Re: [PATCH v1 1/2] cxl_test: enable zero sized decoders under hb0

[Gregory Price <gourry@gourry.net>]

On Mon, Oct 20, 2025 at 12:09:34AM -0700, Alison Schofield wrote:
> > This patch updates cxl_test to enable decoders 1 and 2
> > in the host-bridge 0 port, in a switch uport under hb0,
> > and the endpoints ports with size zero simulating
> > committed zero sized decoders.
> 
> Decoders 1 & 2 - those are after decoder 0, the autoregion.
> That's a problem ATM, when we try to teardown the autoregion we
> get out of order resets. Like I asked in the other patch, if there
> are rules about where these zero size decoders may appear, that
> may make the solution here simpler.
> 

I think this is going to require a quirk-doc like other deviations.

A committed decoder must have a base address, and with 0-size subsequent
or previous decoders would also have an address that covers that address
as well.  This is on top of the ordering issue if the 0-side decoders
come after a programmable decoder.

I'm not convinced this even makes sense as a security thing if you can
reset the bus and re-activate everything (after a graceful teardown).

Seems easier to just report the decoders as unavailable and then not
probe them.

~Gregory