Re: [PATCH] cxl/region: Add decoder check to check_commit_order()

[<dan.j.williams@intel.com>]

Li Ming wrote:
> On 5/1/2025 5:36 AM, Dave Jiang wrote:
> > check_commit_order() attempts to convert a device to a decoder without
> > making sure the device is a decoder. So far this has been working due
> > to pure luck. Issue discovered while doing deferred dport probing when
> > child ports are now in the midst of decoders due to ordering change
> > of child port additions. Add a check before attempting to do decoder
> > conversion.
> >
> > Fixes: 105b6235ad0f ("cxl/port: Prevent out-of-order decoder allocation")
> > Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
> I also have a patch for this issue during I worked on deferred dport probing.
> 
> https://lore.kernel.org/linux-cxl/20250107035708.1134954-4-ming.li@zohomail.com/
> 
> I am not sure if we should define it as a bug, my understanding is
> that it will never happen with current implementation, it only happens
> when we are trying to delay the switch decoders initialization.

Agree. This is not a fix. The current implementation is lucky that ports
are always registered after decoders. So there is zero exposure to this
issue for current kernels.

Dave, please just include this as a prep patch in the same series that
invalidates the port child device ordering assumption.