feat: add microvm module to simplify setup

flake.lock

@@ -258,7 +258,7 @@
       },
       "locked": {
         "lastModified": 1682972682,
-        "narHash": "sha256-IYInF92rLqqVk/dyugT2QVbVeEfYx1rbBJjbUlRD8oE=",
+        "narHash": "sha256-+XyTwr4jZuDlT5l/0LynDVtvdWj8WmAwDEP/2rZ+1hk=",
         "type": "git",
         "url": "file:///root/projects/microvm.nix"
       },

flake.nix

@@ -105,7 +105,16 @@
       };
 
       colmena = import ./nix/colmena.nix inputs;
-      inherit ((colmena.lib.makeHive self.colmena).introspect (x: x)) nodes;
+      colmenaNodes = ((colmena.lib.makeHive self.colmena).introspect (x: x)).nodes;
+      microvmNodes =
+        nixpkgs.lib.concatMapAttrs (
+          nodeName: nodeAttrs:
+            nixpkgs.lib.mapAttrs'
+            (n: nixpkgs.lib.nameValuePair "${nodeName}-microvm-${n}")
+            (self.colmenaNodes.${nodeName}.config.microvm.vms or {})
+        )
+        self.colmenaNodes;
+      nodes = self.colmenaNodes // self.microvmNodes;
 
       # Collect installer packages
       inherit

hosts/common/core/default.nix

@@ -11,6 +11,7 @@
     ./xdg.nix
 
     ../../../modules/wireguard.nix
+    ../../../modules/microvms.nix
   ];
 
   home-manager = {

hosts/common/core/system.nix

@@ -2,6 +2,7 @@
   inputs,
   lib,
   nodeName,
+  nodePath,
   ...
 }: {
   # IP address math library
@@ -30,7 +31,7 @@
     # current system due to yubikey availability.
     forceRekeyOnSystem = builtins.extraBuiltins.unsafeCurrentSystem;
     hostPubkey = let
-      pubkeyPath = ../.. + "/${nodeName}/secrets/host.pub";
+      pubkeyPath = "${nodePath}/secrets/host.pub";
     in
       lib.mkIf (lib.pathExists pubkeyPath || lib.trace "Missing pubkey for ${nodeName}: ${toString pubkeyPath} not found, using dummy replacement key for now." false)
       pubkeyPath;

hosts/ward/default.nix

@@ -2,7 +2,6 @@
   config,
   inputs,
   lib,
-  microvm,
   nixos-hardware,
   pkgs,
   ...
@@ -11,8 +10,6 @@
     nixos-hardware.common-cpu-intel
     nixos-hardware.common-pc-ssd
 
-    microvm.host
-
     ../common/core
     ../common/hardware/intel.nix
     ../common/hardware/physical.nix
@@ -28,21 +25,7 @@
 
   boot.initrd.availableKernelModules = ["xhci_pci" "ahci" "nvme" "usbhid" "usb_storage" "sd_mod" "sdhci_pci" "r8169"];
 
-  microvm.vms = {
-    test = let
-      node =
-        (import ../../nix/generate-node.nix inputs)
-        "ward-microvm-test" {
-          system = "x86_64-linux";
-          config = ./microvms/test;
-        };
-    in {
-      inherit (node) pkgs specialArgs;
-      config = {
-        inherit (node) imports;
-      };
-    };
-  };
+  extra.microvms.test.system = "x86_64-linux";
 
   #services.authelia.instances.main = {
   #  enable = true;

hosts/ward/microvms/test/default.nix

@@ -8,8 +8,6 @@
   ...
 }: {
   imports = [
-    microvm.microvm
-
     ../../../common/core
 
     ../../../../users/root

modules/microvms.nix

@@ -0,0 +1,78 @@
+{
+  inputs,
+  config,
+  lib,
+  nodeName,
+  nodePath,
+  microvm,
+  pkgs,
+  ...
+}: let
+  inherit
+    (lib)
+    mapAttrs
+    mdDoc
+    mkDefault
+    mkForce
+    mkIf
+    mkOption
+    types
+    ;
+
+  cfg = config.extra.microvms;
+
+  defineMicrovm = vmName: vmCfg: let
+    node =
+      (import ../nix/generate-node.nix inputs)
+      "${nodeName}-microvm-${vmName}" {
+        inherit (vmCfg) system;
+        config = nodePath + "/microvms/${vmName}";
+      };
+  in {
+    inherit (node) pkgs specialArgs;
+    config = {
+      imports = [microvm.microvm] ++ node.imports;
+
+      microvm = {
+        hypervisor = mkDefault "cloud-hypervisor";
+
+        # Share the nix-store of the host
+        shares = [
+          {
+            source = "/nix/store";
+            mountPoint = "/nix/.ro-store";
+            tag = "ro-store";
+            proto = "virtiofs";
+          }
+        ];
+      };
+
+      # TODO change once microvms are compatible with stage-1 systemd
+      boot.initrd.systemd.enable = mkForce false;
+    };
+  };
+in {
+  imports = [microvm.host];
+
+  options.extra.microvms = mkOption {
+    default = {};
+    description = "Provides a base configuration for MicroVMs.";
+    type = types.attrsOf (types.submodule {
+      options = {
+        system = mkOption {
+          type = types.str;
+          description = mdDoc "The system that this microvm should use";
+        };
+      };
+    });
+  };
+
+  config = {
+    microvm = {
+      host.enable = cfg != {};
+      declarativeUpdates = true;
+      restartIfChanged = true;
+      vms = mkIf (cfg != {}) (mapAttrs defineMicrovm cfg);
+    };
+  };
+}

nix/generate-node.nix

@@ -14,21 +14,22 @@
 } @ inputs: let
   inherit (nixpkgs.lib) optionals;
 in
-  nodeName: nodeMeta: {
+  nodeName: nodeMeta: let
+    nodePath = nodeMeta.config or (../hosts + "/${nodeName}");
+  in {
     inherit (nodeMeta) system;
     pkgs = self.pkgs.${nodeMeta.system};
     specialArgs = {
       inherit (nixpkgs) lib;
       inherit (self) extraLib nodes stateVersion;
-      inherit inputs;
-      inherit nodeName;
+      inherit inputs nodeName nodePath;
       secrets = self.secrets.content;
-      nodeSecrets = self.secrets.content.nodes.${nodeName};
+      nodeSecrets = self.secrets.content.nodes.${nodeName} or {};
       nixos-hardware = nixos-hardware.nixosModules;
       microvm = microvm.nixosModules;
     };
     imports = [
-      (nodeMeta.config or (../hosts + "/${nodeName}"))
+      nodePath # default module
       agenix.nixosModules.default
       agenix-rekey.nixosModules.default
       disko.nixosModules.disko