I have a Lenovo x1 Carbon Gen5 and when it initially came out if you left the onboard NIC (e1000e) module loaded it would suck CPU/battery life so I have it removed in rc.local on boot.
In 5.4 (also happens on 5.4.0.15.18 which I'm running from proposed right now), this is what happens when the module is unloaded:
[ 608.979789] e1000e 0000:00:1f.6 enp0s31f6: removed PHC
[ 609.008352] ------------[ cut here ]------------
[ 609.008353] kernel BUG at drivers/pci/msi.c:375!
[ 609.008358] invalid opcode: 0000 [#1] SMP PTI
[ 609.008359] CPU: 0 PID: 6829 Comm: rmmod Tainted: P O 5.4.0-15-generic #18-Ubuntu
[ 609.008360] Hardware name: LENOVO 20HRCTO1WW/20HRCTO1WW, BIOS N1MET59W (1.44 ) 11/25/2019
[ 609.008364] RIP: 0010:free_msi_irqs+0x17d/0x1b0
[ 609.008365] Code: 84 df fe ff ff 45 31 f6 eb 11 41 83 c6 01 44 39 73 14 0f 86 cc fe ff ff 8b 7b 10 44 01 f7 e8 ea c3 b6 ff 48 83 78 70 00 74 e0 <0f> 0b 49 8d b5 b0 00 00 00 e8 b5 7d b7 ff e9 cd fe ff ff 49 8b 78
[ 609.008366] RSP: 0018:ffffa7d2072f7d40 EFLAGS: 00010286
[ 609.008367] RAX: ffff8bc9bfb49e00 RBX: ffff8bc9ad69c720 RCX: 0000000000000000
[ 609.008368] RDX: 0000000000000000 RSI: 0000000000000084 RDI: ffffffffa9e65980
[ 609.008369] RBP: ffffa7d2072f7d70 R08: ffff8bc9bb564db0 R09: ffff8bc9bb564df8
[ 609.008369] R10: 0000000000000000 R11: ffffffffa9e65988 R12: ffff8bc9cb5272c0
[ 609.008370] R13: ffff8bc9cb527000 R14: 0000000000000000 R15: dead000000000100
[ 609.008371] FS: 00007f188f1f9500(0000) GS:ffff8bc9ce200000(0000) knlGS:0000000000000000
[ 609.008372] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 609.008373] CR2: 00007f6d1a6af060 CR3: 000000046d9f8006 CR4: 00000000003606f0
[ 609.008373] Call Trace:
[ 609.008376] pci_disable_msi+0x100/0x130
[ 609.008385] e1000e_reset_interrupt_capability+0x52/0x60 [e1000e]
[ 609.008389] e1000_remove+0xc4/0x180 [e1000e]
[ 609.008391] pci_device_remove+0x3e/0xb0
[ 609.008394] device_release_driver_internal+0xf0/0x1d0
[ 609.008396] driver_detach+0x4c/0x8f
[ 609.008397] bus_remove_driver+0x5c/0xd0
[ 609.008399] driver_unregister+0x31/0x50
[ 609.008400] pci_unregister_driver+0x40/0x90
[ 609.008405] e1000_exit_module+0x10/0x3c1 [e1000e]
[ 609.008407] __x64_sys_delete_module+0x147/0x2b0
[ 609.008409] ? exit_to_usermode_loop+0xea/0x160
[ 609.008411] do_syscall_64+0x57/0x190
[ 609.008413] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 609.008414] RIP: 0033:0x7f188f345c9b
[ 609.008416] Code: 73 01 c3 48 8b 0d f5 71 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c5 71 0c 00 f7 d8 64 89 01 48
[ 609.008416] RSP: 002b:00007fffc8d32e68 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
[ 609.008418] RAX: ffffffffffffffda RBX: 0000561e1a391790 RCX: 00007f188f345c9b
[ 609.008419] RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000561e1a3917f8
[ 609.008420] RBP: 00007fffc8d32ec8 R08: 0000000000000000 R09: 0000000000000000
[ 609.008420] R10: 00007f188f3c1ac0 R11: 0000000000000206 R12: 00007fffc8d33090
[ 609.008422] R13: 00007fffc8d3474a R14: 0000561e1a3912a0 R15: 0000561e1a391790
[ 609.008424] Modules linked in: thunderbolt rfcomm xfrm_user xfrm_algo l2tp_ppp l2tp_netlink l2tp_core ip6_udp_tunnel udp_tunnel pppox ccm xt_comment xt_CHECKSUM xt_MASQUERADE ip6table_mangle ip6table_nat dummy iptable_mangle iptable_nat nf_tables nfnetlink bridge stp llc cmac algif_hash algif_skcipher af_alg bnep zfs(PO) zunicode(PO) zavl(PO) icp(PO) zcommon(PO) znvpair(PO) spl(O) zlua(PO) joydev intel_rapl_msr mei_hdcp nls_iso8859_1 snd_seq_midi snd_seq_midi_event snd_hda_codec_hdmi snd_hda_codec_conexant snd_hda_codec_generic intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel snd_hda_intel snd_rawmidi kvm snd_intel_nhlt snd_hda_codec intel_cstate rmi_smbus intel_rapl_perf snd_hda_core snd_hwdep iwlmvm rmi_core mac80211 uvcvideo input_leds videobuf2_vmalloc videobuf2_memops btusb btrtl snd_pcm libarc4 serio_raw snd_seq btbcm intel_wmi_thunderbolt videobuf2_v4l2 btintel videobuf2_common wmi_bmof thinkpad_acpi bluetooth videodev nvram snd_seq_device ledtrig_audio
[ 609.008447] iwlwifi mc snd_timer rtsx_pci_ms ecdh_generic ecc cfg80211 memstick snd mei_me ucsi_acpi typec_ucsi intel_xhci_usb_role_switch mei roles intel_pch_thermal typec soundcore acpi_pad mac_hid nf_log_ipv6 ip6t_REJECT nf_reject_ipv6 xt_hl ip6t_rt nf_log_ipv4 nf_log_common ipt_REJECT nf_reject_ipv4 xt_LOG xt_limit xt_addrtype xt_tcpudp xt_conntrack ip6table_filter ip6_tables nf_conntrack_netbios_ns nf_conntrack_broadcast nf_nat_ftp sch_fq_codel nf_nat nf_conntrack_ftp nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 parport_pc iptable_filter bpfilter ppdev lp parport ip_tables x_tables autofs4 btrfs xor zstd_compress raid6_pq libcrc32c dm_crypt crct10dif_pclmul crc32_pclmul ghash_clmulni_intel i915 rtsx_pci_sdmmc i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt nvme fb_sys_fops aesni_intel crypto_simd cryptd glue_helper psmouse e1000e(-) rtsx_pci drm i2c_i801 nvme_core wmi i2c_hid hid video
[ 609.008470] ---[ end trace 7485502fa763552b ]---
[ 609.008472] RIP: 0010:free_msi_irqs+0x17d/0x1b0
[ 609.008473] Code: 84 df fe ff ff 45 31 f6 eb 11 41 83 c6 01 44 39 73 14 0f 86 cc fe ff ff 8b 7b 10 44 01 f7 e8 ea c3 b6 ff 48 83 78 70 00 74 e0 <0f> 0b 49 8d b5 b0 00 00 00 e8 b5 7d b7 ff e9 cd fe ff ff 49 8b 78
[ 609.008474] RSP: 0018:ffffa7d2072f7d40 EFLAGS: 00010286
[ 609.008475] RAX: ffff8bc9bfb49e00 RBX: ffff8bc9ad69c720 RCX: 0000000000000000
[ 609.008475] RDX: 0000000000000000 RSI: 0000000000000084 RDI: ffffffffa9e65980
[ 609.008476] RBP: ffffa7d2072f7d70 R08: ffff8bc9bb564db0 R09: ffff8bc9bb564df8
[ 609.008477] R10: 0000000000000000 R11: ffffffffa9e65988 R12: ffff8bc9cb5272c0
[ 609.008477] R13: ffff8bc9cb527000 R14: 0000000000000000 R15: dead000000000100
[ 609.008478] FS: 00007f188f1f9500(0000) GS:ffff8bc9ce200000(0000) knlGS:0000000000000000
[ 609.008479] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 609.008480] CR2: 00007f6d1a6af060 CR3: 000000046d9f8006 CR4: 00000000003606f0
At that point the computer will no longer suspend, shutdown, reboot, etc (although it otherwise functions fine).
# first bad commit: [4f2d8236f465f6