From cf47294b9ee7887ca1f21db34d48c346e89f9cec Mon Sep 17 00:00:00 2001
From: Florian Klink <flokli@flokli.de>
Date: Mon, 18 Mar 2024 12:09:49 +0200
Subject: feat(tvix/boot): boot nixos VM

This makes use of the vmCmdline and assertVMOutput to boot a NixOS VM
off of `tvix-store virtiofs` have it write a message on successful
bootup, then have it shut down again.

We check we see the message in the output.

Seeding the store with the closure it's what's currently taking most
of the time (as it's all linear still), so log a message before booting
the VM.

Change-Id: I6887d935f589eb0ad6507033c01337e1ec500a0b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11191
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
---
 tvix/boot/tests/default.nix | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tvix/boot/tests/default.nix b/tvix/boot/tests/default.nix
index 949be35ccf..d16dba79f1 100644
--- a/tvix/boot/tests/default.nix
+++ b/tvix/boot/tests/default.nix
@@ -70,12 +70,38 @@ let
           tvix-store --otlp=false copy
         '' + ''
           # Invoke a VM using tvix as the backing store, ensure the outpath appears in its listing.
+          echo "Starting VM…"
 
           CH_CMDLINE="${vmCmdline}" run-tvix-vm 2>&1 | tee output.txt
           grep "${assertVMOutput}" output.txt
         '';
         requiredSystemFeatures = [ "kvm" ];
       };
+
+  systemFor = sys: (depot.ops.nixos.nixosFor sys).system;
+
+  testSystem = systemFor ({ modulesPath, pkgs, ... }: {
+    # Set some options necessary to evaluate.
+    boot.loader.systemd-boot.enable = true;
+    # TODO: figure out how to disable this without causing eval to fail
+    fileSystems."/" = {
+      device = "/dev/root";
+      fsType = "tmpfs";
+    };
+
+    services.getty.helpLine = "Onwards and upwards.";
+    systemd.services.do-shutdown = {
+      after = [ "getty.target" ];
+      description = "Shut down again";
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig.Type = "oneshot";
+      script = "/run/current-system/sw/bin/systemctl poweroff --when=+10s";
+    };
+
+    # Don't warn about stateVersion.
+    system.stateVersion = "24.05";
+  });
+
 in
 depot.nix.readTree.drvTargets
 {
@@ -101,4 +127,12 @@ depot.nix.readTree.drvTargets
     path = depot.tvix.store;
     isClosure = true;
   });
+
+  closure-nixos = (mkBootTest {
+    blobServiceAddr = "objectstore+file://$PWD/blobs";
+    path = testSystem;
+    isClosure = true;
+    vmCmdline = "init=${testSystem}/init panic=-1"; # reboot immediately on panic
+    assertVMOutput = "Onwards and upwards.";
+  });
 }
-- 
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