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WRPKRU

Writes the value specified in the source operand to the Protection Key Register 0 (PKRU).

The table after the description covers what the source and destinations can be.

DO NOT support LOCK

The instruction is only available if the processor supports Protection Keys and the CR4.PKE bit is set. If CR4.PKE is cleared, executing this instruction SHALL result in an invalid opcode exception (#UD). This instruction is available in both 64-bit mode and compatibility mode.

The source register MUST contain the desired PKRU value; any bits beyond the 32-bit register size are ignored. Because WRPKRU modifies the access rights for the current thread, the effects are local to the logical processor executing the instruction. Failure to properly synchronize PKRU state during context switches in an OS kernel MAY lead to memory access violations or security vulnerabilities.