[PATCH V5 15/17] cxl/pmem_region: Add sysfs attribute cxl region label updation/deletion

Neeraj Kumar
2026-01-09T12:45:34Z

Using these attributes region label is added/deleted into LSA. These
attributes are called from userspace (ndctl) after region creation.

Signed-off-by: Neeraj Kumar <s.neeraj@samsung.com>
---
Documentation/ABI/testing/sysfs-bus-cxl | 22 +++++++
drivers/cxl/core/pmem_region.c | 88 +++++++++++++++++++++++++
drivers/cxl/cxl.h | 7 ++
3 files changed, 117 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index c80a1b5a03db..011a5e8d354f 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -624,3 +624,25 @@ Description:
The count is persistent across power loss and wraps back to 0
upon overflow. If this file is not present, the device does not
have the necessary support for dirty tracking.
+
+
+What: /sys/bus/cxl/devices/regionZ/pmem_regionZ/region_label_update
+Date: Jan, 2026
+KernelVersion: v6.19
+Contact: linux-cxl@vger.kernel.org
+Description:
+ (RW) Write a boolean 'true' string value to this attribute to
+ update cxl region information into LSA as region label. It is
+ used to update cxl region information saved during cxl region
+ creation into LSA. This attribute must be written last during
+ cxl region creation. Reading this attribute indicates whether
+ the region label is active or not.
+
+
+What: /sys/bus/cxl/devices/regionZ/pmem_regionZ/region_label_delete
+Date: Jan, 2026
+KernelVersion: v6.19
+Contact: linux-cxl@vger.kernel.org
+Description:
+ (WO) When a boolean 'true' is written to this attribute then
+ pmem_region driver deletes cxl region label from LSA.
diff --git a/drivers/cxl/core/pmem_region.c b/drivers/cxl/core/pmem_region.c
index dcaab59108fd..53d3d81e9676 100644
--- a/drivers/cxl/core/pmem_region.c
+++ b/drivers/cxl/core/pmem_region.c
@@ -29,8 +29,96 @@ static void cxl_pmem_region_release(struct device *dev)
kfree(cxlr_pmem);
}

+static ssize_t region_label_update_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct cxl_pmem_region *cxlr_pmem = to_cxl_pmem_region(dev);
+ struct cxl_region *cxlr = cxlr_pmem->cxlr;
+ ssize_t rc;
+ bool update;
+
+ rc = kstrtobool(buf, &update);
+ if (rc)
+ return rc;
+
+ ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region);
+ if ((rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem)))
+ return rc;
+
+ /* Region not yet committed */
+ if (update && cxlr && cxlr->params.state != CXL_CONFIG_COMMIT) {
+ dev_dbg(dev, "region not committed, can't update into LSA\n");
+ return -ENXIO;
+ }
+
+ if (!cxlr || !cxlr->cxlr_pmem || !cxlr->cxlr_pmem->nd_region)
+ return 0;
+
+ rc = nd_region_label_update(cxlr->cxlr_pmem->nd_region);
+ if (rc)
+ return rc;
+
+ cxlr->params.state_region_label = CXL_REGION_LABEL_ACTIVE;
+
+ return len;
+}
+
+static ssize_t region_label_update_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct cxl_pmem_region *cxlr_pmem = to_cxl_pmem_region(dev);
+ struct cxl_region *cxlr = cxlr_pmem->cxlr;
+ struct cxl_region_params *p = &cxlr->params;
+ ssize_t rc;
+
+ ACQUIRE(rwsem_read_intr, rwsem)(&cxl_rwsem.region);
+ if ((rc = ACQUIRE_ERR(rwsem_read_intr, &rwsem)))
+ return rc;
+
+ return sysfs_emit(buf, "%d\n", p->state_region_label);
+}
+static DEVICE_ATTR_RW(region_label_update);
+
+static ssize_t region_label_delete_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct cxl_pmem_region *cxlr_pmem = to_cxl_pmem_region(dev);
+ struct cxl_region *cxlr = cxlr_pmem->cxlr;
+ ssize_t rc;
+
+ ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region);
+ if ((rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem)))
+ return rc;
+
+ if (!cxlr && !cxlr->cxlr_pmem && !cxlr->cxlr_pmem->nd_region)
+ return 0;
+
+ rc = nd_region_label_delete(cxlr->cxlr_pmem->nd_region);
+ if (rc)
+ return rc;
+
+ cxlr->params.state_region_label = CXL_REGION_LABEL_INACTIVE;
+
+ return len;
+}
+static DEVICE_ATTR_WO(region_label_delete);
+
+static struct attribute *cxl_pmem_region_attrs[] = {
+ &dev_attr_region_label_update.attr,
+ &dev_attr_region_label_delete.attr,
+ NULL
+};
+
+static struct attribute_group cxl_pmem_region_group = {
+ .attrs = cxl_pmem_region_attrs,
+};
+
static const struct attribute_group *cxl_pmem_region_attribute_groups[] = {
&cxl_base_attribute_group,
+ &cxl_pmem_region_group,
NULL
};

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 6ac3b40cb5ff..8c76c4a981bf 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -473,9 +473,15 @@ enum cxl_config_state {
CXL_CONFIG_COMMIT,
};

+enum region_label_state {
+ CXL_REGION_LABEL_INACTIVE,
+ CXL_REGION_LABEL_ACTIVE,
+};
+
/**
* struct cxl_region_params - region settings
* @state: allow the driver to lockdown further parameter changes
+ * @state: region label state
* @uuid: unique id for persistent regions
* @interleave_ways: number of endpoints in the region
* @interleave_granularity: capacity each endpoint contributes to a stripe
@@ -488,6 +494,7 @@ enum cxl_config_state {
*/
struct cxl_region_params {
enum cxl_config_state state;
+ enum region_label_state state_region_label;
uuid_t uuid;
int interleave_ways;
int interleave_granularity;
--
2.34.1