Home
QNX Hypervisor and QNX Hypervisor for Safety
The QNX Hypervisor and QNX Hypervisor for Safety products allow you to run multiple OSs on a target system so you can separate critical and non-critical functions, support a wide variety of applications, and reduce hardware costs.
Virtual Device Developer's API Reference
The Virtual Device Developer's API Reference presents the QNX hypervisor public virtual device (vdev) API. It is intended for use by developers writing virtual devices (vdevs) in a QNX hypervisor system.
vpci.h
Controls for virtual PCI (vPCI) devices
vpci_bar_base()
Return the base address of the specified BAR

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX software in Amazon Web Services (AWS) and Microsoft Azure (Azure).
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor and QNX Hypervisor for Safety
The QNX Hypervisor and QNX Hypervisor for Safety products allow you to run multiple OSs on a target system so you can separate critical and non-critical functions, support a wide variety of applications, and reduce hardware costs.
- User's Guide
  This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
- Virtual Device Developer's Guide
  The Virtual Device Developer's Guide is intended for use by developers writing virtual devices (vdevs) in a QNX hypervisor system.
- Virtual Device Developer's API Reference
  The Virtual Device Developer's API Reference presents the QNX hypervisor public virtual device (vdev) API. It is intended for use by developers writing virtual devices (vdevs) in a QNX hypervisor system.
  - Function Safety
    This section provides an overview of the restrictions that may apply when using the functions in this API.
  - aarch64/vmid.h
    Functions to access a guest's VMID (ARM)
  - abi.h
    Application binary interface (ABI) information
  - cdev.h
    Support routines for virtual character devices
  - firmware.h
    Functions for working with the firmware components of the VM presented to the guest
  - gasp.h
    Definitions and functions for working in guest address spaces
  - guest.h
    Controls for manipulating a guest system
  - hpci.h
    Host PCI interface for vdevs
  - hw_pci.h
    PCI support for vdevs
  - log.h
    Controls for logging messages
  - types.h
    vdev API base types
  - utils.h
    Miscellaneous utility functions
  - vdev-core.h
    Definitions and functions that support vdev control functions and callbacks
  - vio.h
    Definitions and functions for working with VIRTIO vdevs
  - vpci.h
    Controls for virtual PCI (vPCI) devices
    - Definitions in vpci.h
      Preprocessor macro definitions for the vpci.h header file
    - vpci_bar
      The state of a given PCI BAR
    - vpci_bar_base()
      Return the base address of the specified BAR
    - vpci_bar_writable()
      Generate the writable field for the slice descriptor of a BAR
    - vpci_cfg_read()
      Handle a read from a PCI configuration space register
    - vpci_cfg_write()
      Handle a write to the PCI configuration space
    - vpci_ctrl_pci_bars()
      Handle VDEV_CTRL_PCI_BARS on behalf of a vPCI device
    - vpci_init_rw()
      Initialize the read/write state of a vPCI device
    - vpci_region_update()
      Update the hosting qvm process with new BAR regions
    - vpci_rw_state
      Read and write configuration state for a vPCI device
    - vpci_update_bars()
      Update the BAR regions for the hosting qvm process based solely on the given BAR information
  - wdog.h
    Constants, data types, and functions to support virtual watchdog devices
  - x86_64/apic.h
    Definitions for the virtual APIC bus (x86)
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

vpci_bar_base()

Return the base address of the specified BAR

Synopsis:

#include <qvm/vpci.h>

uint64_t vpci_bar_base(const struct vpci_rw_state *const rw_cfg,
                       unsigned const idx)

Arguments:

rw_cfg: A pointer to read/write data for the vPCI device configuration space.
idx: The index of the BAR register for which information is requested.

Returns:

The base address of the specified BAR.

Page updated: March 14, 2026