linux-kernel - Re: [PATCH v4 4/9] dax/hmem: Defer handling of Soft Reserved ranges that overlap CXL windows

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Message-ID: <34a26e2e-d3f3-4508-94ee-89943144f8fa@amd.com>
Date: Thu, 11 Dec 2025 15:23:09 -0800
From: "Koralahalli Channabasappa, Smita" <skoralah@....com>
To: dan.j.williams@...el.com,
 Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
 linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
 nvdimm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
 linux-pm@...r.kernel.org
Cc: Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Yazen Ghannam <yazen.ghannam@....com>, Dave Jiang <dave.jiang@...el.com>,
 Davidlohr Bueso <dave@...olabs.net>, Matthew Wilcox <willy@...radead.org>,
 Jan Kara <jack@...e.cz>, "Rafael J . Wysocki" <rafael@...nel.org>,
 Len Brown <len.brown@...el.com>, Pavel Machek <pavel@...nel.org>,
 Li Ming <ming.li@...omail.com>, Jeff Johnson
 <jeff.johnson@....qualcomm.com>, Ying Huang <huang.ying.caritas@...il.com>,
 Yao Xingtao <yaoxt.fnst@...itsu.com>, Peter Zijlstra <peterz@...radead.org>,
 Greg KH <gregkh@...uxfoundation.org>,
 Nathan Fontenot <nathan.fontenot@....com>,
 Terry Bowman <terry.bowman@....com>, Robert Richter <rrichter@....com>,
 Benjamin Cheatham <benjamin.cheatham@....com>,
 Zhijian Li <lizhijian@...itsu.com>, Borislav Petkov <bp@...en8.de>,
 Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v4 4/9] dax/hmem: Defer handling of Soft Reserved ranges
 that overlap CXL windows

On 12/2/2025 2:37 PM, dan.j.williams@...el.com wrote:
> Smita Koralahalli wrote:
>> From: Dan Williams <dan.j.williams@...el.com>
>>
>> Defer handling of Soft Reserved ranges that intersect CXL windows at
>> probe time. Delay processing until after device discovery so that the
>> CXL stack can publish windows and assemble regions before HMEM claims
>> those address ranges.
>>
>> Add a deferral path that schedules deferred work when HMEM detects a
>> Soft Reserved range intersecting a CXL window during probe. The deferred
>> work runs after probe completes and allows the CXL subsystem to finish
>> resource discovery and region setup before HMEM takes any action.
>>
>> This change does not address region assembly failures. It only delays
>> HMEM handling to avoid prematurely claiming ranges that CXL may own.
> 
> No, with the changes it just unconditionally disables dax_hmem in the
> presence of CXL. I do not think these changes can stand alone. It
> probably wants to be folded with patch 5 or something like that.

Sure, will include this with changes suggested in Patch 5.

Thanks
Smita