.. _enable-s5:

Enable S5 in ACRN
#################

Introduction
************

S5 is one of the `ACPI sleep states <http://acpi.sourceforge.net/documentation/sleep.html>`_
that refers to the system being shut down (although some power may still be
supplied to certain devices). In this document, S5 means the function to
shut down the **User VMs**, **Service VM**, the hypervisor, and the
hardware. In most cases, directly powering off a computer
system is not advisable because it can damage some components. It can cause
corruption and put the system in an unknown or unstable state. On ACRN, the
User VM must be shut down before powering off the Service VM. Especially for
some use cases, where User VMs could be used in industrial control or other
high safety requirement environment, a graceful system shutdown such as the
ACRN S5 function is required.

S5 Architecture
***************

ACRN provides a mechanism to trigger the S5 state transition throughout the
system. It uses a vUART channel to communicate between the Service VM and User
VMs. The diagram below shows the overall architecture:

.. figure:: images/s5_overall_architecture.png
   :align: center
   :name: s5-architecture

   S5 Overall Architecture

**vUART channel**:

The User VM's serial port device (``/dev/ttySn``) is emulated in the
hypervisor. The channel from the Service VM to the User VM:

.. graphviz:: images/s5-scenario-2.dot
   :name: s5-scenario-2

Lifecycle Manager Overview
==========================

As part of the S5 reference design, a Lifecycle Manager daemon (``life_mngr`` in
Linux, ``life_mngr_win.exe`` in Windows) runs in the Service VM and User VMs to
implement S5. You can use the ``s5_trigger_linux.py`` or
``s5_trigger_win.py`` script to initialize a system S5 in the Service VM or User
VMs. The Lifecycle Manager in the Service VM and User VMs wait for the system S5
request on the local socket port.

Initiate a System S5 from within a User VM (e.g., HMI)
======================================================

As shown in :numref:`s5-architecture`, a request to the Service VM initiates the
shutdown flow. This request could come from a User VM, most likely the human
machine interface (HMI) running Windows or Linux. When a human operator
initiates the flow by running ``s5_trigger_linux.py`` or ``s5_trigger_win.py``,
the Lifecycle Manager (``life_mngr``) running in that User VM sends the system
S5 request via the vUART to the Lifecycle Manager in the Service VM which in
turn acknowledges the request. The Lifecycle Manager in the Service VM sends a
``poweroff_cmd`` request to each User VM. When the Lifecycle Manager in a User
VM receives the ``poweroff_cmd`` request, it sends ``ack_poweroff`` to the
Service VM; then it shuts down the User VM. If a User VM is not ready to shut
down, it can ignore the ``poweroff_cmd`` request.

.. note:: The User VM needs to be authorized to be able to request a system S5.
   This is achieved by configuring  ``ALLOW_TRIGGER_S5`` in the Lifecycle
   Manager service configuration :file:`/etc/life_mngr.conf` in the Service VM.
   Only one User VM in the system can be configured to request a shutdown. If
   this configuration is wrong, the Lifecycle Manager of the Service VM rejects
   the system S5 request from the User VM. The following error message is
   recorded in the Lifecycle Manager log :file:`/var/log/life_mngr.log` of the
   Service VM: ``The user VM is not allowed to trigger system shutdown``.

Initiate a System S5 within the Service VM
==========================================

On the Service VM side, it uses the ``s5_trigger_linux.py`` to trigger the
system S5 flow. Then, the Lifecycle Manager in the Service VM sends a
``poweroff_cmd`` request to the Lifecycle Manager in each User VM through the
vUART channel. When the User VM receives this request, it sends an
``ack_poweroff`` to the Lifecycle Manager in the Service VM. The Service VM
checks whether the User VMs shut down successfully or not, and decides when to
shut itself down.

.. note:: The Service VM is always allowed to trigger system S5 by default.

.. _enable_s5:

Enable S5
*********

1. Configure communication vUARTs for the Service VM and User VMs:

   Add these lines in the hypervisor scenario XML file manually:

   Example::

      /* VM0 */
      <vm_type>SERVICE_VM</vm_type>
      ...
      <legacy_vuart id="1">
         <type>VUART_LEGACY_PIO</type>
         <base>CONFIG_COM_BASE</base>
         <irq>0</irq>
         <target_vm_id>1</target_vm_id>
         <target_uart_id>1</target_uart_id>
      </legacy_vuart>
      <legacy_vuart id="2">
        <type>VUART_LEGACY_PIO</type>
        <base>CONFIG_COM_BASE</base>
        <irq>0</irq>
        <target_vm_id>2</target_vm_id>
        <target_uart_id>2</target_uart_id>
      </legacy_vuart>
      ...
      /* VM1 */
      <vm_type>POST_STD_VM</vm_type>
      ...
      <legacy_vuart id="1">
         <type>VUART_LEGACY_PIO</type>
         <base>COM2_BASE</base>
         <irq>COM2_IRQ</irq>
         <target_vm_id>0</target_vm_id>
         <target_uart_id>1</target_uart_id>
      </legacy_vuart>
      ...
      /* VM2 */
      <vm_type>POST_STD_VM</vm_type>
      ...
      <legacy_vuart id="1">
         <type>VUART_LEGACY_PIO</type>
         <base>INVALID_COM_BASE</base>
         <irq>COM2_IRQ</irq>
         <target_vm_id>0</target_vm_id>
         <target_uart_id>2</target_uart_id>
      </legacy_vuart>
      <legacy_vuart id="2">
         <type>VUART_LEGACY_PIO</type>
         <base>COM2_BASE</base>
         <irq>COM2_IRQ</irq>
         <target_vm_id>0</target_vm_id>
         <target_uart_id>2</target_uart_id>
      </legacy_vuart>
      ...
      /* VM3 */
      ...

   .. note:: These vUARTs are emulated in the hypervisor; expose the node as
      ``/dev/ttySn``. For the User VM with the lowest VM ID, the communication
      vUART id should be 1. For other User VMs, the vUART (id is 1) should be
      configured as invalid; the communication vUART id should be 2 or higher.

2. Build the Lifecycle Manager daemon, ``life_mngr``:

   .. code-block:: none

      cd acrn-hypervisor
      make life_mngr

#. For the Service VM, LaaG VM, and RT-Linux VM, run the Lifecycle Manager
   daemon:

   a. Copy ``life_mngr.conf``, ``s5_trigger_linux.py``, ``life_mngr``,
      and ``life_mngr.service`` into the Service VM and User VMs. These commands
      assume you have a network connection between the development computer and
      target. You can also use a USB stick to transfer files.

      .. code-block:: none

         scp build/misc/services/s5_trigger_linux.py root@<target board address>:~/
         scp build/misc/services/life_mngr root@<target board address>:/usr/bin/
         scp build/misc/services/life_mngr.conf root@<target board address>:/etc/life_mngr/
         scp build/misc/services/life_mngr.service root@<target board address>:/lib/systemd/system/

   #. Copy ``user_vm_shutdown.py`` into the Service VM.

      .. code-block:: none

         scp misc/services/life_mngr/user_vm_shutdown.py root@<target board address>:~/

   #. Edit options in ``/etc/life_mngr/life_mngr.conf`` in the Service VM.

      .. code-block:: none

         VM_TYPE=service_vm
         VM_NAME=Service_VM
         DEV_NAME=tty:/dev/ttyS8,/dev/ttyS9,/dev/ttyS10,/dev/ttyS11,/dev/ttyS12,/dev/ttyS13,/dev/ttyS14
         ALLOW_TRIGGER_S5=/dev/ttySn

      .. note:: The mapping between User VM ID and communication serial device
         name (``/dev/ttySn``) is in the :file:`/etc/serial.conf`. If
         ``/dev/ttySn`` is configured in the  ``ALLOW_TRIGGER_S5``, this means
         system shutdown is allowed to be triggered in the corresponding User
         VM.

   #. Edit options in ``/etc/life_mngr/life_mngr.conf`` in the User VM.

      .. code-block:: none

         VM_TYPE=user_vm
         VM_NAME=<User VM name>
         DEV_NAME=tty:/dev/ttyS1
         #ALLOW_TRIGGER_S5=/dev/ttySn

      .. note:: The User VM name in this configuration file should be
         consistent with the VM name in the launch script for the Post-launched
         User VM or the VM name which is specified in the hypervisor scenario
         XML for the Pre-launched User VM.

   #. Use the following commands to enable ``life_mngr.service`` and restart the Service VM and User VMs.

      .. code-block:: none

         sudo chmod +x /usr/bin/life_mngr
         sudo systemctl enable life_mngr.service
         sudo reboot

      .. note:: For the Pre-launched User VM, restart the Lifecycle Manager
         service manually after the Lifecycle Manager in the Service VM starts.

#. For the WaaG VM, run the Lifecycle Manager daemon:

   a. Build the ``life_mngr_win.exe`` application and ``s5_trigger_win.py``::

        cd acrn-hypervisor
        make life_mngr

      .. note:: If there is no ``x86_64-w64-mingw32-gcc`` compiler, you can run
               ``sudo apt install gcc-mingw-w64-x86-64`` on Ubuntu to install it.

   #. Copy ``s5_trigger_win.py`` into the WaaG VM.

   #. Set up a Windows environment:

      1. Download the Python3 from `<https://www.python.org/downloads/release/python-3810/>`_, install
         "Python 3.8.10" in WaaG.

      #. If the Lifecycle Manager for WaaG will be built in Windows,
         download the Visual Studio 2019 tool from
         `<https://visualstudio.microsoft.com/downloads/>`_, and choose the two
         options in the below screenshots to install "Microsoft Visual C++
         Redistributable for Visual Studio 2015, 2017 and 2019 (x86 or X64)" in
         WaaG:

         .. figure:: images/Microsoft-Visual-C-install-option-1.png

         .. figure:: images/Microsoft-Visual-C-install-option-2.png

         .. note:: If the Lifecycle Manager for WaaG is built in Linux, the
            Visual Studio 2019 tool is not needed for WaaG.

      #. In WaaG, use the :kbd:`Windows` + :kbd:`R` shortcut key, input
         ``shell:startup``, click :kbd:`OK` and then copy the
         ``life_mngr_win.exe`` application into this directory.

         .. figure:: images/run-shell-startup.png

         .. figure:: images/launch-startup.png

   #. Restart the WaaG VM. The COM2 window will automatically open after reboot.

      .. figure:: images/open-com-success.png

#. If ``s5_trigger_linux.py`` is run in the Service VM, the Service VM shuts
   down (transitioning to the S5 state) and sends a poweroff request to shut down the User VMs.

   .. note:: S5 state is not automatically triggered by a Service VM shutdown;
      you need to run ``s5_trigger_linux.py`` in the Service VM.

How to Test
***********

As described in :ref:`vuart_config`, two vUARTs are defined for a User VM in
pre-defined ACRN scenarios: ``vUART0/ttyS0`` for the console and
``vUART1/ttyS1`` for S5-related communication (as shown in
:ref:`s5-architecture`).

For Yocto Project (Poky) or Ubuntu rootfs, the ``serial-getty``
service for ``ttyS1`` conflicts with the S5-related communication
use of ``vUART1``. We can eliminate the conflict by preventing
that service from being started
either automatically or manually, by masking the service
using this command:

::

   systemctl mask serial-getty@ttyS1.service

#. Refer to the :ref:`enable_s5` section to set up the S5 environment for the
   User VMs.

   .. note:: Use the ``systemctl status life_mngr.service`` command to ensure
      the service is working on the LaaG or RT-Linux:

      .. code-block:: console

         * life_mngr.service - ACRN lifemngr daemon
         Loaded: loaded (/lib/systemd/system/life_mngr.service; enabled; vendor preset: enabled)
         Active: active (running) since Thu 2021-11-11 12:43:53 CST; 36s ago
         Main PID: 197397 (life_mngr)

   .. note:: For WaaG, you need to close ``windbg`` by using the
      ``bcdedit /set debug off`` command IF you executed the ``bcdedit /set
      debug on`` command when you set up the WaaG, because it occupies the
      ``COM2``.

#. Run ``user_vm_shutdown.py`` in the Service VM to shut down the User VMs:

   .. code-block:: none

      sudo python3 ~/user_vm_shutdown.py <User VM name>

   .. note:: The User VM name is configured in the :file:`life_mngr.conf` of
      the User VM. For the WaaG VM, the User VM name is "windows".

#. Run the ``acrnctl list`` command to check the User VM status.

   .. code-block:: none

      sudo acrnctl list

   Output example:

   .. code-block:: console

      <User VM name>		stopped

System Shutdown
***************

Using a coordinating script, ``s5_trigger_linux.py`` or ``s5_trigger_win.py``,
in conjunction with the Lifecycle Manager in each VM, graceful system shutdown
can be performed.

In the ``hybrid_rt`` scenario, operator can use the script to send a system
shutdown request via ``/var/lib/life_mngr/monitor.sock`` to a User VM that is
configured to be allowed to trigger system S5. This system shutdown request is
forwarded to the Service VM. The Service VM sends a poweroff request to each
User VM (Pre-launched VM or Post-launched VM) through vUART. The Lifecycle
Manager in the User VM receives the poweroff request, sends an ack message, and
proceeds to shut itself down accordingly.

.. figure:: images/system_shutdown.png
   :align: center

   Graceful System Shutdown Flow

#. The HMI in the Windows User VM uses ``s5_trigger_win.py`` to send a
   system shutdown request to the Lifecycle Manager. The Lifecycle Manager
   forwards this request to the Lifecycle Manager in the Service VM.
#. The Lifecycle Manager in the Service VM responds with an ack message and
   sends a ``poweroff_cmd`` request to the Windows User VM.
#. After receiving the ``poweroff_cmd`` request, the Lifecycle Manager in the 
   Windows User VM responds with an ack message, then shuts down the VM.
#. The Lifecycle Manager in the Service VM sends a ``poweroff_cmd`` request to
   the Linux User VM.
#. After receiving the ``poweroff_cmd`` request, the Lifecycle Manager in the
   Linux User VM responds with an ack message, then shuts down the VM.
#. The Lifecycle Manager in the Service VM sends a ``poweroff_cmd`` request to
   the Pre-launched RTVM.
#. After receiving the ``poweroff_cmd`` request, the Lifecycle Manager in
   the Pre-launched RTVM responds with an ack message.
#. The Lifecycle Manager in the Pre-launched RTVM shuts down the VM using
   ACPI PM registers.
#. After receiving the ack message from all User VMs, the Lifecycle Manager
   in the Service VM shuts down the VM.
#. The hypervisor shuts down the system after all VMs have shut down.

.. note:: If one or more virtual functions (VFs) of a SR-IOV device, e.g., GPU
   on Alder Lake platform, are assigned to User VMs, take extra steps to disable
   all VFs before the Service VM shuts down. Otherwise, the Service VM may fail
   to shut down due to some enabled VFs.