Re: [PATCH v4 2/2] tools/testing/cxl: Enable zero sized decoder under hb0

[Richard Cheng]

On Fri, Jun 12, 2026 at 11:16:00AM +0800, Alison Schofield wrote:
> On Sun, Jun 07, 2026 at 04:13:45PM +0800, Richard Cheng wrote:
> > The kernel now allows committed HDM decoders of zero size so BIOS can
> > burn slots with LOCK; cxl_test needs to exercise that path.
> > 
> > Add a mock_zero_size_decoders module parameter (default off). When set,
> > the special endpoints under host-bridge0 (cxl_mem.0 and cxl_mem.4) commit
> > decoders 1 and 2 as zero-size + locked above the decoder[0] auto-region,
> > mirrored on the parent switch and host bridge. commit_end then lands on a
> > decoder with no DPA resource, exercising the new enumeration and
> > poison-by-endpoint paths.
> > 
> > Gating keeps the default topology, shared by the rest of the cxl suite,
> > unchanged.
> 
> Can you add a unit test case for this?  I think it makes sense in
> cxl-topology.sh. Perhaps before or after the work on the default
> cxl-test topology, load this new topo up and validate the zero size
> decoders are as expected.
>

Hi Alison,

No problem for that, but I want to make sure you are talking about
adding test in ndctl right?

I'll send v5 within this week, want to make sure they are ready
together.

Best regards,
Richard Cheng.