e1000e: I219-V RX CRC errors on ThinkPad P14s Gen6 Intel; disabling K1 restores throughput

e1000e: I219-V RX CRC errors on ThinkPad P14s Gen6 Intel; disabling K1 restores throughput

[Christoph Groth]

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Hello,

I noticed that wired Ethernet throughput from WAN is much lower than
expected on my new ThinkPad P14s Gen6 Intel.  The culprit seems to be
CRC errors.  This is with current firmware.  I updated everything one or
two weeks ago.

Executing ‘ethtool --set-priv-flags enp0s31f6 disable-k1 on’ works
around the problem.  There could be a relation to commit 578294b8b60d
that re-enabled K1 by default.

See below for a shell session demonstrating the problem by downloading
data for 30 seconds.  With K1 enabled, the transfer generated 125 CRC
errors while receiving 156 MiB; with K1 disabled, the error counter
remained unchanged while receiving 2547 MiB (i.e. a 16-fold faster
download).  The following has been recorded using a freshly booted
current Debian testing live system.

I’ve been observing the same problem with different recent kernel
versions, different network cables, routers, and networks.  I also had
the opportunity to reproduce the problem with a second identical
computer.

Cheers
Christoph

----------------------------------------------------------------

root@debian:~# uname -a
Linux debian 7.2.6+deb14-amd64 #1 SMP PREEMPT_DYNAMIC Debian 7.2.6-1 (2026-09-16) x86_64 GNU/Linux
root@debian:~# ethtool --show-priv-flags enp0s31f6
Private flags for enp0s31f6:
s0ix-enabled: on
disable-k1  : off
root@debian:~# ip -s -s link show dev enp0s31f6
2: enp0s31f6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether [hidden] brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
         26981     189      0       0       0      72
    RX errors:  length    crc   frame    fifo overrun
                     0      0       0       0       0
    TX:  bytes packets errors dropped carrier collsns
         10442      89      0       0       0       0
    TX errors: aborted   fifo  window heartbt transns
                     0      0       0       0       2
    altname enx[hidden]
root@debian:~# curl --max-time 30 -o /dev/null http://test-debit.free.fr/10485760.rnd
  % Total    % Received % Xferd  Average Speed  Time    Time    Time   Current
                                 Dload  Upload  Total   Spent   Left   Speed
  1 10.00G   1 153.9M   0      0  5.28M      0   32:18   00:29   31:49  5.58M
curl: (28) Operation timed out after 30000 milliseconds with 163226929 out of 10737418240 bytes received
root@debian:~# ip -s -s link show dev enp0s31f6
2: enp0s31f6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether [hidden] brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
     171179576  112998    250       0       0      96
    RX errors:  length    crc   frame    fifo overrun
                     0    125       0       0       0
    TX:  bytes packets errors dropped carrier collsns
       1102954   15430      0       0       0       0
    TX errors: aborted   fifo  window heartbt transns
                     0      0       0       0       2
    altname enx[hidden]
root@debian:~# ethtool --set-priv-flags enp0s31f6 disable-k1 on
root@debian:~# ethtool --show-priv-flags enp0s31f6
Private flags for enp0s31f6:
s0ix-enabled: on
disable-k1  : on
root@debian:~# curl --max-time 30 -o /dev/null http://test-debit.free.fr/10485760.rnd
  % Total    % Received % Xferd  Average Speed  Time    Time    Time   Current
                                 Dload  Upload  Total   Spent   Left   Speed
 23 10.00G  23  2.38G   0      0 84.23M      0   02:01   00:29   01:32 104.7M
curl: (28) Operation timed out after 30000 milliseconds with 2670737217 out of 10737418240 bytes received
root@debian:~# ip -s -s link show dev enp0s31f6
2: enp0s31f6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether [hidden] brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
    2972820757 1958686    250       0       0     122
    RX errors:  length    crc   frame    fifo overrun
                     0    125       0       0       0
    TX:  bytes packets errors dropped carrier collsns
      13144890  187359      0       0       0       0
    TX errors: aborted   fifo  window heartbt transns
                     0      0       0       0       4
    altname enx[hidden]

----------------------------------------------------------------

Information from /sys/class/dmi/id/:
sys_vendor: LENOVO
product_name: 21QTS28200
product_version: ThinkPad P14s Gen 6
board_name: 21QTS28200
bios_vendor: LENOVO
bios_version: R2WET44W (1.26 )
bios_date: 06/30/2026

Information about the Ethernet adapter:
# lspci -nnvv -s 00:1f.6
00:1f.6 Ethernet controller [0200]: Intel Corporation Ethernet Connection (24) I219-V [8086:57a1]
	Subsystem: Lenovo Device [17aa:512b]
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin D routed to IRQ 128
	IOMMU group: 17
	Region 0: Memory at af780000 (32-bit, non-prefetchable) [size=128K]
	Capabilities: [c8] Power Management version 3
		Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
		Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=1 PME-
	Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
		Address: 00000000fee00318  Data: 0000
	Kernel driver in use: e1000e
	Kernel modules: e1000e

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