linux-kernel - Re: [RFC PATCH 01/20] nvdimm/label: Introduce NDD_CXL

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Message-ID: <1983025922.01750943702980.JavaMail.epsvc@epcpadp1new>
Date: Thu, 26 Jun 2025 15:18:40 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: dan.j.williams@...el.com, dave@...olabs.net, dave.jiang@...el.com,
	alison.schofield@...el.com, vishal.l.verma@...el.com, ira.weiny@...el.com,
	a.manzanares@...sung.com, nifan.cxl@...il.com, anisa.su@...sung.com,
	vishak.g@...sung.com, krish.reddy@...sung.com, arun.george@...sung.com,
	alok.rathore@...sung.com, neeraj.kernel@...il.com,
	linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org,
	nvdimm@...ts.linux.dev, gost.dev@...sung.com, cpgs@...sung.com
Subject: Re: [RFC PATCH 01/20] nvdimm/label: Introduce NDD_CXL_LABEL flag to
 set cxl label format

On 20/06/25 05:40PM, Jonathan Cameron wrote:
>On Tue, 17 Jun 2025 18:09:25 +0530
>Neeraj Kumar <s.neeraj@...sung.com> wrote:
>
>> NDD_CXL_LABEL is introduced to set cxl LSA 2.1 label format
>> Accordingly updated label index version
>>
>> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
>A few local comments.  I'll need to read on to figure out how this
>fits in generally.
>
>> ---
>>  drivers/nvdimm/dimm.c      |  1 +
>>  drivers/nvdimm/dimm_devs.c | 10 ++++++++++
>>  drivers/nvdimm/label.c     | 16 ++++++++++++----
>>  drivers/nvdimm/nd.h        |  1 +
>>  include/linux/libnvdimm.h  |  3 +++
>>  5 files changed, 27 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/nvdimm/dimm.c b/drivers/nvdimm/dimm.c
>> index 91d9163ee303..8753b5cd91cc 100644
>> --- a/drivers/nvdimm/dimm.c
>> +++ b/drivers/nvdimm/dimm.c
>> @@ -62,6 +62,7 @@ static int nvdimm_probe(struct device *dev)
>>  	if (rc < 0)
>>  		dev_dbg(dev, "failed to unlock dimm: %d\n", rc);
>>
>> +	ndd->cxl = nvdimm_check_cxl_label_format(ndd->dev);
>>
>>  	/*
>>  	 * EACCES failures reading the namespace label-area-properties
>> diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
>> index 21498d461fde..e8f545f889fd 100644
>> --- a/drivers/nvdimm/dimm_devs.c
>> +++ b/drivers/nvdimm/dimm_devs.c
>> @@ -18,6 +18,16 @@
>>
>>  static DEFINE_IDA(dimm_ida);
>>
>> +bool nvdimm_check_cxl_label_format(struct device *dev)
>> +{
>> +	struct nvdimm *nvdimm = to_nvdimm(dev);
>> +
>> +	if (test_bit(NDD_CXL_LABEL, &nvdimm->flags))
>> +		return true;
>> +
>> +	return false;
>
>	return test_bit(NDD_CXL_LABEL, &nvdimm->flags);
>
>Unless this is going to get more complex in later patches, in which case
>may be fine to ignore this comment.
>

Okay. I will fix in V1 patch.

>> +}
>> +
>>  /*
>>   * Retrieve bus and dimm handle and return if this bus supports
>>   * get_config_data commands
>> diff --git a/drivers/nvdimm/label.c b/drivers/nvdimm/label.c
>> index 082253a3a956..48b5ba90216d 100644
>> --- a/drivers/nvdimm/label.c
>> +++ b/drivers/nvdimm/label.c
>> @@ -687,11 +687,19 @@ static int nd_label_write_index(struct nvdimm_drvdata *ndd, int index, u32 seq,
>>  		- (unsigned long) to_namespace_index(ndd, 0);
>>  	nsindex->labeloff = __cpu_to_le64(offset);
>>  	nsindex->nslot = __cpu_to_le32(nslot);
>> -	nsindex->major = __cpu_to_le16(1);
>> -	if (sizeof_namespace_label(ndd) < 256)
>> +
>> +	/* Support CXL LSA 2.1 label format */
>
>Might be good to sprinkle some extra details in the references.
>E.g. CXL r3.2 Table 9-9 Label Index Block Layout
>

Sure, I will update it in V1

>> +	if (ndd->cxl) {
>> +		nsindex->major = __cpu_to_le16(2);
>>  		nsindex->minor = __cpu_to_le16(1);
>> -	else
>> -		nsindex->minor = __cpu_to_le16(2);
>> +	} else {
>> +		nsindex->major = __cpu_to_le16(1);
>
>Same for these.  Case of making reviewers jobs easier by
>giving them breadcrumb trails to follow.
>

Sure, I will update it in V1

>> +		if (sizeof_namespace_label(ndd) < 256)
>> +			nsindex->minor = __cpu_to_le16(1);
>> +		else
>> +			nsindex->minor = __cpu_to_le16(2);
>> +	}
>> +
>>  	nsindex->checksum = __cpu_to_le64(0);
>>  	if (flags & ND_NSINDEX_INIT) {
>>  		unsigned long *free = (unsigned long *) nsindex->free;
>> diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
>> index 5ca06e9a2d29..304f0e9904f1 100644
>> --- a/drivers/nvdimm/nd.h
>> +++ b/drivers/nvdimm/nd.h
>> @@ -522,6 +522,7 @@ void nvdimm_set_labeling(struct device *dev);
>>  void nvdimm_set_locked(struct device *dev);
>>  void nvdimm_clear_locked(struct device *dev);
>>  int nvdimm_security_setup_events(struct device *dev);
>> +bool nvdimm_check_cxl_label_format(struct device *dev);
>>  #if IS_ENABLED(CONFIG_NVDIMM_KEYS)
>>  int nvdimm_security_unlock(struct device *dev);
>>  #else
>> diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
>> index e772aae71843..0a55900842c8 100644
>> --- a/include/linux/libnvdimm.h
>> +++ b/include/linux/libnvdimm.h
>> @@ -44,6 +44,9 @@ enum {
>>  	/* dimm provider wants synchronous registration by __nvdimm_create() */
>>  	NDD_REGISTER_SYNC = 8,
>>
>> +	/* dimm supports region labels (LSA Format 2.1) */
>> +	NDD_CXL_LABEL = 9,
>> +
>>  	/* need to set a limit somewhere, but yes, this is likely overkill */
>>  	ND_IOCTL_MAX_BUFLEN = SZ_4M,
>>  	ND_CMD_MAX_ELEM = 5,
>