issue-1588 : Allow extra driver config args as a passthrough for qemu…

client/driver/qemu.go

@@ -46,6 +46,7 @@ type QemuDriverConfig struct {
 	ImagePath   string           `mapstructure:"image_path"`
 	Accelerator string           `mapstructure:"accelerator"`
 	PortMap     []map[string]int `mapstructure:"port_map"` // A map of host port labels and to guest ports.
+	Args        []string         `mapstructure:"args"`     // extra arguments to qemu executable
 }
 
 // qemuHandle is returned from Start/Open as a handle to the PID
@@ -82,6 +83,9 @@ func (d *QemuDriver) Validate(config map[string]interface{}) error {
 			"port_map": &fields.FieldSchema{
 				Type: fields.TypeArray,
 			},
+			"args": &fields.FieldSchema{
+				Type: fields.TypeArray,
+			},
 		},
 	}
 
@@ -169,11 +173,16 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (DriverHandle,
 		"-name", vmID,
 		"-m", mem,
 		"-drive", "file=" + vmPath,
-		"-nodefconfig",
-		"-nodefaults",
 		"-nographic",
 	}
 
+	// Add pass through arguments to qemu executable. A user can specify
+	// these arguments in driver task configuration. These arguments are
+	// passed directly to the qemu driver as command line options.
+	// For example, args = [ "-nodefconfig", "-nodefaults" ]
+	// This will allow a VM with embedded configuration to boot successfully.
+	args = append(args, driverConfig.Args...)
+
 	// Check the Resources required Networks to add port mappings. If no resources
 	// are required, we assume the VM is a purely compute job and does not require
 	// the outside world to be able to reach it. VMs ran without port mappings can

client/driver/qemu_test.go

@@ -46,6 +46,7 @@ func TestQemuDriver_StartOpen_Wait(t *testing.T) {
 				"main": 22,
 				"web":  8080,
 			}},
+			"args": []string{"-nodefconfig", "-nodefaults"},
 		},
 		LogConfig: &structs.LogConfig{
 			MaxFiles:      10,
@@ -105,6 +106,7 @@ func TestQemuDriverUser(t *testing.T) {
 				"main": 22,
 				"web":  8080,
 			}},
+			"args": []string{"-nodefconfig", "-nodefaults"},
 		},
 		LogConfig: &structs.LogConfig{
 			MaxFiles:      10,

website/source/docs/drivers/qemu.html.md

@@ -40,6 +40,9 @@ The `Qemu` driver supports the following configuration in the job spec:
   `port_map { db = 6539 }` would forward the host port with label `db` to the
   guest VM's port 6539.
 
+* `args` - (Optional) A `[]string` that is passed to qemu as command line options.
+  For example, `args = [ "-nodefconfig", "-nodefaults" ]
+
 ## Examples
 
 A simple config block to run a `Qemu` image:
@@ -51,6 +54,7 @@ task "virtual" {
   config {
     image_path = "local/linux.img"
     accelerator = "kvm"
+    args = [ "-nodefaults", "-nodefconfig" ]
   }
 
   # Specifying an artifact is required with the "qemu"