https://i-riscv.org/linux/index.html The i-RISCV SoC boots an unmodified, stock Linux kernel. Both v6.6 and v7.2 are maintained as sibling boot harnesses sharing the same RTL, both firmware paths, and one device tree – a release 2.5 years newer booting with zero RTL or firmware changes is itself a stability test, and v7.2’s extension-detection table additionally recognizes six extensions v6.6’s doesn’t (Zicond, Zfa, Zawrs, Zicbop, Zihintpause, Zkt). What Boots Unmodified upstream Linux (v6.6 and v7.2), configured for every extension this core implements Two interchangeable M-mode boot-firmware paths: unmodified upstream OpenSBI (default) or this project’s own standalone SBI – both hand off to the exact same kernel image at the same address from the same device tree (see SBI) A single generated device tree (firmware/dts/gen_soc_dts.py) advertising all ratified ISA strings plus the real UART, PLIC, APLIC, IOMMU, and IMSIC nodes – v6.6 leaves the IOMMU/IMSIC/APLIC nodes unprobed (it has no in-tree drivers for them), while v7.2 genuinely resolves all three What Works During Boot Full extension detection by the kernel itself (base ISA plus every Z/S extension its version recognizes) Sstc: the kernel writes stimecmp directly from S-mode for every tick – no SBI TIME calls at all Real serial console: the stock 8250 driver binds to the ns16550a UART (earlycon bootconsole, then ttyS0) Full boot-to-poweroff confirmed end to end: memory management, RCU, the ASID allocator, devtmpfs, IOMMU/IMSIC/APLIC driver init (v7.2), a real clocksource switch, and KVM all initialize; the non-interactive /init then dumps /proc/cpuinfo and powers off cleanly at roughly 143M-234M simulated cycles with no panic or hang Real 2-hart SMP boot on both kernel versions (CONFIG_SMP=y against the multicore top): the second hart is parked at reset and released by SBI HSM, with IPIs via CLINT MSIP and synchronous cross-hart RFENCE TLB shootdowns (see SBI) KVM: on v6.6 riscv_kvm_init() completes cleanly; on v7.2 the full KVM AIA SGEI path resolves against the real IMSIC S-file node and returns success within seconds of kernel time This project’s own IOPMP platform driver binds on both kernels Non-interactive userspace: PID 1 is a minimal POSIX-C program built against the kernel’s own vendored nolibc – it mounts devtmpfs/proc/sysfs, dumps /proc/cpuinfo to the console between fixed delimiters, and powers off; no interactive shell (an honest scope cut: one would need a full userspace cross-toolchain) The simulator polls a testbench-only DBG_EXIT register that both firmware paths write on SRST shutdown, so a completed run stops itself immediately instead of idling to its cycle ceiling – the register is dead-code-eliminated from any real synthesis Linux Boot Log + /proc/cpuinfo Output The following listing is taken from a Verilator simulation run showing the unmodified OpenSBI booting an unmodified Linux 7.2.4 kernel. Hugo en-us