I'm happy seeing that the commit can be cleanly cherry-picked from all
affected releases (impish, hirsute and focal).

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https://bugs.launchpad.net/bugs/1950144

Title:
  [UBUNTU 20.04] kernel:  unable to read partitions on virtio-block dasd
  (kvm)

Status in Ubuntu on IBM z Systems:
  Triaged
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Focal:
  New
Status in linux source package in Hirsute:
  New
Status in linux source package in Impish:
  New
Status in linux source package in Jammy:
  Fix Released

Bug description:
  Description:  kernel:  unable to read partitions on virtio-block dasd (kvm)
  Symptom:      unable to read partitions on virtio-block dasd (kvm)
  Problem:      verify is called before virtio_finalize_features() , so a
                transitional s390 virtio device still serves native endian
                (i.e. big endian) config space, while the driver knows that it
                is going to accept VERSION_1, so when reading the config space,
                it assumes it got little endian, and byteswaps.
  Solution:     For QEMU, we can work around the issue by writing out the
                feature bits with VIRTIO_F_VERSION_1 bit set.  We (ab)use the
                finalize_features config op for this. This isn't enough to
                address all vhost devices since these do not get the features
                until FEATURES_OK, however it looks like the affected devices
                actually never handled the endianness for legacy mode correctly,
                so at least that's not a regression.

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