bfe-core1106-sdk/qemu/README.md

qemu/ — the WardenOS device simulator

A QEMU virtual machine that boots the real forward-ported kernel (build/ + patches/) and real userspace, so the device — init, daemons, networking, OTA, watchdog, display — can be tested off-hardware. The third simulator in the stack, deliberately not named "sim":

• lvglsim (flare-edge) — SDL desktop build of the UI. Rendering only.
• sim/ (this repo) — register-level Rust models of RV1106 blocks behind driver seams.
• qemu/ (this) — the whole machine above the kernel entry point, running the real binaries.

Decision record: docs/decisions/0006-qemu-device-sim.md.

The boundary (read this before trusting a green run)

There is no RV1106 machine model in QEMU and everything below the kernel is closed rkbin blobs plus mask ROM, so the VM enters at -kernel zImage on -M virt,highmem=off (single Cortex-A7, 256M — the RV1106G3's shape).

Emulated / substituted	Not emulated (stays bench / sim/ territory)
Kernel boot, init ordering, switch_root	BootROM, idblock/DDR-init, SPL, U-Boot
A/B outcome (warden.slot= cmdline)	Real BCB A/B selection, bootcount auto-revert
Storage: virtio-blk with the device's exact blkdevparts= layout + /dev/block/by-name/ contract	eMMC controller itself
Network: virtio-net (slirp, hostfwd 22/80/28443)	GMAC, AIC8800 wifi, usb0 gadget
Display: virtio-gpu 720x720 via fbdev emulation	VOP/RGB666 pipeline, CH32V003 panel init, RGA blits
Touch: virtio-tablet (QMP input-send-event)	GT911 on I2C3
Watchdog: i6300esb (PCI), -action watchdog=reset	DW watchdog @0xff5a0000, HPMCU supervisor
RS485: pci-serial chardev bridged to sim/'s ModbusSlave	Real UART4 timing/electrical behavior
RTC: PL031 (--rtc reproduces the no-RTC 2021-clock incident class)	The unpopulated backup-cell reality

"Boots/works under emulation" is never evidence of "works on silicon." The VM narrows which claims need a panel; on-device claims still need on-device evidence. Conversely, the VM is the first environment that runs production binaries on a non-RV1106 memory map — it found flare-edge #106 (fatal SIGBUS in flared's HPMCU probe) and #107 (Y2038 time_t truncation) on its first two boots of real userspace.

Documented guest deviations from production, set by stage-2 init: WARDEN_FLARE_INSECURE=1 (the desk mock portal is plain HTTP) and WARDEN_HPMCU=0 (no mailbox SRAM on virt; flared >= flare-edge#106 fix required, or the daemon dies of SIGBUS).

Quick start

# 1. kernel: canonical build boots the VM as-is; the fragment variant adds
#    the scenario devices (PCI serial, watchdog, WireGuard, virtio-gpu/input)
WORK=$HOME/kbuild-out CROSS_COMPILE=arm-linux-gnueabihf- \
  WARDEN_KCONFIG_FRAGMENT=qemu/configs/virt.fragment bash build/build-kernel.sh

# 2. initramfs (sha256-pinned static busybox + qemu/rootfs/) and A/B disk
bash qemu/mkinitramfs.sh
bash qemu/mkimage.sh                  # options: --portal-url --state K=V --fw-version

# 3. run (see run.sh header for all flags)
bash qemu/run.sh --kernel $HOME/kbuild-out/linux-6.18.46/arch/arm/boot/zImage --shell

Payload: drop static musl armv7 binaries into qemu/payload/ (see its README) — warden-flared, warden-modbus, and warden-ui (the LVGL fbdev+evdev build from flare-edge tools/build-ui-vm.sh) are started by stage-2 init when present.

Scenario tests (qemu/tests/)

• boot-smoke.sh <zImage> — sentinel-asserting boot; runs in CI inside the kernel-build job.
• portal-scenario.sh <zImage> (needs FLARE_EDGE=<checkout>) — the real flared in the VM against the desk mock portal: authenticated check-in, firmware desired-state pull, and download of a real signed tier-1 .wfw offer. Verify/stage/APPLYING run as a dry run (no WARDEN_FW_ALLOW_APPLY); flipping it on inside the VM is the documented stretch — apply writes /dev/block/by-name/rootfs_b inside disk.img, then --slot _b boots it.
• ui-shot.sh <zImage> — display+touch: boots headless with virtio-gpu, QMP-screendumps the 720x720 UI, taps the Metrics tab via input-send-event (a 200 ms hold — an instantaneous press+release lands inside one LVGL poll and never clicks), and asserts the frame changed. qmp.py is the tiny QMP client.
• ota-apply.sh <zImage> (needs FLARE_EDGE) — the FULL apply loop the portal scenario stops short of: a real signed tier-1 .wfw whose payload is a bootable rootfs is pulled, verified, WRITTEN to rootfs_b (run.sh --allow-apply gates it per boot), the AvbABData in misc is flipped (mkimage provisions real A/B metadata), and the harness reboots slot _b and asserts the applied version is running. The BCB slot CHOICE and the physical reset stay emulated by the harness (ADR-0006 boundary); the VM exports WARDEN_HARD_RESET=0 so flared's post-apply reset surfaces as a clean reported error instead of a /dev/mem fault.
• Watchdog: run.sh --watchdog, arm /dev/watchdog in the guest, don't pet — the VM resets ~30 s later (verified). Do NOT combine with a flared payload expecting survival: flared pets only while the UI heartbeat is fresh.

Gotchas that cost time (so they cost it once)

• AF_UNIX socket paths cap at ~108 chars — keep --rs485/--qmp paths short.
• A serial port that is closed discards incoming bytes: hold ONE fd open across write and read when scripting the guest side of the RS485 bridge.
• highmem=off and -global virtio-mmio.force-legacy=false are load-bearing (32-bit ECAM reach; virtio-1-only gpu/input) — both live ONLY in run.sh, which every script (boot smoke included) delegates to.
• Never pass earlyprintk: DEBUG_UART_PHYS is the RV1106's 0xff4c0000.

Host requirements

qemu-system-arm (Debian 13 ships QEMU 10), curl, cpio, mkfs.ext4, gcc-arm-linux-gnueabihf (kernel build), python3 (+cryptography for the portal scenario's .wfw signing). CI: the hosted qemu-tools job builds the tooling; the boot smoke runs inside the (also hosted, dispatch-only) kernel-build job, which apt-installs its own toolchain and qemu (ADR-0007).