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nixos/manual: add a section about Vulkan drivers #93591

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91 changes: 90 additions & 1 deletion nixos/doc/manual/configuration/gpu-accel.xml
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Expand Up @@ -52,7 +52,7 @@
<para>
The proper installation of OpenCL drivers can be verified through
the <command>clinfo</command> command of the <package>clinfo</package>
package. This command will report the number of hardware devides
package. This command will report the number of hardware devices
that is found and give detailed information for each device:
</para>

Expand Down Expand Up @@ -101,4 +101,93 @@ ROCR_EXT_DIR=`nix-build '&lt;nixpkgs&gt;' --no-out-link -A rocm-runtime-ext`/lib
</para>
</section>
</section>

<section xml:id="sec-gpu-accel-vulkan">
<title>Vulkan</title>

<para>
<link xlink:href="https://en.wikipedia.org/wiki/Vulkan_(API)">Vulkan</link> is a
graphics and compute API for GPUs. It is used directly by games or indirectly though
compatibility layers like <link xlink:href="https://github.com/doitsujin/dxvk/wiki">DXVK</link>.
</para>

<para>
By default, if <xref linkend="opt-hardware.opengl.driSupport"/> is enabled,
<package>mesa</package> is installed and provides Vulkan for supported hardware.
</para>

<para>
Similar to OpenCL, Vulkan drivers are loaded through the <emphasis>Installable Client
Driver</emphasis> (ICD) mechanism. ICD files for Vulkan are JSON files that specify
the path to the driver library and the supported Vulkan version. All successfully
loaded drivers are exposed to the application as different GPUs.
In NixOS, there are two ways to make ICD files visible to Vulkan applications: an
environment variable and a module option.
</para>

<para>
The first option is through the <varname>VK_ICD_FILENAMES</varname>
environment variable. This variable can contain multiple JSON files, separated by
<literal>:</literal>. For example:

<screen><prompt>$</prompt> export \
VK_ICD_FILENAMES=`nix-build '&lt;nixpkgs&gt;' --no-out-link -A amdvlk`/share/vulkan/icd.d/amd_icd64.json</screen>
</para>

<para>
The second mechanism is to add the Vulkan driver package to
<xref linkend="opt-hardware.opengl.extraPackages"/>. This links the
ICD file under <filename>/run/opengl-driver</filename>, where it will
be visible to the ICD loader.
</para>

<para>
The proper installation of Vulkan drivers can be verified through
the <command>vulkaninfo</command> command of the <package>vulkan-tools</package>
package. This command will report the hardware devices and drivers found,
in this example output amdvlk and radv:
</para>

<screen><prompt>$</prompt> vulkaninfo | grep GPU
GPU id : 0 (Unknown AMD GPU)
GPU id : 1 (AMD RADV NAVI10 (LLVM 9.0.1))
...
GPU0:
deviceType = PHYSICAL_DEVICE_TYPE_DISCRETE_GPU
deviceName = Unknown AMD GPU
GPU1:
deviceType = PHYSICAL_DEVICE_TYPE_DISCRETE_GPU</screen>

<para>
A simple graphical application that uses Vulkan is <command>vkcube</command>
from the <package>vulkan-tools</package> package.
</para>

<section xml:id="sec-gpu-accel-vulkan-amd">
<title>AMD</title>

<para>
Modern AMD <link
xlink:href="https://en.wikipedia.org/wiki/Graphics_Core_Next">Graphics
Core Next</link> (GCN) GPUs are supported through either radv, which is
part of <package>mesa</package>, or the <package>amdvlk</package> package.
Adding the <package>amdvlk</package> package to
<xref linkend="opt-hardware.opengl.extraPackages"/> makes both drivers
available for applications and lets them choose. A specific driver can
be forced as follows:

<programlisting><xref linkend="opt-hardware.opengl.extraPackages"/> = [
<package>amdvlk</package>
];

# For amdvlk
<xref linkend="opt-environment.variables"/>.VK_ICD_FILENAMES =
"/run/opengl-driver/share/vulkan/icd.d/amd_icd64.json";
# For radv
<xref linkend="opt-environment.variables"/>.VK_ICD_FILENAMES =
"/run/opengl-driver/share/vulkan/icd.d/radeon_icd.x86_64.json";
</programlisting>
</para>
</section>
</section>
</chapter>