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UMONITOR

Sets the address of a memory region to be monitored for writes. The processor monitors the specified memory address; if a write access occurs to the monitored address, the processor clears the monitor state, which can then be detected by the UMWAIT or TPAUSE instructions.

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

DO NOT support LOCK

The UMONITOR instruction is only available in 64-bit mode. It is NOT supported in compatibility mode.

To avoid incorrect behavior or failure of the monitoring mechanism, the following details MUST be observed:

• The memory address specified in the register MUST be aligned to a cache line boundary; otherwise, the behavior is undefined.
• A call to UMONITOR MUST be followed by a waiting instruction (such as UMWAIT) before any other instruction that might trigger a cache line eviction or modification occurs.
• If the processor is in a state where monitoring is already active, UMONITOR will overwrite the previously monitored address.
• Memory monitoring is local to the logical processor; writes from other processors will trigger the monitor clear, but the setup is specific to the core executing the instruction.