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LithosAnanake/experiments/bare_metal/runs/doe-riscv64-20260913-142834.csv
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Robert Allan JamesandClaude Sonnet 5 57ac3fc304
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Stage 1: per-VM native stacks, allocated but not yet executed on (FABRIC-3.md §XXVIII)
Second stage of the preemptive context-switching plan. Every VM (Hera,
every capsule_birth_baby()-born VM including WIREBIND identities) now
gets its own dedicated 2 MiB native C stack at birth -- but nothing runs
on it yet, that's Stage 2. Pure allocation-machinery proof.

Design correction made before writing code: the plan called for cloning
sk_vm_arena_alloc()'s guard-page pattern, but that pattern turns out to
be Mama-only -- host_services.c's kernel_alloc() gives every baby VM a
plain kmalloc() block for its dictionary arena, not a real guarded PMM
allocation. Stacks get the real treatment instead (new
sk_vm_native_stack_alloc()/_free() in arena.c): independent
pmm_alloc_contiguous() + guard pages for every VM without exception, no
singleton, no kmalloc fallback -- a stack overflow is exactly the
failure mode guard pages exist for, and a corrupted stack could corrupt
whatever saved context Stage 2 trusts.

2 MiB size matches this project's own established kernel-stack
convention (g_kernel_stack/g_rpi5_native_stack), not a guess -- that one
shared 2 MiB stack today already carries all VMs' combined nested
VM-EXEC recursion.

Three new VM struct fields, freed in vm_cleanup() alongside the existing
call_stack free. Allocation failure is non-fatal to birth.

All 3 architectures re-verified clean boot to ok>, no native-stack
allocation failures for any Tripod-fleet VM.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016UNhH1mhi52i6Qihh7ZV5S
2026-09-13 14:30:46 -04:00

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