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Add a caption to the figure describing the Real-Time Linux VM running on ACRN. Without this text, the HTML output does not add the Figure number below it. That figure number is still used in the paragraph making it hard for the reader to understand which figure is really referenced (except by clicking on the hyperlink) Signed-off-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>
129 lines
4.7 KiB
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129 lines
4.7 KiB
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.. _rt_linux_setup:
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Using PREEMPT_RT-Linux for real-time UOS
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########################################
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The ACRN project uses various techniques to support a User OS (UOS)
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runing as virtual machine (VM) with real-time characteristics, also
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called a "Privileged VM" in ACRN terminology. Some of these techniques
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include device passthrough and cache allocation technology (CAT), as
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shown in :numref:`rt-linux-arch`.
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To benefit from these techniques,
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the OS running in the VM should also
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behave as a real-time system. In this tutorial, we explain how to run a
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Privileged VM based on a modified Clear Linux* OS using PREEMPT_RT
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real-time kernel patches from the `Real-Time Linux collaborative project
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<https://wiki.linuxfoundation.org/realtime/start>`_.
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The PREEMPT_RT patch add preemption models to the mainline
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Linux kernel. The "Fully Preemptible Kernel" model is the one that
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turns Linux into an RTOS, allowing the system to react to an external
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event such as an interrupt within a defined time frame.
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.. figure:: images/RT-NUC-setup.png
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:align: center
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:width: 400px
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:name: rt-linux-arch
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Real-Time Linux (PREEMPT_RT) VM on ACRN
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The privileged VM exclusively owns its passthrough devices, so in
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addition to the controller and file system used by the SOS, a dedicated
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storage controller and device are needed to host the privileged VM's
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root filesystem. The two storage devices should be under different PCI
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controllers because the system can only pass through PCI-based devices
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to a guest OS. The Intel NUC7ixDNHE NUC (KBL) is a good platform to set
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up a real-time system because it has both an NVMe and a SATA controller.
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You will need both NVMe and SATA storage devices in order to proceed.
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The following procedures show an example for setting up a real-time
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system on Intel KBL NUC with a SATA SSD as ``/dev/sda`` and an NVME SSD as
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``/dev/nvme0n1p``.
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1. Follow the :ref:`set-up-CL` instructions in the
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:ref:`getting-started-apl-nuc` to:
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a. Install ClearLinux (version 26800 or higher) onto the NVMe
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#. Install ClearLinux (version 26800 or higher) onto the SATA SSD
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#. Set up ClearLinux on the SATA SSD as the Service OS (SOS) following
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the :ref:`add-acrn-to-efi` instructions in the same guide.
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#. Patch and build the Real-Time kernel
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a. Download Linux kernel real-time patch::
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$ wget https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/4.19/patch-4.19.15-rt12.patch.xz
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#. Sync the kernel code to acrn-2019w04.5-150000p::
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$ git clone https://github.com/projectacrn/acrn-kernel.git
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$ git checkout acrn-2019w04.5-150000p
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$ cd acrn-kernel
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$ xzcat ../patch-4.19.15-rt12.patch.xz | patch -p1
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.. note:: This patch will report one conflict with ``base.c`` that
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you can ignore.
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#. Edit the ``kernel_config_uos`` config file: search for the keyword
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"NVME Support", delete ``# CONFIG_BLK_DEV_NVME is not set`` and add two lines under "NVME Support" to enable
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the NVME driver in RT kernel::
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CONFIG_NVME_CORE=y
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CONFIG_BLK_DEV_NVME=y
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#. Build the RT kernel::
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$ cp kernel_config_uos .config
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$ make targz-pkg
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Choose "Fully Preemptible Kernel (RT)" when prompted, and
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choose default for all the other options.
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#. Copy the generated package to SOS::
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$ scp linux-4.19.8-rt6+-x86.tar.gz <user name>@<SOS ip>:~/
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#. Configure the system on SOS
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a. Extract kernel boot and lib modules from the package::
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$ cd ~/
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$ tar xzvf linux-4.19.8-rt6+-x86.tar.gz
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#. Copy the extracted lib modules to NVME SSD::
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$ mount /dev/nvme0n1p3 /mnt
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$ cp -r ~/lib/modules/4.19.8-rt6+ /mnt/lib/modules
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#. Edit and run the ``launch_hard_rt_vm.sh`` script to launch the UOS.
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A sample ``launch_hard_rt_vm.sh`` is included in the Clear Linux
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release, and is also available in the acrn-hypervisor/devicemodel
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GitHub repo (in the samples folder).
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You'll need to modify two places:
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1. Replace ``/root/rt_uos_kernel`` with ``~/boot/vmlinuz-4.19.8-rt6+``
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#. Replace ``root=/dev/sda3`` with ``root=/dev/nvme0n1p3``
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#. Run the launch script::
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$ sudo ./launch_hard_rt_vm.sh
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#. At this point, you've successfully launched the real-time VM and
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Guest OS. You can verify a preemptible kernel was loaded using
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the ``uname -a`` command:
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.. code-block:: console
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root@rtvm-02 ~ # uname -a
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Linux rtvm-02 4.19.8-rt6+ #1 SMP PREEMPT RT Tue Jan 22 04:17:40 UTC 2019 x86_64 GNU/Linux
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#. Now you can run all kinds of performance tools to experience real-time
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performance. One popular tool is ``cyclictest``. You can install this
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tool and run it with::
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swupd bundle-add dev-utils
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cyclictest -N -p80 -D300
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