[PATCH for-5.2 v2 0/9] Continue booting in case the first device is not bootable

[Thomas Huth]

The traditional / architected way of booting on s390x is to always
specify the device where the guest should be booted from - that means
s390x guests should be always started with a device that has the
"bootindex" property set.

For the users that are used to a firmware from a different CPU archi-
tecture (or the lazy s390x folks like myself), the s390-ccw bios also
tries to find a bootable device on its own in case the user did not
specify a "bootindex" property. Unfortunately, it always stops at the
very first device that it can find, no matter whether it's bootable or
not. That causes some weird behavior, for example while

 qemu-system-s390x -hda bootable.qcow2

boots perfectly fine, the bios refuses to work if you just specify
a virtio-scsi controller in front of it:

 qemu-system-s390x -device virtio-scsi -hda bootable.qcow2

While this is perfectly fine from the Z architecture point of view, it
still could be a little bit uncomfortable and confusing for the lazy
or ignorant users who did not specify a "bootindex". And since all major
firmwares on other architectures correctly boot in such cases, too,
let's also try to teach the s390-ccw bios how to boot in such cases.

For this, we have to get rid of the various panic()s and IPL_assert()
statements at the "low-level" function and let the main code handle
the decision instead whether a boot from a device should fail or not,
so that the main code can continue searching in case it wants to.

 Thomas

v2:
 - Add patch to remove superfluous call to enable_subchannel()
 - Add patch to test the new behavior in the tests/qtest/cdrom-test
 - Added Reviewed-bys from v1
 - Renamed check_sch_no() to is_dev_possibly_bootable()
 - Reworked the return codes to use 0/-ENODEV instead of true/false

Thomas Huth (9):
  pc-bios/s390-ccw/Makefile: Compile with -std=gnu99, -fwrapv and
    -fno-common
  pc-bios/s390-ccw: Move ipl-related code from main() into a separate
    function
  pc-bios/s390-ccw: Introduce ENODEV define and remove guards of others
  pc-bios/s390-ccw: Move the inner logic of find_subch() to a separate
    function
  pc-bios/s390-ccw: Do not bail out early if not finding a SCSI disk
  pc-bios/s390-ccw: Scan through all devices if no boot device specified
  pc-bios/s390-ccw: Allow booting in case the first virtio-blk disk is
    bad
  pc-bios/s390-ccw/main: Remove superfluous call to enable_subchannel()
  tests/qtest/cdrom: Add more s390x-related boot tests

 pc-bios/s390-ccw/Makefile        |   7 +-
 pc-bios/s390-ccw/bootmap.c       |  34 ++++--
 pc-bios/s390-ccw/main.c          | 172 +++++++++++++++++++------------
 pc-bios/s390-ccw/s390-ccw.h      |   8 +-
 pc-bios/s390-ccw/virtio-blkdev.c |   7 +-
 pc-bios/s390-ccw/virtio-scsi.c   |  28 +++--
 pc-bios/s390-ccw/virtio-scsi.h   |   2 +-
 tests/qtest/cdrom-test.c         |  12 +++
 8 files changed, 174 insertions(+), 96 deletions(-)

-- 
2.18.1