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VIRTIO(4)             DragonFly Kernel Interfaces Manual             VIRTIO(4)


NAME

     virtio -- VirtIO Device Support


SYNOPSIS

     To compile VirtIO device support into the kernel, place the following
     lines in your kernel configuration file:

           device virtio

     Alternatively, to load VirtIO support as modules at boot time, place the
     following lines in loader.conf(5):

           virtio_pci_load="YES"


DESCRIPTION

     VirtIO is a specification for para-virtualized I/O in a virtual machine
     (VM).  Traditionally, the hypervisor emulated real devices such as an
     Ethernet interface or disk controller to provide the VM with I/O.  This
     emulation is often inefficient.

     VirtIO defines an interface for efficient I/O between the hypervisor and
     VM.  The virtio module provides a shared memory transport called a
     virtqueue.  The virtio_pci device driver represents an emulated PCI
     device that the hypervisor makes available to the VM.  This device
     provides the probing, configuration, and interrupt notifications needed
     to interact with the hypervisor.  DragonFly supports the following VirtIO
     devices:

           Ethernet  An emulated Ethernet device is provided by the vtnet(4)
                     device driver.

           Block     An emulated disk controller is provided by the
                     virtio_blk(4) device driver.

           SCSI      An emulated SCSI HBA is provided by the virtio_scsi(4)
                     device driver.

           Balloon   A pseudo-device to allow the VM to release memory back to
                     the hypervisor is provided by the virtio_balloon(4)
                     device driver.


LOADER TUNABLES

     Tunables can be set at the loader(8) prompt before booting the kernel or
     stored in loader.conf(5).

     hw.virtio.pci.disable_msix
             This tunable disables MSI-X interrupt usage.  The default value
             is 0 (use MSI-X interrupts if available).


SEE ALSO

     virtio_balloon(4), virtio_blk(4), virtio_random(4), virtio_scsi(4),
     vtnet(4)


HISTORY

     Support for VirtIO first appeared in FreeBSD 9.0.


AUTHORS

     FreeBSD support for VirtIO was first added by Bryan Venteicher
     <bryanv@FreeBSD.org>.

     DragonFly support for Virtio Memory Balloon adapted by Diederik de Groot
     <info@talon.nl>.

DragonFly 5.5                  October 26, 2018                  DragonFly 5.5

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