linux-kernel - Re: [PATCH V3 20/20] cxl/pmem: Add CXL LSA 2.1 support in cxl pmem

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Message-ID: <28d78d2b-c17d-4910-9f28-67af1fbb10ee@intel.com>
Date: Wed, 24 Sep 2025 13:47:21 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Neeraj Kumar <s.neeraj@...sung.com>, linux-cxl@...r.kernel.org,
 nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org, gost.dev@...sung.com
Cc: a.manzanares@...sung.com, vishak.g@...sung.com, neeraj.kernel@...il.com,
 cpgs@...sung.com
Subject: Re: [PATCH V3 20/20] cxl/pmem: Add CXL LSA 2.1 support in cxl pmem



On 9/17/25 6:41 AM, Neeraj Kumar wrote:
> Add support of CXL LSA 2.1 using NDD_REGION_LABELING flag. It creates
> cxl region based on region information parsed from LSA.
> 
> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
> ---
>  drivers/cxl/core/pmem_region.c | 53 ++++++++++++++++++++++++++++++++++
>  drivers/cxl/cxl.h              |  4 +++
>  drivers/cxl/pmem.c             |  2 ++
>  3 files changed, 59 insertions(+)
> 
> diff --git a/drivers/cxl/core/pmem_region.c b/drivers/cxl/core/pmem_region.c
> index 665b603c907b..3ef9c7d15041 100644
> --- a/drivers/cxl/core/pmem_region.c
> +++ b/drivers/cxl/core/pmem_region.c
> @@ -290,3 +290,56 @@ int devm_cxl_add_pmem_region(struct cxl_region *cxlr)
>  	return rc;
>  }
>  EXPORT_SYMBOL_NS_GPL(devm_cxl_add_pmem_region, "CXL");
> +
> +static int match_free_ep_decoder(struct device *dev, const void *data)
> +{
> +	struct cxl_decoder *cxld = to_cxl_decoder(dev);

I think this is needed if the function is match_free_ep_decoder().

if (!is_endpoint_decoder(dev))
	return 0;

> +
> +	return !cxld->region;
> +}

May want to borrow some code from match_free_decoder() in core/region.c. I think the decoder commit order matters?

> +
> +static struct cxl_decoder *cxl_find_free_ep_decoder(struct cxl_port *port)
> +{
> +	struct device *dev;
> +
> +	dev = device_find_child(&port->dev, NULL, match_free_ep_decoder);
> +	if (!dev)
> +		return NULL;
> +
> +	/* Release device ref taken via device_find_child() */
> +	put_device(dev);

Should have the caller put the device.

> +	return to_cxl_decoder(dev);
> +}
> +
> +void create_pmem_region(struct nvdimm *nvdimm)
> +{
> +	struct cxl_nvdimm *cxl_nvd;
> +	struct cxl_memdev *cxlmd;
> +	struct cxl_pmem_region_params *params;
> +	struct cxl_root_decoder *cxlrd;
> +	struct cxl_decoder *cxld;
> +	struct cxl_region *cxlr;
> +
> +	if (!nvdimm_has_cxl_region(nvdimm))
> +		return;
> +
> +	lockdep_assert_held(&cxl_rwsem.region);
> +	cxl_nvd = nvdimm_provider_data(nvdimm);
> +	params = nvdimm_get_cxl_region_param(nvdimm);
> +	cxlmd = cxl_nvd->cxlmd;
> +	cxlrd = cxlmd->cxlrd;
> +
> +	 /* TODO: Region creation support only for interleave way == 1 */
> +	if (!(params->nlabel == 1))
> +		dev_info(&cxlmd->dev,
> +			 "Region Creation is not supported with iw > 1\n");

Why not just exit here. Then the else is not necessary.

Also maybe deb_dbg().

> +	else {
> +		cxld = cxl_find_free_ep_decoder(cxlmd->endpoint);
> +		cxlr = cxl_create_region(cxlrd, CXL_PARTMODE_PMEM,
> +					 atomic_read(&cxlrd->region_id),
> +					 params, cxld);
> +		if (IS_ERR(cxlr))
> +			dev_info(&cxlmd->dev, "Region Creation failed\n");

dev_warn()

> +	}
> +}
> +EXPORT_SYMBOL_NS_GPL(create_pmem_region, "CXL");
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index f01f8c942fdf..0a87ea79742a 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -910,6 +910,7 @@ cxl_create_region(struct cxl_root_decoder *cxlrd,
>  bool is_cxl_pmem_region(struct device *dev);
>  struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev);
>  int devm_cxl_add_pmem_region(struct cxl_region *cxlr);
> +void create_pmem_region(struct nvdimm *nvdimm);
>  #else
>  static inline bool is_cxl_pmem_region(struct device *dev)
>  {
> @@ -923,6 +924,9 @@ static inline int devm_cxl_add_pmem_region(struct cxl_region *cxlr)
>  {
>  	return 0;
>  }
> +static inline void create_pmem_region(struct nvdimm *nvdimm)
> +{
> +}
>  #endif
>  
>  void cxl_endpoint_parse_cdat(struct cxl_port *port);
> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> index 38a5bcdc68ce..0cdef01dbc68 100644
> --- a/drivers/cxl/pmem.c
> +++ b/drivers/cxl/pmem.c
> @@ -135,6 +135,7 @@ static int cxl_nvdimm_probe(struct device *dev)
>  		return rc;
>  
>  	set_bit(NDD_LABELING, &flags);
> +	set_bit(NDD_REGION_LABELING, &flags);
>  	set_bit(NDD_REGISTER_SYNC, &flags);
>  	set_bit(ND_CMD_GET_CONFIG_SIZE, &cmd_mask);
>  	set_bit(ND_CMD_GET_CONFIG_DATA, &cmd_mask);
> @@ -155,6 +156,7 @@ static int cxl_nvdimm_probe(struct device *dev)
>  		return -ENOMEM;
>  
>  	dev_set_drvdata(dev, nvdimm);
> +	create_pmem_region(nvdimm);
>  	return devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
>  }
>