We now have the ability to selectively alter the default K1 value on a system-by-system basis. I will send a follow-up patch.
From: ghrafn <[email protected]> Sent: Monday, 5 October 2026 21:52 To: Nguyen, Anthony L <[email protected]> Cc: Ruinskiy, Dima <[email protected]>; Kitszel, Przemyslaw <[email protected]>; [email protected]; [email protected]; [email protected]; [email protected] Subject: Re: [REGRESSION] e1000e: heavy packet loss on Lenovo ThinkPad P14s Gen 5 (I219-LM, Meteor Lake) after K1 re-enable; fixed by disable-k1 (Following up on this regression report: https://lists.openwall.net/netdev/2026/09/15/253<https://lists.openwall.net/netdev/2026/09/15/253?utm_source=chatgpt.com>) Hi, I appear to be seeing the same issue on a Lenovo ThinkPad T14 Gen 6, with an Intel Ethernet Connection (24) I219-LM [8086:57a0]. With the default e1000e configuration (disable-k1: off), wired Ethernet experiences severe packet loss even to the local gateway. The interface still negotiates normally at 1000 Mb/s, full duplex, and the e1000e statistics do not report CRC, frame, DMA, or other RX errors. For example: $ ping -c 10 192.168.0.1 10 packets transmitted, 3 received, 70% packet loss ARP traffic is affected as well: $ sudo arping -I enp0s31f6 -c 20 192.168.0.1 20 packets transmitted, 11 packets received, 45% unanswered A tcpdump on enp0s31f6 showed the outgoing ICMP echo requests, but replies were absent for the lost packets. The NIC identifies as: Intel Corporation Ethernet Connection (24) I219-LM [8086:57a0] and uses e1000e. Setting the existing private flag: # ethtool --set-priv-flags enp0s31f6 disable-k1 on immediately eliminates the problem. After setting disable-k1: $ ping -c 30 192.168.0.1 30 packets transmitted, 30 received, 0% packet loss rtt min/avg/max/mdev = 0.384/0.538/0.885/0.098 ms and: $ sudo arping -I enp0s31f6 -c 20 192.168.0.1 20 packets transmitted, 20 packets received, 0% unanswered The result is repeatable within the same session: the severe local packet loss disappeared immediately after disabling K1. System information: Laptop: Lenovo ThinkPad T14 Gen 6 DMI sys_vendor: LENOVO DMI product_name: 21QCS01600 DMI product_version: ThinkPad T14 Gen 6 DMI board_name: 21QCS01600 BIOS: N4JET28W (1.18 ) (date: 06/16/2026) CPU: Intel(R) Core(TM) Ultra 5 235U Kernel: Linux 7.0.0-38-generic NIC: 00:1f.6 Intel Ethernet Connection (24) I219-LM [8086:57a0] e1000e firmware: 0.1-4 Link: 1000 Mb/s Full Duplex OS: Ubuntu 26.04.1 LTS I am currently working around the issue by setting disable-k1 on. This looks sufficiently similar to the reported P14s Gen 5 issue that I wanted to report the additional affected platform in case the T14 Gen 6 also needs to be added to disable_k1_list. I'm happy to test a patch or provide additional diagnostics if useful. Thanks, Gísli
