poky/documentation/dev-manual/dev-manual-qemu.xml

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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >

<chapter id='dev-manual-qemu'>

<title>Using the Quick EMUlator (QEMU)</title>

    <para>
        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.
    </para>

    <section id='qemu-dev-overview'>
        <title>Overview</title>

        <para>
            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.
            </note>
            This section provides a brief reference for the Yocto Project
            implementation of QEMU.
        </para>

        <para>
            For official information and documentation on QEMU in general, see
            the following references:
            <itemizedlist>
                <listitem><para>
                    <emphasis><ulink url='http://wiki.qemu.org/Main_Page'>QEMU Website</ulink>:</emphasis>
                    The official website for the QEMU Open Source project.
                    </para></listitem>
                <listitem><para>
                    <emphasis><ulink url='http://wiki.qemu.org/Manual'>Documentation</ulink>:</emphasis>
                    The QEMU user manual.
                    </para></listitem>
            </itemizedlist>
        </para>
    </section>

    <section id='qemu-running-qemu'>
        <title>Running QEMU</title>

        <para>
            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:
            <orderedlist>
                <listitem><para>
                    <emphasis>Install QEMU:</emphasis>
                    QEMU is made available with the Yocto Project a number of
                    ways.
                    One method is to install a Software Development Kit (SDK).
                    See
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#the-qemu-emulator'>The QEMU Emulator</ulink>"
                    section in the Yocto Project Application Development and
                    the Extensible Software Development Kit (eSDK) manual
                    for information on how to install QEMU.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Setting Up the Environment:</emphasis>
                    How you set up the QEMU environment depends on how you
                    installed QEMU:
                    <itemizedlist>
                        <listitem><para>
                            If you cloned the <filename>poky</filename>
                            repository or you downloaded and unpacked a
                            Yocto Project release tarball, you can source
                            the build environment script (i.e.
                            <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>):
                            <literallayout class='monospaced'>
     $ cd ~/poky
     $ source oe-init-build-env
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            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
                            <filename>poky_sdk</filename> directory:
                            <literallayout class='monospaced'>
     . ~/poky_sdk/environment-setup-core2-64-poky-linux
                            </literallayout>
                            </para></listitem>
                    </itemizedlist>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Ensure the Artifacts are in Place:</emphasis>
                    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:
                    <itemizedlist>
                        <listitem><para>
                            If you have previously built an image for QEMU
                            (e.g. <filename>qemux86</filename>,
                            <filename>qemuarm</filename>, and so forth),
                            then the artifacts are in place in your
                            <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>.
                            </para></listitem>
                        <listitem><para>
                            If you have not built an image, you can go to the
                            <ulink url='&YOCTO_MACHINES_DL_URL;'>machines/qemu</ulink>
                            area and download a pre-built image that matches
                            your architecture and can be run on QEMU.
                            </para></listitem>
                    </itemizedlist></para>

                    <para>See the
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-extracting-the-root-filesystem'>Extracting the Root Filesystem</ulink>"
                    section in the Yocto Project Application Development and
                    the Extensible Software Development Kit (eSDK) manual
                    for information on how to extract a root filesystem.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Run QEMU:</emphasis>
                    The basic <filename>runqemu</filename> command syntax is as
                    follows:
                    <literallayout class='monospaced'>
     $ runqemu [<replaceable>option</replaceable> ]  [...]
                    </literallayout>
                    Based on what you provide on the command line,
                    <filename>runqemu</filename> 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
                    (<filename>*wic.vmdk</filename>), or a kernel image
                    (<filename>*.bin</filename>).</para>

                    <para>Here are some additional examples to help illustrate
                    further QEMU:
                    <itemizedlist>
                        <listitem><para>
                            This example starts QEMU with
                            <replaceable>MACHINE</replaceable> set to "qemux86-64".
                            Assuming a standard
                            <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>,
                            <filename>runqemu</filename> automatically finds the
                            <filename>bzImage-qemux86-64.bin</filename> image file and
                            the
                            <filename>core-image-minimal-qemux86-64-20200218002850.rootfs.ext4</filename>
                            (assuming the current build created a
                            <filename>core-image-minimal</filename> 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.
                            </note>
                            <literallayout class='monospaced'>
     $ runqemu qemux86-64
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            This example produces the exact same results as the
                            previous example.
                            This command, however, specifically provides the image
                            and root filesystem type.
                            <literallayout class='monospaced'>
     $ runqemu qemux86-64 core-image-minimal ext4
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            This example specifies to boot an initial RAM disk image
                            and to enable audio in QEMU.
                            For this case, <filename>runqemu</filename> set the
                            internal variable <filename>FSTYPE</filename> to
                            "cpio.gz".
                            Also, for audio to be enabled, an appropriate driver must
                            be installed (see the previous description for the
                            <filename>audio</filename> option for more information).
                            <literallayout class='monospaced'>
     $ runqemu qemux86-64 ramfs audio
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            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
                            <replaceable>MACHINE</replaceable>,
                            <replaceable>KERNEL</replaceable>, or
                            <replaceable>VM</replaceable> option.
                            <literallayout class='monospaced'>
     $ runqemu ext4
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            This example specifies to boot a virtual machine
                            image (<filename>.wic.vmdk</filename> file).
                            From the <filename>.wic.vmdk</filename>,
                            <filename>runqemu</filename> determines the QEMU
                            architecture (<replaceable>MACHINE</replaceable>) to be
                            "qemux86-64" and the root filesystem type to be "vmdk".
                            <literallayout class='monospaced'>
     $ runqemu /home/scott-lenovo/vm/core-image-minimal-qemux86-64.wic.vmdk
                            </literallayout>
                            </para></listitem>
                    </itemizedlist>
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='switching-between-consoles'>
        <title>Switching Between Consoles</title>

        <para>
            When booting or running QEMU, you can switch between
            supported consoles by using
            Ctrl+Alt+<replaceable>number</replaceable>.
            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.
            </note>
        </para>
    </section>

    <section id='removing-the-splash-screen'>
        <title>Removing the Splash Screen</title>

        <para>
            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.
        </para>
    </section>

    <section id='disabling-the-cursor-grab'>
        <title>Disabling the Cursor Grab</title>

        <para>
            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.
        </para>
    </section>

    <section id='qemu-running-under-a-network-file-system-nfs-server'>
        <title>Running Under a Network File System (NFS) Server</title>

        <para>
            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.
            <orderedlist>
                <listitem><para>
                    <emphasis>Extract a Root Filesystem:</emphasis>
                    Once you are able to run QEMU in your environment, you can
                    use the <filename>runqemu-extract-sdk</filename> script,
                    which is located in the <filename>scripts</filename>
                    directory along with the <filename>runqemu</filename>
                    script.</para>

                    <para>The <filename>runqemu-extract-sdk</filename> 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
                    <filename>test-nfs</filename>:
                    <literallayout class='monospaced'>
     runqemu-extract-sdk ./tmp/deploy/images/qemux86-64/core-image-sato-qemux86-64.tar.bz2 test-nfs
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Start QEMU:</emphasis>
                    Once you have extracted the file system, you can run
                    <filename>runqemu</filename> normally with the additional
                    location of the file system.
                    You can then also make changes to the files within
                    <filename>./test-nfs</filename> and see those changes
                    appear in the image in real time.
                    Here is an example using the <filename>qemux86</filename>
                    image:
                    <literallayout class='monospaced'>
     runqemu qemux86-64 ./test-nfs
                    </literallayout>
                    </para></listitem>
            </orderedlist>
            <note>
                <para>
                    Should you need to start, stop, or restart the NFS share,
                    you can use the following commands:
                    <itemizedlist>
                        <listitem><para>
                            The following command starts the NFS share:
                            <literallayout class='monospaced'>
     runqemu-export-rootfs start <replaceable>file-system-location</replaceable>
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            The following command stops the NFS share:
                            <literallayout class='monospaced'>
         runqemu-export-rootfs stop <replaceable>file-system-location</replaceable>
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            The following command restarts the NFS share:
                            <literallayout class='monospaced'>
     runqemu-export-rootfs restart <replaceable>file-system-location</replaceable>
                            </literallayout>
                            </para></listitem>
                    </itemizedlist>
                </para>
            </note>
        </para>
    </section>

    <section id='qemu-kvm-cpu-compatibility'>
        <title>QEMU CPU Compatibility Under KVM</title>

        <para>
            By default, the QEMU build compiles for and targets 64-bit and x86
            <trademark class='registered'>Intel</trademark> <trademark class='trademark'>Core</trademark>2
            Duo processors and 32-bit x86
            <trademark class='registered'>Intel</trademark> <trademark class='registered'>Pentium</trademark>
            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.
        </para>

        <para>
            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 <filename>QB_CPU_KVM</filename>
            variable in <filename>qemuboot.conf</filename> in the
            <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory's</ulink>
            <filename>deploy/image</filename> directory.
            This setting specifies a <filename>-cpu</filename> option
            passed into QEMU in the <filename>runqemu</filename> script.
            Running <filename>qemu -cpu help</filename> returns a list of
            available supported CPU types.
        </para>
    </section>

    <section id='qemu-dev-performance'>
        <title>QEMU Performance</title>

        <para>
            Using QEMU to emulate your hardware can result in speed issues
            depending on the target and host architecture mix.
            For example, using the <filename>qemux86</filename> 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 <filename>qemuarm</filename> image
            on the same Intel-based host can be slower.
            But, you still achieve faithful emulation of ARM-specific issues.
        </para>

        <para>
            To speed things up, the QEMU images support using
            <filename>distcc</filename> to call a cross-compiler outside the
            emulated system.
            If you used <filename>runqemu</filename> to start QEMU, and the
            <filename>distccd</filename> 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 <filename>distcc</filename>.
            You can accomplish this by defining the cross-compiler variable
            (e.g. <filename>export CC="distcc"</filename>).
            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:
                <itemizedlist>
                    <listitem><para>
                        QEMU provides a framebuffer interface that makes
                        standard consoles available.
                        </para></listitem>
                    <listitem><para>
                        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.
                        </para></listitem>
                    <listitem><para>
                        SSH servers exist in some QEMU images.
                        The <filename>core-image-sato</filename> QEMU image
                        has a Dropbear secure shell (SSH) server that runs
                        with the root password disabled.
                        The <filename>core-image-full-cmdline</filename> and
                        <filename>core-image-lsb</filename> QEMU images
                        have OpenSSH instead of Dropbear.
                        Including these SSH servers allow you to use standard
                        <filename>ssh</filename> and <filename>scp</filename>
                        commands.
                        The <filename>core-image-minimal</filename> QEMU image,
                        however, contains no SSH server.
                        </para></listitem>
                    <listitem><para>
                        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
                        <filename>runqemu-extract-sdk</filename> command.
                        After running the command, you must then point the
                        <filename>runqemu</filename>
                        script to the extracted directory instead of a root
                        filesystem image file.
                        See the
                        "<link linkend='qemu-running-under-a-network-file-system-nfs-server'>Running Under a Network File System (NFS) Server</link>"
                        section for more information.
                        </para></listitem>
                </itemizedlist>
            </note>
        </para>
    </section>

    <section id='qemu-dev-command-line-syntax'>
        <title>QEMU Command-Line Syntax</title>

        <para>
            The basic <filename>runqemu</filename> command syntax is as
            follows:
            <literallayout class='monospaced'>
     $ runqemu [<replaceable>option</replaceable> ]  [...]
            </literallayout>
            Based on what you provide on the command line,
            <filename>runqemu</filename> 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
            (<filename>*wic.vmdk</filename>), or a kernel image
            (<filename>*.bin</filename>).
        </para>

        <para>
            Following is the command-line help output for the
            <filename>runqemu</filename> command:
            <literallayout class='monospaced'>
     $ 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=&lt;port&gt; - specify tcp serial port number
       biosdir=&lt;dir&gt; - specify custom bios dir
       biosfilename=&lt;filename&gt; - specify bios filename
       qemuparams=&lt;xyz&gt; - specify custom parameters to QEMU
       bootparams=&lt;xyz&gt; - 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/&lt;qemuboot.conf&gt;
       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/&lt;image&gt;-&lt;machine&gt;.wic
       runqemu path/to/&lt;image&gt;-&lt;machine&gt;.wic.vmdk
            </literallayout>
        </para>
    </section>

    <section id='qemu-dev-runqemu-command-line-options'>
        <title><filename>runqemu</filename> Command-Line Options</title>

        <para>
            Following is a description of <filename>runqemu</filename>
            options you can provide on the command line:
            <note><title>Tip</title>
                If you do provide some "illegal" option combination or perhaps
                you do not provide enough in the way of options,
                <filename>runqemu</filename> provides appropriate error
                messaging to help you correct the problem.
            </note>
            <itemizedlist>
                <listitem><para>
                    <replaceable>QEMUARCH</replaceable>:
                    The QEMU machine architecture, which must be "qemuarm",
                    "qemuarm64", "qemumips", "qemumips64", "qemuppc",
                    "qemux86", or "qemux86-64".
                    </para></listitem>
                <listitem><para>
                    <filename><replaceable>VM</replaceable></filename>:
                    The virtual machine image, which must be a
                    <filename>.wic.vmdk</filename> file.
                    Use this option when you want to boot a
                    <filename>.wic.vmdk</filename> image.
                    The image filename you provide must contain one of the
                    following strings: "qemux86-64", "qemux86", "qemuarm",
                    "qemumips64", "qemumips", "qemuppc", or "qemush4".
                    </para></listitem>
                <listitem><para>
                    <replaceable>ROOTFS</replaceable>:
                    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.
                    </para></listitem>
                <listitem><para>
                    <replaceable>KERNEL</replaceable>:
                    A kernel image, which is a <filename>.bin</filename> file.
                    When you provide a <filename>.bin</filename> file,
                    <filename>runqemu</filename> detects it and assumes the
                    file is a kernel image.
                    </para></listitem>
                <listitem><para>
                    <replaceable>MACHINE</replaceable>:
                    The architecture of the QEMU machine, which must be one
                    of the following: "qemux86", "qemux86-64", "qemuarm",
                    "qemuarm64", "qemumips", “qemumips64", or "qemuppc".
                    The <replaceable>MACHINE</replaceable> and
                    <replaceable>QEMUARCH</replaceable> options are basically
                    identical.
                    If you do not provide a <replaceable>MACHINE</replaceable>
                    option, <filename>runqemu</filename> tries to determine
                    it based on other options.
                    </para></listitem>
                <listitem><para>
                    <filename>ramfs</filename>:
                    Indicates you are booting an initial RAM disk (initramfs)
                    image, which means the <filename>FSTYPE</filename> is
                    <filename>cpio.gz</filename>.
                    </para></listitem>
                <listitem><para>
                    <filename>iso</filename>:
                    Indicates you are booting an ISO image, which means the
                    <filename>FSTYPE</filename> is
                    <filename>.iso</filename>.
                    </para></listitem>
                <listitem><para>
                    <filename>nographic</filename>:
                    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.
                    </para></listitem>
                <listitem><para>
                    <filename>serial</filename>:
                    Enables a serial console on
                    <filename>/dev/ttyS0</filename>.
                    </para></listitem>
                <listitem><para>
                    <filename>biosdir</filename>:
                    Establishes a custom directory for BIOS, VGA BIOS and
                    keymaps.
                    </para></listitem>
                <listitem><para>
                    <filename>biosfilename</filename>:
                    Establishes a custom BIOS name.
                    </para></listitem>
                <listitem><para>
                    <filename>qemuparams=\"<replaceable>xyz</replaceable>\"</filename>:
                    Specifies custom QEMU parameters.
                    Use this option to pass options other than the simple
                    "kvm" and "serial" options.
                    </para></listitem>
                <listitem><para><filename>bootparams=\"<replaceable>xyz</replaceable>\"</filename>:
                    Specifies custom boot parameters for the kernel.
                    </para></listitem>
                <listitem><para>
                    <filename>audio</filename>:
                    Enables audio in QEMU.
                    The <replaceable>MACHINE</replaceable> option must be
                    either "qemux86" or "qemux86-64" in order for audio to be
                    enabled.
                    Additionally, the <filename>snd_intel8x0</filename>
                    or <filename>snd_ens1370</filename> driver must be
                    installed in linux guest.
                    </para></listitem>
                <listitem><para>
                    <filename>slirp</filename>:
                    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.
                    </para></listitem>
                <listitem><para id='kvm-cond'>
                    <filename>kvm</filename>:
                    Enables KVM when running "qemux86" or "qemux86-64"
                    QEMU architectures.
                    For KVM to work, all the following conditions must be met:
                    <itemizedlist>
                        <listitem><para>
                            Your <replaceable>MACHINE</replaceable> must be either
qemux86" or "qemux86-64".
                            </para></listitem>
                        <listitem><para>
                            Your build host has to have the KVM modules
                            installed, which are
                            <filename>/dev/kvm</filename>.
                            </para></listitem>
                        <listitem><para>
                            The  build host <filename>/dev/kvm</filename>
                            directory has to be both writable and readable.
                            </para></listitem>
                    </itemizedlist>
                    </para></listitem>
                <listitem><para>
                    <filename>kvm-vhost</filename>:
                    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:
                    <itemizedlist>
                        <listitem><para>
                            <link linkend='kvm-cond'>kvm</link> option
                            conditions must be met.
                            </para></listitem>
                        <listitem><para>
                            Your build host has to have virtio net device, which
                            are <filename>/dev/vhost-net</filename>.
                            </para></listitem>
                        <listitem><para>
                            The build host <filename>/dev/vhost-net</filename>
                            directory has to be either readable or writable
                            and “slirp-enabled”.
                            </para></listitem>
                    </itemizedlist>
                    </para></listitem>
                <listitem><para>
                    <filename>publicvnc</filename>:
                    Enables a VNC server open to all hosts.
                    </para></listitem>
            </itemizedlist>
        </para>
    </section>
</chapter>
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