ACK: [SRU][B][PATCH 0/1] Ubuntu 18.04 kernel 4.15.0-194 crashes on IPL (LP: 1994601)

Luke Nowakowski-Krijger luke.nowakowskikrijger at canonical.com
Thu Oct 27 15:47:09 UTC 2022


Acked-by: Luke Nowakowski-Krijger <luke.nowakowskikrijger at canonical.com>

On Thu, Oct 27, 2022 at 8:30 AM <frank.heimes at canonical.com> wrote:

> BugLink: https://bugs.launchpad.net/bugs/1994601
>
> SRU Justification:
>
> [ Impact ]
>
>  * Ubuntu 18.04 / bionic installations with latest kernel 4.15.0-194
>    are no longer able to IPL (boot) on IBM z14 or newer hardware.
>
>  * This issue got introduced by upstream commit e4f74400308c
>    "s390/archrandom: simplify back to earlier design and initialize
> earlier"
>    that was SRUed to 18.04/bionic based on LP#1989625,
>    which made changes in the s390s IPL/boot area of kernel/arch/random.
>
>  * The reason seems to be that the bad patch moves the decision about
>    if arch randomness is available to setup.c function setup_randomness().
>    This code uses a static_key s390_arch_random_available.
>    But in the Canonical kernel the initialization function
>    for the jump labels (where the static keys are based on)
>    jump_label_init() is called in generic start_kernel()
>    wheres in the upstream kernel the init function is
>    called early in setup_arch().
>
>  * Reverting this commit from bionic master-next makes bionic systems
>    again bootable.
>    (https://launchpad.net/~fheimes/+archive/ubuntu/test/)
>
> [ Test Plan ]
>
>  * An IBM z14 or LinuxONE II or newer system is needed.
>
>  * Now install latest bionic on that system - doesn't if it's on LPAR,
>    z/VM or KVM.
>
>  * After the installation (an the trigger of the post install reboot),
>    the system will not come up.
>
>  * To test a patched kernel with e4f74400308c can be tested in the
>    following way:
>
>  * Install 18.04 GA and prevent it from doing any kernel updates.
>
>  * Means, install in 'island' mode
>    or select in d-i 'Advanced Installation'
>    and explicitly choose '4.15.0-50 generic' to install.
>
>  * That allows the system to come up and to update the kernel to
>    a modified one.
>
>  * Then reboot and verify if the system comes up properly.
>
> [ Where problems could occur ]
>
>  * Problems could occur due to the fact that the commit
>    was not cleanly reversible because of minor context changes.
>
>  * Adjustments that were needed might break other things if not
>    done carefully.
>
>  * Further commits (applied after e4f74400308c) may still rely
>    on the bad e4f74400308c commit - or even further patches
>    (from upstream stable).
>
>  * In worst case IPL / boot might get broken,
>    even on hardware older than z14.
>
>  * If the revert works fine can be easily tested and was tested based on
>    https://launchpad.net/~fheimes/+archive/ubuntu/test/
>    and the above test plan.
>
> [ Other Info ]
>
>  * Ubuntu 20.04 (focal, using legacy image with virt-install)
>    was tested as well, but is not affected by this issue.
>
> Frank Heimes (1):
>   Revert "s390/archrandom: simplify back to earlier design and
>     initialize earlier"
>
>  arch/s390/crypto/arch_random.c     | 111 ++++++++++++++++++++++++++++-
>  arch/s390/include/asm/archrandom.h |  27 +++----
>  arch/s390/kernel/setup.c           |   5 --
>  3 files changed, 121 insertions(+), 22 deletions(-)
>
> --
> 2.25.1
>
>
> --
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
>
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