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virtio(4) [freebsd man page]

VIRTIO(4)						   BSD Kernel Interfaces Manual 						 VIRTIO(4)

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 device 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. 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. SEE ALSO
virtio_balloon(4), virtio_blk(4), virtio_console(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 <>. BSD
January 22, 2012 BSD

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VTNET(4)						   BSD Kernel Interfaces Manual 						  VTNET(4)

vtnet -- VirtIO Ethernet driver SYNOPSIS
To compile this driver into the kernel, place the following lines in your kernel configuration file: device vtnet Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5): if_vtnet_load="YES" DESCRIPTION
The vtnet device driver provides support for VirtIO Ethernet devices. If the hypervisor advertises the appreciate features, the vtnet driver supports TCP/UDP checksum offload for both transmit and receive, TCP segmentation offload (TSO), TCP large receive offload (LRO), and hardware VLAN tag stripping/insertion features, as well as a multicast hash filter, as well as Jumbo Frames (up to 9216 bytes), which can be configured via the interface MTU setting. Selecting an MTU larger than 1500 bytes with the ifconfig(8) utility configures the adapter to receive and transmit Jumbo Frames. For more information on configuring this device, see ifconfig(8). LOADER TUNABLES
Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5). hw.vtnet.csum_disable hw.vtnet.X.csum_disable This tunable disables receive and send checksum offload. The default value is 0. hw.vtnet.tso_disable hw.vtnet.X.tso_disable This tunable disables TSO. The default value is 0. hw.vtnet.lro_disable hw.vtnet.X.lro_disable This tunable disables LRO. The default value is 0. hw.vtnet.mq_disable hw.vtnet.X.mq_disable This tunable disables multiqueue. The default value is 0. hw.vtnet.mq_max_pairs hw.vtnet.X.mq_max_pairs This tunable sets the maximum number of transmit and receive queue pairs. Multiple queues are only supported when the Multiqueue feature is negotiated. This driver supports a maximum of 8 queue pairs. The number of queue pairs used is the lesser of the maximum supported by the driver and the hypervisor, the number of CPUs present in the guest, and this tunable if not zero. The default value is 0. SEE ALSO
arp(4), netintro(4), ng_ether(4), virtio(4), vlan(4), ifconfig(8) HISTORY
The vtnet driver was written by Bryan Venteicher <>. It first appeared in FreeBSD 9.0. CAVEATS
The vtnet driver only supports LRO when the hypervisor advertises the mergeable buffer feature. BSD
January 22, 2012 BSD
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