Re: [RFC PATCH 18/20] cxl/pmem: Add support of cxl lsa 2.1 support in cxl pmem

[Neeraj Kumar]

On 10/07/25 10:18AM, Dave Jiang wrote:

On 6/17/25 5:39 AM, Neeraj Kumar wrote:

Add support of cxl lsa 2.1 using NDD_CXL_LABEL flag. It also creates cxl
region based on region information parsed from LSA.

Signed-off-by: Neeraj Kumar <s.nee...@samsung.com>
---
 drivers/cxl/pmem.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
index ffcebb8d382f..2733d79b32d5 100644
--- a/drivers/cxl/pmem.c
+++ b/drivers/cxl/pmem.c
@@ -58,6 +58,63 @@ static const struct attribute_group 
*cxl_dimm_attribute_groups[] = {
        NULL
 };

+static int match_ep_decoder(struct device *dev, void *data)
+{
+       struct cxl_decoder *cxld = to_cxl_decoder(dev);
+
+       if (!cxld->region)
+               return 1;
+       else
+               return 0;
+}

return !cxld->region;

Thanks, I will fix it in next patch-set

+
+static struct cxl_decoder *cxl_find_free_decoder(struct cxl_port *port)
+{
+       struct device *dev;
+
+       dev = device_find_child(&port->dev, NULL, match_ep_decoder);
+       if (!dev)
+               return NULL;
+
+       return to_cxl_decoder(dev);
+}
+
+static int create_pmem_region(struct nvdimm *nvdimm)
+{
+       struct cxl_nvdimm *cxl_nvd;
+       struct cxl_memdev *cxlmd;
+       struct cxl_nvdimm_bridge *cxl_nvb;
+       struct cxl_pmem_region_params *params;
+       struct cxl_root_decoder *cxlrd;
+       struct cxl_decoder *cxld;
+       struct cxl_region *cxlr;
+

probably need a lockdep_assert_held(&cxl_region_rwsem).

Thanks Dave, Sure i will fix it with V2

+       if (!nvdimm)
+               return -ENOTTY;

-ENODEV?

Sure I will fix it with V2

+
+       if (!nvdimm_has_cxl_region(nvdimm))
+               return 0;
+
+       cxl_nvd = nvdimm_provider_data(nvdimm);
+       params = nvdimm_get_cxl_region_param(nvdimm);
+       cxlmd = cxl_nvd->cxlmd;
+       cxl_nvb = cxlmd->cxl_nvb;
+       cxlrd = cxlmd->cxlrd;
+
+       /* FIXME: Limitation: Region creation only when interleave way == 1 */
+       if (params->nlabel == 1) {
+               cxld = cxl_find_free_decoder(cxlmd->endpoint);
+               cxlr = cxl_create_pmem_region(cxlrd, cxld, params,
+                               atomic_read(&cxlrd->region_id));
+               if (IS_ERR(cxlr))
+                       dev_dbg(&cxlmd->dev, "Region Creation failed\n");

return PTR_ERR(cxlr); ?

Thanks, I will fix it in next patch-set

+       } else {
+               dev_dbg(&cxlmd->dev, "Region Creation is not supported with iw > 
1\n");
+       }
+
+       return 0;
+}
+
 static int cxl_nvdimm_probe(struct device *dev)
 {
        struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
@@ -74,6 +131,7 @@ static int cxl_nvdimm_probe(struct device *dev)
                return rc;

        set_bit(NDD_LABELING, &flags);
+       set_bit(NDD_CXL_LABEL, &flags);

Ok here's the NDD_CXL_LABEL set. I think the driver should be probing the label 
index block and retrieve the label version and determine how to support from 
there instead of hard coding a flag.

Hi Dave,

We actually write label index information into LSA during namespace/region 
label updation.
During that time we update its major/minor.

So during first time updation of LSA we must need some way to inform nvdimm 
about LSA versioning.


Regards,
Neeraj