qemu driver: Add option to configure drive_interface

.changelog/11864.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+qemu: Added option to configure `drive_interface`
+```

drivers/qemu/driver.go

@@ -92,6 +92,7 @@ var (
 	// a taskConfig within a job. It is returned in the TaskConfigSchema RPC
 	taskConfigSpec = hclspec.NewObject(map[string]*hclspec.Spec{
 		"image_path":        hclspec.NewAttr("image_path", "string", true),
+		"drive_interface":   hclspec.NewAttr("drive_interface", "string", false),
 		"accelerator":       hclspec.NewAttr("accelerator", "string", false),
 		"graceful_shutdown": hclspec.NewAttr("graceful_shutdown", "bool", false),
 		"args":              hclspec.NewAttr("args", "list(string)", false),
@@ -121,6 +122,7 @@ type TaskConfig struct {
 	Args             []string           `codec:"args"`     // extra arguments to qemu executable
 	PortMap          hclutils.MapStrInt `codec:"port_map"` // A map of host port and the port name defined in the image manifest file
 	GracefulShutdown bool               `codec:"graceful_shutdown"`
+	DriveInterface   string             `codec:"drive_interface"` // Use interface for image
 }
 
 // TaskState is the state which is encoded in the handle returned in StartTask.
@@ -344,6 +346,19 @@ func isAllowedImagePath(allowedPaths []string, allocDir, imagePath string) bool
 	return false
 }
 
+// hardcoded list of drive interfaces, Qemu currently supports
+var allowedDriveInterfaces = []string{"ide", "scsi", "sd", "mtd", "floppy", "pflash", "virtio", "none"}
+
+func isAllowedDriveInterface(driveInterface string) bool {
+	for _, ai := range allowedDriveInterfaces {
+		if driveInterface == ai {
+			return true
+		}
+	}
+
+	return false
+}
+
 // validateArgs ensures that all QEMU command line params are in the
 // allowlist. This function must be called after all interpolation has
 // taken place.
@@ -414,12 +429,20 @@ func (d *Driver) StartTask(cfg *drivers.TaskConfig) (*drivers.TaskHandle, *drive
 		return nil, nil, err
 	}
 
+	driveInterface := "ide"
+	if driverConfig.DriveInterface != "" {
+		driveInterface = driverConfig.DriveInterface
+	}
+	if !isAllowedDriveInterface(driveInterface) {
+		return nil, nil, fmt.Errorf("Unsupported drive_interface")
+	}
+
 	args := []string{
 		absPath,
 		"-machine", "type=pc,accel=" + accelerator,
 		"-name", vmID,
 		"-m", mem,
-		"-drive", "file=" + vmPath,
+		"-drive", "file=" + vmPath + ",if=" + driveInterface,
 		"-nographic",
 	}
 

drivers/qemu/driver_test.go

@@ -399,6 +399,7 @@ func TestConfig_ParseAllHCL(t *testing.T) {
 	cfgStr := `
 config {
   image_path = "/tmp/image_path"
+  drive_interface = "virtio"
   accelerator = "kvm"
   args = ["arg1", "arg2"]
   port_map {
@@ -409,9 +410,10 @@ config {
 }`
 
 	expected := &TaskConfig{
-		ImagePath:   "/tmp/image_path",
-		Accelerator: "kvm",
-		Args:        []string{"arg1", "arg2"},
+		ImagePath:      "/tmp/image_path",
+		DriveInterface: "virtio",
+		Accelerator:    "kvm",
+		Args:           []string{"arg1", "arg2"},
 		PortMap: map[string]int{
 			"http":  80,
 			"https": 443,
@@ -425,6 +427,19 @@ config {
 	require.EqualValues(t, expected, tc)
 }
 
+func TestIsAllowedDriveInterface(t *testing.T) {
+	validInterfaces := []string{"ide", "scsi", "sd", "mtd", "floppy", "pflash", "virtio", "none"}
+	invalidInterfaces := []string{"foo", "virtio-foo"}
+
+	for _, i := range validInterfaces {
+		require.Truef(t, isAllowedDriveInterface(i), "drive_interface should be allowed: %v", i)
+	}
+
+	for _, i := range invalidInterfaces {
+		require.Falsef(t, isAllowedDriveInterface(i), "drive_interface should be not allowed: %v", i)
+	}
+}
+
 func TestIsAllowedImagePath(t *testing.T) {
 	allowedPaths := []string{"/tmp", "/opt/qemu"}
 	allocDir := "/opt/nomad/some-alloc-dir"

website/content/docs/drivers/qemu.mdx

@@ -42,6 +42,10 @@ The `qemu` driver supports the following configuration in the job spec:
   contains the image in a subfolder, the path will need to be the relative path
   (`subdir/from_archive/my.img`).
 
+- `drive_interface` - (Optional) This option defines on which type of interface
+  the drive is connected. Available types are: `ide`, `scsi`, `sd`, `mtd`,
+  `floppy`, `pflash`, `virtio` and `none`. Default is `ide`.
+
 - `accelerator` - (Optional) The type of accelerator to use in the invocation.
   If the host machine has `qemu` installed with KVM support, users can specify
   `kvm` for the `accelerator`. Default is `tcg`.