1. In else case we do not handle anything. Why do you leave it?
2. In this function do not need result variable isn't it?

You might want to fix it as below.
      if (type == GENERIC_TIMER_HYP) {
          _tvals[type] = tval;
          generic_timer_reg_write(GENERIC_TIMER_REG_HYP_TVAL, tval);
          return HVMM_STATUS_SUCCESS;
      } else {
          return HVMM_STATUS_UNSUPPORTED_FEATURE;
      }