chrony: add nixos test for ptp_kvm

nixos/tests/all-tests.nix

···
   cfssl = handleTestOn ["aarch64-linux" "x86_64-linux"] ./cfssl.nix {};
   charliecloud = handleTest ./charliecloud.nix {};
   chromium = (handleTestOn ["aarch64-linux" "x86_64-linux"] ./chromium.nix {}).stable or {};
+  chrony-ptp = handleTestOn ["aarch64-linux" "x86_64-linux"] ./chrony-ptp.nix {};
   cinnamon = handleTest ./cinnamon.nix {};
   cjdns = handleTest ./cjdns.nix {};
   clickhouse = handleTest ./clickhouse.nix {};

nixos/tests/chrony-ptp.nix

···
+import ./make-test-python.nix ({ lib, ... }:
+{
+  name = "chrony-ptp";
+
+  nodes = {
+    qemuGuest = { lib, ... }: {
+      boot.kernelModules = [ "ptp_kvm" ];
+
+      services.chrony = {
+        enable = true;
+        extraConfig = ''
+          refclock PHC /dev/ptp_kvm poll 2 dpoll -2 offset 0 stratum 3
+        '';
+      };
+    };
+  };
+
+  testScript = ''
+    start_all()
+
+    qemuGuest.wait_for_unit('multi-user.target')
+    qemuGuest.succeed('systemctl is-active chronyd.service')
+  '';
+})