anchor.diff:      else if pkgs.stdenv.isAarch64 then "${pkgs.OVMF.fd}/FV/AAVMF"
       else throw "No EFI firmware available for platform";
     efiFirmware = "${efiPrefix}_CODE.fd";
  -  efiVars = "${efiPrefix}_VARS.fd";
  +  efiVarsDefault = "${efiPrefix}_VARS.fd";
   
     # Shell script to start the VM.
     startVM =
  
positive.code:           '';
        };
  
      virtualisation.bios =
        mkOption {
          default = null;
  
negative.code:         # A writable boot disk can be booted from automatically.
          ${qemu}/bin/qemu-img create -f qcow2 -b ${bootDisk}/disk.img $TMPDIR/disk.img || exit 1
  
          NIX_EFI_VARS=$(readlink -f ''${NIX_EFI_VARS:-${cfg.efiVars}})
  
          ${if cfg.useEFIBoot then ''
            # VM needs writable EFI vars
            if ! test -e "$NIX_EFI_VARS"; then
              cp ${bootDisk}/efi-vars.fd "$NIX_EFI_VARS" || exit 1
              chmod 0644 "$NIX_EFI_VARS" || exit 1
            fi
          '' else ''
          ''}
        '' else ''
  