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: <692f6a2035c79_261c1100d2@dwillia2-mobl4.notmuch>
Date: Tue, 2 Dec 2025 14:37:20 -0800
From: <dan.j.williams@...el.com>
To: 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>, Dan Williams
	<dan.j.williams@...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

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.