A2O ISA Compliance - Workstream Summary

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Instruction Count Summary

• Total New Instructions: 463+ (40 scalar + 400 VMX/VSX + 18 prefixed + 5 other)
• Total Removed Instructions: 38+ (15 user-mode + 7 interrupt + 15 MMU + 1 hypervisor)
• Net Instruction Growth: +425 instructions

Dependency Order & Execution Strategy

Phase 1 - Foundation (No Dependencies):
┌─────────────────────────────────────────────┐
│ WS1: Instructions   (12-16 weeks)           │
│ WS3: Interrupts     (10-12 weeks)           │
│ WS4: MMU/Radix      (20-24 weeks) ← CRITICAL│
│ WS6: PMU            (6-8 weeks)              │
└─────────────────────────────────────────────┘
         ↓                    ↓
Phase 2 - Dependent on Phase 1:
┌─────────────────────────────────────────────┐
│ WS2: Hypervisor     (16-20 weeks) ← WS3     │
│ WS7: VMX/VSX        (24-32 weeks) ← WS1     │
│ WS8: Prefixed       (10-12 weeks) ← WS1     │
└─────────────────────────────────────────────┘
         ↓
Phase 3 - Dependent on Phase 2:
┌─────────────────────────────────────────────┐
│ WS5: Debug          (8-10 weeks)  ← WS2     │
└─────────────────────────────────────────────┘
         ↓
Phase 4 - Integration:
┌─────────────────────────────────────────────┐
│ WS9: Integration    (16-20 weeks) ← ALL     │
│      ★ COMPLIANCE SUITE EXECUTION           │
└─────────────────────────────────────────────┘

Start in Parallel:

• WS1, WS3, WS4, WS6 (week 1)
• WS4 (MMU) is on critical path - must complete first

Start When Dependencies Met:

• WS2 starts when WS3 complete (week 12)
• WS7, WS8 start when WS1 complete (week 16)
• WS5 starts when WS2 complete (week 28)
• WS9 starts when WS4, WS2 substantially complete (week 36)

Where Compliance Suite Runs

Primary Execution: WS9 - Integration & Verification (Weeks 36-56)

Timeline:
├─ Week 36-40: Initial compliance suite execution
│  ├─ Book I tests (user mode)
│  ├─ Book II tests (virtual mode)  
│  └─ Book III tests (privileged mode)
│
├─ Week 41-48: Debug compliance failures
│  ├─ Fix identified issues
│  ├─ Re-run failed tests
│  └─ Iterate until passing
│
├─ Week 49-52: Final compliance verification
│  ├─ Full suite re-run
│  ├─ Linux Test Project
│  └─ glibc test suite
│
└─ Week 53-56: Certification
   ├─ Generate compliance report
   ├─ Document any deviations
   └─ Submit for certification

Test Suites Used

1. OpenPOWER Foundation ISA Compliance Tests

   • Source: https://github.com/OpenPOWER-Foundation
   • Coverage: All three ISA books
   • Format: Automated test vectors

2. Linux Test Project (LTP)

   • Validates OS-level ISA compliance
   • Tests system calls, threading, signals
   • Execution: On booted Linux

3. glibc Test Suite

   • Critical for LCS compliance
   • Tests VMX/VSX usage in standard library
   • Execution: During Linux userspace bring-up

4. KVM Selftests

   • Validates hypervisor functionality
   • Tests guest isolation, nested paging
   • Execution: Under KVM on Linux

Testing Infrastructure

Test Execution Strategy

Phase 1 (Weeks 36-40): Discovery
└─ Run full compliance suite
└─ Identify all failures
└─ Categorize by workstream
└─ Assign to responsible teams

Phase 2 (Weeks 41-48): Resolution  
└─ Fix bugs in parallel
└─ Re-test incrementally
└─ Track pass rate improvement
└─ Target 95%+ pass rate

Phase 3 (Weeks 49-52): Certification
└─ Achieve 100% pass rate
└─ Document exceptions (if any)
└─ Performance validation
└─ Generate compliance report

Phase 4 (Weeks 53-56): Validation
└─ Boot Linux distributions
└─ Run application workloads
└─ KVM multi-guest testing
└─ Final sign-off

Workstream Dependencies & Critical Path

Critical Path (56 weeks total):
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

WS4: Storage Management (Radix MMU)
[████████████████████████] (20-24 weeks)
                         ↓
           WS2: Hypervisor & Virtualization
           [████████████████] (16-20 weeks)
                         ↓
              WS9: Integration & Verification
              [████████████] (16-20 weeks)

Parallel Workstreams (Off Critical Path)

Week: 0    10   20   30   40   50   56
      |    |    |    |    |    |    |
WS1:  [████████████]
WS3:  [██████████]
WS6:  [██████]
WS5:      [████████]
WS8:         [██████████]
WS7:  [████████████████████████████]

Key Outcomes by Workstream

WS1: Instruction Set Updates

✓ 40+ new arithmetic, logic, and bit manipulation instructions
✓ Quadword atomic operations (lq/stq/lqarx/stqcx)
✓ Set and compare instructions (setb, cmpeqb, cmprb)
✓ Modern CPU instructions (darn for random numbers)
✓ Clean removal of deprecated Book III-E instructions

WS2: Hypervisor & Virtualization

✓ LPAR support with LPCR, HRMOR, PCR
✓ Per-thread partitioning (critical for KVM)
✓ MSR[HV] replaces MSR[GS] with proper privilege model
✓ Hypervisor-specific SPRs (HSRR0/1, HSPRG0/1, HDAR, HDSISR)
✓ Enables unmodified KVM with multi-threaded guests

WS3: Interrupt Architecture

✓ Single HSRR0/1 save/restore (removes GSRR, CSRR, MCSRR)
✓ rfid and hrfid for proper privilege transitions
✓ LPCR[AIL]/[HAIL] for flexible interrupt addressing
✓ System Call Vectored (scv/rfscv) for modern syscalls
✓ Book III-S compliant interrupt vectors

WS4: Storage Management (CRITICAL PATH)

✓ Full radix tree page table walker
✓ Two-level (radix-on-radix) translation for LPAR
✓ Page walk cache for performance (<100 cycle TLB miss)
✓ PTCR, partition table, process table support
✓ Clean removal of Book III-E TLB management
✓ Enables modern Linux memory management

WS5: Debug Facilities

✓ DAWR0/1 and DAWRX0/1 for data watchpoints
✓ CIABR for instruction breakpoints
✓ Trace interrupt support
✓ ISA-compliant debug architecture

WS6: Performance Monitor Unit

✓ Architected PMU with MMCR0/1/2/A
✓ PMC1-6 performance counters
✓ SIER for sampled instruction events
✓ Standard event codes for portability

WS7: VMX/VSX Implementation (FOR LCS)

✓ 400+ vector and scalar instructions
✓ 32 x 128-bit vector registers (VR0-31)
✓ 64 x 128-bit VSX registers (VSR0-63)
✓ Enables glibc and standard Linux distributions
✓ Required for Fedora, Ubuntu, RHEL

WS8: Prefixed Instructions (v3.1)

✓ 64-bit instruction support
✓ 18 prefixed load/store instructions
✓ paddi for large immediates
✓ Enhanced addressing modes

WS9: Integration & Verification

✓ Full ISA compliance test suite execution
✓ OpenPOWER certification
✓ Unmodified Linux distribution boot
✓ KVM functionality validation
✓ Performance benchmarking
✓ Final release preparation

Decision Points

Decision #1: ISA Version

• v3.0C: Skip WS8, simpler (54 weeks total)
• v3.1C: Include WS8, current spec (56 weeks total)
• Recommendation: v3.1C (stay current)

Decision #2: Compliance Level

• SFFS: Skip WS7, custom Linux only (32 weeks saved)
• LCS: Include WS7, run standard distros (56 weeks total)
• Recommendation: LCS (enables wider adoption)

Decision #3: VMX/VSX Strategy

• Build: 24-32 weeks, full control
• License: 8-12 weeks, $$$ cost
• Open Source: 12-16 weeks, integration effort
• Recommendation: Evaluate open source cores first

Testing Locations Summary

Resource Requirements

Engineering Team

• Core RTL Engineers: 6-8
• Verification Engineers: 4-5
• Integration Engineers: 2-3
• Total: 12-16 engineers

Infrastructure

• High-performance simulation servers
• FPGA prototyping boards (optional but recommended)
• Compliance test licenses
• Linux distribution access

Timeline

• Aggressive: 18 months (high risk)
• Nominal: 20-22 months (recommended)
• Conservative: 24 months (low risk)

For detailed task breakdowns, see individual workstream documents.

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