Re: [PATCH v8 0/3] mm/hmm/test: add self tests for HMM

[Leon Romanovsky <leon@kernel.org>]

On Sat, Mar 21, 2020 at 06:55:05PM -0300, Jason Gunthorpe wrote:
> On Sat, Mar 21, 2020 at 10:27:46AM -0700, Ralph Campbell wrote:
> >
> > On 3/21/20 2:00 AM, Leon Romanovsky wrote:
> > > On Fri, Mar 20, 2020 at 05:31:05PM -0700, Ralph Campbell wrote:
> > > > This series adds basic self tests for HMM and are intended for Jason
> > > > Gunthorpe's rdma tree which has a number of HMM patches applied.
> > > >
> > > > Changes v7 -> v8:
> > > > Rebased to Jason's rdma/hmm tree, plus Jason's 6 patch series
> > > >    "Small hmm_range_fault() cleanups".
> > > > Applied a number of changes from Jason's comments.
> > > >
> > > > Changes v6 -> v7:
> > > > Rebased to linux-5.6.0-rc6
> > > > Reverted back to just using mmu_interval_notifier_insert() and making
> > > >    this series only introduce HMM self tests.
> > > >
> > > > Changes v5 -> v6:
> > > > Rebased to linux-5.5.0-rc6
> > > > Refactored mmu interval notifier patches
> > > > Converted nouveau to use the new mmu interval notifier API
> > > >
> > > > Changes v4 -> v5:
> > > > Added mmu interval notifier insert/remove/update callable from the
> > > >    invalidate() callback
> > > > Updated HMM tests to use the new core interval notifier API
> > > >
> > > > Changes v1 -> v4:
> > > > https://lore.kernel.org/linux-mm/20191104222141.5173-1-rcampbell@nvidia.com
> > > >
> > > > Ralph Campbell (3):
> > > >    mm/hmm/test: add selftest driver for HMM
> > > >    mm/hmm/test: add selftests for HMM
> > > >    MAINTAINERS: add HMM selftests
> > > >
> > > >   MAINTAINERS                            |    3 +
> > > >   include/uapi/linux/test_hmm.h          |   59 ++
> > >
> > > Isn't UAPI folder supposed to be for user-visible interfaces that follow
> > > the rule of non-breaking user space and not for selftests?
> > >
> > > Thanks
> > >
> >
> > Most of the other kernel module tests seem to invoke the test as part of the
> > module load/init. I'm open to moving it if there is a more appropriate location.
>
> Is it even possible to create a user mm_struct and put crazy things in
> it soley from a kernel module?

I didn't look very closely of what Ralph did in his patchsets, but from
what I know, if you want in-kernel interface, you use in-kernel module,
if you want to test user visible uapi, you write application. You don't
create new UAPI just to test something in the kernel.

Can kunit help here?
https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html

Thanks

>
> Jason
>