arm64 QEMU virt

The arm64 development target. Boots to a shell.

Building

nix build .#kernel-arm64-virt      # or -debug
nix build .#kexts-arm64
nix build .#kc-arm64
nix build .#image-arm64-virt-minimal
nix run .#arm64-virt

userland-arm64 and the ports with an -arm64 suffix supply the guest software. image-arm64-virt-wayland adds a Wayland session.

State

Boots to a shell from an ext4 root, with the platform expert, the GIC, the virtio devices and xHCI input working. FreeBSD’s e1000 driver runs here too and gets a DHCP lease.

Machine Notes

Use -cpu neoverse-n2 or cortex-a710. With -cpu max, the EDK2 firmware crashes before printing anything. That looks like a silent serial port and a loader problem, and it is neither.

Use -M virt,gic-version=3. The platform expects a GICv3.

16K page granule. The virt target uses 16K pages. That touches L2 block congruence, the trustcache, segLOWEST handling and the TSD layout, all of which had to be fixed to get here.

Display is ramfb. The loader fills a 64-bit Video structure, and the kernel wants v_display == 0. The virt machine also needs the xHCI keyboard for input.

Timer interrupts. The timer interrupt has to be routed as Group 0, delivered as an FIQ. Routed any other way, the system stalls before reaching a shell.

Root Filesystem Options

Two shapes are available. image-arm64-virt is a normal disk image. image-arm64-virt-minimal uses a 512 MB RAM disk with rd=md0. It is faster to iterate on, and it is the shape shared with the netboot and T8010 paths.

Other Things Proven Here

JIT works. MAP_JIT, live code rewriting and cross-thread patching all pass, and asmjit runs. Plain RWX mappings are refused by vm_map_enter, as they should be. Nothing on the JIT side stands in the way of running an emulator on this target.