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<li class="toctree-l4"><a class="reference internal" href="devices/net.html">Network emulation</a></li>
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<section id="device-emulation">
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<span id="id1"></span><h1>Device Emulation<a class="headerlink" href="#device-emulation" title="Link to this heading"></a></h1>
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<p>QEMU supports the emulation of a large number of devices from
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peripherals such network cards and USB devices to integrated systems
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on a chip (SoCs). Configuration of these is often a source of
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confusion so it helps to have an understanding of some of the terms
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used to describes devices within QEMU.</p>
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<section id="common-terms">
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<h2>Common Terms<a class="headerlink" href="#common-terms" title="Link to this heading"></a></h2>
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<section id="device-front-end">
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<h3>Device Front End<a class="headerlink" href="#device-front-end" title="Link to this heading"></a></h3>
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<p>A device front end is how a device is presented to the guest. The type
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of device presented should match the hardware that the guest operating
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system is expecting to see. All devices can be specified with the
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<code class="docutils literal notranslate"><span class="pre">--device</span></code> command line option. Running QEMU with the command line
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options <code class="docutils literal notranslate"><span class="pre">--device</span> <span class="pre">help</span></code> will list all devices it is aware of. Using
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the command line <code class="docutils literal notranslate"><span class="pre">--device</span> <span class="pre">foo,help</span></code> will list the additional
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configuration options available for that device.</p>
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<p>A front end is often paired with a back end, which describes how the
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host’s resources are used in the emulation.</p>
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</section>
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<section id="device-buses">
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<h3>Device Buses<a class="headerlink" href="#device-buses" title="Link to this heading"></a></h3>
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<p>Most devices will exist on a BUS of some sort. Depending on the
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machine model you choose (<code class="docutils literal notranslate"><span class="pre">-M</span> <span class="pre">foo</span></code>) a number of buses will have been
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automatically created. In most cases the BUS a device is attached to
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can be inferred, for example PCI devices are generally automatically
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allocated to the next free address of first PCI bus found. However in
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complicated configurations you can explicitly specify what bus
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(<code class="docutils literal notranslate"><span class="pre">bus=ID</span></code>) a device is attached to along with its address
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(<code class="docutils literal notranslate"><span class="pre">addr=N</span></code>).</p>
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<p>Some devices, for example a PCI SCSI host controller, will add an
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additional buses to the system that other devices can be attached to.
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A hypothetical chain of devices might look like:</p>
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<blockquote>
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<div><p>–device foo,bus=pci.0,addr=0,id=foo
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–device bar,bus=foo.0,addr=1,id=baz</p>
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</div></blockquote>
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<p>which would be a bar device (with the ID of baz) which is attached to
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the first foo bus (foo.0) at address 1. The foo device which provides
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that bus is itself is attached to the first PCI bus (pci.0).</p>
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</section>
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<section id="device-back-end">
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<h3>Device Back End<a class="headerlink" href="#device-back-end" title="Link to this heading"></a></h3>
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<p>The back end describes how the data from the emulated device will be
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processed by QEMU. The configuration of the back end is usually
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specific to the class of device being emulated. For example serial
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devices will be backed by a <code class="docutils literal notranslate"><span class="pre">--chardev</span></code> which can redirect the data
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to a file or socket or some other system. Storage devices are handled
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by <code class="docutils literal notranslate"><span class="pre">--blockdev</span></code> which will specify how blocks are handled, for
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example being stored in a qcow2 file or accessing a raw host disk
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partition. Back ends can sometimes be stacked to implement features
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like snapshots.</p>
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<p>While the choice of back end is generally transparent to the guest,
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there are cases where features will not be reported to the guest if
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the back end is unable to support it.</p>
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</section>
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<section id="device-pass-through">
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<h3>Device Pass Through<a class="headerlink" href="#device-pass-through" title="Link to this heading"></a></h3>
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<p>Device pass through is where the device is actually given access to
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the underlying hardware. This can be as simple as exposing a single
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USB device on the host system to the guest or dedicating a video card
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in a PCI slot to the exclusive use of the guest.</p>
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</section>
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</section>
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<section id="emulated-devices">
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<h2>Emulated Devices<a class="headerlink" href="#emulated-devices" title="Link to this heading"></a></h2>
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<div class="toctree-wrapper compound">
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<ul>
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<li class="toctree-l1"><a class="reference internal" href="devices/can.html">CAN Bus Emulation Support</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/ccid.html">Chip Card Interface Device (CCID)</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/cxl.html">Compute Express Link (CXL)</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/ivshmem.html">Inter-VM Shared Memory device</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/keyboard.html">Sparc32 keyboard</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/net.html">Network emulation</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/nvme.html">NVMe Emulation</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/usb.html">USB emulation</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/vhost-user.html">vhost-user back ends</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/virtio-gpu.html">virtio-gpu</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/virtio-pmem.html">virtio pmem</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/virtio-snd.html">virtio sound</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/vhost-user-rng.html">QEMU vhost-user-rng - RNG emulation</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/canokey.html">CanoKey QEMU</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/usb-u2f.html">Universal Second Factor (U2F) USB Key Device</a></li>
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<li class="toctree-l1"><a class="reference internal" href="devices/igb.html">igb</a></li>
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