LithosAnanake/FABRIC-3.10.8.md

# FABRIC-3.10.8.md — Multi-core: execution plan and log

**Status: IN PROGRESS.** Design and rulings are in `FABRIC-3.10.0.md` (ruled 2026-09-25, §7).
Multi-core runs ahead of O-D (MC-R6 as ruled); O-D relaunches afterwards with row path A.

Each stage:
- needs Captain Bob's explicit go;
- gets its own commit;
- gets its own three-architecture acceptance (`clean qemu`; amd64, then aarch64, then riscv64;
  foreground; visible framebuffer; one at a time; coupled images reset before each).

Evidence is named **before** each stage runs.

**The standing acceptance sequence**, unchanged from `FABRIC-3.9.8.md`:
- a boot to `[zuse@Hera] ok>` with zero `UNKNOWN WORD`, faults and frame corruption;
- the `dict_hash` set identical across ISAs;
- the Stage G interleave (A/B), byte-identical across ISAs while there is one worker core; by
  counts (A = 40, B = 40) once there are more (MC-R4);
- the O-A checks (observer precedence, console responsive under load);
- mint → WIREBIND → `USE` → `1 2 + .` → `3`;
- 0 bytes of idle log growth over 20 s.

**No DoE execution until everything is closed** (Captain Bob, 2026-09-25: *"until we close
everything, do not do ant DoE eecution."*). MC-4's campaigns wait for that too. Stage
evidence is the standard sequence plus probes, never a campaign.

**Never `make clean` an ISA while its QEMU runs:** it deletes that QEMU's QMP and serial
sockets (found 2026-09-25).

## 1. What MC-0 must cover (traced 2026-09-25)

Everything that would break if two cores ran kernel or VM code at the same moment.

**Kernel subsystems** (`src/starkernel/`), one lock each (MC-R2), except where noted:

| Subsystem | Shared state | Treatment |
|---|---|---|
| `kmalloc`, `pmm`, `vmm` | free lists, bitmaps, page tables | heap lock; PMM lock; VMM lock |
| kernel-Hermes | arena directory and segments, queue table, channel table, ledger, event counters | one lock |
| Stadium | reservoirs, cells, quotas, word rows | **per-dispatch path partitioned by quota slot** (a VM's own row and cells need no lock while it runs on its one core); reservoir arithmetic atomic; cross-slot operations (admission evicting another VM's cell, grants, audits) take the Stadium lock |
| VM registry, birth, kill, reap | registry list, names | registry lock; `KILL` refuses a VM running on another core |
| switch-signal table | slots, stamps, decision-due flag | compare-and-swap for claim/release (MC-3); lock for register/unregister |
| current VM, frame stack | `g_switch_current_vm` and friends | move to the per-core block |
| console | UART, framebuffer VT100 state, line prefix state | one line lock |
| log region, DoE region, block subsystem | rings, block chain, caches | a lock each |
| heartbeat | tick counters | per-core counters (MC-3); one core until then |

**Shared VM code** (`src/`, vendored; runs inside every VM):

| File | Global | Treatment |
|---|---|---|
| `dictionary_management.c` | `sf_fc_list`/`sf_fc_count`/`sf_fc_cap`/`sf_cached_latest`: **one dictionary lookup index for all VMs**, rebuilt whenever a different VM's dictionary is searched | move into `VM` (per-VM index). Also stops the rebuild thrash on every switch today. |
| `word_source/starforth_words.c` | `g_prng_state`: one PRNG stream for all VMs (accepted at Stage H) | an atomic step, so the stream stays one stream (order is nondeterministic across cores anyway, MC-R4) |
| `physics_runtime.c` | `g_runtime` | inventory in MC-0; per-VM or atomic |
| `word_source/dictionary_manipulation_words.c` | `state_variable` (STATE) | inventory in MC-0; per-VM |
| `physics_hotwords_cache.c` | `g_hotwords_cache` | retired under `__STARKERNEL__` (item 4.1); confirm unused |
| `word_source/ttf_words.c` | font and raster cache | core 0 only (Hestia's framebuffer) |

## 2. Staged plan

| Stage | Change | Evidence (named in advance) |
|---|---|---|
| **MC-0a** | **The per-core block, on one core.** A per-core structure reached through each ISA's per-CPU register (GS base / `TPIDR_EL1` / `tp`), set up for core 0 at boot. `g_switch_current_vm` moves into it. | Standard sequence unchanged. A probe reads the per-core pointer from a normal kernel path and from an interrupt handler, and gets core 0's block both times on all three ISAs. |
| **MC-0b** | **Real spinlocks.** A kernel spinlock primitive (atomic exchange, interrupts masked while held on the owning core). `sf_mutex_*` stop being no-ops. The §1 kernel locks are added. | Standard sequence unchanged. A probe counts every lock's acquisitions and releases through a boot and the standard sequence: counts balance, and no lock is held across a context switch or on return to the idle point. |
| **MC-0b2** | **The block subsystem's lock** (split from MC-0b, Captain Bob 2026-09-25). The vendored `block_subsystem.c` calls its own public functions in cycles (`blk_set_meta` → migration check → relocate → `blk_set_meta`), so it is refactored into locking public functions over unlocked internals, under `__STARKERNEL__`. | Standard sequence unchanged. The MC-0b probe, extended to the block lock: counts balance, 0 recursions. |
| **MC-0c** | **Shared VM code made per-VM or atomic** (§1, second table). The dictionary lookup index moves into `VM`. | The `dict_hash` set unchanged (the index is not hashed). A probe: two VMs searched alternately never rebuild each other's index. Standard sequence. |
| **MC-0d** | **Stadium's dispatch path partitioned** (§1). | Standard sequence; conservation holds (`stadium_conserved()` on every VM, the ledger audit). A probe proves the dispatch path takes no shared lock. |
| **MC-1** | **Bring up the extra cores and park them halted**, per ISA: amd64 (MADT, INIT-SIPI-SIPI, a position-independent trampoline below 1 MiB), aarch64 (DTB `/cpus`, PSCI `CPU_ON`), riscv64 (DTB harts, SBI HSM `hart_start`). QEMU gets `-smp 2`. | The boot reports each core online with its own per-core block; the extra cores sit halted (0 idle growth, no spin); the standard sequence unchanged. |
| **MC-2** | **Observers get core-0 affinity.** | With one worker core, behaviour identical to today. A probe shows no observer ever claimed off core 0. |
| **MC-3** | **Worker cores claim through the shared decision:** `running_on` with compare-and-swap, per-core idle contexts, per-core beats, wake by inter-processor interrupt. | Two workers genuinely overlapping in time on two cores. A probe counts double claims: 0. Conservation holds. G by counts. Idle worker cores halted (0 idle growth). |
| **MC-4** | **DoE with cores as a factor** (after O-D): per-ISA campaigns at 1, 2 and 4 cores (MC-R5). | Per ISA and core count: 18 `MU-TRIAL` markers, `fail=0`, `MU-CAMPAIGN: complete`. |

**Stop conditions** (re-plan rather than push on):
- `dict_hash` diverges across ISAs;
- conservation goes false;
- a lock held across a switch, or an unbalanced lock count;
- a double claim;
- an idle core spinning.

## 3. Execution log

### 3.1 MC-0a — the per-core block, on one core (2026-09-25)

**Change.**
- `include/starkernel/percpu.h` (new): `sk_percpu_t { self, core_id, current_vm }`, with `self` first.
  - `sk_percpu()` reads this core's block: `movq %gs:0` on amd64, `mrs tpidr_el1` on aarch64, `mv tp` on riscv64.
  - `sk_percpu_install()` writes the register: `IA32_GS_BASE` via `wrmsr`, `TPIDR_EL1`, or `tp`.
- `src/starkernel/hal/percpu.c` (new): the boot core's block is one static object, not a table sized to a core count. Secondary cores get theirs as they come online (MC-1).
- `kernel_main.c`: `sk_percpu_boot_init()` runs straight after `arch_early_init()`, because on amd64 that call reloads GS, which would reset the base.
- `switch.c`: the global `g_switch_current_vm` is gone.
  - `sk_vm_switch_current_vm()`, the setter, the idle point and `sk_vm_context_switch()` use `sk_percpu()->current_vm`.
  - After resume, the context switch re-reads the block rather than trusting a pointer cached before the switch.

**Probe** (temporary; removed before commit).
- `kernel_main.c` checked, from the normal path after the Tripod came up, that:
  - `sk_percpu()->self == sk_percpu()`;
  - `core_id == 0`;
  - `current_vm` is Hera;
  - `sk_vm_switch_current_vm()` agrees.
- `heartbeat_tick()` ran the same self-check from interrupt context on every beat.

| ISA | log | normal path | core_id | current_vm is Hera | switch.c agrees | interrupt path ok / bad |
|---|---|---|---|---|---|---|
| amd64 | `logs/20260925-130335` | ok | 0 | 1 | 1 | 889 / 0 |
| aarch64 | `logs/20260925-130905` | ok | 0 | 1 | 1 | 1877 / 0 |
| riscv64 | `logs/20260925-131337` | ok | 0 | 1 | 1 | 1625 / 0 |

**Standard sequence** (clean build, with the probe reverted; the tree was checked byte-for-byte against the saved stage diff).

| ISA | log | O-A (G, PREC, LOAD) | M7.1a hash | MINT / WIREBIND / USE / `1 2 + .` | idle growth | UNKNOWN / faults |
|---|---|---|---|---|---|---|
| amd64 | `logs/20260925-131805` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |
| aarch64 | `logs/20260925-133049` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |
| riscv64 | `logs/20260925-134357` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |

- The `dict_hash` values (Hera `0x00340a8b2c842eb7`, Hestia `0x78bf28439e4a643f`, Artemis `0x66886d174d5f3b5a`) are identical across ISAs and unchanged from O-C.
- The ledger line matches across ISAs: held=2048, pulled=258048, returned=255263, consumed=737, conserved=true.
- No stop condition was hit. **MC-0a done.**

### 3.2 MC-0b — real spinlocks (2026-09-25)

**The primitive** (`include/starkernel/spinlock.h`, `src/starkernel/hal/spinlock.c`, new).
- One lock word per lock: 0 = free, `core_id + 1` = held.
  - Taken by compare-and-swap. The atomics are inline on every ISA (`nm -u` is empty on all three ELFs).
  - Interrupts stay masked on the owning core while it holds any lock.
- The mask state lives in the per-core block, not in the lock (`lock_depth`, `saved_irq` in `sk_percpu_t`):
  - the first lock taken saves the interrupt state and masks;
  - the last lock released restores it;
  - so release order doesn't matter.
- **The rule: no lock crosses a switch or reaches the idle point.** Each of these sites checks it and counts any violation:
  - `sk_vm_context_switch()`, when leaving and on resume;
  - `sk_vm_idle_point()`.
- Failures are counted and logged at the idle point (`LOCK:` lines, LOG_ERROR):
  - **recursion** (a core takes a lock it already holds): let through, so the core doesn't hang, and counted. It is never legitimate, because on one core "the owner is me" can't tell a nested call from a second VM on the same core;
  - release of a lock not held;
  - a lock held at a switch or idle point;
  - a VM mutex destroyed while held.
- The locks are no-ops until the boot core's block is installed (`sk_percpu_ready`). This was found during the probe runs:
  - riscv64 is built monolithic, and its `arch_early_init()` prints through the console before `sk_percpu_boot_init()`;
  - the first lock therefore read `tp` while it still held the firmware's value, and the load hit OpenSBI memory (`stval` = `tp`+8, a firmware load access fault);
  - early boot is one core with interrupts off, so skipping the locks there is correct.
  
  That crashed run's log was deleted as flawed.
- `sf_mutex_*` (the vendored VM's `dict_lock` and `tuning_lock`, `shim.c`) now use the same lock word. They are no longer no-ops.

**The kernel locks, in acquisition order** (spinlock.h; MC-3's deadlock freedom rests on this order; checked by reading the code, not yet by a counted check; MC-0b2 inserts `block` between `log` and `console`, §3.3):
1. `hermes`
2. `switch`
3. `registry`
4. `doe`
5. `log`
6. `console`
7. `heap`
8. `vmm`
9. `pmm`

Stadium's lock comes with MC-0d, below Hermes. Stadium today runs inside `dict_lock` (`vm_core.c`'s heat bump calls `stadium_word_dispatch()`); MC-0d's order must account for that.

| Lock | Covers | Shape |
|---|---|---|
| heap | `kmalloc`/`kfree`, stats, censuses | `kmalloc()` delegates to `kmalloc_aligned()`, and only the latter locks |
| vmm | page-table walks | `*_locked` bodies. The map-conflict print moved outside the lock (the console lock sits above it). Takes `pmm` for table pages |
| pmm | bitmap | `pmm_alloc_page()`/`pmm_free_page()` delegate to the contiguous forms |
| console | output path and line state (name, line start, pending line close, the framebuffer terminal) | A string goes out under one hold. Unlocked on purpose: `console_get_vm_name()` (the prefix provider calls it under the lock), the boot-time `console_fb_init()`/`console_fb_enable_ttf()` (they log), and input |
| log, doe | control-block read-modify-write plus the slot write | `*_locked` bodies |
| registry | node list, entry copies, single-field writes | Never held while calling out. KILL and reap take it only for their reads and final writes. A birth fills its embryo unlocked (private until LIVE). `kill_all_nonmama` (cold-reset path) walks unlocked |
| switch | slot table, stamps, decision-due flag, counters | Never held while calling out. The decision, the Stage H floor and the reap sweep copy one slot under the lock (`slot_copy()`) and judge it outside |
| hermes | arena, ledger, channels, queues, event counters | Public functions lock over `*_locked` statics. Never held across `vm_interpret_kind()` (the drain) or a policy word. The switch notifications after a send go out once the lock is dropped (the floor reads Hermes queues back). Publish and event walk members one copied member at a time. `sk_hermes_event()`'s static payload moved onto the stack |

The block subsystem is **split out as MC-0b2** (Captain Bob, 2026-09-25), because its internal call cycles need a locked/unlocked refactor of vendored code. See §2.

**Probe** (temporary, removed before commit). A `MC0B-PROBE` word in Hera's and every child's vocabulary printed every counter, snapshotted before printing:
- each lock's acquisitions and releases, and its owner;
- the VM mutexes (the core total minus the kernel locks);
- the core-0 total and its depth;
- the number of switch/idle checks and violations;
- recursions, bad releases and destroyed-while-held.

It ran at Hera's prompt (after O-A's G, PREC and LOAD), and again on rajames after MINT, WIREBIND, `USE` and `1 2 + .`. The table shows the final (rajames) reading:

| ISA | log | total acquired = released | depth | switch/idle checks | held at switch | recursions / bad releases / destroyed held |
|---|---|---|---|---|---|---|
| amd64 | `logs/20260925-150735` | 1,503,458,645 | 0 | 51,137,748 | 0 | 0 / 0 / 0 |
| aarch64 | `logs/20260925-152109` | 235,854,532 | 0 | 7,565,646 | 0 | 0 / 0 / 0 |
| riscv64 | `logs/20260925-155048` | 566,894,806 | 0 | 19,029,507 | 0 | 0 / 0 / 0 |

- Every lock balances individually on every ISA, at both readings.
- The amd64 and aarch64 probe runs predate the `sk_percpu_ready` guard. That guard only changes behaviour before `sk_percpu_boot_init()`, and the acceptance runs below are on the final code.
- The riscv64 `vblk_io timed out` count, watched because known defect 3 sits in code that now runs with interrupts masked, is 2 in the probe run, the same as MC-0a's acceptance run. It is 0 in this stage's acceptance run.

**Finding, for MC-3.** Hera's input-poll idle loop runs the switch decision without pause, and every pass takes the registry, switch and Hermes locks once per slot. That is the hundreds of millions of acquisitions above (amd64: registry 379 M, switch 858 M, Hermes 266 M). It is harmless on one core. With several cores, core 0 spinning through these same locks would contend with every worker's claim. MC-3 should settle how that loop waits before cores share these locks.

**Standard sequence** (clean build, with the probe reverted; checked against the saved stage diff, which differs only by the guard added after it).

| ISA | log | O-A (G, PREC, LOAD) | M7.1a hash | MINT / WIREBIND / USE / `1 2 + .` | idle growth | UNKNOWN / faults |
|---|---|---|---|---|---|---|
| amd64 | `logs/20260925-160434` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |
| aarch64 | `logs/20260925-161720` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |
| riscv64 | `logs/20260925-163024` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |

- The G string is byte-identical to MC-0a on all three ISAs, so masking interrupts under the locks didn't move the interleave.
- The `dict_hash` set and the ledger line are unchanged from MC-0a.
- No stop condition was hit. **MC-0b done** (the block subsystem follows as MC-0b2).

### 3.3 MC-0b2 — the block subsystem's lock (2026-09-25)

**Change.** `src/block_subsystem.c` (vendored) is split into bodies and wrappers:
- Every public function's body is now a static `*_locked` function.
- Bodies call each other only through the `_locked` forms. That breaks the internal cycles:
  - relocate → get buffer / update / mark free;
  - meta relocate → relocate;
  - migration scan → meta relocate;
  - firsttouch → get meta / set meta / mark allocated;
  - the six meta accessors.
- A block of thin public wrappers at the end of the file takes the lock around each body.
  - Under `__STARKERNEL__` that lock is `g_lock_block`.
  - The hosted build has no lock, and the vendored hosted `make` still builds clean.
- The lock covers the device chain, every slot's cache and BAM, the relocation table, and the device I/O issued on their behalf.
- Its place in the order is **below `log` and `doe`** (both regions write through the block subsystem) and **above `console`** (block logs), `heap` (`calloc`/`free`), `vmm` and `pmm`:
  1. `hermes`
  2. `switch`
  3. `registry`
  4. `doe`
  5. `log`
  6. `block`
  7. `console`
  8. `heap`
  9. `vmm`
  10. `pmm`
  
  Stadium (MC-0d) sits above `block`, because `STADIUM_BEHAVIOUR_MIGRATE` calls `blk_flush()`.

**Not covered, and not coverable by this lock:** `blk_get_buffer()` returns a pointer into RAM, a ramdrive, or a device cache slot. The caller (`BLOCK`/`BUFFER`, Artemis) reads and writes through that pointer after the lock is released. On one core nothing can evict the slot in between; with worker cores (MC-3) another core's block access can. Block-buffer ownership across cores is an open item for MC-3.

**The masking risk, measured.** `virtio_blk.c` records (2026-09-09) that masking interrupts around `vblk_io()` once made missed completions worse. All block I/O now runs with interrupts masked (the MC-0b primitive), so the probe runs counted `vblk_io timed out` on every ISA:

| Where | amd64 | aarch64 | riscv64 |
|---|---|---|---|
| This stage's probe runs | 0 | 0 | 4 |
| This stage's acceptance runs | 0 | 0 | 2 |

The riscv64 counts sit inside the pre-lock baseline: the 24 most recent riscv64 logs, from 2026-09-24 (no locks at all) through this stage, range from 0 to 6, with 4, 5 and 6 all seen before MC-0b. No regression is visible at this sample size. The masking stays as MC-0b ruled.

**Probe** (temporary, removed before commit). This is MC-0b's `MC0B-PROBE` word, extended with the block lock. Same sequence: O-A, then Hera's prompt, then MINT, WIREBIND, `USE` and `1 2 + .`, then rajames. The table shows the final (rajames) reading:

| ISA | log | block acquired = released | total acquired = released | depth | switch/idle checks | held at switch | recursions / bad releases / destroyed held |
|---|---|---|---|---|---|---|---|
| amd64 | `logs/20260925-173901` | 2,379 | 1,387,861,111 | 0 | 46,795,001 | 0 | 0 / 0 / 0 |
| aarch64 | `logs/20260925-175215` | 2,057 | 247,761,816 | 0 | 8,014,413 | 0 | 0 / 0 / 0 |
| riscv64 | `logs/20260925-180546` | 2,300 | 555,650,314 | 0 | 18,447,619 | 0 | 0 / 0 / 0 |

Every lock balances individually on every ISA, at both readings. 0 recursions means no public-to-public call inside `block_subsystem.c` was missed.

**Standard sequence** (clean build, with the probe reverted; the tree is byte-identical to the saved stage diff).

| ISA | log | O-A (G, PREC, LOAD) | M7.1a hash | MINT / WIREBIND / USE / `1 2 + .` | idle growth | UNKNOWN / faults |
|---|---|---|---|---|---|---|
| amd64 | `logs/20260925-181908` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |
| aarch64 | `logs/20260925-183151` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |
| riscv64 | `logs/20260925-184454` | A=40 B=40, HHH, ok | `0x99b01134c3d3049c` | all ok, `3` | 0 B / 20 s | 0 / 0 |

- The G string is byte-identical to MC-0b and MC-0a on all three ISAs.
- The `dict_hash` set and the ledger line are unchanged.
- No stop condition was hit. **MC-0b2 done.**