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STI

Sets the IF (Interrupt Flag) bit in the RFLAGS register to 1, enabling maskable hardware interrupts.

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

DO NOT support LOCK

The instruction is available in 64-bit mode, compatibility mode, and 32-bit protected mode. It does not require any specific privilege level to execute in real mode, but in protected mode or 64-bit mode, it is a privileged instruction and SHALL only be executed by code running at CPL 0.

Execution of STI is not immediate; it is delayed until the instruction following the STI has been executed. This prevents a race condition where an interrupt could occur between the execution of a CLI and the subsequent instruction that requires atomicity.