retroSoC/docs/hp-rv64-validation.md

HP RV64 Migration Validation

The active contract is HP platform, phases 2–5. LP remains RV32 Hazard3. All PRODUCT profiles select RV64IMAFDC with Zicbom, Sv39 and 32-bit physical addresses. No upstream CPU or RT-Thread source is modified.

Reproduction

make setup-vexiiriscv setup-hp-rtthread setup-hp-linux
make CONFIG=configs/ci/ihp130-hp.mk SIMU=VERILATOR hp-smoke-sim
make CONFIG=configs/ci/ihp130-rtthread.mk SIMU=VERILATOR hp-rtthread-sim
make CONFIG=configs/ci/ihp130-hp.mk SIMU=VERILATOR hp-linux-sim
python3 scripts/regress.py --root . --suite pr --pdk IHP130 --behavioral-only

HP_CROSS is independent of LP CROSS and resolves to the compiler in the dependency lock. RT-Thread is official v5.3.0 at 99428a1e7f7447955aa860f7c969273a12095b8f, compiled with RV64 lp64d. Its selftest qualifies integer contexts; it does not qualify FCSR preservation or floating-point tasks. Linux uses its Buildroot RV64 Linux compiler, Sv39, static musl/BusyBox and a small uncompressed CPIO with a dedicated /init.

V2 flash bundles discriminate Linux (1, four entries), smoke (2, one executable) and RT-Thread (3, one executable). Rebuild V1 bundles. The loader checks strict flags, workload/count/types, fixed addresses, bounds, non-overlap, unused slots and CRC. Only smoke enters the GA2D/cache lifecycle protocol. LP alone owns the final SYSCTRL TEST_STATUS write for all workloads.

Measured runs

Initial RV64 validation uses configs/ci/ihp130-hp.mk and BUILD_TIMESTAMP=2026-09-25-11-42, producing build/ihp130-hp-2026-09-25-11-42-bb2e93b39338/.

Run	Result	Evidence below variant
RV64 generated core and Verilator compile	Pass	generated/vexiiriscv/manifest.json, sim/verilator/result-compile.json
GA2D/cache lifecycle smoke	SIM_TEST_PASS code=0, 3,446,054 cycles, 191 seconds	sim/verilator/sim.log, result-hp-smoke-sim-check.json in the same directory
RT-Thread kernel/platform	All required markers and SIM_TEST_PASS code=0, 6,412,946 cycles, 360 seconds	sim/verilator/hp-rtthread/sim.log, result-sim-check.json

The final dedicated configs/ci/ihp130-rtthread.mk profile passed all markers and TEST_STATUS at 6,395,372 cycles in 357 seconds, using BUILD_TIMESTAMP=2026-09-25-12-18. Its evidence is build/ihp130-rtthread-2026-09-25-12-18-bb2e93b39338/sim/verilator/hp-rtthread/. The final context probe compares registers against an original 64-bit sentinel stored on each task's stack, catching identical truncation of multiple registers. The final smoke also passed at 3,460,934 cycles in 195 seconds, with evidence in sim/verilator/hp-smoke/ under the initial variant.

Linux Image is 2,152,448 bytes; the static, uncompressed CPIO is 302,080 bytes. BusyBox is expanded from allnoconfig and an explicit allowlist; effective options and static ELF linkage are checked. Linux acceptance is still running without an emulator wall-clock timeout; no Linux pass is claimed yet. New workload runs write logs to sim/verilator/hp-{smoke,rtthread,linux}/. Structured results start as running; failures/interruption replace old passes. A UART banner is diagnostic, never the final verdict.

The affected Python and publication bindings pass 177 tests; one PDF-inspection test is skipped because pypdf is not installed. C format, C policy and host tests, Ruff, dependency-lock validation, setup-hp-rtthread and the dedicated profile's Verilator doctor pass. The final publication-focused run passes 193 tests with one missing-pypdf skip. The full Python run reports 974 passed and 5 skipped; its two missing-FLAC-corpus failures were resolved by installing the checksum-locked corpus and rerunning both tests (2 passed). Thus 976 cases have passing evidence. The other skips are optional P7 model/MFCC inputs; no test expectation was weakened to hide a missing input. After the firmware-reservation correction, all 62 affected platform and publication checks pass.

The IHP130 behavioral PR regression completed successfully with BUILD_TIMESTAMP=2026-09-25-12-14: strict lint, firmware builds, Verilator ci_smoke (6,783,746 cycles, 384 seconds), DEBUG_GDB_PASS, and Icarus SIM_TEST_PASS. Artifacts use build/ihp130-2026-09-25-12-14-* and build/ihp130-debug-2026-09-25-12-14-*. Warning-baseline comparisons report new/increased signatures as non-blocking observations; baselines were not modified. No synthesis or STA result is implied by this regression.

RT-Thread first-schedule failure and correction

The first BSP run reached HP_RTTHREAD_BOOT and then reported RTTHREAD_TRAP cause=1 epc=deadbeee, failure 92, followed by LP failure 18. Evidence is retained in sim/verilator/hp-rtthread-idle-stack-failure/ under the initial variant. This was a BSP integration error:

1. The BSP used RT_IDLE_THREAD_STACK_SIZE; the locked upstream src/idle.c reads IDLE_THREAD_STACK_SIZE and otherwise selects 128 bytes without heap.
2. The failing ELF's idle_thread_stack was 128 bytes at 0x38004530. Upstream rt_hw_stack_init reserves 512 bytes for 32 RV64 integer slots and 32 double-precision slots, filling them with 0xdeadbeef.
3. That frame starts at 0x380043b0, 384 bytes before the allocated stack, overwriting _object_container, interrupt-switch state, the scheduler's ready bitmap and other globals. This explains the invalid first-schedule state and is independent of the AXI crossbar.
4. The BSP now uses the correct macro with 2048 bytes and a compile-time lower bound. The same integrated test then passed scheduling, RV64 context, IPC, timer timeout, and mailbox IRQ checks. Vendor source stayed unchanged.

Linux firmware reservation correction

The first RV64 run reached Linux 6.12.105 and memory initialization. Its log reported no /reserved-memory node and included the full SDRAM range beginning at 0x38000000. OpenSBI's preceding PMP report protected its resident code/data from S-mode. Static inspection confirmed that the custom platform has no generic fdt_fixups() final-init hook; Linux arch/riscv/mm/init.c:setup_bootmem reserves the kernel, initrd, DTB and DT-declared regions, not an implicit firmware window. Thus the DT omitted a live firmware allocation. No resulting crash was observed; the run was deliberately interrupted to correct this integration defect.

The retained log is sim/verilator/hp-linux-before-firmware-reservation/ under the initial variant. The DT now reserves the complete, already allocated 512 KiB OpenSBI window with no-map, and the effective-config guard requires CONFIG_OF_RESERVED_MEM=y. The DTB test checks both the exact range and no-map. The corrected runtime now prints 0x0000000038000000..0x000000003807ffff (512 KiB) nomap non-reusable opensbi@38000000, confirming that Linux consumed the reservation. Userspace acceptance is still in progress.

During the subsequent quiet Initmem setup node 0 interval, two read-only host debugger samples captured 64,772,063 and 66,503,381 emulator cycles. The sampled Sv39 PCs resolve to __init_single_page and memmap_init_range in the actual vmlinux; disassembly passes s0 as the PFN and increments it at loop end. s0 advanced from 0x3b0c4 to 0x3b6ed, toward the s1=0x3c000 bound. Privilege remained S-mode and SATP mode was 8. This establishes loop progress during that interval, not a complete boot verdict. Samples and disassembly are retained under meta/hp-rv64-validation/; no DUT state was written. Later samples at 84,162,019 and 92,239,597 cycles resolve to should_skip_region / __next_mem_range and __free_pages_ok called by memblock_free_all, respectively. A further sample at 97,866,745 cycles is in __free_pages_core, with a later page-descriptor block address. These locate the later allocator work separately from the earlier page-descriptor loop. After IRQ initialization, samples landed in timer handling. The interrupted SEPC then moved from memset to add_device_randomness; the latter frame was decoded from valid, matching-tag L1 data-cache lines and checked against the RISC-V pt_regs layout. UART subsequently reported the 9-bit ASID allocator. These observations avoid treating an IRQ-handler PC or stale raw SDRAM as evidence of main-thread progress.

Coverage limits

The repository's mechanical C format/policy checks are partial MISRA evidence; no complete MISRA certification or new approved Required-rule deviation is claimed. Board MMIO uses fixed, naturally aligned 32-bit accesses to declared register windows; RV64 pointer width does not widen device accesses.

Synthesis, netlist simulation, STA and synthesis-dependent metrics are deferred by explicit user instruction. PPA, CDC/RDC, physical SRAM mapping, hardware board runs and silicon qualification are not established by these simulations. The behavioral evidence is IHP130-specific; other PDK matrices and extended nightly benchmarking were not rerun in this migration. The GDB regression exercises LP Hazard3 debug; it is not independent RV64 HP debug/JTAG qualification. The minimal Linux configuration leaves CONFIG_RISCV_ISA_ZICBOM disabled. The custom OpenSBI platform does not import Zicbom into its hart-extension mask, so it leaves MENVCFG CBIE/CBCFE disabled. The cache-maintenance evidence here is the M-mode smoke; enabling native Linux non-coherent DMA requires the matching firmware extension/permission setup and a separate S-mode CBO acceptance test. Publication source bindings are updated separately from the previously reviewed PDF snapshot; a fresh PDF requires an explicitly reviewed committed snapshot.