Merge pull request #20500 from aszlig/qemu-patched-for-nixos-tests

nixos/tests: Use a patched QEMU for testing

nixos/modules/virtualisation/qemu-vm.nix

@@ -70,7 +70,7 @@ let
       '')}
 
       # Start QEMU.
-      exec ${pkgs.qemu_kvm}/bin/qemu-kvm \
+      exec ${cfg.qemu.program} \
           -name ${vmName} \
           -m ${toString config.virtualisation.memorySize} \
           ${optionalString (pkgs.stdenv.system == "x86_64-linux") "-cpu kvm64"} \
@@ -299,6 +299,14 @@ in
       };
 
     virtualisation.qemu = {
+      program = mkOption {
+        type = types.path;
+        default = "${pkgs.qemu_kvm}/bin/qemu-kvm";
+        defaultText = "\${pkgs.qemu_kvm}/bin/qemu-kvm";
+        example = literalExample "\${pkgs.qemu_test}/bin/qemu-kvm";
+        description = "The QEMU variant used to start the VM.";
+      };
+
       options =
         mkOption {
           type = types.listOf types.unspecified;