Patent ID: 8176280

Claim:
A computer program product for executing an instruction, said computer program product comprising: a non-transitory computer readable storage medium readable by a processor and storing instructions for execution by the processor for performing a method comprising: obtaining a test protection machine instruction configured to provide indications regarding protection of storage and to distinguish between host-level protection of the storage and guest-level protection of the storage, the test protection machine instruction comprising an opcode field specifying the test protection machine instruction and a first operand; and executing, by a pageable guest, the obtained test protection machine instruction, the executing comprising: testing a location of storage designated by the first operand for one or more storage protection exception conditions, wherein said storage is subject to host-level protection and guest-level protection and the location of storage specifies a first frame of host main storage; responsive to the testing determining a storage protection exception condition for the location of storage is due to a host-level protection and responsive to determining that the location of storage is part of a host copy-on-write scheme, assigning a second frame to the location of storage and copying contents of the first frame to the second frame, and permitting the pageable guest to store to the location of storage comprising the second frame; and responsive to the testing determining a storage protection exception condition for the location of storage is due to a guest-level protection, setting a condition code indicating to the pageable guest one of: fetching and storing are permitted, only fetching is permitted, neither fetching nor storing is permitted, or translation is not available.