Coverage-Driven Verification: Interview Drills

PROMPT
You observe Risk-weighted closure across functional coverage, assertion coverage, code coverage, and bug escape trend. on Coverage-Driven Verification. Walk through root cause and release decision.

STRONG ANSWER
1. Defines workload and earliest failing mechanism.
2. Explains mechanism: Coverage-driven verification converts architecture risk into measurable closure targets for instructions, privilege modes, interrupts, memory ordering, and exception sequencing. Constrained-random stimulus and scenario weighting should be guided by uncovered bins and historical bug classes, not only raw percentage goals. Signoff readiness combines stable regressions, reviewed exclusions, and evidence that critical cross-products are hit under realistic contention so final quality is based on demonstrated behavior breadth.
3. Requests proving artifact: Verification closure report with risk bins, uncovered-item action plan, and signoff recommendation.
4. Proposes bounded fix + owner + rollback-safe validation.

WEAK ANSWER
Suggests generic optimization ideas without mechanism proof or owner accountability.

RISC-V EVIDENCE MATRIX - Coverage-Driven Verification

+--------------------------+--------------------------------+--------------------------------+---------------------------+
| Evidence                 | Tells you                      | Does not prove                 | Next action               |
+--------------------------+--------------------------------+--------------------------------+---------------------------+
| perf counter timeline    | where regression appears       | exact mechanism causality      | correlate with trace      |
| decode/control dump      | control intent per instruction | pipeline side-effect ordering  | inspect retire semantics  |
| trap + CSR logs          | privilege/fault behavior       | performance bottleneck alone   | pair with CPI buckets     |
| MMU/TLB walk trace       | translation behavior           | full system QoS impact         | test mixed workloads      |
| post-fix trend graph     | movement after fix             | long-term stability            | run stress matrix         |
+--------------------------+--------------------------------+--------------------------------+---------------------------+