Status at a glance:

• Current  Definition-of-Done (wiki.riscv.org -> tech -> policies -> approved)   Status: kickoff  DoD status directory
• Next  update DoD checklist Plan tab, decide on any waivers needed?  Send to Chairs info below to transition from Kickoff to Plan  

To Reach Definition-of-Done Plan status: extension lifecycle and milestone definitions

• Develop final charter and plan with the group and send to Chairs (tech-chairs@lists.riscv.org) for approval within 4 weeks
• Fill in DoD Plan tab in checklist and send to chairs for approval of any deliverables that don't match the defaults along with any requested waivers
• Freeze-time preliminary POC definition approved by IC
• Fill in task group and specification status spreadsheet information including extension or extension group names, projected dates, DoD component effort sizing, DoD tasks your group needs resource help with,...
• Develop Rationale document and send to chairs for approval
• Notify TSC and Chairs when you complete this milestone and include any waivers and an updated DoD spreadsheet.
• Plan: RISCV has prioritized RVA22.  expect CLIC to possibly be ratified at similar times with other embedded extensions like Zfinx, new compressed, rv32e, p-extension.  So CLIC still on roadmap but probably next gen RISC-V grouping.  Continue working on issues and refining spec.
• Hypervisor support? One simple option is CLIC doesn’t work with H?  Both CLIC and AIA are evolving.  CLIC problematic places: table read hardware vectoring.  Otherwise no real complication.  If systems have both AIA and CLIC, how would it work. Maybe don’t need to worry about it?
• Impact of N-extension on CLIC?

Charter

• Current Charter at https://github.com/riscv/groups/tree/main/Fast-Interrupts to be moved to https://github.com/riscv-admin-docs (possibly renamed)
• Develop a low-latency, vectored, priority-based, preemptive interrupt scheme for interrupts directed to a single hart, compatible with the existing RISC-V standards. Provide both hardware specifications and software ABIs/APIs. Standardize compiler conventions for annotating interrupt handler functions.

Specification

• Latest Draft Fast Interrupt Specification (v0.9-draft-20210525)
  • clarified 32-bit writes to clicint registers are legal but effects are not defined.
  • clarified that MPRV and SUM are obeyed on vector table accesses
• What's next:
  • 36 outstanding issues to be addressed.  (previously 35).

Encoding/OpCode consistency review

• Need to propose new CLIC CSR Registers and addresses

• What's next: when outstanding issues are reduced, start planning for review

Architecture Tests

• Deterministic Test plan for the fast-interrupt is available.  Discussion on-going on how to add async/undeterministic testing of interrupts.
• YAML config needs to be created.  See info here.
• Discussion in Arch tests group to add automation (docker?) to validate check-in so that arch-test-suite is run against sail, spike, gcc/toolchain, with versions used recorded.  So sail and spike will need to work for CLIC before CLIC tests can be added to riscv-config github.

Compilers / Toolchains

GCC and Binutils

• No new instructions are added.  Needs to be aware CSR names?  Need to choose arch string like ziclic

LLVM

• No new instructions are added.  Needs to be aware of CSR names? 

Simulators

Though all listed under "simulators", these are actually a collection of formal model / virtual machine / architectural simulators / DV simulators etc.

SAIL

• TBD - Waiver until SAIL privilege model is completed?  e.g. add CLIC support to OS like Zephyr.
• which github?  https://github.com/rems-project/sail-riscv or https://github.com/riscv/riscv-sail
  • Allen is working on this with the SAIL team from Cambridge.  ultimately it will be in the RISC-V repo as soon as we have maintainers

Spike

• TBD

riscvOVPSimPlus

• Imperas Commercial Simulator
• Freeware version

QEMU

• QEMU implementation of CLIC-0.9 specification (Version 0.9-draft-20210217)

Proof-of-Concept implementations

Hardware

Software

ABI Extensions (no new ABI required)

• Regular C function that save/restores all caller-save registers
• Inline handler gcc interrupt attribute to always callee-save every register (save as you go)
• EABI Task Group - improve interrupt latency by reducing the number of caller-save registers