<div dir="ltr"><div>Acked-by: Luke Nowakowski-Krijger <<a href="mailto:luke.nowakowskikrijger@canonical.com">luke.nowakowskikrijger@canonical.com</a>> </div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Oct 27, 2022 at 8:30 AM <<a href="mailto:frank.heimes@canonical.com">frank.heimes@canonical.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">BugLink: <a href="https://bugs.launchpad.net/bugs/1994601" rel="noreferrer" target="_blank">https://bugs.launchpad.net/bugs/1994601</a> 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. (<a href="https://launchpad.net/~fheimes/+archive/ubuntu/test/" rel="noreferrer" target="_blank">https://launchpad.net/~fheimes/+archive/ubuntu/test/</a>) [ 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 <a href="https://launchpad.net/~fheimes/+archive/ubuntu/test/" rel="noreferrer" target="_blank">https://launchpad.net/~fheimes/+archive/ubuntu/test/</a> 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 <a href="mailto:kernel-team@lists.ubuntu.com" target="_blank">kernel-team@lists.ubuntu.com</a> <a href="https://lists.ubuntu.com/mailman/listinfo/kernel-team" rel="noreferrer" target="_blank">https://lists.ubuntu.com/mailman/listinfo/kernel-team</a> </blockquote></div></div>