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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5061c1f975bsm29957261cf.26.2026.02.04.20.22.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Feb 2026 20:22:36 -0800 (PST) Date: Wed, 4 Feb 2026 23:22:34 -0500 From: Gregory Price To: Alison Schofield Cc: dan.j.williams@intel.com, Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Vishal Verma , Ira Weiny , linux-cxl@vger.kernel.org Subject: Re: [PATCH 2/2] cxl/region: Unregister auto-created region when assembly fails Message-ID: References: <3bcc5143777acc6d45675d78dd8c57079406bc53.1769746294.git.alison.schofield@intel.com> <2a613604c0cdda6d9f838ae9b47ea6d936c5e4ce.1769746294.git.alison.schofield@intel.com> <697cee39ed313_1d6f100bd@dwillia2-mobl4.notmuch> Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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