Created attachment 1823527 [details]
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1. Please describe the problem:

Updating to a kernel 5.14 (from Koji) makes system unbootable when running on top of Xen-server.

This seems like a general kernel 5.14 bug, not specific to Fedora as same problem occurs on openSuSE/Tumbleweed with 5.14 kernel. (Crossposted here: https://bugzilla.opensuse.org/show_bug.cgi?id=1190326)

On Fedora during boot it hangs after "Reached target Basic System" and times out waiting for /dev/disk/by-uuid/xxxx

It seems like kernel cannot identify the disks at all (working fine on 5.13)

After entering the recovery-mode, following is observed:

- lsblk shows only the CD-rom drive
- ls /dev/disk/ only has by-path and by-id. by-uuid directory is gone.

2. What is the Version-Release number of the kernel:

kernel-core-5.14.3-300.fc34 (Downloaded as pr. https://fedoraproject.org/wiki/Test_Day:2021-09-12_Kernel_5.14_Test_Week)

3. Did it work previously in Fedora? If so, what kernel version did the issue
   *first* appear?  Old kernels are available for download at
   https://koji.fedoraproject.org/koji/packageinfo?packageID=8 :

5.13 working fine. All versions of 5.14.x seems to be at fault. Tested up to (and including) 5.14.3


4. Can you reproduce this issue? If so, please provide the steps to reproduce
   the issue below:

On stable Fedora 34, install a 5.14 kernel from Koji (https://fedoraproject.org/wiki/Test_Day:2021-09-12_Kernel_5.14_Test_Week) while running on top of a Xen-based hypervisor.

Can be reproducedwith both clean BTRFS and XFS/LVM install, so not specific to BTRFS filesystem

Reproduced on two seperate XCP-ng 8.2 (xen-based) Hypervisors.

From hypervisors:
# yum info qemu
Installed Packages
Name        : qemu
Arch        : x86_64
Epoch       : 2
Version     : 2.10.2
Release     : 4.5.3.xcpng8.2
Size        : 19 M
Repo        : installed
From repo   : install
Summary     : qemu-dm device model
License     : GPL
Description : This package contains Qemu.

# uname -a
Linux hostname 4.19.0+1 #1 SMP Wed Dec 16 12:16:11 CET 2020 x86_64 x86_64 x86_64 GNU/Linux


5. Does this problem occur with the latest Rawhide kernel? To install the
   Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by
   ``sudo dnf update --enablerepo=rawhide kernel``:
N/A

6. Are you running any modules that not shipped with directly Fedora's kernel?:

No

7. Please attach the kernel logs. You can get the complete kernel log
   for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the
   issue occurred on a previous boot, use the journalctl ``-b`` flag.