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

Dave Jiang
2026-01-14T17:00:20Z

On 1/9/26 5:44 AM, Neeraj Kumar wrote:
> 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>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

You'll need to update the KernelVersion to v7.0.

> ---
> 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;