CXGBEV(4)

💖 CXGBEV(4) — Chelsio T4-, T5-, and T6-based 100Gb, 40Gb, 25Gb, 10Gb, and 1Gb Ethernet VF driver 💖

okay bestie, sit down, hydrate, because this is the kernel interfaces manual page for cxgbev and we're gonna get through it together. it's giving network driver, it's giving PCI Express Virtual Functions, it's giving slay. let's go 🦋

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✨ NAME ✨

cxgbev — the Chelsio T4-, T5-, and T6-based 100Gb, 40Gb, 25Gb, 10Gb, and 1Gb Ethernet VF driver. no cap, that's the whole name, it's a lot, we love her for it 💅

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🌸 SYNOPSIS 🌸

so to compile this driver into the kernel, you drop these lines into your kernel configuration file:

device cxgbe
device cxgbev

and if you wanna load the driver as a module at boot time instead, you put this line in loader.conf(5):

if_cxgbev_load="YES"

that's it. that's the whole vibe check. periodt 🎀

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💫 DESCRIPTION 💫

the cxgbev driver provides support for Virtual Functions on PCI Express Ethernet adapters based on the Chelsio Terminator 4, Terminator 5, and Terminator 6 ASICs (T4, T5, and T6). like, the whole Terminator lineup, iconic behavior honestly 👑

and what does she support? literally everything:

• Jumbo Frames
• Transmit/Receive checksum offload
• TCP segmentation offload (TSO)
• Large Receive Offload (LRO)
• VLAN tag insertion/extraction
• VLAN checksum offload
• VLAN TSO
• Receive Side Steering (RSS)

for further hardware info and any questions about hardware requirements, go look at http://www.chelsio.com/. iykyk 🌈

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🧚 the names thing (important!!)

okay so the cxgbev driver uses different names for devices depending on which ASIC is in play. this is the part where you actually pay attention:

• ASIC T4 → port name cxgbev, parent device t4vf
• ASIC T5 → port name cxlv, parent device t5vf
• ASIC T6 → port name ccv, parent device t6vf

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🫶 tunables + sysctl MIBs, the lore

Loader tunables with the hw.cxgbe prefix apply to VFs from all cards. the Physical Function driver for Chelsio Terminator adapters shares these tunables, bestie, they're literally sharing. the driver also provides sysctl MIBs for both ports and parent devices using the names above. for example — and this is the example, i'm not making it up — a T5 VF provides port MIBs under dev.cxlv and parent device MIBs under dev.t5vf. 📚

references to sysctl MIBs for the rest of this page use dev.<port> for port MIBs and dev.<nexus> for parent device MIBs. memorize it, it's on the test.

for more info on configuring this device, see ifconfig(8).

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🔥 HARDWARE 🔥

T6 ASIC — 100Gb and 25Gb Ethernet adapters, Virtual Functions:

• Chelsio T6225-CR
• Chelsio T6225-SO-CR
• Chelsio T62100-LP-CR
• Chelsio T62100-SO-CR
• Chelsio T62100-CR

T5 ASIC — 40Gb, 10Gb and 1Gb Ethernet adapters, Virtual Functions:

• Chelsio T580-CR
• Chelsio T580-LP-CR
• Chelsio T580-LP-SO-CR
• Chelsio T560-CR
• Chelsio T540-CR
• Chelsio T540-LP-CR
• Chelsio T522-CR
• Chelsio T520-LL-CR
• Chelsio T520-CR
• Chelsio T520-SO
• Chelsio T520-BT
• Chelsio T504-BT

T4 ASIC — 10Gb and 1Gb Ethernet adapters, Virtual Functions:

• Chelsio T420-CR
• Chelsio T422-CR
• Chelsio T440-CR
• Chelsio T420-BCH
• Chelsio T440-BCH
• Chelsio T440-CH
• Chelsio T420-SO
• Chelsio T420-CX
• Chelsio T420-BT
• Chelsio T404-BT

that's a whole lotta part numbers and every single one of them is in the list. ate. 💅

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🌟 LOADER TUNABLES 🌟

these tunables can be set at the loader(8) prompt before booting the kernel, or stored in loader.conf(5). pick your fighter, both are valid. ✨

• hw.cxgbe.ntxq — number of tx queues used for a port. the default is 16 or the number of CPU cores in the system, whichever is less.
• hw.cxgbe.nrxq — number of rx queues used for a port. the default is 8 or the number of CPU cores in the system, whichever is less.
• hw.cxgbe.holdoff_timer_idx — timer index value used to delay interrupts. the holdoff timer list has the values 1, 5, 10, 50, 100, and 200 by default (all values are in microseconds) and the index selects a value from this list. the default value is 1 which means the timer value is 5us. different interfaces can be assigned different values at any time via the dev.<port>.X.holdoff_tmr_idx sysctl.
• hw.cxgbe.holdoff_pktc_idx — packet-count index value used to delay interrupts. the packet-count list has the values 1, 8, 16, and 32 by default, and the index selects a value from this list. the default value is -1 which means packet counting is disabled and interrupts are generated based solely on the holdoff timer value. different interfaces can be assigned different values via the dev.<port>.X.holdoff_pktc_idx sysctl. this sysctl works only when the interface has never been marked up (as done by ifconfig up).
• hw.cxgbe.qsize_txq — number of entries in a transmit queue's descriptor ring. a buf_ring of the same size is also allocated for additional software queuing. see ifnet(9). the default value is 1024. different interfaces can be assigned different values via the dev.<port>.X.qsize_txq sysctl. this sysctl works only when the interface has never been marked up (as done by ifconfig up).
• hw.cxgbe.qsize_rxq — number of entries in a receive queue's descriptor ring. the default value is 1024. different interfaces can be assigned different values via the dev.<port>.X.qsize_rxq sysctl. this sysctl works only when the interface has never been marked up (as done by ifconfig up).
• hw.cxgbe.interrupt_types — permitted interrupt types. bit 0 represents INTx (line interrupts), bit 1 MSI, and bit 2 MSI-X. the default is 7 (all allowed). the driver selects the best possible type out of the allowed types. note that Virtual Functions do not support INTx interrupts and fail to attach if neither MSI nor MSI-X are enabled. 💀
• hw.cxgbe.fl_pktshift — number of padding bytes inserted before the beginning of an Ethernet frame in the receive buffer. the default value of 2 ensures that the Ethernet payload (usually the IP header) is at a 4 byte aligned address. 0-7 are all valid values.
• hw.cxgbe.fl_pad — a non-zero value ensures that writes from the hardware to a receive buffer are padded up to the specified boundary. the default is -1 which lets the driver pick a pad boundary. 0 disables trailer padding completely.
• hw.cxgbe.buffer_packing — allow the hardware to deliver multiple frames in the same receive buffer opportunistically. the default is -1 which lets the driver decide. 0 or 1 explicitly disable or enable this feature.
• hw.cxgbe.allow_mbufs_in_cluster — 1 allows the driver to lay down one or more mbufs within the receive buffer opportunistically. this is the default. 0 prohibits the driver from doing so.
• hw.cxgbe.largest_rx_cluster, hw.cxgbe.safest_rx_cluster — sizes of rx clusters. each of these must be set to one of the sizes available (usually 2048, 4096, 9216, and 16384) and largest_rx_cluster must be greater than or equal to safest_rx_cluster. the defaults are 16384 and 4096 respectively. the driver never attempts to allocate a receive buffer larger than largest_rx_cluster and falls back to allocating buffers of safest_rx_cluster size if an allocation larger than safest_rx_cluster fails. note that largest_rx_cluster merely establishes a ceiling — the driver is allowed to allocate buffers of smaller sizes.

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🙈 the VF / PF situationship (read this, fr fr)

certain settings and resources for Virtual Functions are dictated by the parent Physical Function driver. for example, the Physical Function driver limits the number of queues available to a Virtual Function. some of these limits can be adjusted in the firmware configuration file used with the Physical Function driver.

the PAUSE settings on the port of a Virtual Function are inherited from the settings of the same port on the Physical Function. Virtual Functions cannot modify the setting and track changes made to the associated port's setting by the Physical Function driver. so like, she's not in charge of her own PAUSE settings, the parent is, we don't make the rules 😭

Receive queues on a Virtual Function always drop packets in response to congestion (equivalent to setting hw.cxgbe.cong_drop to 1).

💀 heads up: the VF driver currently depends on the PF driver. as a result, loading the VF driver also loads the PF driver as a dependency. that's not a bug, that's just the relationship.

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💜 SUPPORT 💜

for general information and support, go to the Chelsio support website at: http://www.chelsio.com/. 🫶

if an issue is identified with this driver with a supported adapter, email all the specific information related to the issue to ⟨support@chelsio.com⟩. be thorough bestie, they want the specific info, not just "it's broken" 🍓

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👑 SEE ALSO 👑

• altq(4)
• arp(4)
• cxgbe(4)
• netintro(4)
• ng_ether(4)
• ifconfig(8)

the whole friend group, honestly. go read them next. 💖

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🌸 HISTORY 🌸

the cxgbev device driver first appeared in FreeBSD 11.1 and FreeBSD 11.1. (yes, it says it twice — that's the page, that's the lore, i don't make the rules ✨)

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⭐ AUTHORS ⭐

the cxgbev driver was written by Navdeep Parhar <np@FreeBSD.org> and John Baldwin <jhb@FreeBSD.org>. legends, both of them, no notes. 🔥

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and that's the whole page bestie — this was CXGBEV(4) from the Kernel Interfaces Manual, coming to you from Debian, dated May 9, 2017. mwah, go configure your VFs responsibly 💅✨