RISC-V Design · All levels
Extension Compatibility Policy: Interview Drills
Interview Drills for Extension Compatibility Policy.
Interview drills
Interview Drills for Extension Compatibility Policy is anchored on Software portability rate across SKUs and zero-regression compliance against declared ISA profiles.. Convert observations into mechanism-backed decisions with explicit ownership.
diagram
PROMPT
You observe Software portability rate across SKUs and zero-regression compliance against declared ISA profiles. on Extension Compatibility Policy. Walk through root cause and release decision.
STRONG ANSWER
1. Defines workload and earliest failing mechanism.
2. Explains mechanism: A compatibility policy defines mandatory, optional, and forbidden extensions per product tier, then ties those contracts to toolchain defaults, ABI rules, and runtime feature discovery. Policy quality depends on deterministic multi-version dispatch, clear deprecation windows, and compatibility tests that prevent accidental reliance on unavailable extensions. Mature teams align policy with upstream profile initiatives and publish explicit migration guidance so ecosystem partners can ship one codebase across heterogeneous RISC-V deployments.
3. Requests proving artifact: ISA policy document with profile tables, ABI commitments, compiler flags, and conformance regression gates.
4. Proposes bounded fix + owner + rollback-safe validation.
WEAK ANSWER
Suggests generic optimization ideas without mechanism proof or owner accountability.Decision matrix
diagram
RISC-V EVIDENCE MATRIX - Extension Compatibility Policy
+--------------------------+--------------------------------+--------------------------------+---------------------------+
| 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 |
+--------------------------+--------------------------------+--------------------------------+---------------------------+