We found that after upgrading openQA workers to Leap 15.3, tests which boot
.iso images using a "usb-storage" device fail with disk read issues. There are
various failure modes, the one that appears the most is incredible slowness
during disk access (loading the kernel times out in openQA:
https://openqa.opensuse.org/tests/1997827#step/finish_desktop/2), but there are
also read errors in grub
(https://openqa.opensuse.org/tests/1996844#step/finish_desktop/7) or corruption
while loading the initrd
(https://openqa.opensuse.org/tests/1996844#step/finish_desktop/3).

To not require a full openQA setup for reproducing, I have a qemu cmdline here
which shows a similar issue:

qemu-system-x86_64 -accel kvm -m 1024 -device usb-ehci -blockdev
driver=file,read-only=on,filename=openSUSE-Tumbleweed-KDE-Live-x86_64-Snapshot20211027-Media.iso,node-name=iso
-device usb-storage,drive=iso,bootindex=0

(using any TW live cd iso "works")

Most of the time, it results in this error message at some point during the
boot process and causes it to fail at that stage:

cpage out of range (5)
processing error - resetting ehci HC

Unlike in openQA, it does boot successfully some of the time though.

I did some tests and narrowed it down to the update of qemu-seabios to
1.14.0_0_g155821a-103.2.
The issues disappear when using bios(-256k).bin from Leap 15.2's qemu-seabios
package (qemu-seabios-1.12.1+-lp152.9.20.1 and older).