qemu_test: Remove hostCpuOnly flag (#541354)

nixos/tests/all-tests.nix

@@ -153,6 +153,7 @@ in
     console-log = runTest ./nixos-test-driver/console-log.nix;
     containers = runTest ./nixos-test-driver/containers.nix;
     nspawn-daemon-reexec-dbus = runTest ./nspawn-daemon-reexec-dbus.nix;
+    multi-arch-test = runTest ./nixos-test-driver/multi-arch-test.nix;
     skip-typecheck = runTest ./nixos-test-driver/skip-typecheck.nix;
     console-timeout = runTest ./nixos-test-driver/console-timeout.nix;
     options-doc-regression = import ./nixos-test-driver/options-doc-regression.nix { inherit pkgs; };

nixos/tests/nixos-test-driver/multi-arch-test.nix

@@ -0,0 +1,55 @@
+{ pkgs, lib, ... }:
+{
+  name = "multi-arch-test";
+  meta.maintainers = with pkgs.lib.maintainers; [ tfc ];
+
+  node.pkgsReadOnly = false;
+
+  nodes = {
+    # Setting build = host platform because such standard VM setups
+    # are well-cached by the multi-arch build infrastructure of the
+    # project.
+    vmIntel = {
+      nixpkgs.buildPlatform = "x86_64-linux";
+      nixpkgs.hostPlatform = "x86_64-linux";
+    };
+    vmArm = {
+      nixpkgs.buildPlatform = "aarch64-linux";
+      nixpkgs.hostPlatform = "aarch64-linux";
+    };
+  };
+
+  defaults = {
+    # not needed for this test and shrinks the closure
+    # because we dont' need qemu for all architectures
+    virtualisation.qemu.guestAgent.enable = false;
+
+    # the test is already very slow but we don't need DHCP anyway
+    networking.dhcpcd.enable = false;
+
+    # fix the network-online target, otherwise it doesn't work
+    # properly as a synchronization mechanism.
+    systemd.network.wait-online.enable = true;
+    systemd.network.wait-online.anyInterface = true;
+  };
+
+  # slow due to SW emulation but shouldn't be slower than that
+  globalTimeout = 5 * 60;
+
+  testScript = { nodes, ... }: /* python */ ''
+    start_all()
+
+    vmIntel.systemctl("start network-online.target")
+    vmArm.systemctl("start network-online.target")
+    vmIntel.wait_for_unit("network-online.target")
+    vmArm.wait_for_unit("network-online.target")
+
+    vmIntel.succeed("ping -c 1 vmArm")
+    vmArm.succeed("ping -c 1 vmIntel")
+
+    archIntel = vmIntel.succeed("uname -m")
+    t.assertIn("${nodes.vmIntel.nixpkgs.hostPlatform.qemuArch}", archIntel, "machine1 is an intel VM")
+    archArm = vmArm.succeed("uname -m")
+    t.assertIn("${nodes.vmArm.nixpkgs.hostPlatform.qemuArch}", archArm, "machine1 is an ARM VM")
+  '';
+}

pkgs/top-level/all-packages.nix

@@ -7981,7 +7981,6 @@ with pkgs;
 
   qemu_test = lowPrio (
     qemu.override {
-      hostCpuOnly = true;
       nixosTestRunner = true;
     }
   );