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SWAPGS

Exchanges the current value of the GS base register with the value stored in the KernelGSBase MSR.

The following table covers what the source and destinations can be:

DO NOT support LOCK

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

The instruction is intended for use by the operating system to switch between user-mode and kernel-mode GS segments. If SWAPGS is executed while the processor is already using the kernel GS base, it will swap it back to the user GS base. Failure to properly track the state of the GS base across privilege level transitions SHALL result in the processor accessing incorrect memory regions, potentially leading to a General Protection exception (#GP) or memory corruption.