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VIRTIO(4) 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 device virtio_pci Alternatively, to load VirtIO support as modules at boot time, place the following lines in loader.conf(5): virtio_load="YES" 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 de- vice that the hypervisor makes available to the VM. This device pro- vides the probing, configuration, and interrupt notifications needed to interact with the hypervisor. FreeBSD 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. Console Provided by the virtio_console(4) driver. Entropy Provided by the virtio_random(4) 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. GPU Graphics support is provided by the virtio_gpu(4) de- vice driver. SCSI An emulated SCSI HBA is provided by the virtio_scsi(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 If set to 1, disables MSI-X. The default value is 0. hw.virtio.pci.transitional For a transitional virtio device, this tun- able specifies whether to negotiate modern mode and use the modern virtio driver (1) or to negotiate legacy mode and use the legacy virtio driver (0). The default value is 0. SEE ALSO virtio_balloon(4), virtio_blk(4), virtio_console(4), virtio_gpu(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>. FreeBSD ports 15.quarterly April 4, 2026 VIRTIO(4)
NAME | SYNOPSIS | DESCRIPTION | LOADER TUNABLES | SEE ALSO | HISTORY | AUTHORS
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