{ config, lib, pkgs, modulesPath, ... }:

# Contains the configuration to make a VM bootable with qemu.

{
  imports = [
    "${modulesPath}/virtualisation/qemu-vm.nix"
  ];

  boot = {
    kernelParams = [
      "console=tty1"
      "console=ttyS0,115200"
      "boot.shell_on_fail"
    ];
    consoleLogLevel = lib.mkDefault 7;
    initrd.kernelModules = [
      "virtio_pci"
      "virtio_blk"
      "virtio_input"
      "9pnet"
      "9pnet_virtio"
    ];

    kernelPatches = [ {
      name = "qemu";
      patch = null;
      extraConfig = ''
        # For qemu
        BLOCK y
        BLK_DEV y
        DEVTMPFS y
        VIRTIO_MENU y
        VIRTIO_BLK y
        VIRTIO_NET y
        EXT4_FS y

        # For 9P: https://wiki.qemu.org/Documentation/9psetup
        NET_9P y
        NET_9P_VIRTIO y
        NET_9P_DEBUG y
        NET_DEVICES y
        NET_CORE y
        INET y
        NETWORK_FILESYSTEMS y
        OVERLAY_FS y
        "9P_FS" y
        "9P_FS_POSIX_ACL" y
        PCI y
        VIRTIO_PCI y
        PCI_HOST_GENERIC y
      '';
    } ];

    loader = {
      grub.enable = false;
      generic-extlinux-compatible.enable = true;
    };
  };

  nixpkgs.overlays = [
    (final: prev: {
      qemu = prev.qemu.override { rutabagaSupport = false; };

      uboot-custom = prev.ubootQemuRiscv64Smode.override {
        # Override preboot to set 'bootcmd' directly to the kernel address in RAM
        extraConfig = ''
          CONFIG_PREBOOT="setenv fdt_addr ''${fdtcontroladdr}; fdt addr ''${fdtcontroladdr}; setenv bootcmd booti ''${kernel_addr_r} - ''${fdtcontroladdr};"
          CONFIG_RISCV_ISA_C=n
        '';
        # Also include debug u-boot
        filesToInstall = ["u-boot.bin" "u-boot"];
      };

      opensbi-uboot = prev.opensbi.overrideAttrs (old: {
        makeFlags = old.makeFlags ++ [
            # Build OpenSBI without compressed instructions
            "PLATFORM_RISCV_ISA=rv64g"
            # Check with: riscv64-unknown-elf-objdump -d -M no-aliases rotate
            "FW_PAYLOAD_PATH=${final.uboot-custom}/u-boot.bin"
        ];
      });
    })
  ];
}