GPU Driver Internals

This page will detail the internals of various GPU drivers for use with I/O Virtualization.

i915

Initialization

During initialization of the i915 driver the GuC binary blob is offloaded into the Graphics Translation Table (GTT). This allows the GuC to read GTT-loaded binary blob from shared framebuffer memory so that it may boot.

Scheduling

In-VM Scheduling

vExeclist

The vExeclist is a method to submit commands directly to the GPU without the use of an intermediate microcontroller.

vGuC

vGuC is a command submission interface used to process commands to the Intel Graphics Microcontroller (GuC).

Memory Management

i915 Clients

Processes which make use of the Intel i915 driver receive an i915 Client ID.

Translation Tables

GTT (Graphics Translation Table)

GPU Memory on-device is a part of a GTT or Graphics Translation Table. This table stores information globally for all graphics processes within the system. Some processes access the GTT such as DRI while other's receive a Per Process Graphics Translation Table (PPGTT) buffer based on their i915 Client ID.

PPGTT (Per Process Graphics Translation Table)

Process-specific memory buffers are stored inside a Per Process Graphics Translation Table or PPGTT. This is an GPU MMU translated subregion or IOVA of global GPU memory specific to a GPU process's client ID.

OpenRM

High Level Architecture

The Open Resource Manager driver (also known as OpenRM) refers to Nvidia's open-kernel-modules.

Broadly speaking the OpenRM driver consists of two parts.

• The Driver RM
• The Firmware RM

Initialization

During bring up of the hardware several binary blobs are loaded from embedded boot-ROM memory to bootstrap embedded controller bring up from which point additional software is loaded from onboard SPI flash memory. Software loaded from SPI flash is necessary for the full initialization of the Falcon/NvRISC processor as well as a cached version of the software necessary to run the GPU System Processor (GSP). Once the platform is posted it is ready to communicate with the host platform's RM driver. The OpenRM driver offloads a binary blob containing the RM Core to the GPU System Processor (GSP) which is likely to contain a more recent version than the cached version contained in on-board SPI flash.

Memory Management

RM Clients

Processes which make use of the RM driver receive an RM Client ID.

Citations (Talks and Reading Material)

1. Intel Graphics Programmer's Reference Manuals (PRM)
2. i915: Hardware Contexts (and some bits about batchbuffers)
3. i915: The Global GTT Part 1
4. i915: Aliasing PPGTT Part 2
5. i915: True PPGTT Part 3
6. i915: Future PPGTT Part 4 (Dynamic page table allocations, 64 bit address space, GPU "mirroring", and yeah, something about relocs too)
7. i915: Security of the Intel Graphics Stack - Part 1 - Introduction
8. i915: Security of the Intel Graphics Stack - Part 2 - FW <-> GuC
9. i915: An Introduction to Intel GVT-g (with new architecture)