"Smdbltrp" Double Trap Extension, Version 1.0

The Smdbltrp extension addresses a double trap (See Double Trap Control in mstatus Register) in M-mode. When the Smrnmi extension ("Smrnmi" Extension for Resumable Non-Maskable Interrupts) is implemented, it enables invocation of the RNMI handler on a double trap in M-mode to handle the critical error. If the Smrnmi extension is not implemented or if a double trap occurs during the RNMI handler’s execution, this extension helps transition the hart to a critical error state and enables signaling the critical error to the platform.

To improve error diagnosis and resolution, this extension supports debugging harts in a critical error state. The extension introduces a mechanism to enter Debug Mode instead of asserting a critical-error signal to the platform when the hart is in a critical error state. See [92] for details.

See Double Trap Control in mstatus Register for the operational details.