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 -arm64 suffixed ports supply the guest software.

State

Boots to a shell from an ext4 root, with the platform expert, GIC, virtio devices and xHCI input working. Xorg can be started. GL on virt is currently broken on the reference machine; treat that as an open bug rather than a general statement about the target.

Machine notes

Use -cpu neoverse-n2 or cortex-a710, not -cpu max. With max, the EDK2 firmware crashes before printing anything, which presents as a completely silent serial port and looks like a loader problem. It is not.

16K page granule. The virt target uses 16K pages. That interacts with L2 block congruence, the trustcache and 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.

Interrupts. PDArmGIC routes the virtual timer (CNTV) as Group 1.

Root filesystem options

Two shapes are available. image-arm64-virt is a conventional disk image; image-arm64-virt-minimal uses a 512 MB RAM disk with rd=md0, which is faster to iterate on and 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. There is no JIT-side blocker for running an emulator on this target.