From: Ira Weiny <[email protected]>
Extent information can be helpful to the user to coordinate memory
usage with the external orchestrator and FM.
Expose the details of each dc_extent by creating the following sysfs
entries.
/sys/bus/cxl/devices/dax_regionX/extentX.Y
/sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
/sys/bus/cxl/devices/dax_regionX/extentX.Y/length
/sys/bus/cxl/devices/dax_regionX/extentX.Y/uuid
Each dc_extent surfaces as its own extentX.Y device under the parent
dax_region. offset and length describe that dc_extent's HPA range,
not an aggregate bounding box across the containing tagged
allocation — so when a tagged allocation has multiple
DPA-discontiguous extents, each is reported with its own offset and
length. uuid is the tag identifying the containing allocation; it
is shared across dc_extents that belong to the same tagged
allocation and is hidden for untagged extents.
Based on an original patch by Navneet Singh.
Reviewed-by: Jonathan Cameron <[email protected]>
Reviewed-by: Fan Ni <[email protected]>
Tested-by: Fan Ni <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>
---
Documentation/ABI/testing/sysfs-bus-cxl | 36 +++++++++++++++
drivers/cxl/core/extent.c | 58 +++++++++++++++++++++++++
2 files changed, 94 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-cxl
b/Documentation/ABI/testing/sysfs-bus-cxl
index 3080aef9ad67..38cf0a2894b9 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -661,3 +661,39 @@ 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/dax_regionX/extentX.Y/offset
+Date: May, 2025
+KernelVersion: v6.16
+Contact: [email protected]
+Description:
+ (RO) [For Dynamic Capacity regions only] Users can use the
+ extent information to create DAX devices on specific extents.
+ This is done by creating and destroying DAX devices in specific
+ sequences and looking at the mappings created. Extent offset
+ within the region.
+
+
+What: /sys/bus/cxl/devices/dax_regionX/extentX.Y/length
+Date: May, 2025
+KernelVersion: v6.16
+Contact: [email protected]
+Description:
+ (RO) [For Dynamic Capacity regions only] Users can use the
+ extent information to create DAX devices on specific extents.
+ This is done by creating and destroying DAX devices in specific
+ sequences and looking at the mappings created. Extent length
+ within the region.
+
+
+What: /sys/bus/cxl/devices/dax_regionX/extentX.Y/uuid
+Date: May, 2025
+KernelVersion: v6.16
+Contact: [email protected]
+Description:
+ (RO) [For Dynamic Capacity regions only] Users can use the
+ extent information to create DAX devices on specific extents.
+ This is done by creating and destroying DAX devices in specific
+ sequences and looking at the mappings created. UUID of this
+ extent.
diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c
index f66fa8c600c5..34babfe032d1 100644
--- a/drivers/cxl/core/extent.c
+++ b/drivers/cxl/core/extent.c
@@ -6,6 +6,63 @@
#include "core.h"
+static ssize_t offset_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct dc_extent *dc_extent = to_dc_extent(dev);
+
+ return sysfs_emit(buf, "%#llx\n", dc_extent->hpa_range.start);
+}
+static DEVICE_ATTR_RO(offset);
+
+static ssize_t length_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct dc_extent *dc_extent = to_dc_extent(dev);
+ u64 length = range_len(&dc_extent->hpa_range);
+
+ return sysfs_emit(buf, "%#llx\n", length);
+}
+static DEVICE_ATTR_RO(length);
+
+static ssize_t uuid_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct dc_extent *dc_extent = to_dc_extent(dev);
+
+ return sysfs_emit(buf, "%pUb\n", &dc_extent->group->uuid);
+}
+static DEVICE_ATTR_RO(uuid);
+
+static struct attribute *dc_extent_attrs[] = {
+ &dev_attr_offset.attr,
+ &dev_attr_length.attr,
+ &dev_attr_uuid.attr,
+ NULL
+};
+
+static uuid_t empty_uuid = { 0 };
+
+static umode_t dc_extent_visible(struct kobject *kobj,
+ struct attribute *a, int n)
+{
+ struct device *dev = kobj_to_dev(kobj);
+ struct dc_extent *dc_extent = to_dc_extent(dev);
+
+ if (a == &dev_attr_uuid.attr &&
+ uuid_equal(&dc_extent->group->uuid, &empty_uuid))
+ return 0;
+
+ return a->mode;
+}
+
+static const struct attribute_group dc_extent_attribute_group = {
+ .attrs = dc_extent_attrs,
+ .is_visible = dc_extent_visible,
+};
+
+__ATTRIBUTE_GROUPS(dc_extent_attribute);
+
static void cxled_release_extent(struct cxl_endpoint_decoder *cxled,
struct dc_extent *dc_extent)
@@ -93,6 +150,7 @@ static void dc_extent_release(struct device *dev)
static const struct device_type dc_extent_type = {
.name = "extent",
.release = dc_extent_release,
+ .groups = dc_extent_attribute_groups,
};
bool is_dc_extent(struct device *dev)
--
2.43.0
