RISC-V Design · All levels

Formal Pipeline Checks: Debug Playbook

Debug Playbook for Formal Pipeline Checks.

Debug playbook

Debug Playbook for Formal Pipeline Checks is anchored on Proof closure on pipeline safety/liveness properties with bounded-depth convergence and vacuity review.. Convert observations into mechanism-backed decisions with explicit ownership.

Freeze workload seed, binary, compiler, firmware, and platform setup.
Find earliest persistent mechanism failure in the timeline.
Build one reduced reproducer for dominant hypothesis.
Patch minimal fix with explicit rollback gate.
Rerun correctness + performance + power matrix.

Decision tree

diagram

ROOT CAUSE TREE - Formal Pipeline Checks

Proof closure on pipeline safety/liveness properties with bounded-depth convergence and vacuity review. regressed
          |
   reproducible on fixed seed?
      /                 \
    no                   yes
    |                     |
env/tool drift       first failing domain?
                     /        |         \
                  decode    execute    memory/MMU
                    |         |            |
               control map  bypass/FU   TLB/walk/perm
                    |
         privilege/CSR side effects checked?

Stop at first confirmed mechanism, then assign explicit owner + fix proof.

Review memo template

diagram

RISC-V REVIEW MEMO - Verification & Debug / Formal Pipeline Checks

1. Symptom
   - Failing metric: Proof closure on pipeline safety/liveness properties with bounded-depth convergence and vacuity review.
   - Failing workload slice: <name>
   - Triggering mode: <privilege/virtualization/interrupt/cache/boot>
   - Build and runtime tags: <toolchain/firmware/RTL revision>

2. Mechanism hypothesis
   - Primary mechanism: Formal pipeline checks encode invariants such as precise exception behavior, hazard handling correctness, no-commit-on-kill guarantees, and forward progress under legal assumptions. These properties expose corner-state bugs in control logic, bypass paths, and flush interactions that simulation may miss due to insufficient interleaving coverage. Successful deployment partitions checks by stage and protocol interface, constrains environments transparently, and tracks counterexample quality so proofs represent real architecture guarantees rather than over-constrained models.
   - Competing hypotheses: <decode control / hazard / MMU / privilege / integration>
   - Missing evidence: <trace/counter/proof/report>

3. Proposed action
   - Smallest reversible change: <RTL/compiler/runtime/config>
   - Expected movement: <throughput/latency/tail/perf-per-watt>
   - Regression risk: correctness, security, power, timing, software compatibility

4. Signoff
   - Required artifact: Property dashboard including assumptions, proof status, vacuity outcomes, and counterexample triage log.
   - Required owners: formal verification owner, CPU microarchitecture owner, CPU verification lead, RTL owner
   - Final decision: ship, bounded rollout, rollback, or escalate

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