linux-kernel - Re: [PATCH v4 3/9] dax/hmem: Gate Soft Reserved deferral on DEV_DAX

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Message-ID: <20251217120748.0000581e@huawei.com>
Date: Wed, 17 Dec 2025 12:07:48 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Dave Jiang <dave.jiang@...el.com>
CC: 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>, 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>, Yazen Ghannam <yazen.ghannam@....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 3/9] dax/hmem: Gate Soft Reserved deferral on
 DEV_DAX_CXL

On Tue, 2 Dec 2025 16:32:24 -0700
Dave Jiang <dave.jiang@...el.com> wrote:

> On 11/19/25 8:19 PM, Smita Koralahalli wrote:
> > From: Dan Williams <dan.j.williams@...el.com>
> > 
> > Replace IS_ENABLED(CONFIG_CXL_REGION) with IS_ENABLED(CONFIG_DEV_DAX_CXL)
> > so that HMEM only defers Soft Reserved ranges when CXL DAX support is
> > enabled. This makes the coordination between HMEM and the CXL stack more
> > precise and prevents deferral in unrelated CXL configurations.
> > 
> > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> > Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>  
> 
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>> ---

Something odd happened with that tag from Dave so that might need manual
application if you use b4 or similar.

This seems sensible to me.
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>


> >  drivers/dax/hmem/hmem.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
> > index 02e79c7adf75..c2c110b194e5 100644
> > --- a/drivers/dax/hmem/hmem.c
> > +++ b/drivers/dax/hmem/hmem.c
> > @@ -66,7 +66,7 @@ static int hmem_register_device(struct device *host, int target_nid,
> >  	long id;
> >  	int rc;
> >  
> > -	if (IS_ENABLED(CONFIG_CXL_REGION) &&
> > +	if (IS_ENABLED(CONFIG_DEV_DAX_CXL) &&
> >  	    region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
> >  			      IORES_DESC_CXL) != REGION_DISJOINT) {
> >  		dev_dbg(host, "deferring range to CXL: %pr\n", res);  
> 
>