.. _vuart_config: Enable vUART Configurations ########################### Introduction ============ The virtual universal asynchronous receiver/transmitter (vUART) supports two functions: one is the console, the other is communication. vUART only works on a single function. Only two vUART configurations are added to the predefined scenarios, but you can customize the scenarios to enable more using the :ref:`ACRN configurator tool `. Console Enable List =================== +-----------------+-----------------------+--------------------+----------------+----------------+ | Scenarios | vm0 | vm1 | vm2 | vm3 | +=================+=======================+====================+================+================+ | SDC | Service VM | Post-launched | Post-launched | | | | (vUART enable) | | | | +-----------------+-----------------------+--------------------+----------------+----------------+ | Hybrid | Pre-launched (Zephyr) | Service VM | Post-launched | | | | (vUART enable) | (vUART enable) | | | +-----------------+-----------------------+--------------------+----------------+----------------+ | Industry | Service VM | Post-launched | Post-launched | Post-launched | | | (vUART enable) | | (vUART enable) | | +-----------------+-----------------------+--------------------+----------------+----------------+ | Logic_partition | Pre-launched | Pre-launched RTVM | Post-launched | | | | (vUART enable) | (vUART enable) | RTVM | | +-----------------+-----------------------+--------------------+----------------+----------------+ .. _how-to-configure-a-console-port: How to Configure a Console Port =============================== To enable the console port for a VM, change only the ``port_base`` and ``irq``. If the IRQ number is already in use in your system (``cat /proc/interrupt``), choose another IRQ number. If you set the ``.irq =0``, the vUART will work in polling mode. - ``COM1_BASE (0x3F8) + COM1_IRQ(4)`` - ``COM2_BASE (0x2F8) + COM2_IRQ(3)`` - ``COM3_BASE (0x3E8) + COM3_IRQ(6)`` - ``COM4_BASE (0x2E8) + COM4_IRQ(7)`` Example: .. code-block:: none .vuart[0] = { .type = VUART_LEGACY_PIO, .addr.port_base = COM1_BASE, .irq = COM1_IRQ, }, .. _how-to-configure-a-communication-port: How to Configure a Communication Port ===================================== To enable the communication port, configure ``vuart[1]`` in the two VMs that want to communicate. The port_base and IRQ should differ from the ``vuart[0]`` in the same VM. ``t_vuart.vm_id`` is the target VM's vm_id, start from 0. (0 means VM0) ``t_vuart.vuart_id`` is the target vUART index in the target VM. Start from ``1``. (``1`` means ``vuart[1]``) Example: .. code-block:: none /* VM0 */ ... /* VM1 */ .vuart[1] = { .type = VUART_LEGACY_PIO, .addr.port_base = COM2_BASE, .irq = COM2_IRQ, .t_vuart.vm_id = 2U, .t_vuart.vuart_id = 1U, }, ... /* VM2 */ .vuart[1] = { .type = VUART_LEGACY_PIO, .addr.port_base = COM2_BASE, .irq = COM2_IRQ, .t_vuart.vm_id = 1U, .t_vuart.vuart_id = 1U, }, Communication vUART Enable List =============================== +-----------------+-----------------------+--------------------+---------------------+----------------+ | Scenarios | vm0 | vm1 | vm2 | vm3 | +=================+=======================+====================+=====================+================+ | SDC | Service VM | Post-launched | Post-launched | | +-----------------+-----------------------+--------------------+---------------------+----------------+ | Hybrid | Pre-launched (Zephyr) | Service VM | Post-launched | | | | (vUART enable COM2) | (vUART enable COM2)| | | +-----------------+-----------------------+--------------------+---------------------+----------------+ | Industry | Service VM | Post-launched | Post-launched RTVM | Post-launched | | | (vUART enable COM2) | | (vUART enable COM2) | | +-----------------+-----------------------+--------------------+---------------------+----------------+ | Logic_partition | Pre-launched | Pre-launched RTVM | | | +-----------------+-----------------------+--------------------+---------------------+----------------+ Launch Script ============= - ``-s 1:0,lpc -l com1,stdio`` This option is only needed for WaaG and VxWorks (and also when using OVMF). They depend on the ACPI table, and only ``acrn-dm`` can provide the ACPI table for UART. - ``-B " ....,console=ttyS0, ..."`` Add this to the kernel-based system. Test the Communication Port =========================== After you have configured the communication port in hypervisor, you can access the corresponding port. For example, in Linux OS: 1. With ``echo`` and ``cat`` On VM1: ``# cat /dev/ttyS1`` On VM2: ``# echo "test test" > /dev/ttyS1`` You can find the message from VM1 ``/dev/ttyS1``. If you are not sure which one is the communication port, you can run ``dmesg | grep ttyS`` under the Linux shell to check the base address. If it matches what you have set in the ``vm_configuration.c`` file, it is the correct port. #. With Minicom Run ``minicom -D /dev/ttyS1`` on both VM1 and VM2 and enter ``test`` in VM1's Minicom. The message should appear in VM2's Minicom. Disable flow control in Minicom. #. Limitations - The msg cannot be longer than 256 bytes. - This cannot be used to transfer files because flow control is not supported so data may be lost. vUART Design ============ **Console vUART** .. figure:: images/vuart-config-1.png :align: center :name: console-vuart **Communication vUART (between VM0 and VM1)** .. figure:: images/vuart-config-2.png :align: center :name: communication-vuart COM Port Configurations for Post-Launched VMs ============================================= For a post-launched VM, the ``acrn-dm`` cmdline also provides a COM port configuration: ``-s 1:0,lpc -l com1,stdio`` This adds ``com1 (0x3f8)`` and ``com2 (0x2f8)`` modules in the Guest VM, including the ACPI info for these two ports. **Data Flows** Three different data flows exist based on how the post-launched VM is started, as shown in the diagram below: * Figure 1 data flow: The post-launched VM is started with the vUART enabled in the hypervisor configuration file only. * Figure 2 data flow: The post-launched VM is started with the ``acrn-dm`` cmdline of ``-s 1:0,lpc -l com1,stdio`` only. * Figure 3 data flow: The post-launched VM is started with both vUART enabled and the ``acrn-dm`` cmdline of ``-s 1:0,lpc -l com1,stdio``. .. figure:: images/vuart-config-post-launch.png :align: center :name: Post-Launched VMs .. note:: For operating systems such as VxWorks and Windows that depend on the ACPI table to probe the UART driver, adding the vUART configuration in the hypervisor is not sufficient. We recommend that you use the configuration in the figure 3 data flow. This may be refined in the future. Use PCI-vUART ############# PCI Interface of ACRN vUART =========================== When you set :ref:`vuart[0] and vuart[1] `, the ACRN hypervisor emulates virtual legacy serial devices (I/O port and IRQ) for VMs. So ``vuart[0]`` and ``vuart[1]`` are legacy vUARTs. ACRN hypervisor can also emulate virtual PCI serial devices (BDF, MMIO registers and MSIX capability). These virtual PCI serial devices are called PCI-vUART, and have an advantage in device enumeration for the guest OS. It is easy to add new PCI-vUART ports to a VM. .. _index-of-vuart: Index of vUART ============== ACRN hypervisor supports PCI-vUARTs and legacy vUARTs as ACRN vUARTs. Each vUART port has its own ``vuart_idx``. ACRN hypervisor supports up to 8 vUART for each VM, from ``vuart_idx=0`` to ``vuart_idx=7``. Suppose we use vUART0 for a port with ``vuart_idx=0``, vUART1 for ``vuart_idx=1``, and so on. Pay attention to these points: * vUART0 is the console port, vUART1-vUART7 are inter-VM communication ports. * Each communication port must set the connection to another communication vUART port of another VM. * When legacy ``vuart[0]`` is available, it is vUART0. A PCI-vUART can't be vUART0 unless ``vuart[0]`` is not set. * When legacy ``vuart[1]`` is available, it is vUART1. PCI-vUART can't be vUART1 unless ``vuart[1]`` is not set. Setup ACRN vUART Using Configuration Tools ========================================== When you set up ACRN VM configurations with PCI-vUART, it is better to use the ACRN configuration tools because of all the PCI resources required: BDF number, address and size of mmio registers, and address and size of MSIX entry tables. These settings can't conflict with another PCI device. Furthermore, whether PCI-vUART can use ``vuart_idx=0`` and ``vuart_idx=1`` depends on legacy vUART settings. Configuration tools will override your settings in :ref:`How to Configure a Console Port ` and :ref:`How to Configure a Communication Port `. You can configure both Legacy vUART and PCI-vUART in :ref:`scenario configurations `. For example, if VM0 has a legacy vUART0 and a PCI-vUART1, VM1 has no legacy vUART but has a PCI-vUART0 and a PCI-vUART1, VM0's PCI-vUART1 and VM1's PCI-vUART1 are connected to each other. You should configure then like this: .. code-block:: none VUART_LEGACY_PIO /* vuart[0] is console port */ COM1_BASE /* vuart[0] is used */ COM1_IRQ VUART_LEGACY_PIO INVALID_COM_BASE /* vuart[1] is not used */ INVALID_PCI_BASE /* PCI-vUART0 can't be used, because vuart[0] */ PCI_VUART /* PCI-vUART1 is communication port, connect to vUART1 of VM1 */ 1 1 VUART_LEGACY_PIO INVALID_COM_BASE /* vuart[0] is not used */ VUART_LEGACY_PIO INVALID_COM_BASE /* vuart[1] is not used */ PCI_VUART /* PCI-vUART0 is console port */ PCI_VUART /* PCI-vUART1 is communication port, connect to vUART1 of VM0 */ 0 1 The ACRN vUART related XML fields: - ``id`` in ````, value of ``vuart_idx``, ``id=0`` is for legacy ``vuart[0]`` configuration, ``id=1`` is for ``vuart[1]``. - ``type`` in ````, type is always ``VUART_LEGACY_PIO`` for legacy vUART. - ``base`` in ````, if using the legacy vUART port, set COM1_BASE for ``vuart[0]``, set ``COM2_BASE`` for ``vuart[1]``. ``INVALID_COM_BASE`` means do not use the legacy vUART port. - ``irq`` in ````, if you use the legacy vUART port, set ``COM1_IRQ`` for ``vuart[0]``, set ``COM2_IRQ`` for ``vuart[1]``. - ``id`` in ```` and ````, ``vuart_idx`` for PCI-vUART - ``base`` in ```` and ````, ``PCI_VUART`` means use this PCI-vUART, ``INVALID_PCI_BASE`` means do not use this PCI-VUART. - ``target_vm_id`` and ``target_uart_id``, connection settings for this vUART port. Run the command to build ACRN with this XML configuration file:: make BOARD= SCENARIO= The configuration tools will test your settings, and check :ref:`vUART Rules ` for compilation issue. After compiling, you can find the generated sources under ``build/hypervisor/configs/scenarios//pci_dev.c``, based on the XML settings, something like: .. code-block:: none struct acrn_vm_pci_dev_config vm0_pci_devs[] = { { .emu_type = PCI_DEV_TYPE_HVEMUL, .vbdf.bits = {.b = 0x00U, .d = 0x05U, .f = 0x00U}, .vdev_ops = &vmcs9900_ops, .vbar_base[0] = 0x80003000, .vbar_base[1] = 0x80004000, .vuart_idx = 1, /* PCI-vUART1 of VM0 */ .t_vuart.vm_id = 1U, /* connected to VM1's vUART1 */ .t_vuart.vuart_id = 1U, }, } This struct shows a PCI-vUART with ``vuart_idx=1``, ``BDF 00:05.0``, it's a PCI-vUART1 of VM0, and it is connected to VM1's vUART1 port. When VM0 wants to communicate with VM1, it can use ``/dev/ttyS*``, the character device file of VM0's PCI-vUART1. Usually, legacy ``vuart[0]`` is ``ttyS0`` in VM, and ``vuart[1]`` is ``ttyS1``. So we hope PCI-vUART0 is ``ttyS0``, PCI-VUART1 is ``ttyS1`` and so on through PCI-vUART7 is ``ttyS7``, but that is not true. We can use BDF to identify PCI-vUART in VM. If you run ``dmesg | grep tty`` at a VM shell, you may see: .. code-block:: none [ 1.276891] 0000:00:05.0: ttyS4 at MMIO 0xa1414000 (irq = 124, base_baud = 115200) is a 16550A We know for VM0 guest OS, ``ttyS4`` has BDF 00:05.0 and is PCI-vUART1. VM0 can communicate with VM1 by reading from or writing to ``/dev/ttyS4``. If VM0 and VM1 are pre-launched VMs, or Service VM, ACRN hypervisor will create PCI-vUART virtual devices automatically. For post-launched VMs, created by ``acrn-dm``, an additional ``acrn-dm`` option is needed to create a PCI-vUART virtual device: .. code-block:: none -s ,uart,vuart_idx: Kernel Config for Legacy vUART ============================== When ACRN hypervisor passthroughs a local APIC to a VM, there is IRQ injection issue for legacy vUART. The kernel driver must work in polling mode to avoid the problem. The VM kernel should have these config symbols set: .. code-block:: none CONFIG_SERIAL_8250_EXTENDED=y CONFIG_SERIAL_8250_DETECT_IRQ=y Kernel Cmdline for PCI-vUART Console ==================================== When an ACRN VM does not have a legacy ``vuart[0]`` but has a PCI-vUART0, you can use PCI-vUART0 for VM serial input/output. Check which TTY has the BDF of PCI-vUART0; usually it is not ``/dev/ttyS0``. For example, if ``/dev/ttyS4`` is PCI-vUART0, you must set ``console=/dev/ttyS4`` in the kernel cmdline.