From 8ab2f09522d5aefabf1100b3f59a3bde628cb2b4 Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Wed, 14 Jun 2023 21:54:39 +0000
Subject: [PATCH] nixos/qemu-vm: fix infinite recursion

The virtualisation.directBoot.initrd option was added for netboot
images, but the assertion to check directBoot enabled if it was used
caused an infinite recursion if it was.  Minimal reproduction:

	import nixos/tests/make-test-python.nix ({ pkgs, ... }: {
	  name = "";

	  nodes = {
	    machine = { config, ...}: {
	      imports = [ nixos/modules/installer/netboot/netboot-minimal.nix ];

	      virtualisation.directBoot = {
	        enable = true;
	        initrd = "${config.system.build.netbootRamdisk}/${config.system.boot.loader.initrdFile}";
	      };
	    };
	  };
	  testScript = "";
	}) {}

The fix is to swap the two conditions, so that cfg.directBoot.enable
is checked first, and the initrd comparision will be short circuited.

This wasn't noticed during review because in earlier versions of the
virtualisation.directBoot patch, the assertion was accidentally in the
conditional above, so wasn't evaluated unless port forwarding was in
use.
---
 nixos/modules/virtualisation/qemu-vm.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nixos/modules/virtualisation/qemu-vm.nix b/nixos/modules/virtualisation/qemu-vm.nix
index e625c6322d9c..6f275baf60dc 100644
--- a/nixos/modules/virtualisation/qemu-vm.nix
+++ b/nixos/modules/virtualisation/qemu-vm.nix
@@ -997,7 +997,7 @@ in
               virtualisation.memorySize is above 2047, but qemu is only able to allocate 2047MB RAM on 32bit max.
             '';
           }
-          { assertion = cfg.directBoot.initrd != options.virtualisation.directBoot.initrd.default -> cfg.directBoot.enable;
+          { assertion = cfg.directBoot.enable || cfg.directBoot.initrd == options.virtualisation.directBoot.initrd.default;
             message =
               ''
                 You changed the default of `virtualisation.directBoot.initrd` but you are not