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update tutorials with Using RT-Linux for real-time UOS Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
127 lines
4.6 KiB
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127 lines
4.6 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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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 the keyword
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"NVME Support" 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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