1. A computer-readable medium encoded with computer-executable instructions to perform a method of processing a memory access request, the method comprising: receiving a request to access a portion of a memory, said request identifying the portion of memory to be accessed through an identifier that is translatable through an address translation map; determining, based on cached information about said address translation map, whether execution of said request will violate a policy that limits access to said memory; if execution of said request will not violate said policy, then allowing access to said memory in accordance with said request; and if execution of said request will violate said policy, then either: blocking said request; or modifying said request such that said request does not violate the policy, and carrying out the modified request.