linux-kernel - Re: [PATCH v5 4/7] cxl/region: Add helper to check Soft Reserved containment by CXL regions

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Message-ID: <ee064449-d0a3-41df-a83e-d83ca17b61dd@intel.com>
Date: Fri, 23 Jan 2026 15:19:53 -0700
From: Dave Jiang <dave.jiang@...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: 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>, 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 4/7] cxl/region: Add helper to check Soft Reserved
 containment by CXL regions

On 1/21/26 9:55 PM, Smita Koralahalli wrote:
> Add a helper to determine whether a given Soft Reserved memory range is
> fully contained within the committed CXL region.
> 
> This helper provides a primitive for policy decisions in subsequent
> patches such as co-ordination with dax_hmem to determine whether CXL has
> fully claimed ownership of Soft Reserved memory ranges.
> 
> No functional changes are introduced by this patch.
> 
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>

Just a nit below.

> ---
>  drivers/cxl/core/region.c | 29 +++++++++++++++++++++++++++++
>  drivers/cxl/cxl.h         |  5 +++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 45ee598daf95..9827a6dd3187 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3875,6 +3875,35 @@ static int cxl_region_debugfs_poison_clear(void *data, u64 offset)
>  DEFINE_DEBUGFS_ATTRIBUTE(cxl_poison_clear_fops, NULL,
>  			 cxl_region_debugfs_poison_clear, "%llx\n");
>  
> +static int cxl_region_contains_sr_cb(struct device *dev, void *data)

Since it's a local helper, maybe just call it region_contains_soft_reserve()?

DJ

> +{
> +	struct resource *res = data;
> +	struct cxl_region *cxlr;
> +	struct cxl_region_params *p;
> +
> +	if (!is_cxl_region(dev))
> +		return 0;
> +
> +	cxlr = to_cxl_region(dev);
> +	p = &cxlr->params;
> +
> +	if (p->state != CXL_CONFIG_COMMIT)
> +		return 0;
> +
> +	if (!p->res)
> +		return 0;
> +
> +	return resource_contains(p->res, res) ? 1 : 0;
> +}
> +
> +bool cxl_region_contains_soft_reserve(const struct resource *res)
> +{
> +	guard(rwsem_read)(&cxl_rwsem.region);
> +	return bus_for_each_dev(&cxl_bus_type, NULL, (void *)res,
> +				cxl_region_contains_sr_cb) != 0;
> +}
> +EXPORT_SYMBOL_GPL(cxl_region_contains_soft_reserve);
> +
>  static int cxl_region_can_probe(struct cxl_region *cxlr)
>  {
>  	struct cxl_region_params *p = &cxlr->params;
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index c796c3db36e0..b0ff6b65ea0b 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -906,6 +906,7 @@ struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev);
>  int cxl_add_to_region(struct cxl_endpoint_decoder *cxled);
>  struct cxl_dax_region *to_cxl_dax_region(struct device *dev);
>  u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint, u64 spa);
> +bool cxl_region_contains_soft_reserve(const struct resource *res);
>  #else
>  static inline bool is_cxl_pmem_region(struct device *dev)
>  {
> @@ -928,6 +929,10 @@ static inline u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint,
>  {
>  	return 0;
>  }
> +static inline bool cxl_region_contains_soft_reserve(const struct resource *res)
> +{
> +	return false;
> +}
>  #endif
>  
>  void cxl_endpoint_parse_cdat(struct cxl_port *port);