Merge pull request intel#1149 from eero-t/gpu-reqs

Add GPU plugin README prerequisites section

Author: bart0sh

cmd/gpu_plugin/README.md

@@ -5,6 +5,11 @@ Table of Contents
 * [Introduction](#introduction)
 * [Modes and Configuration Options](#modes-and-configuration-options)
 * [Installation](#installation)
+ * [Prerequisites](#prerequisites)
+ * [Drivers for discrete GPUs](#drivers-for-discrete-gpus)
+ * [Kernel driver](#kernel-driver)
+ * [User-space drivers](#user-space-drivers)
+ * [Drivers for older (integrated) GPUs](#drivers-for-older-integrated-gpus)
  * [Pre-built Images](#pre-built-images)
  * [Install to all nodes](#install-to-all-nodes)
  * [Install to nodes with Intel GPUs with NFD](#install-to-nodes-with-intel-gpus-with-nfd)
@@ -19,7 +24,8 @@ Table of Contents
 ## Introduction
 
 Intel GPU plugin facilitates Kubernetes workload offloading by providing access to
-discrete (including Intel® Data Center GPU Flex Series) and integrated Intel GPU device files.
+discrete (including Intel® Data Center GPU Flex Series) and integrated Intel GPU devices
+supported by the host kernel.
 
 Use cases include, but are not limited to:
 - Media transcode
@@ -50,6 +56,73 @@ The following sections detail how to obtain, build, deploy and test the GPU devi
 
 Examples are provided showing how to deploy the plugin either using a DaemonSet or by hand on a per-node basis.
 
+### Prerequisites
+
+Access to a GPU device requires firmware, kernel and user-space
+drivers supporting it. Firmware and kernel driver need to be on the
+host, user-space drivers in the GPU workload containers.
+
+Intel GPU devices supported by the current kernel can be listed with:
+```
+$ grep i915 /sys/class/drm/card?/device/uevent
+/sys/class/drm/card0/device/uevent:DRIVER=i915
+/sys/class/drm/card1/device/uevent:DRIVER=i915
+```
+
+#### Drivers for discrete GPUs
+
+##### Kernel driver
+
+For now, kernel needs to be built from sources. Later on there will
+also be pre-built kernels and/or DKMS GPU module distro packages for
+the enterprise / long-term-support kernels.
+
+While last 5.x upstream Linux kernel releases already had preliminary
+discrete Intel GPU support, one should really use kernel v6.x.
+
+In upstream kernels, discrete GPU support needs to be enabled with kernel
+`i915.force_probe=<PCI_ID>` command line option until relevant kernel
+driver features have been completed in upstream:
+https://www.kernel.org/doc/html/latest/gpu/rfc/index.html
+
+PCI IDs for the Intel GPUs on given host can be listed with:
+```
+$ lspci | grep -e VGA -e Display | grep Intel
+88:00.0 Display controller: Intel Corporation Device 56c1 (rev 05)
+8d:00.0 Display controller: Intel Corporation Device 56c1 (rev 05)
+```
+
+(`lspci` lists GPUs with display support as "VGA compatible controller",
+and server GPUs without display support, as "Display controller".)
+
+Mesa "Iris" 3D driver header provides a mapping between GPU PCI IDs and their Intel brand names:
+https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/include/pci_ids/iris_pci_ids.h
+
+If your kernel build does not find the correct firmware version for
+a given GPU from the host (see `dmesg | grep i915` output), latest
+firmware versions are available in upstream:
+https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/i915
+
+##### User-space drivers
+
+Until new enough user-space drivers (supporting also discrete GPUs)
+are available directly from distribution package repositories, they
+can be installed to containers from Intel package repositories. See:
+https://dgpu-docs.intel.com/installation-guides/index.html
+
+Example container is listed in [Testing and demos](#testing-and-demos).
+
+Validation status against *upstream* kernel is listed in the user-space drivers release notes:
+* Media driver: https://github.com/intel/media-driver/releases
+* Compute driver: https://github.com/intel/compute-runtime/releases
+
+#### Drivers for older (integrated) GPUs
+
+For the older (integrated) GPUs, new enough firmware and kernel driver
+are typically included already with the host OS, and new enough
+user-space drivers (for the GPU containers) are in the host OS
+repositories.
+
 ### Pre-built Images
 
 [Pre-built images](https://hub.docker.com/r/intel/intel-gpu-plugin)
@@ -155,8 +228,8 @@ master
 ## Testing and Demos
 
 We can test the plugin is working by deploying an OpenCL image and running `clinfo`.
-The sample OpenCL image can be built using `make intel-opencl-icd` and must be made
-available in the cluster.
+[intel-opencl-icd](../../demo/intel-opencl-icd/) sample OpenCL image, built using
+`make intel-opencl-icd` and available from DockerHub, is used for this.
 
 1. Create a job:
 
@@ -174,8 +247,8 @@ available in the cluster.
  <log output>
  ```
 
- If the pod did not successfully launch, possibly because it could not obtain the gpu
- resource, it will be stuck in the `Pending` status:
+ If the pod did not successfully launch, possibly because it could not obtain
+ the requested GPU resource, it will be stuck in the `Pending` status:
 
  ```bash
  $ kubectl get pods