Hello Pasha,
On Tue, Dec 30, 2025 at 10:03:38AM -0500, Pasha Tatashin wrote: > On Tue, Dec 30, 2025 at 9:13 AM Breno Leitao <[email protected]> wrote: > > > > Introduce a new Kconfig option, CONFIG_KEXEC_SHOW_PREVIOUS_RELEASE, > > I don't think we need a config for this. Let's just show the previous > kernel version unconditionally when KHO is enabled. > > > which enables the storage and display of the previous kernel's release > > version across kexec boots when using Kexec Handover (KHO). > > > > Motivation > > ========== > > > > Kernel bugs that depend on the version of the previously running kernel > > are not uncommon, especially in scenarios where a buggy kernel kexecs > > into a new one and the issue only manifests in the subsequent kernel. > > > > Recent examples include: > > > > * eb2266312507 ("x86/boot: Fix page table access in 5-level to 4-level > > paging transition") > > * 77d48d39e991 ("efistub/tpm: Use ACPI reclaim memory for event log to > > avoid corruption") > > * 64b45dd46e15 ("x86/efi: skip memattr table on kexec boot") > > > > As kexec-based reboots become more widespread among Linux users, these > > issues are becoming increasingly prominent. > > > > When such crashes occur, correlating them to the previous kernel version > > is challenging, especially at scale, where the problem may only appear in > > specific cases and it is hard to correlate. > > > > With the introduction of Kexec Handover (KHO), we now have a reliable > > mechanism to pass information between kernels. This presents an > > opportunity to address the problem by carrying the previous kernel's > > release version to the next kernel and printing it at boot time. > > LUO added the number of times a machine has been live updated to help > debugging problems that are related to live update, perhaps, in > addition to the previous kernel version, we should also add a number > of times the machine has been kexec'd. It is useful when a bug > manifests only after a number of kexec's which is also sometimes a > case. Thanks for bringing this up, I am on the same page as you here. In fact, this was on my TODO list, but I didn't want to send in this RFC to avoid too much changes/code. I will wait a bit more and add the number of kexec'ed kernels in the next revision. Thanks for your input, --breno
