Efficient exception handling in trusted execution environments

A method comprising:

• enabling an architecturally protected execution environment for code executing in an architecturally protected enclave in memory in response to a field of a register of a hardware processor being set;
• decoding a single instruction having a format including a first field for an opcode, the opcode to indicate execution circuitry of the hardware processor is to perform a context change;
• encountering, by the architecturally protected enclave, an enclave exiting event;
• and
• performing, by the execution circuitry, one or more operations corresponding to the single instruction, the one or more operations including:
• decrementing an index to an array of save areas, each save area corresponding to a different context, wherein the index is used to select a save area for a corresponding context in the array of save areas to store a state for the corresponding context in response to the enclave exiting event;
• and
• changing, within the architecturally protected enclave, from one context of a plurality of contexts to an other context of the plurality of contexts, wherein the state of the other context is provided from the corresponding context in the array of save areas.

A system comprising:

• a memory to store an architecturally protected enclave;
• and
• a processor including:
• a register having a field set to enable an architecturally protected execution environment for code in the architecturally protected enclave;
• a decoder to decode a single instruction having a format including a first field for an opcode, the opcode to indicate execution circuitry is to perform a context change;
• and
• the execution circuitry to perform one or more operations corresponding to the single instruction, the one or more operations including:
• decrementing an index to an array of save areas, each save area corresponding to a different context, wherein the index is used to select a save area for a corresponding context in the array of save areas to store a state for the corresponding context in response to an enclave exiting event encountered by the architecturally protected enclave;
• and
• changing, within the architecturally protected enclave, from a first context to a second context, wherein the state of the second context is provided from the corresponding context of the save area, referenced by the index, in the architecturally protected enclave in the memory.