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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