Re: [PATCH v4 7/7] selftests: prctl: introduce tests for disabling THPs except for madvise

[Lorenzo Stoakes]

On Thu, Aug 14, 2025 at 02:08:57PM +0100, Mark Brown wrote:
> On Thu, Aug 14, 2025 at 02:59:13PM +0200, David Hildenbrand wrote:
> > On 14.08.25 14:09, Mark Brown wrote:
>
> > > Perhaps this is something that needs considering in the ABI, so
> > > userspace can reasonably figure out if it failed to configure whatever
> > > is being configured due to a missing feature (in which case it should
> > > fall back to not using that feature somehow) or due to it messing
> > > something else up?  We might be happy with the tests being version
> > > specific but general userspace should be able to be a bit more robust.
>
> > Yeah, the whole prctl() ship has sailed, unfortunately :(
>
> Perhaps a second call or sysfs file or something that returns the
> supported mask?  You'd still have a boostrapping issue with existing
> versions but at least at any newer stuff would be helped.

Ack yeah I do wish we had better APIs for expressing what was
available/not. Will put this sort of thing on the TODO...

Overall I don't want to hold this up unnecesarily, and I bow to the
consensus if others feel we ought not to _assume_ same kernel at least best
effort.

Usama - It's ok to leave it as is in this case since obviously only tip
kernel will have this feature.

Cheers, Lorenzo