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+*******************************
+Using the Quick EMUlator (QEMU)
+*******************************
+
+The Yocto Project uses an implementation of the Quick EMUlator (QEMU)
+Open Source project as part of the Yocto Project development "tool set".
+This chapter provides both procedures that show you how to use the Quick
+EMUlator (QEMU) and other QEMU information helpful for development
+purposes.
+
+.. _qemu-dev-overview:
+
+Overview
+========
+
+Within the context of the Yocto Project, QEMU is an emulator and
+virtualization machine that allows you to run a complete image you have
+built using the Yocto Project as just another task on your build system.
+QEMU is useful for running and testing images and applications on
+supported Yocto Project architectures without having actual hardware.
+Among other things, the Yocto Project uses QEMU to run automated Quality
+Assurance (QA) tests on final images shipped with each release.
+
+.. note::
+
+   This implementation is not the same as QEMU in general.
+
+This section provides a brief reference for the Yocto Project
+implementation of QEMU.
+
+For official information and documentation on QEMU in general, see the
+following references:
+
+-  `QEMU Website <http://wiki.qemu.org/Main_Page>`__\ *:* The official
+   website for the QEMU Open Source project.
+
+-  `Documentation <http://wiki.qemu.org/Manual>`__\ *:* The QEMU user
+   manual.
+
+.. _qemu-running-qemu:
+
+Running QEMU
+============
+
+To use QEMU, you need to have QEMU installed and initialized as well as
+have the proper artifacts (i.e. image files and root filesystems)
+available. Follow these general steps to run QEMU:
+
+1. *Install QEMU:* QEMU is made available with the Yocto Project a
+   number of ways. One method is to install a Software Development Kit
+   (SDK). See "`The QEMU
+   Emulator <&YOCTO_DOCS_SDK_URL;#the-qemu-emulator>`__" section in the
+   Yocto Project Application Development and the Extensible Software
+   Development Kit (eSDK) manual for information on how to install QEMU.
+
+2. *Setting Up the Environment:* How you set up the QEMU environment
+   depends on how you installed QEMU:
+
+   -  If you cloned the ``poky`` repository or you downloaded and
+      unpacked a Yocto Project release tarball, you can source the build
+      environment script (i.e.
+      ````` <&YOCTO_DOCS_REF_URL;#structure-core-script>`__): $ cd
+      ~/poky $ source oe-init-build-env
+
+   -  If you installed a cross-toolchain, you can run the script that
+      initializes the toolchain. For example, the following commands run
+      the initialization script from the default ``poky_sdk`` directory:
+      . ~/poky_sdk/environment-setup-core2-64-poky-linux
+
+3. *Ensure the Artifacts are in Place:* You need to be sure you have a
+   pre-built kernel that will boot in QEMU. You also need the target
+   root filesystem for your target machine’s architecture:
+
+   -  If you have previously built an image for QEMU (e.g. ``qemux86``,
+      ``qemuarm``, and so forth), then the artifacts are in place in
+      your `Build Directory <&YOCTO_DOCS_REF_URL;#build-directory>`__.
+
+   -  If you have not built an image, you can go to the
+      `machines/qemu <&YOCTO_MACHINES_DL_URL;>`__ area and download a
+      pre-built image that matches your architecture and can be run on
+      QEMU.
+
+   See the "`Extracting the Root
+   Filesystem <&YOCTO_DOCS_SDK_URL;#sdk-extracting-the-root-filesystem>`__"
+   section in the Yocto Project Application Development and the
+   Extensible Software Development Kit (eSDK) manual for information on
+   how to extract a root filesystem.
+
+4. *Run QEMU:* The basic ``runqemu`` command syntax is as follows: $
+   runqemu [option ] [...] Based on what you provide on the command
+   line, ``runqemu`` does a good job of figuring out what you are trying
+   to do. For example, by default, QEMU looks for the most recently
+   built image according to the timestamp when it needs to look for an
+   image. Minimally, through the use of options, you must provide either
+   a machine name, a virtual machine image (``*wic.vmdk``), or a kernel
+   image (``*.bin``).
+
+   Here are some additional examples to help illustrate further QEMU:
+
+   -  This example starts QEMU with MACHINE set to "qemux86-64".
+      Assuming a standard `Build
+      Directory <&YOCTO_DOCS_REF_URL;#build-directory>`__, ``runqemu``
+      automatically finds the ``bzImage-qemux86-64.bin`` image file and
+      the ``core-image-minimal-qemux86-64-20200218002850.rootfs.ext4``
+      (assuming the current build created a ``core-image-minimal``
+      image).
+
+      .. note::
+
+         When more than one image with the same name exists, QEMU finds
+         and uses the most recently built image according to the
+         timestamp.
+
+      $ runqemu qemux86-64
+
+   -  This example produces the exact same results as the previous
+      example. This command, however, specifically provides the image
+      and root filesystem type. $ runqemu qemux86-64 core-image-minimal
+      ext4
+
+   -  This example specifies to boot an initial RAM disk image and to
+      enable audio in QEMU. For this case, ``runqemu`` set the internal
+      variable ``FSTYPE`` to "cpio.gz". Also, for audio to be enabled,
+      an appropriate driver must be installed (see the previous
+      description for the ``audio`` option for more information). $
+      runqemu qemux86-64 ramfs audio
+
+   -  This example does not provide enough information for QEMU to
+      launch. While the command does provide a root filesystem type, it
+      must also minimally provide a MACHINE, KERNEL, or VM option. $
+      runqemu ext4
+
+   -  This example specifies to boot a virtual machine image
+      (``.wic.vmdk`` file). From the ``.wic.vmdk``, ``runqemu``
+      determines the QEMU architecture (MACHINE) to be "qemux86-64" and
+      the root filesystem type to be "vmdk". $ runqemu
+      /home/scott-lenovo/vm/core-image-minimal-qemux86-64.wic.vmdk
+
+Switching Between Consoles
+==========================
+
+When booting or running QEMU, you can switch between supported consoles
+by using Ctrl+Alt+number. For example, Ctrl+Alt+3 switches you to the
+serial console as long as that console is enabled. Being able to switch
+consoles is helpful, for example, if the main QEMU console breaks for
+some reason.
+
+.. note::
+
+   Usually, "2" gets you to the main console and "3" gets you to the
+   serial console.
+
+Removing the Splash Screen
+==========================
+
+You can remove the splash screen when QEMU is booting by using Alt+left.
+Removing the splash screen allows you to see what is happening in the
+background.
+
+Disabling the Cursor Grab
+=========================
+
+The default QEMU integration captures the cursor within the main window.
+It does this since standard mouse devices only provide relative input
+and not absolute coordinates. You then have to break out of the grab
+using the "Ctrl+Alt" key combination. However, the Yocto Project's
+integration of QEMU enables the wacom USB touch pad driver by default to
+allow input of absolute coordinates. This default means that the mouse
+can enter and leave the main window without the grab taking effect
+leading to a better user experience.
+
+.. _qemu-running-under-a-network-file-system-nfs-server:
+
+Running Under a Network File System (NFS) Server
+================================================
+
+One method for running QEMU is to run it on an NFS server. This is
+useful when you need to access the same file system from both the build
+and the emulated system at the same time. It is also worth noting that
+the system does not need root privileges to run. It uses a user space
+NFS server to avoid that. Follow these steps to set up for running QEMU
+using an NFS server.
+
+1. *Extract a Root Filesystem:* Once you are able to run QEMU in your
+   environment, you can use the ``runqemu-extract-sdk`` script, which is
+   located in the ``scripts`` directory along with the ``runqemu``
+   script.
+
+   The ``runqemu-extract-sdk`` takes a root filesystem tarball and
+   extracts it into a location that you specify. Here is an example that
+   takes a file system and extracts it to a directory named
+   ``test-nfs``: runqemu-extract-sdk
+   ./tmp/deploy/images/qemux86-64/core-image-sato-qemux86-64.tar.bz2
+   test-nfs
+
+2. *Start QEMU:* Once you have extracted the file system, you can run
+   ``runqemu`` normally with the additional location of the file system.
+   You can then also make changes to the files within ``./test-nfs`` and
+   see those changes appear in the image in real time. Here is an
+   example using the ``qemux86`` image: runqemu qemux86-64 ./test-nfs
+
+.. note::
+
+   Should you need to start, stop, or restart the NFS share, you can use
+   the following commands:
+
+   -  The following command starts the NFS share: runqemu-export-rootfs
+      start file-system-location
+
+   -  The following command stops the NFS share: runqemu-export-rootfs
+      stop file-system-location
+
+   -  The following command restarts the NFS share:
+      runqemu-export-rootfs restart file-system-location
+
+.. _qemu-kvm-cpu-compatibility:
+
+QEMU CPU Compatibility Under KVM
+================================
+
+By default, the QEMU build compiles for and targets 64-bit and x86 Intel
+Core2 Duo processors and 32-bit x86 Intel Pentium II processors. QEMU
+builds for and targets these CPU types because they display a broad
+range of CPU feature compatibility with many commonly used CPUs.
+
+Despite this broad range of compatibility, the CPUs could support a
+feature that your host CPU does not support. Although this situation is
+not a problem when QEMU uses software emulation of the feature, it can
+be a problem when QEMU is running with KVM enabled. Specifically,
+software compiled with a certain CPU feature crashes when run on a CPU
+under KVM that does not support that feature. To work around this
+problem, you can override QEMU's runtime CPU setting by changing the
+``QB_CPU_KVM`` variable in ``qemuboot.conf`` in the `Build
+Directory's <&YOCTO_DOCS_REF_URL;#build-directory>`__ ``deploy/image``
+directory. This setting specifies a ``-cpu`` option passed into QEMU in
+the ``runqemu`` script. Running ``qemu -cpu help`` returns a list of
+available supported CPU types.
+
+.. _qemu-dev-performance:
+
+QEMU Performance
+================
+
+Using QEMU to emulate your hardware can result in speed issues depending
+on the target and host architecture mix. For example, using the
+``qemux86`` image in the emulator on an Intel-based 32-bit (x86) host
+machine is fast because the target and host architectures match. On the
+other hand, using the ``qemuarm`` image on the same Intel-based host can
+be slower. But, you still achieve faithful emulation of ARM-specific
+issues.
+
+To speed things up, the QEMU images support using ``distcc`` to call a
+cross-compiler outside the emulated system. If you used ``runqemu`` to
+start QEMU, and the ``distccd`` application is present on the host
+system, any BitBake cross-compiling toolchain available from the build
+system is automatically used from within QEMU simply by calling
+``distcc``. You can accomplish this by defining the cross-compiler
+variable (e.g. ``export CC="distcc"``). Alternatively, if you are using
+a suitable SDK image or the appropriate stand-alone toolchain is
+present, the toolchain is also automatically used.
+
+.. note::
+
+   Several mechanisms exist that let you connect to the system running
+   on the QEMU emulator:
+
+   -  QEMU provides a framebuffer interface that makes standard consoles
+      available.
+
+   -  Generally, headless embedded devices have a serial port. If so,
+      you can configure the operating system of the running image to use
+      that port to run a console. The connection uses standard IP
+      networking.
+
+   -  SSH servers exist in some QEMU images. The ``core-image-sato``
+      QEMU image has a Dropbear secure shell (SSH) server that runs with
+      the root password disabled. The ``core-image-full-cmdline`` and
+      ``core-image-lsb`` QEMU images have OpenSSH instead of Dropbear.
+      Including these SSH servers allow you to use standard ``ssh`` and
+      ``scp`` commands. The ``core-image-minimal`` QEMU image, however,
+      contains no SSH server.
+
+   -  You can use a provided, user-space NFS server to boot the QEMU
+      session using a local copy of the root filesystem on the host. In
+      order to make this connection, you must extract a root filesystem
+      tarball by using the ``runqemu-extract-sdk`` command. After
+      running the command, you must then point the ``runqemu`` script to
+      the extracted directory instead of a root filesystem image file.
+      See the "`Running Under a Network File System (NFS)
+      Server <#qemu-running-under-a-network-file-system-nfs-server>`__"
+      section for more information.
+
+.. _qemu-dev-command-line-syntax:
+
+QEMU Command-Line Syntax
+========================
+
+The basic ``runqemu`` command syntax is as follows: $ runqemu [option ]
+[...] Based on what you provide on the command line, ``runqemu`` does a
+good job of figuring out what you are trying to do. For example, by
+default, QEMU looks for the most recently built image according to the
+timestamp when it needs to look for an image. Minimally, through the use
+of options, you must provide either a machine name, a virtual machine
+image (``*wic.vmdk``), or a kernel image (``*.bin``).
+
+Following is the command-line help output for the ``runqemu`` command: $
+runqemu --help Usage: you can run this script with any valid combination
+of the following environment variables (in any order): KERNEL - the
+kernel image file to use ROOTFS - the rootfs image file or nfsroot
+directory to use MACHINE - the machine name (optional, autodetected from
+KERNEL filename if unspecified) Simplified QEMU command-line options can
+be passed with: nographic - disable video console serial - enable a
+serial console on /dev/ttyS0 slirp - enable user networking, no root
+privileges is required kvm - enable KVM when running x86/x86_64
+(VT-capable CPU required) kvm-vhost - enable KVM with vhost when running
+x86/x86_64 (VT-capable CPU required) publicvnc - enable a VNC server
+open to all hosts audio - enable audio [*/]ovmf\* - OVMF firmware file
+or base name for booting with UEFI tcpserial=<port> - specify tcp serial
+port number biosdir=<dir> - specify custom bios dir
+biosfilename=<filename> - specify bios filename qemuparams=<xyz> -
+specify custom parameters to QEMU bootparams=<xyz> - specify custom
+kernel parameters during boot help, -h, --help: print this text
+Examples: runqemu runqemu qemuarm runqemu tmp/deploy/images/qemuarm
+runqemu tmp/deploy/images/qemux86/<qemuboot.conf> runqemu qemux86-64
+core-image-sato ext4 runqemu qemux86-64 wic-image-minimal wic runqemu
+path/to/bzImage-qemux86.bin path/to/nfsrootdir/ serial runqemu qemux86
+iso/hddimg/wic.vmdk/wic.qcow2/wic.vdi/ramfs/cpio.gz... runqemu qemux86
+qemuparams="-m 256" runqemu qemux86 bootparams="psplash=false" runqemu
+path/to/<image>-<machine>.wic runqemu path/to/<image>-<machine>.wic.vmdk
+
+.. _qemu-dev-runqemu-command-line-options:
+
+``runqemu`` Command-Line Options
+================================
+
+Following is a description of ``runqemu`` options you can provide on the
+command line:
+
+.. note::
+
+   If you do provide some "illegal" option combination or perhaps you do
+   not provide enough in the way of options,
+   runqemu
+   provides appropriate error messaging to help you correct the problem.
+
+-  QEMUARCH: The QEMU machine architecture, which must be "qemuarm",
+   "qemuarm64", "qemumips", "qemumips64", "qemuppc", "qemux86", or
+   "qemux86-64".
+
+-  ``VM``: The virtual machine image, which must be a ``.wic.vmdk``
+   file. Use this option when you want to boot a ``.wic.vmdk`` image.
+   The image filename you provide must contain one of the following
+   strings: "qemux86-64", "qemux86", "qemuarm", "qemumips64",
+   "qemumips", "qemuppc", or "qemush4".
+
+-  ROOTFS: A root filesystem that has one of the following filetype
+   extensions: "ext2", "ext3", "ext4", "jffs2", "nfs", or "btrfs". If
+   the filename you provide for this option uses “nfs”, it must provide
+   an explicit root filesystem path.
+
+-  KERNEL: A kernel image, which is a ``.bin`` file. When you provide a
+   ``.bin`` file, ``runqemu`` detects it and assumes the file is a
+   kernel image.
+
+-  MACHINE: The architecture of the QEMU machine, which must be one of
+   the following: "qemux86", "qemux86-64", "qemuarm", "qemuarm64",
+   "qemumips", “qemumips64", or "qemuppc". The MACHINE and QEMUARCH
+   options are basically identical. If you do not provide a MACHINE
+   option, ``runqemu`` tries to determine it based on other options.
+
+-  ``ramfs``: Indicates you are booting an initial RAM disk (initramfs)
+   image, which means the ``FSTYPE`` is ``cpio.gz``.
+
+-  ``iso``: Indicates you are booting an ISO image, which means the
+   ``FSTYPE`` is ``.iso``.
+
+-  ``nographic``: Disables the video console, which sets the console to
+   "ttys0". This option is useful when you have logged into a server and
+   you do not want to disable forwarding from the X Window System (X11)
+   to your workstation or laptop.
+
+-  ``serial``: Enables a serial console on ``/dev/ttyS0``.
+
+-  ``biosdir``: Establishes a custom directory for BIOS, VGA BIOS and
+   keymaps.
+
+-  ``biosfilename``: Establishes a custom BIOS name.
+
+-  ``qemuparams=\"xyz\"``: Specifies custom QEMU parameters. Use this
+   option to pass options other than the simple "kvm" and "serial"
+   options.
+
+-  ``bootparams=\"xyz\"``: Specifies custom boot parameters for the
+   kernel.
+
+-  ``audio``: Enables audio in QEMU. The MACHINE option must be either
+   "qemux86" or "qemux86-64" in order for audio to be enabled.
+   Additionally, the ``snd_intel8x0`` or ``snd_ens1370`` driver must be
+   installed in linux guest.
+
+-  ``slirp``: Enables "slirp" networking, which is a different way of
+   networking that does not need root access but also is not as easy to
+   use or comprehensive as the default.
+
+-  ``kvm``: Enables KVM when running "qemux86" or "qemux86-64" QEMU
+   architectures. For KVM to work, all the following conditions must be
+   met:
+
+   -  Your MACHINE must be either qemux86" or "qemux86-64".
+
+   -  Your build host has to have the KVM modules installed, which are
+      ``/dev/kvm``.
+
+   -  The build host ``/dev/kvm`` directory has to be both writable and
+      readable.
+
+-  ``kvm-vhost``: Enables KVM with VHOST support when running "qemux86"
+   or "qemux86-64" QEMU architectures. For KVM with VHOST to work, the
+   following conditions must be met:
+
+   -  `kvm <#kvm-cond>`__ option conditions must be met.
+
+   -  Your build host has to have virtio net device, which are
+      ``/dev/vhost-net``.
+
+   -  The build host ``/dev/vhost-net`` directory has to be either
+      readable or writable and “slirp-enabled”.
+
+-  ``publicvnc``: Enables a VNC server open to all hosts.