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

[Joe Lawrence <joe.lawrence@redhat.com>]

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.

--
Joe