You could compare the dmesg of 5.3 kernel and 5.4 kernel, for those lines which contains the iwlwifi.
In your 5.4 kernel dmesg: [ 2.757791] compat: loading out-of-tree module taints kernel. [ 2.757807] compat: module verification failed: signature and/or required key missing - tainting kernel [ 2.757934] Loading modules backported from iwlwifi [ 2.757934] iwlwifi-stack-public:master:8324:9176b151 Looks like your 5.4 kernel load an out-of-tree wifi driver. And please also compare the "loading firmware part" of iwlwifi. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1892163 Title: Major networking regression linux-image-5.4.0-42-generic Status in linux package in Ubuntu: Incomplete Status in linux source package in Focal: Incomplete Bug description: When booting into linux-image-5.4.0-42-generic networking grinds to a halt. It is 10000x times slower than usual. Selecting an older kernel like linux-image-5.3.0-62-generic makes networking normal again. Description: Ubuntu 18.04.4 LTS Release: 18.04 ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: linux-image-5.4.0-42-generic 5.4.0-42.46~18.04.1 ProcVersionSignature: Ubuntu 5.3.0-62.56~18.04.1-generic 5.3.18 Uname: Linux 5.3.0-62-generic x86_64 ApportVersion: 2.20.9-0ubuntu7.16 Architecture: amd64 Date: Wed Aug 19 11:11:51 2020 InstallationDate: Installed on 2019-11-19 (273 days ago) InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805) SourcePackage: linux-signed-hwe-5.4 UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1892163/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
