RISC-V Design · All levels
Trap Entry/Exit, Interrupt Priority, and Exception Precision: Theory Deep Dive
Theory Deep Dive for Trap Entry/Exit, Interrupt Priority, and Exception Precision.
Theory deep dive
Theory Deep Dive for Trap Entry/Exit, Interrupt Priority, and Exception Precision is anchored on Worst-case trap-entry cycles, interrupt response jitter, and precise-exception replay success rate under pipeline backpressure.. Convert observations into mechanism-backed decisions with explicit ownership.
Theory matters when it predicts engineering outcomes. Tie abstract ISA and microarchitecture concepts to measurable behavior in trace and counter data.
Pipeline model
diagram
RISC-V PIPELINE DIAGRAM - Trap Entry/Exit, Interrupt Priority, and Exception Precision
PC -> IF -> ID -> EX -> MEM -> WB
| | | | |
i-cache decode ALU/BR LSU regfile write
\ |
+-> branch resolve + redirect
Hot paths:
- branch + load-use dependencies in ID/EX
- memory latency stretching MEM stage
- writeback arbitration for integer/vector units
Focus: keep control hazards predictablePrivilege model
diagram
PRIVILEGE MODE STACK - Trap Entry/Exit, Interrupt Priority, and Exception Precision
+------------------------------+
| Machine mode (M) |
| firmware, PMP, trap root |
+---------------+--------------+
|
delegated traps
v
+------------------------------+
| Supervisor mode (S) |
| kernel, page tables, drivers |
+---------------+--------------+
|
ecall / syscall
v
+------------------------------+
| User mode (U) |
| applications, libraries |
+------------------------------+
Key rule: each upward transition records cause + PC in trap CSRs.