Upload gagal di codeigniter

jadi gini master,setiap kali browse data nama file sudah ke index ke database tapi kok selalu gagal terus ke upload yah (file Ga masuk ke direktori)

ini controller

public function save()
	{
		$path = ROOT_UPLOAD_IMPORT_PATH; //C:/xampp2/htdocs/nilai/uploads/
		$config['upload_path'] = $path;
		$config['allowed_types'] = 'doc|docx|ppt|pptx|pdf';
		$config['remove_spaces'] = TRUE;
		$this->upload->initialize($config);

		$this->load->library('upload', $config);
		if (!$this->upload->do_upload('cv_file')) {
			$error = $this->upload->display_errors();

			print_r($error);
		} else {
			$result = $this->upload->data();
			echo "";
			print_r($result);
			echo "</pre>";
		}

		redirect(site_url('admin/nilai/pegawai'));
	}

ini view nya
<form action="<?php echo site_url('admin/nilai/pegawai/save'); ?>" method="post">
				<div class="modal-body">
					<div class="form-group">
						<label>CV</label>
						<input type="file" class="form-control" id="userfile" name="cv_file" required>
					</div>
				</div>
				<div class="modal-footer">
					<button type="submit" class="btn btn-sign" id="btn-sign" name="importfile">Simpan</button>
				</div>
			</form>

terimakasih master, mohon bimbingannya. pclapclapclapclpa