ctos — taken SError opt-in sequence Diagram

Taken path (opt-in)

Pinned virt implements TYPE_NMI → ARM_CPU_SERROR
stop/inject/cont avoids racing past the A-clear window
Serial bare el0: serror satisfies CTOS_REQUIRE_TAKEN_SERROR=1
Arm A-clear window (qemu-smoke, ctos guest, Serial): Guest arms standing EL0 with PSTATE.A clear and prints el0: serror-arm.
QMP stop / inject / cont (serial-inject, Pinned QEMU, ctos guest): Host pauses TCG, inject-nmi raises ARM_CPU_SERROR on the pin, then continues.

Stock contrast

Without the pin, inject-nmi errors: machine does not provide NMIs
Default smoke still requires el0: serror-park
Diagram is a doc aid — not production Live status
EXPECT gate (ctos guest, Serial, qemu-smoke): Opt-in smoke requires bare el0: serror; stock path would park instead.

Honesty

Not FEAT_NMI; not FIQ/BRK as SError
Not umbrella EL0 isolated
ADR-083 tip ~6ec1f4e; CloudAgent HELD for the amd64 workstation