Hang on boot after 'fb0: switching to inteldrmfb from EFI VGA'

[Simon Tatham]

I'm running Ubuntu 20.04 with HWE kernels. The 5.11 kernel stream has been working fine for me (and supported the network device on my reasonably recent PC, which 20.04's default kernel didn't). But the 5.13 and 5.14 kernels all hang on boot.

If I edit the GRUB boot commands to let me see the boot messages, the hang occurs immediately after printing the message

[ 1.044456] fb0: switching to inteldrmfb from EFI VGA

I can boot this kernel fine if I add 'nomodeset' to the kernel command line. But then I get unusably low screen resolution. Instead, my workaround is to manually select a 5.11 kernel from the GRUB menu on every boot.

I'm not able to provide a full set of kernel messages from a failed boot attempt, because of course the kernel doesn't boot to a point where I can save them to a file. But I attach a screenshot of the last screenful of messages before the hang, in case those are useful. I'll also attach dmesg logs from a successful boot of the 5.14 kernel with nomodeset, and from a boot of the 5.11 kernel which gives me full functionality.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.14.0-1031-oem 5.14.0-1031.34
ProcVersionSignature: Ubuntu 5.11.0-46.51~20.04.1-generic 5.11.22
Uname: Linux 5.11.0-46-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.21
Architecture: amd64
CasperMD5CheckResult: skip
Date: Wed Mar 30 12:47:47 2022
InstallationDate: Installed on 2013-06-01 (3223 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
SourcePackage: linux-signed-oem-5.14
UpgradeStatus: Upgraded to focal on 2020-08-31 (575 days ago)
modified.conffile..etc.default.apport: [modified]
mtime.conffile..etc.default.apport: 2013-06-02T15:20:08.886312

[Simon Tatham (sgtatham)]

I don't really know what information I should be reporting about my hardware. My first guess is that the output of 'lspci -v' relating to the video device might be useful, so here it is:

00:02.0 VGA compatible controller: Intel Corporation Device 4c8a (rev 04) (prog-
if 00 [VGA controller])
        DeviceName: Onboard - Video
        Subsystem: ASUSTeK Computer Inc. Device 8694
        Flags: bus master, fast devsel, latency 0, IRQ 145
        Memory at 6000000000 (64-bit, non-prefetchable) [size=16M]
        Memory at 4000000000 (64-bit, prefetchable) [size=256M]
        I/O ports at 5000 [size=64]
        Expansion ROM at 000c0000 [virtual] [disabled] [size=128K]
        Capabilities: <access denied>
        Kernel driver in use: i915
        Kernel modules: i915

[Simon Tatham (sgtatham)]

This also happens with the kernel in xubuntu-22.04-beta-desktop-amd64.iso, so it will block me upgrading that machine to Jammy when it's released.

Is there anything I can do to help? I'm not familiar with debugging kernel drivers, but I'm a competent general developer, and I'm prepared to put in some effort if given some guidance on where to start.

[Simon Tatham (sgtatham)]

Update: linux-image-5.14.0-1034-oem appeared in my normal apt upgrade today and has booted successfully, so perhaps whatever the problem was has been fixed?

[Simon Tatham (sgtatham)]

And the *release* version of Jammy has a 5.15 kernel that boots on the machine in question, so I've managed a successful upgrade, and this doesn't seem to be a problem for me any more.