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QNX Hypervisor
The QNX Hypervisor allows 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.
QNX Hypervisor for Safety Virtual Device Developer's API Reference
gasp.h
Functions for working in guest address spaces
gram_find_free()
Find a free memory space from a guest system's RAM/ROM regions

QNX Momentics IDE User's Guide
This User's Guide describes version 7.1 of the Integrated Development Environment (IDE) that's part of the QNX Momentics 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 QNX Neutrino 7.1.
QNX Hypervisor
The QNX Hypervisor allows 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.
- QNX Hypervisor for Safety User's Guide
- QNX Hypervisor for Safety Virtual Device Developer's Guide
- QNX Hypervisor for Safety Virtual Device Developer's API Reference
  - Function Safety
    This section provides an overview of the restrictions that may apply when using the functions in this API.
  - aarch64/vmid.h
    Definitions to access a guest's VMID (ARM)
  - abi.h
    Application binary interface (ABI) version of the vdev API
  - cdev.h
    Functions to create virtual character devices for guests
  - firmware.h
    Functions for working with the firmware components of the VM presented to the guest
  - gasp.h
    Functions for working in guest address spaces
    - Definitions in gasp.h
      Preprocessor macro definitions for the gasp.h header file
    - gasp_find_free()
      Find a free region of a particular space type
    - gasp_find_free_range()
      Find a free region of a particular space type inside a specified address range
    - gasp_lock()
      Lock access to regions of the specified type
    - gasp_map_contig()
      Map a guest-physical address range into the qvm process address space for virtual hardware access
    - gasp_map_sys()
      Map a guest-physical address range into the qvm process address space for virtual firmware access
    - gasp_map_vdma()
      Map a guest-physical address range into the qvm process address space for virtual hardware access
    - gasp_region_info()
      Query information about a guest location
    - gasp_region_set()
      Add, modify, or delete address-space regions in the guest system
    - gasp_region_set_soft()
      Add, modify, or delete address-space regions in the guest system
    - gasp_unlock()
      Release access to regions of the specified type
    - gasp_unmap()
      Unmap a qvm process address space range that mapped a guest-physical address range
    - gasp_walk_count()
      Return the number of RAM/ROM entries found in the guest's address space
    - gasp_walk_count_filtered()
      Return the number of RAM/ROM entries found in the guest's address space that can be accessed through the memory walk filter
    - gasp_walk_filter_t
      Prototype for function that applies a walk filter
    - gasp_walk_init()
      Initialize a memory walk state structure
    - gasp_walk_init_filtered()
      Initialize a memory walk filter state structure
    - gasp_walk_next()
      Return information about the next RAM/ROM block of memory
    - gasp_walk_next_filtered()
      Return information about the next RAM/ROM block of memory that can be accessed through the memory walk filter
    - gasp_walk_state
      Structure with the guest system's walk state
    - gasp_walk_state_filtered
      Structure with the guest system's walk filter state
    - gasp_walk_state_flags
      Flags to specify what guest address space information is needed
    - gram_find_free()
      Find a free memory space from a guest system's RAM/ROM regions
    - gram_find_free_range()
      Find a free memory space from a guest system's RAM/ROM regions within a specified range
    - GRAM_HINT_* enum
      Preferred locations in which to look for available memory
    - gram_reserve()
      Mark a RAM/ROM range as being in use
  - guest.h
    Definitions for manipulating a guest system
  - hpci.h
    Host PCI interface for vdevs
  - hw_pci.h
    PCI support for vdevs
  - outpipe.h
    Definitions for the output pipe (outpipe)
  - types.h
    vdev API base types
  - utils.h
    Miscellaneous utility functions
  - vdev.h
    Source compatibility header file
  - vdev-core.h
    Definitions for vdevs
  - vio.h
    Definitions for VIRTIO vdevs
  - vpci.h
    Definitions for virtual PCI devices
  - wdog.h
    Definitions to support virtual watchdog devices
  - x86_64/apic.h
    Definitions for the virtual APIC bus (x86)
- QNX Hypervisor User's Guide
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 Advanced Virtualization Frameworks User's Guide
This User's Guide is aimed at all systems integrators and developers who want to design and build embedded systems using the QNX Advanced Virtualization Frameworks.
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation and explains how to obtain technical support.

gram_find_free()

Find a free memory space from a guest system's RAM/ROM regions

Synopsis:

#include <qvm/gasp.h>

static uint64_t gram_find_free(struct guest_system *const gsp,
                               uint64_t const size,
                               uint64_t const align,
                               unsigned const flags)

Arguments:

gsp: A pointer to the system where we want to find the free space.
size: The number of bytes of free space that we need.
align: The requested alignment of the space.
flags: A GRAM_HINT_* combination.

Description:

This function calls gram_reserve() on the region it returns, so you don't need to do that.

Returns:

The location of the free space, or QSL_NO_LOCATION if no space is available.

Page updated: March 12, 2026