allow configuring whether a node uses QEMU

infra/common/nixos/hardware.nix

@@ -1,27 +1,47 @@
-{ modulesPath, ... }:
+{ config, lib, ... }:
 
+let
+  inherit (lib) mkIf mkMerge;
+
+in
 {
   _class = "nixos";
 
-  imports = [ (modulesPath + "/profiles/qemu-guest.nix") ];
-
-  boot = {
-    loader = {
+  config = mkMerge [
+    {
+      boot.loader = {
         systemd-boot.enable = true;
         efi.canTouchEfiVariables = true;
       };
+    }
 
-    initrd = {
+    (mkIf config.fediversityVm.isQemuVm {
+
+      boot.initrd = {
         availableKernelModules = [
           "ata_piix"
           "uhci_hcd"
-        "virtio_pci"
-        "virtio_scsi"
           "sd_mod"
           "sr_mod"
+
+          # from `/profiles/qemu-guest.nix`
+          "virtio_net"
+          "virtio_pci"
+          "virtio_mmio"
+          "virtio_blk"
+          "virtio_scsi"
+          "9p"
+          "9pnet_virtio"
+        ];
+        kernelModules = [
+          "dm-snapshot"
+
+          # from `/profiles/qemu-guest.nix`
+          "virtio_balloon"
+          "virtio_console"
+          "virtio_rng"
+          "virtio_gpu"
         ];
-      kernelModules = [ "dm-snapshot" ];
-    };
       };
 
       disko.devices.disk.main = {
@@ -61,4 +81,6 @@
           };
         };
       };
+    })
+  ];
 }

infra/common/options.nix

@@ -155,5 +155,13 @@ in
         this for testing machines, as it is a security hole for so many reasons.
       '';
     };
+
+    isQemuVm = mkOption {
+      description = ''
+        Whether the machine is a QEMU VM. This will import all the necessary
+        things.
+      '';
+      default = true;
+    };
   };
 }