Crash on startup using linux 5.8.0-25

[Rauno]

I installed Ubuntu 20.04 on my new Lenovo ThinkPad L15 and upgraded it to Ubuntu 20.10 for a newer kernel to fix minor compatibility issues with AMD Renoir.
When using the newer kernel it freezes before splash. I did my best to follow instructions to create a crash file but none were ever created.
Booting to recovery mode with 5.8 works, 5.4 kernel works. Booting from USB the (safe graphics) option works but not the default. On that USB I have latest available daily build (Oct 21 2020) of 20.10. I tried a fresh reinstall of Ubuntu 20.10 and still getting stuck.

[Ubuntu Foundations Team Bug Bot (crichton)]

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[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1901024

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Rauno (rmoisto)]

I can't start a web browser in recovery mode so apport-collect is unusable.

[Rauno (rmoisto)]

For some reason switching to amd graphics drivers caused the crash. Also for some reason grub boot option pci=noats fixes it.

[Mauricio Faria de Oliveira (mfo)]

Hi Rauno,

Thanks for reporting this bug; nice finding on pci=noats.

$ grep -A1 noats ~/git/linux/Documentation/admin-guide/kernel-parameters.txt
  noats [PCIE, Intel-IOMMU, AMD-IOMMU]
    do not use PCIe ATS (and IOMMU device IOTLB).

Wondering if the amd gfx drivers with ats/iommu (ie, w/out pci=noats) causes memory corruption:

The screenshot in #1 shows that initramfs unpacking failed -- say, something corrupted the compressed initramfs image loaded in memory -- and this happened closely to when AMD-Vi failed to access an IOMMU perf count(er? I guess.)

And it seems to be graphics related, not just ats/iommu code alone, which prints 'AMD-Vi' (it's in linux/drivers/iommu/amd/) since recovery mode, with 'nomodeset', works fine.

When you boot in recovery mode, do you see initramfs unpacking failed as well? (please check 'dmesg | grep -i initramfs')

[Rauno (rmoisto)]

I don't think the screenshot is relevant. That initramfs error is also shown in recovery mode.
It's pretty obivous that it's an AMD graphics driver issue in the kernel. Possibly I have defective hardware. This really has nothing to do with Ubuntu. As part of debugging I also tried installing Manjaro and that had similar issues.

[Aleksandr Panzin (jalexoid)]

@rmoisto - I have the same issue. It's not your system error, it's 5.8.0_25 + AMD driver issue.
5.4 kernel works well.

[calonfir (laurent1u)]

Crash on startup same kernel, but with 20.04 lts. I had to reverse to linux kernel 5.4 to boot into system