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<li class="toctree-l3 current"><a class="current reference internal" href="#">RISC-V System emulator</a><ul>
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  <div class="section" id="risc-v-system-emulator">
<span id="id1"></span><h1>RISC-V System emulator<a class="headerlink" href="#risc-v-system-emulator" title="Permalink to this headline">¶</a></h1>
<p>QEMU can emulate both 32-bit and 64-bit RISC-V CPUs. Use the
<code class="docutils literal notranslate"><span class="pre">qemu-system-riscv64</span></code> executable to simulate a 64-bit RISC-V machine,
<code class="docutils literal notranslate"><span class="pre">qemu-system-riscv32</span></code> executable to simulate a 32-bit RISC-V machine.</p>
<p>QEMU has generally good support for RISC-V guests. It has support for
several different machines. The reason we support so many is that
RISC-V hardware is much more widely varying than x86 hardware. RISC-V
CPUs are generally built into “system-on-chip” (SoC) designs created by
many different companies with different devices, and these SoCs are
then built into machines which can vary still further even if they use
the same SoC.</p>
<p>For most boards the CPU type is fixed (matching what the hardware has),
so typically you don’t need to specify the CPU type by hand, except for
special cases like the <code class="docutils literal notranslate"><span class="pre">virt</span></code> board.</p>
<div class="section" id="choosing-a-board-model">
<h2>Choosing a board model<a class="headerlink" href="#choosing-a-board-model" title="Permalink to this headline">¶</a></h2>
<p>For QEMU’s RISC-V system emulation, you must specify which board
model you want to use with the <code class="docutils literal notranslate"><span class="pre">-M</span></code> or <code class="docutils literal notranslate"><span class="pre">--machine</span></code> option;
there is no default.</p>
<p>Because RISC-V systems differ so much and in fundamental ways, typically
operating system or firmware images intended to run on one machine
will not run at all on any other. This is often surprising for new
users who are used to the x86 world where every system looks like a
standard PC. (Once the kernel has booted, most user space software
cares much less about the detail of the hardware.)</p>
<p>If you already have a system image or a kernel that works on hardware
and you want to boot with QEMU, check whether QEMU lists that machine
in its <code class="docutils literal notranslate"><span class="pre">-machine</span> <span class="pre">help</span></code> output. If it is listed, then you can probably
use that board model. If it is not listed, then unfortunately your image
will almost certainly not boot on QEMU. (You might be able to
extract the file system and use that with a different kernel which
boots on a system that QEMU does emulate.)</p>
<p>If you don’t care about reproducing the idiosyncrasies of a particular
bit of hardware, such as small amount of RAM, no PCI or other hard
disk, etc., and just want to run Linux, the best option is to use the
<code class="docutils literal notranslate"><span class="pre">virt</span></code> board. This is a platform which doesn’t correspond to any
real hardware and is designed for use in virtual machines. You’ll
need to compile Linux with a suitable configuration for running on
the <code class="docutils literal notranslate"><span class="pre">virt</span></code> board. <code class="docutils literal notranslate"><span class="pre">virt</span></code> supports PCI, virtio, recent CPUs and
large amounts of RAM. It also supports 64-bit CPUs.</p>
</div>
<div class="section" id="board-specific-documentation">
<h2>Board-specific documentation<a class="headerlink" href="#board-specific-documentation" title="Permalink to this headline">¶</a></h2>
<p>Unfortunately many of the RISC-V boards QEMU supports are currently
undocumented; you can get a complete list by running
<code class="docutils literal notranslate"><span class="pre">qemu-system-riscv64</span> <span class="pre">--machine</span> <span class="pre">help</span></code>, or
<code class="docutils literal notranslate"><span class="pre">qemu-system-riscv32</span> <span class="pre">--machine</span> <span class="pre">help</span></code>.</p>
<div class="toctree-wrapper compound">
<ul>
<li class="toctree-l1"><a class="reference internal" href="riscv/microchip-icicle-kit.html">Microchip PolarFire SoC Icicle Kit (<code class="docutils literal notranslate"><span class="pre">microchip-icicle-kit</span></code>)</a></li>
<li class="toctree-l1"><a class="reference internal" href="riscv/shakti-c.html">Shakti C Reference Platform (<code class="docutils literal notranslate"><span class="pre">shakti_c</span></code>)</a></li>
<li class="toctree-l1"><a class="reference internal" href="riscv/sifive_u.html">SiFive HiFive Unleashed (<code class="docutils literal notranslate"><span class="pre">sifive_u</span></code>)</a></li>
<li class="toctree-l1"><a class="reference internal" href="riscv/virt.html">‘virt’ Generic Virtual Platform (<code class="docutils literal notranslate"><span class="pre">virt</span></code>)</a></li>
</ul>
</div>
</div>
<div class="section" id="risc-v-cpu-firmware">
<h2>RISC-V CPU firmware<a class="headerlink" href="#risc-v-cpu-firmware" title="Permalink to this headline">¶</a></h2>
<p>When using the <code class="docutils literal notranslate"><span class="pre">sifive_u</span></code> or <code class="docutils literal notranslate"><span class="pre">virt</span></code> machine there are three different
firmware boot options:
1. <code class="docutils literal notranslate"><span class="pre">-bios</span> <span class="pre">default</span></code> - This is the default behaviour if no -bios option
is included. This option will load the default OpenSBI firmware automatically.
The firmware is included with the QEMU release and no user interaction is
required. All a user needs to do is specify the kernel they want to boot
with the -kernel option
2. <code class="docutils literal notranslate"><span class="pre">-bios</span> <span class="pre">none</span></code> - QEMU will not automatically load any firmware. It is up
to the user to load all the images they need.
3. <code class="docutils literal notranslate"><span class="pre">-bios</span> <span class="pre">&lt;file&gt;</span></code> - Tells QEMU to load the specified file as the firmware.</p>
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