circuitry invalidates entries in the cache where the virtual address corresponds with the physical address. Coherency is thereby achieved when using a cache that is indexed using virtual addresses.

A data processing apparatus is provided, which includes a cache to store operations produced by decoding instructions fetched from memory. The cache is indexed by virtual addresses of the instructions in the memory. Receiving circuitry receives an incoming invalidation request that references a physical address in the memory. Invalidation circuitry invalidates entries in the cache where the virtual address corresponds with the physical address. Coherency is thereby achieved when using a cache that is indexed using virtual addresses.

In an example, there is disclosed a host-fabric interface (HFI), including: an interconnect interface to communicatively couple the HFI to an interconnect; a network interface to communicatively couple the HFI to a network; network interface logic to provide communication between the interconnect and the network; a coprocessor configured to provide an offloaded function for the network; a memory; and a caching agent configured to: designate a region of the memory as a shared memory between the HFI and a core communicatively coupled to the HFI via the interconnect; receive a memory operation directed to the shared memory; and issue a memory instruction to the memory according to the memory operation.