GVE(4)

NAME
gve - Ethernet driver for Google Virtual NIC (gVNIC)

SYNOPSIS
To compile this driver into the kernel, place the following lines in your kernel configuration file:

device gve

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

    if_gve_load="YES"

DESCRIPTION
gVNIC is a virtual network interface designed specifically for Google Compute Engine (GCE). It is required to support per-VM Tier-1 networking performance, and for using certain VM shapes on GCE.

gve is the driver for gVNIC. It supports the following features:

•   RX checksum offload
•   TX chesksum offload
•   TCP Segmentation Offload (TSO)
•   Large Receive Offload (LRO) in software
•   Jumbo frames
•   Receive Side Scaling (RSS)

For more information on configuring this device, see ifconfig(8).

HARDWARE
gve binds to a single PCI device ID presented by gVNIC:

•   0x1AE0:0x0042

EXAMPLES

Change the TX queue count to 4 for the gve0 interface:
    sysctl dev.gve.0.num_tx_queues=4

Change the RX queue count to 4 for the gve0 interface:
    sysctl dev.gve.0.num_rx_queues=4

Change the TX ring size to 512 for the gve0 interface:
    sysctl dev.gve.0.tx_ring_size=512

Change the RX ring size to 512 for the gve0 interface:
    sysctl dev.gve.0.rx_ring_size=512

DIAGNOSTICS
The following messages are recorded during driver initialization:

Enabled MSIX with %d vectors

Configured device resources

Successfully attached %s

Deconfigured device resources

These messages are seen if driver initialization fails. Global (across-queues) allocation failures:

Failed to configure device resources: err=%d

No compatible queue formats

Failed to allocate ifnet struct

Failed to allocate admin queue mem

Failed to alloc DMA mem for DescribeDevice

Failed to allocate QPL page

irq and BAR allocation failures:

Failed to acquire any msix vectors

Tried to acquire %d msix vectors, got only %d

Failed to setup irq %d for Tx queue %d

Failed to setup irq %d for Rx queue %d

Failed to allocate irq %d for mgmnt queue

Failed to setup irq %d for mgmnt queue, err: %d

Failed to allocate BAR0

Failed to allocate BAR2

Failed to allocate msix table

Rx queue-specific allocation failures:

No QPL left for rx ring %d

Failed to alloc queue resources for rx ring %d

Failed to alloc desc ring for rx ring %d

Failed to alloc data ring for rx ring %d

Tx queue-specific allocation failures:

No QPL left for tx ring %d

Failed to alloc queue resources for tx ring %d

Failed to alloc desc ring for tx ring %d

Failed to vmap fifo, qpl_id = %d

The following messages are recorded when the interface detach fails:

Failed to deconfigure device resources: err=%d

If bootverbose is on, the following messages are recorded when the interface is being brought up:

Created %d rx queues

Created %d tx queues

MTU set to %d

The following messages are recorded when the interface is being brought down:

Destroyed %d rx queues

Destroyed %d tx queues

These messages are seen if errors are encountered when bringing the interface up or down:

Failed to destroy rxq %d, err: %d

Failed to destroy txq %d, err: %d

Failed to create rxq %d, err: %d

Failed to create txq %d, err: %d

Failed to set MTU to %d

Invalid new MTU setting. new mtu: %d max mtu: %d min mtu: %d

Cannot bring the iface up when detached

Reached max number of registered pages %lu > %lu

Failed to init lro for rx ring %d

These messages are seen if any admin queue command fails:

AQ command(%u): failed with status %d

AQ command(%u): unknown status code %d

AQ commands timed out, need to reset AQ

Unknown AQ command opcode %d

These messages appear if a TX timeout is detected:

Found %d timed out packet(s) on txq%d, kicking it for completions

Found %d timed out packet(s) on txq%d with its last kick %ld sec ago which is less than the cooldown period %d. Resetting device

These messages are recorded when the device is being reset due to an error:

Scheduling reset task!

Waiting until admin queue is released.

Admin queue released

If it was the NIC that requested the reset, this message is recorded:

Device requested reset

If the reset fails during the reinitialization phase, this message is recorded:

Restore failed!

These two messages correspoond to the NIC alerting the driver to link state changes:

Device link is up.

Device link is down.

Apart from these messages, the driver exposes per-queue packet and error counters as sysctl nodes. Global (across queues) counters can be read using netstat(1).

SYSCTL VARIABLES
gve exposes the following sysctl(8) variables:

hw.gve.driver_version
    The driver version. This is read-only.

hw.gve.queue_format
    The queue format in use. This is read-only.

hw.gve.disable_hw_lro
    Setting this boot-time tunable to 1 disables Large Receive Offload (LRO) in the NIC. The default value is 0, which means hardware LRO is enabled by default. The software LRO stack in the kernel is always used. This sysctl variable needs to be set before loading the driver, using loader.conf(5).

hw.gve.allow_4k_rx_buffers
    Setting this boot-time tunable to 1 enables support for 4K RX Buffers. The default value is 0, which means 2K RX Buffers will be used. 4K RX Buffers are only supported on DQO_RDA and DQO_QPL queue formats. When enabled, 4K RX Buffers will be used either when HW LRO is enabled or mtu is greated than 2048. This sysctl variable needs to be set before loading the driver, using loader.conf(5).

dev.gve.X.num_rx_queues and dev.gve.X.num_tx_queues
    Run-time tunables that represent the number of currently used RX/TX queues. The default value is the max number of RX/TX queues the device can support.

    This call turns down the interface while setting up the new queues, which may potentially cause any new packets to be dropped. This call can fail if the system is not able to provide the driver with enough resources. In that situation, the driver will revert to the previous number of RX/TX queues. If this also fails, a device reset will be triggered.

    Note: sysctl nodes for queue stats remain available even if a queue is removed.

dev.gve.X.rx_ring_size and dev.gve.X.tx_ring_size
    Run-time tunables that represent the current ring size for RX/TX queues. The default value is set to device defaults for ring size.

    This call turns down the interface while setting up the queues with the new ring size, which may potentially cause any new packets to be dropped. This call can fail if the system is not able to provide the driver with enough resources. In that situation, the driver will try to revert to the previous ring size for RX/TX queues. If this also fails, the device will be in an unhealthy state and will need to be reloaded. This value must be a power of 2 and within the defined range.

LIMITATIONS
gve does not support the transmission of VLAN-tagged packets. All VLAN-tagged traffic is dropped.

QUEUE FORMATS
gve features different datapath modes called queue formats:

•   GQI_QPL: "QPL" stands for "Queue Page List" and refers to the fact that hardware expects a fixed bounce buffer and cannot access arbitrary memory. GQI is the older descriptor format. The G in "GQI" refers to an older generation of hardware, and the "QI" stands for "Queue In-order" referring to the fact that the NIC sends Tx and Rx completions in the same order as the one in which the corresponding descriptors were posted by the driver.
•   DQO_RDA: DQO is the descriptor format required to take full advantage of next generation VM shapes. "RDA" stands for "Raw DMA Addressing" and refers to the fact that hardware can work with DMA-ed packets and does not expect them to be copied into or out of a fixed bounce buffer. The D in "DQO" refers to a newer generation of hardware, and the "QO" stands for "Queue Out-of-order" referring to the fact that the NIC might send Tx and Rx completions in an order different from the one in which the corresponding descriptors were posted by the driver.
•   DQO_QPL: The next generation descriptor format in the "QPL" mode.

SUPPORT
Please email gvnic-drivers@google.com with the specifics of the issue encountered.

SEE ALSO
netstat(1), loader.conf(5), ifconfig(8), sysctl(8)

HISTORY
The gve device driver first appeared in FreeBSD 14.0.

AUTHORS
The gve driver was written by Google.