nixos/hosts/gerg-desktop/vfio.nix

_:
{
  pkgs,
  lib,
  config,
  ...
}:
###TAKEN FROM HERE:https://github.com/NixOS/nixpkgs/blob/4787ebf7ae2ab071389be7ff86cf38edeee7e9f8/nixos/modules/services/x11/xserver.nix#L106-L136
let
  xcfg = config.services.xserver;
  xserverbase =
    let
      fontsForXServer = config.fonts.packages ++ [
        pkgs.xorg.fontadobe100dpi
        pkgs.xorg.fontadobe75dpi
      ];
      fontpath =
        lib.optionalString (xcfg.fontPath != null)
          ''FontPath "${xcfg.fontPath}"'';
    in
    ''
      echo 'Section "Files"' >> $out
      echo ${fontpath} >> $out
      for i in ${toString fontsForXServer}; do
        if test "''${i:0:''${#NIX_STORE}}" == "$NIX_STORE"; then
          for j in $(find $i -name fonts.dir); do
            echo "  FontPath \"$(dirname $j)\"" >> $out
          done
        fi
      done
      for i in $(find ${toString xcfg.modules} -type d); do
        if test $(echo $i/*.so* | wc -w) -ne 0; then
          echo "  ModulePath \"$i\"" >> $out
        fi
      done
      echo '${xcfg.filesSection}' >> $out
      echo 'EndSection' >> $out
      echo >> $out
    '';
  ###END OF TAKEN PART

  cfg_monitors = pkgs.writeShellApplication {
    name = "cfg_monitors";
    runtimeInputs = [
      pkgs.xorg.xrandr
      pkgs.xorg.xset
      pkgs.gawk
      pkgs.gnugrep
    ];
    text = ''
      xrandr --output DP-0 --auto --mode 3440x1440 --rate 120 --primary --pos 0x0
      xrandr --output "$(xrandr | grep -e 'HDMI.* connected.*'| awk '{ print$1 }')" --auto --mode 1920x1080 --rate 144 --set TearFree on --pos 3440x360
      xset -dpms
    '';
  };
in
{
  environment.etc = {
    "Xorg/1_mon.conf".source = pkgs.runCommand "1_mon.conf" { } (
      xserverbase
      + ''
        cat ${./1_mon.conf} >> $out
      ''
    );
    "Xorg/2_mon.conf".source = pkgs.runCommand "2_mon.conf" { } (
      xserverbase
      + ''
        cat ${./2_mon.conf} >> $out
      ''
    );
  };
  boot = {
    kernelParams = [
      "amd_iommu=on"
      "vfio_iommu_type1.allow_unsafe_interrupts=1"
      "kvm.ignore_msrs=1"
    ];
  };
  virtualisation = {
    libvirtd = {
      enable = true;
      qemu = {
        #don't hook evdev at vm start
        package = pkgs.qemu_kvm.overrideAttrs (
          old: {
            patches = old.patches ++ [
              (pkgs.writeText "qemu.diff" ''
                diff --git a/ui/input-linux.c b/ui/input-linux.c
                index e572a2e..a9d76ba 100644
                --- a/ui/input-linux.c
                +++ b/ui/input-linux.c
                @@ -397,12 +397,6 @@ static void input_linux_complete(UserCreatable *uc, Error **errp)
                     }

                     qemu_set_fd_handler(il->fd, input_linux_event, NULL, il);
                -    if (il->keycount) {
                -        /* delay grab until all keys are released */
                -        il->grab_request = true;
                -    } else {
                -        input_linux_toggle_grab(il);
                -    }
                     QTAILQ_INSERT_TAIL(&inputs, il, next);
                     il->initialized = true;
                     return;
              '')
            ];
          }
        );
        runAsRoot = true;
        ovmf.enable = true;
        verbatimConfig = ''
          user = "gerg"
          group = "kvm"
          namespaces = []
        '';
      };
    };
  };
  environment = {
    systemPackages = [
      pkgs.virt-manager
      pkgs.dmidecode
      cfg_monitors
    ];
    shellAliases = {
      vm-start = "virsh start Windows";
      vm-stop = "virsh shutdown Windows";
    };
  };

  programs.dconf.enable = true;

  users.users.gerg.extraGroups = [
    "kvm"
    "libvirtd"
  ];

  services.xserver.displayManager.xserverArgs = lib.mkAfter [
    "-config /etc/Xorg/active.conf"
  ];
  services.xserver.displayManager.sessionCommands = lib.mkBefore ''
    if ! [ -e "/etc/Xorg/ONE_MONITOR" ] ; then
      ${lib.getExe cfg_monitors}
    fi

  '';

  systemd.tmpfiles.rules =
    let
      qemuHook = pkgs.writeShellApplication {
        name = "qemu-hook";

        runtimeInputs = [
          pkgs.libvirt
          pkgs.systemd
          pkgs.kmod
        ];
        text = ''
          GUEST_NAME="$1"
          OPERATION="$2"

          if [ "$GUEST_NAME" == "Windows" ]; then
            if [ "$OPERATION" == "prepare" ]; then
                systemctl stop display-manager.service
                modprobe -r -a nvidia_uvm nvidia_drm nvidia nvidia_modeset
                virsh nodedev-detach pci_0000_01_00_0
                virsh nodedev-detach pci_0000_01_00_1
                systemctl set-property --runtime -- user.slice AllowedCPUs=8-15,24-31
                systemctl set-property --runtime -- system.slice AllowedCPUs=8-15,24-31
                systemctl set-property --runtime -- init.scope AllowedCPUs=8-15,24-31
                ln -fs /etc/Xorg/1_mon.conf /etc/Xorg/active.conf
                touch /etc/Xorg/ONE_MONITOR
                systemctl start display-manager.service
            fi
            if [ "$OPERATION" == "release" ]; then
              systemctl stop display-manager.service
              systemctl set-property --runtime -- user.slice AllowedCPUs=0-31
              systemctl set-property --runtime -- system.slice AllowedCPUs=0-31
              systemctl set-property --runtime -- init.scope AllowedCPUs=0-31
              virsh nodedev-reattach pci_0000_01_00_0
              virsh nodedev-reattach pci_0000_01_00_1
              modprobe -a nvidia_uvm nvidia_drm nvidia nvidia_modeset
              ln -fs /etc/Xorg/2_mon.conf /etc/Xorg/active.conf
              rm /etc/Xorg/ONE_MONITOR
              systemctl start display-manager.service
            fi
          fi
        '';
      };
    in
    [
      "L  /etc/Xorg/active.conf - - - - /etc/Xorg/2_mon.conf"
      "C /var/lib/libvirt/hooks/qemu - - - - ${lib.getExe qemuHook}"
      "C /var/lib/libvirt/qemu/Windows.xml - - - - ${./Windows.xml}"
    ];
  _file = ./vfio.nix;
}