Re: [PATCH 2/2] cxl/region: Unregister auto-created region when assembly fails

[Gregory Price <gourry@gourry.net>]

On Wed, Feb 04, 2026 at 04:32:39PM -0800, Alison Schofield wrote:
> On Sat, Jan 31, 2026 at 10:49:11AM -0500, Gregory Price wrote:
> > i.e. auto-decoders should be intended for trivial SysRAM regions only
> 
> It has not been my impression that we have that much control over what
> BIOS may present. ie. If it is CXL Spec legal they may build it. I
> recall you wrote a doc of Linux Expectations of BIOS. Did you actually
> try to limit what BIOS does?
> 
> 

I should rephrase - barring any new specification updates that actually
allow the BIOS to say what a region may be used for, the only two
reasonable endpoints are sysram and dax - and realistically only sysram
unless you build kmem out of the dax driver (kmem is the auto
destination).

But for non-trivial setups, recovery might not actually get you
anything.  If a device fails to actually come up after having been
programmed by bios, it may not even be feasible to tear-down and recreate
what the BIOS tried to do because of platform specifics (Zen5).

So while you can time out and clean up, I'm not sure you can actually do
anything after that reliably in the general case - and i'm not sure how
much effort we should put into fighting those fires.

I suppose you could leave the driver in a state that allows a user to
see it's broken.

~Gregory