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WRUSSD

Writes a 64-bit value from a register to the User State Segment Descriptor (USSD) in the processor's internal state.

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

DO NOT support LOCK

This instruction is only available when the processor is operating in 64-bit mode. It is not supported in compatibility mode or 32-bit protected mode.

Failure to provide a valid r64 register as the source will result in an invalid opcode exception. The instruction does not affect the EFLAGS register.