Virtual Configuration Space (VCFS) is a software implementation that enables the emulation and manipulation of PCI Express (PCIe) configuration space. Unlike traditional PCI configuration mechanisms that may have hardware-imposed limitations, VCFS provides a fully virtualized environment where users have complete control to view and modify all aspects of the PCIe configuration.

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Overview

PCIe devices expose their capabilities, settings, and control interfaces through a standardized configuration space - a memory area with predefined register layouts. VCFS creates a software representation of this configuration space, allowing for:
  • Inspection of the complete configuration hierarchy
  • Modification of any configuration register value
  • Creation of custom device configurations that may not exist in physical hardware
  • Testing and development without physical PCIe devices

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Features

  • Complete Editability: All configuration registers can be viewed and modified, including typically read-only fields in physical hardware
  • Flexible Configuration: Create custom device profiles with specific capabilities, BARs, and other attributes
  • Runtime Modification: Change device characteristics on the fly without physical constraints
  • Debugging Tools: Inspect and understand configuration space layout and register purposes
  • Configuration Snapshots: Save and restore complete device configurations

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Implementation

VCFS provides a programmatic interface to create, modify, and interact with PCIe configuration space. It handles the complexities of PCI Express specifications while giving users direct access to the underlying configuration structures. The crate can be used as a standalone tool for PCIe configuration exploration, or integrated into larger virtualization or emulation systems that need to present PCIe devices to guest operating systems or applications.