Description:

After upgrading kernel 6.2.2.arch1-1 to linux 6.2.2.arch2-1 in Dom0 of the Xen Hypervisor, all virtual machines fail to start.
Downgrading 'kernel' and 'kernel-headers' back to 6.2.2.arch1-1 restores the functionality.

A kernel upgrade a couple of days before (6.0.12.arch1-1 -> 6.2.2.arch1-1), did not result in this breakage.

The error message reported in the xen logging is (example of 1 VM):

qemu-system-i386: failed to create 'qdisk' device '51712': failed to create drive: Could not stat file '/dev/nvme0n1p12': No such file or directory

The partition referred in the error message does exist and is accessible.
I am not sure if this is a Xen, Libvirt, Qemu or kernel issue, but the problem gets resolved by the downgrade from '6.2.2.arch2-1' to '6.2.2.arch1-1'.

Additional info:
* package version(s)
xen 4.17.0-1 (Xen Hypervisor)
xen-pvhgrub 2.11.119.3c60d90-1
xen-qemu 7.2.0-1
kernel: 6.2.2.arch2-1 (Xen Dom0)
libvirt-xen 9.0.0-1
qemu-audio-spice 7.2.0-3
qemu-base 7.2.0-3
qemu-block-curl 7.2.0-3
qemu-block-dmg 7.2.0-3
qemu-block-nfs 7.2.0-3
qemu-block-ssh 7.2.0-3
qemu-chardev-spice 7.2.0-3
qemu-common 7.2.0-3
qemu-hw-display-qxl 7.2.0-3
qemu-hw-display-virtio-gpu 7.2.0-3
qemu-hw-display-virtio-gpu-gl 7.2.0-3
qemu-hw-display-virtio-gpu-pci 7.2.0-3
qemu-hw-display-virtio-gpu-pci-gl 7.2.0-3
qemu-hw-display-virtio-vga 7.2.0-3
qemu-hw-display-virtio-vga-gl 7.2.0-3
qemu-hw-s390x-virtio-gpu-ccw 7.2.0-3
qemu-hw-usb-host 7.2.0-3
qemu-hw-usb-redirect 7.2.0-3
qemu-hw-usb-smartcard 7.2.0-3
qemu-img 7.2.0-3
qemu-pr-helper 7.2.0-3
qemu-system-x86 7.2.0-3
qemu-system-x86-firmware 7.2.0-3
qemu-tools 7.2.0-3
qemu-ui-curses 7.2.0-3
qemu-ui-opengl 7.2.0-3
qemu-ui-spice-app 7.2.0-3
qemu-ui-spice-core 7.2.0-3
qemu-virtiofsd 7.2.0-3

Steps to reproduce:

Upgrade kernel in Dom0 to 6.2.2.arch2-1
Reboot Dom0
systemctl start libvirtd
VM's fail to start
Errors in: /var/log/xen/qemu-dm-*.log