Enable S5 in ACRN

Introduction

S5 is one of the ACPI sleep states 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, the Service VM, the hypervisor, and the hardware. In most cases, directly shutting down the power of 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 and User VMs. The diagram below shows the overall architecture:

../_images/s5_overall_architecture.png

Figure 73 S5 overall architecture

  • Scenario I:

    The User VM’s serial port device (ttySn) is emulated in the Device Model, the channel from the Service VM to the User VM:

    digraph G {
   node [shape=plaintext fontsize=12];
   graph [rankdir=LR];

   subgraph cluster_0 {
        node [shape=box];
        label="PTY"
        "Master" -> "Slave" [dir=both arrowsize=.5];
    }

   "ACRN-DM" -> "Master" [arrowsize=.5];
   "Slave" -> "User VM:/dev/ttyS1" [arrowsize=.5];

}
  • Scenario II:

    The User VM’s (like RT-Linux or other RT-VMs) serial port device (ttySn) is emulated in the Hypervisor, the channel from the Service OS to the User VM:

    digraph G {
   node [shape=plaintext fontsize=12];
   rankdir=LR;
   bgcolor="transparent";
   "ACRN-DM" -> "Service VM:/dev/ttyS1" -> "ACRN hypervisor" -> "User VM:/dev/ttyS1" [arrowsize=.5];
}

Trigger the User VM’s S5

On the Service VM side, it uses the acrnctl tool to trigger the User VM’s S5 flow: acrnctl stop user-vm-name. Then, the Device Model sends a shutdown command to the User VM through a channel. If the User VM receives the command, it will send an “ACK” to the Device Model. It is the Service VM’s responsibility to check if the User VMs shutdown successfully or not, and decides when to power off itself.

User VM “life-cycle manager”

As part of the current S5 reference design, a life-cycle manager daemon (life_mngr) runs in the User VM to implement S5. It waits for the command from the Service VM on the paired serial port. The simple protocol between the Service VM and User VM is as follows: When the daemon receives shutdown, it sends “acked” to the Service VM; then it can power off the User VM. If the User VM is not ready to power off, it can ignore the shutdown command.

Enable S5

The procedure for enabling S5 is specific to the particular OS:

  • For Linux (LaaG) or Windows (WaaG), refer to the following configurations in the devicemodel/samples/nuc/launch_uos.sh launch script for acrn-dm.

    Code Block 1 LaaG/WaaG launch script
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    #for pm by vuart setting
    pm_channel="--pm_notify_channel uart "
    pm_by_vuart="--pm_by_vuart pty,/run/acrn/life_mngr_"$vm_name
    pm_vuart_node=" -s 1:0,lpc -l com2,/run/acrn/life_mngr_"$vm_name
    
    #for memsize setting
    mem_size=2048M
    
    acrn-dm -A -m $mem_size -s 0:0,hostbridge \
      -s 2,pci-gvt -G "$2" \
      -s 5,virtio-console,@stdio:stdio_port \
      -s 6,virtio-hyper_dmabuf \
      -s 3,virtio-blk,/home/clear/uos/uos.img \
      -s 4,virtio-net,tap0 \
      -s 7,virtio-rnd \
      --ovmf /usr/share/acrn/bios/OVMF.fd \
      $pm_channel $pm_by_vuart $pm_vuart_node \
      $logger_setting \
      --mac_seed $mac_seed \
      $vm_name
    }
    
  • For RT-Linux, refer to the devicemodel/samples/nuc/launch_hard_rt_vm.sh script:

    Code Block 2 RT-Linux launch script
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    # for pm setting
    pm_channel="--pm_notify_channel uart "
    pm_by_vuart="--pm_by_vuart tty,/dev/ttyS1"
    
    
    /usr/bin/acrn-dm -A -m $mem_size -s 0:0,hostbridge \
       --lapic_pt \
       --rtvm \
       --virtio_poll 1000000 \
       -U 495ae2e5-2603-4d64-af76-d4bc5a8ec0e5 \
       -s 2,passthru,02/0/0 \
       -s 3,virtio-console,@stdio:stdio_port \
       $pm_channel $pm_by_vuart \
       --ovmf /usr/share/acrn/bios/OVMF.fd \
       hard_rtvm
    
    }
    

    Note

    For RT-Linux, the vUART is emulated in the hypervisor; expose the node as /dev/ttySn.

  1. For LaaG and RT-Linux VMs, run the life-cycle manager daemon:

    1. Use these commands to build the life-cycle manager daemon, life_mngr.

      $ cd acrn-hypervisor/misc/life_mngr
      $ make life_mngr
      
    2. Copy life_mngr and life_mngr.service into the User VM:

      $ scp life_mngr root@<test board address>:/usr/bin/life_mngr
      $ scp life_mngr.service root@<test board address>:/lib/systemd/system/life_mngr.service
      
    3. Use the below commands to enable life_mngr.service and restart the User VM.

      # chmod +x /usr/bin/life_mngr
      # systemctl enable life_mngr.service
      # reboot
      
  2. For the WaaG VM, run the life-cycle manager daemon:

    1. Build the life_mngr_win.exe application:

      $ cd acrn-hypervisor/misc
      $ make life_mngr
      

      Note

      If there is no x86_64-w64-mingw32-gcc compiler, you must run swupd bundle-add c-basic-mingw to install it.

    2. Set up a Windows environment:

      1. 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:

        ../_images/Microsoft-Visual-C-install-option-1.png
        ../_images/Microsoft-Visual-C-install-option-2.png
      2. In WaaG, use the WIN + R shortcut key, input “shell:startup”, click OK and then copy the life_mngr_win.exe application into this directory.

        ../_images/run-shell-startup.png
        ../_images/launch-startup.png
    3. Restart the WaaG VM. The COM2 window will automatically open after reboot.

      ../_images/open-com-success.png
  3. If the Service VM is being shut down (transitioning to the S5 state), it can call acrnctl stop vm-name to shut down the User VMs.

    Note

    S5 state is not automatically triggered by a Service VM shutdown; this needs to be run before powering off the Service VM.

How to test

Note

The CBC tools and service installed by the software-defined-cockpit bundle will conflict with the vUART and hence need to be masked.

systemctl mask cbc_attach
systemctl mask cbc_thermal_fuse
systemctl mask cbc_thermald
systemctl mask cbc_lifecycle.service

Or:

ps -ef|grep cbc; kill -9 cbc_pid
  1. Refer to the Enable S5 section to set up the S5 environment for the User VMs.

    Note

    RT-Linux’s UUID must use 495ae2e5-2603-4d64-af76-d4bc5a8ec0e5. Also, the industry EFI image is required for launching the RT-Linux VM.

    Note

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

    * life_mngr.service - ACRN lifemngr daemon
    Loaded: loaded (/usr/lib/systemd/system/life_mngr.service; enabled; vendor p>
    Active: active (running) since Tue 2019-09-10 07:15:06 UTC; 1min 11s ago
    Main PID: 840 (life_mngr)
    

    Note

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

  2. Use the``acrnctl stop`` command on the Service VM to trigger S5 to the User VMs:

    # acrnctl stop vm1
    
  3. Use the acrnctl list command to check the User VM status.

    # acrnctl list
    vm1               stopped