Message-ID: <148912029.181757055784505.JavaMail.epsvc@epcpadp2new>
Date: Thu, 4 Sep 2025 20:25:20 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: Dave Jiang <dave.jiang@...el.com>
Cc: linux-cxl@...r.kernel.org, nvdimm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, gost.dev@...sung.com,
	a.manzanares@...sung.com, vishak.g@...sung.com, neeraj.kernel@...il.com,
	cpgs@...sung.com
Subject: Re: [PATCH V2 14/20] cxl/region: Add devm_cxl_pmem_add_region() for
 pmem region creation

On 19/08/25 05:30PM, Dave Jiang wrote:
>
>
>On 7/30/25 5:12 AM, Neeraj Kumar wrote:
>> devm_cxl_pmem_add_region() is used to create cxl region based on region
>> information scanned from LSA.
>>
>> devm_cxl_add_region() is used to just allocate cxlr and its fields are
>> filled later by userspace tool using device attributes (*_store()).
>>
>> Inspiration for devm_cxl_pmem_add_region() is taken from these device
>> attributes (_store*) calls. It allocates cxlr and fills information
>> parsed from LSA and calls device_add(&cxlr->dev) to initiate further
>> region creation porbes
>>
>> Renamed __create_region() to cxl_create_region() and make it an exported
>> routine. This will be used in later patch to create cxl region after
>> fetching region information from LSA.
>>
>> Also created some helper routines and refactored dpa_size_store(),
>> commit_store() to avoid duplicate code usage in devm_cxl_pmem_add_region()
>
>"Some helper routines are created to...."
>
>I would drop the "Also"

Sure Dave, I will drop it in next patch-set

>
>
>>
>> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
>> ---
>>  drivers/cxl/core/core.h   |   1 +
>>  drivers/cxl/core/port.c   |  29 ++++++----
>>  drivers/cxl/core/region.c | 118 +++++++++++++++++++++++++++++++++-----
>>  drivers/cxl/cxl.h         |  12 ++++
>>  4 files changed, 134 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
>> index 2669f251d677..80c83e0117c6 100644
>> --- a/drivers/cxl/core/core.h
>> +++ b/drivers/cxl/core/core.h
>> @@ -94,6 +94,7 @@ int cxl_dpa_free(struct cxl_endpoint_decoder *cxled);
>>  resource_size_t cxl_dpa_size(struct cxl_endpoint_decoder *cxled);
>>  resource_size_t cxl_dpa_resource_start(struct cxl_endpoint_decoder *cxled);
>>  bool cxl_resource_contains_addr(const struct resource *res, const resource_size_t addr);
>> +ssize_t resize_or_free_dpa(struct cxl_endpoint_decoder *cxled, u64 size);
>>
>>  enum cxl_rcrb {
>>  	CXL_RCRB_DOWNSTREAM,
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index 29197376b18e..ba743e31f721 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -243,16 +243,9 @@ static ssize_t dpa_size_show(struct device *dev, struct device_attribute *attr,
>>  	return sysfs_emit(buf, "%pa\n", &size);
>>  }
>>
>> -static ssize_t dpa_size_store(struct device *dev, struct device_attribute *attr,
>> -			      const char *buf, size_t len)
>> +ssize_t resize_or_free_dpa(struct cxl_endpoint_decoder *cxled, u64 size)
>
>Maybe it should be called cxl_realloc_dpa()? More comments later on...

Sure Dave, I will rename it to cxl_realloc_dpa().

>
>>  {
>> -	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
>> -	unsigned long long size;
>> -	ssize_t rc;
>> -
>> -	rc = kstrtoull(buf, 0, &size);
>> -	if (rc)
>> -		return rc;
>> +	int rc;
>>
>>  	if (!IS_ALIGNED(size, SZ_256M))
>>  		return -EINVAL;
>> @@ -262,9 +255,23 @@ static ssize_t dpa_size_store(struct device *dev, struct device_attribute *attr,
>>  		return rc;
>>
>>  	if (size == 0)
>> -		return len;
>> +		return 0;
>> +
>> +	return cxl_dpa_alloc(cxled, size);
>> +}
>> +
>> +static ssize_t dpa_size_store(struct device *dev, struct device_attribute *attr,
>> +			      const char *buf, size_t len)
>> +{
>> +	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
>> +	unsigned long long size;
>> +	ssize_t rc;
>> +
>> +	rc = kstrtoull(buf, 0, &size);
>> +	if (rc)
>> +		return rc;
>>
>> -	rc = cxl_dpa_alloc(cxled, size);
>> +	rc = resize_or_free_dpa(cxled, size);
>>  	if (rc)
>>  		return rc;
>>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index eef501f3384c..8578e046aa78 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -703,6 +703,23 @@ static int free_hpa(struct cxl_region *cxlr)
>>  	return 0;
>>  }
>>
>> +static ssize_t resize_or_free_region_hpa(struct cxl_region *cxlr, u64 size)
>> +{
>> +	int rc;
>> +
>> +	ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region);
>> +	rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem);
>> +	if (rc)
>> +		return rc;
>> +
>> +	if (size)
>> +		rc = alloc_hpa(cxlr, size);
>> +	else
>> +		rc = free_hpa(cxlr);
>> +
>> +	return rc;
>> +}
>
>I think it's better to have 2 helper functions rather a single ambiguous one here. alloc_region_hpa() and free_region_hpa(). More on why later.

Sure, I will handle it accordingly.

>
>> +
>>  static ssize_t size_store(struct device *dev, struct device_attribute *attr,
>>  			  const char *buf, size_t len)
>>  {
>> @@ -714,15 +731,7 @@ static ssize_t size_store(struct device *dev, struct device_attribute *attr,
>>  	if (rc)
>>  		return rc;
>>
>> -	ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region);
>> -	if ((rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem)))
>> -		return rc;
>> -
>> -	if (val)
>> -		rc = alloc_hpa(cxlr, val);
>> -	else
>> -		rc = free_hpa(cxlr);
>> -
>> +	rc = resize_or_free_region_hpa(cxlr, val);
>>  	if (rc)
>>  		return rc;
>>
>> @@ -2569,6 +2578,76 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
>>  	return ERR_PTR(rc);
>>  }
>>
>> +static struct cxl_region *
>> +devm_cxl_pmem_add_region(struct cxl_root_decoder *cxlrd,
>> +			 int id,
>> +			 enum cxl_partition_mode mode,
>> +			 enum cxl_decoder_type type,
>> +			 struct cxl_pmem_region_params *params,
>> +			 struct cxl_decoder *cxld)
>> +{
>> +	struct cxl_port *root_port;
>> +	struct cxl_region *cxlr;
>> +	struct cxl_endpoint_decoder *cxled;
>> +	struct cxl_region_params *p;
>> +	struct device *dev;
>> +	int rc;
>> +
>> +	cxlr = cxl_region_alloc(cxlrd, id);
>I think you can use __free() here to drop all the gotos.
>
>struct cxl_region *cxlr __free(put_cxl_region) = cxl_region_alloc(cxlrd, id);
>
>Just make sure to 'return no_free_ptr(cxlr)' at the successful end.

Sure Dave, Thanks for your suggestion. I will handle it accordingly in
next patch-set.

>
>
>> +	if (IS_ERR(cxlr))
>> +		return cxlr;
>> +	cxlr->mode = mode;
>> +	cxlr->type = type;
>> +
>> +	dev = &cxlr->dev;
>> +	rc = dev_set_name(dev, "region%d", id);
>> +	if (rc)
>> +		goto err;
>> +
>> +	p = &cxlr->params;
>> +	p->uuid = params->uuid;
>> +	p->interleave_ways = params->nlabel;
>> +	p->interleave_granularity = params->ig;
>> +
>> +	if (resize_or_free_region_hpa(cxlr, params->rawsize))
>> +		goto err;
>
>Given this is _add_region(), it really should only be calling alloc_region_hpa() and not have to deal with free. Maybe a check before this and make sure params->rawsize is not 0 is needed.

Sure, Let me re-look at it.

>
>> +
>> +	cxled = to_cxl_endpoint_decoder(&cxld->dev);
>> +	if (resize_or_free_dpa(cxled, 0))
>Given that resize_or_free_dpa() always frees, is this call necessary here?

Yes, Its required here as in first call to resize_or_free_dpa(), we are
just freeing dpa and returning as its size is 0. But anyway, Let me
double check it here.

>
>> +		goto err;
>> +
>> +	if (cxl_dpa_set_part(cxled, CXL_PARTMODE_PMEM))
>> +		goto err;
>> +
>> +	if (resize_or_free_dpa(cxled, params->rawsize))
>
>Seems like it can be called once here instead and it'll just free and then re-allocate whatever size in params->rawsize.

Sure, I will re-look at it

>
>> +		goto err;
>> +
>> +	/* Attaching only one target due to interleave_way == 1 */
>Is it missing a check of interleave_ways here? Also maybe additional comments on why support iw==1 only?

Sure, I will look at this and update the comments properly.

>
>> +	if (attach_target(cxlr, cxled, params->position, TASK_INTERRUPTIBLE))
>> +		goto err;
>> +
>> +	if (__commit(cxlr))
>> +		goto err;
>> +
>> +	rc = device_add(dev);
>> +	if (rc)
>> +		goto err;
>> +
>> +	root_port = to_cxl_port(cxlrd->cxlsd.cxld.dev.parent);
>> +	rc = devm_add_action_or_reset(root_port->uport_dev,
>> +			unregister_region, cxlr);
>> +	if (rc)
>> +		return ERR_PTR(rc);
>> +
>> +	dev_dbg(root_port->uport_dev, "%s: created %s\n",
>> +		dev_name(&cxlrd->cxlsd.cxld.dev), dev_name(dev));
>> +	return cxlr;
>> +
>> +err:
>> +	put_device(dev);
>> +	return ERR_PTR(rc);
>> +}
>> +
>>  static ssize_t __create_region_show(struct cxl_root_decoder *cxlrd, char *buf)
>>  {
>>  	return sysfs_emit(buf, "region%u\n", atomic_read(&cxlrd->region_id));
>> @@ -2586,8 +2665,10 @@ static ssize_t create_ram_region_show(struct device *dev,
>>  	return __create_region_show(to_cxl_root_decoder(dev), buf);
>>  }
>>
>> -static struct cxl_region *__create_region(struct cxl_root_decoder *cxlrd,
>> -					  enum cxl_partition_mode mode, int id)
>> +struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
>> +				     enum cxl_partition_mode mode, int id,
>> +				     struct cxl_pmem_region_params *params,
>
>Maybe name it pmem_params to avoid confusion with cxl region params.
>
>> +				     struct cxl_decoder *cxld)
>>  {
>>  	int rc;
>>
>> @@ -2609,8 +2690,14 @@ static struct cxl_region *__create_region(struct cxl_root_decoder *cxlrd,
>>  		return ERR_PTR(-EBUSY);
>>  	}
>>
>> -	return devm_cxl_add_region(cxlrd, id, mode, CXL_DECODER_HOSTONLYMEM);
>> +	if (params)
>> +		return devm_cxl_pmem_add_region(cxlrd, id, mode,
>> +				CXL_DECODER_HOSTONLYMEM, params, cxld);
>> +	else
>
>'else' not needed here. Just directly return.

Thanks Dave, I will fix it in next patch-set.

>
>> +		return devm_cxl_add_region(cxlrd, id, mode,
>> +				CXL_DECODER_HOSTONLYMEM);
>>  }
>> +EXPORT_SYMBOL_NS_GPL(cxl_create_region, "CXL");
>>
>>  static ssize_t create_region_store(struct device *dev, const char *buf,
>>  				   size_t len, enum cxl_partition_mode mode)
>> @@ -2623,7 +2710,7 @@ static ssize_t create_region_store(struct device *dev, const char *buf,
>>  	if (rc != 1)
>>  		return -EINVAL;
>>
>> -	cxlr = __create_region(cxlrd, mode, id);
>> +	cxlr = cxl_create_region(cxlrd, mode, id, NULL, NULL);
>>  	if (IS_ERR(cxlr))
>>  		return PTR_ERR(cxlr);
>>
>> @@ -3414,8 +3501,9 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>>  	struct cxl_region *cxlr;
>>
>>  	do {
>> -		cxlr = __create_region(cxlrd, cxlds->part[part].mode,
>> -				       atomic_read(&cxlrd->region_id));
>> +		cxlr = cxl_create_region(cxlrd, cxlds->part[part].mode,
>> +					 atomic_read(&cxlrd->region_id),
>> +					 NULL, NULL);
>>  	} while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY);
>>
>>  	if (IS_ERR(cxlr)) {
>> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
>> index 6edcec95e9ba..129db2e49aa7 100644
>> --- a/drivers/cxl/cxl.h
>> +++ b/drivers/cxl/cxl.h
>> @@ -865,6 +865,10 @@ 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);
>>  void cxl_region_discovery(struct cxl_port *port);
>> +struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
>> +				     enum cxl_partition_mode mode, int id,
>> +				     struct cxl_pmem_region_params *params,
>> +				     struct cxl_decoder *cxld);
>>  #else
>>  static inline bool is_cxl_pmem_region(struct device *dev)
>>  {
>> @@ -890,6 +894,14 @@ static inline u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint,
>>  static inline void cxl_region_discovery(struct cxl_port *port)
>>  {
>>  }
>> +static inline struct cxl_region *
>> +cxl_create_region(struct cxl_root_decoder *cxlrd,
>> +		  enum cxl_partition_mode mode, int id,
>> +		  struct cxl_pmem_region_params *params,
>> +		  struct cxl_decoder *cxld)
>> +{
>> +	return NULL;
>
>return ERR_PTR(-EOPNOTSUPP);

Sure Dave, I will fix it


Regards,
Neeraj

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