linux-kernel - Re: [PATCH v5 3/7] cxl/region: Skip decoder reset on detach for autodiscovered regions

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Message-ID: <0f0a2be8-6b09-4342-be1c-e5dca818ad93@amd.com>
Date: Fri, 23 Jan 2026 10:42:05 +0000
From: Alejandro Lucero Palau <alucerop@....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: Ard Biesheuvel <ardb@...nel.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>,
 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 Kroah-Hartman <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>,
 Tomasz Wolski <tomasz.wolski@...itsu.com>
Subject: Re: [PATCH v5 3/7] cxl/region: Skip decoder reset on detach for
 autodiscovered regions

On 1/22/26 04:55, Smita Koralahalli wrote:
> __cxl_decoder_detach() currently resets decoder programming whenever a
> region is detached if cxl_config_state is beyond CXL_CONFIG_ACTIVE. For
> autodiscovered regions, this can incorrectly tear down decoder state
> that may be relied upon by other consumers or by subsequent ownership
> decisions.
>
> Skip cxl_region_decode_reset() during detach when CXL_REGION_F_AUTO is
> set.
>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> ---
>   drivers/cxl/core/region.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index ae899f68551f..45ee598daf95 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2178,7 +2178,9 @@ __cxl_decoder_detach(struct cxl_region *cxlr,
>   		cxled->part = -1;
>   
>   	if (p->state > CXL_CONFIG_ACTIVE) {
> -		cxl_region_decode_reset(cxlr, p->interleave_ways);
> +		if (!test_bit(CXL_REGION_F_AUTO, &cxlr->flags))
> +			cxl_region_decode_reset(cxlr, p->interleave_ways);
> +
>   		p->state = CXL_CONFIG_ACTIVE;
>   	}
>   

I think for some Type2 drivers this should not be the case, and some 
kind of leverage should be implemented, but I guess this is enough with 
the current supported cases, so;

Reviewed-by: Alejandro Lucero <alucerop@....com>