Files
StarForth/src/starkernel/vm
Robert Allan JamesandClaude Sonnet 5 00e657019e stadium: make VM population bound RAM-derived, not a static array of 4
Replaces STADIUM_MAX_VM_COUNT (Kconfig, hardcoded default 4) with a
boot-time computation, mirroring the pattern stadium_boot_init() already
used for the cell pool. New Kconfig STADIUM_VM_MEMORY_PERCENT (default
50): max_vm_count = (kmalloc_get_stats().free_bytes after the cell array
* STADIUM_VM_MEMORY_PERCENT / 100) / VM_MEMORY_SIZE, floored to 1, no
ceiling (population is not knowable in advance - could be 4, could be
4000). stadium_quotas and word_slots (plus stat_promotions/stat_evictions)
are now kmalloc'd to the computed count instead of declared with a macro.
New accessor stadium_max_vm_count() replaces every STADIUM_MAX_VM_COUNT
reference, including capsule_birth.c's birth-refusal gate.

Two things found and fixed along the way:

- The existing cell-pool budget was sourced from pmm_get_stats(), which
  reflects physical pages PMM hasn't handed to any subsystem yet - but
  the actual allocation is kmalloc(), which draws from the separate,
  fixed-size heap kmalloc_init() (M6) already carved out of PMM before
  stadium_boot_init() ever runs. Budgeting against PMM's leftover and
  allocating from the kmalloc heap are two different pools. Both the
  cell budget and the new VM-count budget now source from
  kmalloc_get_stats() instead.

- stadium_owner[] (which VM's quota owns each cell) was uint8_t, capped
  at 255 slots by a compile-time assert tied to the old macro. Widened
  to uint16_t (65535 slots of headroom) with a runtime clamp + log if
  the computed count ever exceeds that, since there's no ceiling anymore.

Three-arch QEMU acceptance: all clean to ok>, computed VM count genuinely
differs by actual available RAM (amd64/riscv64: 50 slots at -m 1024,
aarch64: 101 slots), Stadium conservation invariant identical across all
three (resident_sum=43691 reservoir=21845 sum=65536).
logs/20260815-080526/amd64, logs/20260815-080826/aarch64,
logs/20260815-080952/riscv64.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-08-15 08:11:21 -04:00
..
2026-08-01 07:49:56 -04:00

src/starkernel/vm/

Kernel-side StarForth VM subsystem.

  • vm_core.c — kernel port of the core interpreter loop.
  • vm_runtime.c — kernel VM runtime support.
  • vm_bootstrap.c — kernel VM bootstrap (distinct from bootstrap/sk_vm_bootstrap.c, which owns the higher-level subsystem wiring called from kernel_main.c).
  • arena.c — capsule arena allocator (fixed-region allocation for capsule payload data).
  • parity.c — birth/execution parity logging (VM ID + capsule hash + dictionary hash), enabling offline determinism verification.
  • alloc_kernel.c — the kernel-side implementation of the VM's allocator interface actually referenced by Makefile.starkernel's build (see src/platform/README.md for a note on a second, unwired copy).
  • q48_stubs.c — deliberate no-op stubs for q48_from_double()/ q48_to_double() in the freestanding kernel build, where floating point is unavailable; always returns zero, safe because shared VM code only uses these results for logging/diagnostic paths that are inactive in the kernel build.
  • vm_internal.h — internal-only declarations shared across this directory's files.

Subdirectories:

  • bootstrap/sk_vm_bootstrap.c — owns VM init + capsule loading wiring, called from kernel_main.c; kernel_main.c itself only owns hardware milestones.
  • host/shim.c — host-service shim bridging the kernel VM to src/starkernel/hal/host_services.c.