Re: [PATCH v2 0/6] kselftests: livepatch: Adapt tests to be executed on 4.12 kernels

[Miroslav Benes <mbenes@suse.cz>]

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On Fri, 17 Apr 2026, Joe Lawrence wrote:

> On Thu, Apr 16, 2026 at 03:18:33PM -0300, Marcos Paulo de Souza wrote:
> > On Thu, 2026-04-16 at 10:07 -0700, Josh Poimboeuf wrote:
> > > On Mon, Apr 13, 2026 at 02:26:11PM -0300, Marcos Paulo de Souza
> > > wrote:
> > > > A new version of the patchset, with fewer patches now. Please take
> > > > a look!
> > > > 
> > > > Original cover-letter:
> > > > These patches don't really change how the patches are run, just
> > > > skip
> > > > some tests on kernels that don't support a feature (like kprobe and
> > > > livepatched living together) or when a livepatch sysfs attribute is
> > > > missing.
> > > > 
> > > > The last patch slightly adjusts check_result function to skip dmesg
> > > > messages on SLE kernels when a livepatch is removed.
> > > 
> > > Why are we adding complexity to support Linux 4.12 in mainline? 
> > > Isn't
> > > that what enterprise distros are for?
> > 
> > These changes do not add any new complex code, just checks to enable
> > the tests to run on older kernels. I believe that it would be good for
> > all enterprises distros if they could run more tests in maintenance
> > updates of their kernels using the upstream tests.
> > 
> > The changes are not really that big. Some patches were removed from v1
> > because there were adding checks for out-of-tree messages (like the
> > last paragraph of the v2 erroneously shows), and another one was to
> > check if kprobes could live alongside livepatches, which fails for 4.12
> > kernels.
> > 
> > The patches for this versions introduce only checks to avoid testing
> > sysfs attributes for kernels that don't supports them.
> > 
> 
> IMHO when the changes are reasonably small, I think we should consider
> accomodating older kernels for the selftest suite.  If we reach the
> point of having to introduce version #ifdef-erry, that opinion would
> flip pretty quickly.  It's pretty amazing that modern tests still run on
> older kernels (with this patchset) -- not an explicit kselftest goal
> AFAIK, but nice to have.
> 
> If we do merge this patchset, it should update the doc
> tools/testing/selftests/livepatch/README to note the oldest
> expected/tested upstream kernel.  (So new selftest authors may have some
> idea of what API / sysfs features to use.)  And that this compatibility
> was only an incidental "feature" that came for nearly free.  It's not a
> promise to never add backwards-incompatible tests in the future.

I agree with Joe on both points.

Miroslav