[PATCH v4 22/28] cxl/region/extent: Expose region extent information in sysfs

From: ira . weiny
Date: Mon Oct 07 2024 - 19:22:54 EST


From: Navneet Singh <navneet.singh@xxxxxxxxx>

Extent information can be helpful to the user to coordinate memory usage
with the external orchestrator and FM.

Expose the details of region extents 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/tag

Signed-off-by: Navneet Singh <navneet.singh@xxxxxxxxx>
Co-developed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

---
Changes:
[djiang: Split sysfs docs up]
[iweiny: Adjust sysfs docs dates]
---
Documentation/ABI/testing/sysfs-bus-cxl | 32 ++++++++++++++++++
drivers/cxl/core/extent.c | 58 +++++++++++++++++++++++++++++++++
2 files changed, 90 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index b63ab622515f..64918180a3c9 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -632,3 +632,35 @@ Description:
See Documentation/ABI/stable/sysfs-devices-node. access0 provides
the number to the closest initiator and access1 provides the
number to the closest CPU.
+
+What: /sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
+Date: December, 2024
+KernelVersion: v6.13
+Contact: linux-cxl@xxxxxxxxxxxxxxx
+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: December, 2024
+KernelVersion: v6.13
+Contact: linux-cxl@xxxxxxxxxxxxxxx
+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/tag
+Date: December, 2024
+KernelVersion: v6.13
+Contact: linux-cxl@xxxxxxxxxxxxxxx
+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 tag.
diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c
index 69a7614ba6a9..a1eb6e8e4f1a 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 region_extent *region_extent = to_region_extent(dev);
+
+ return sysfs_emit(buf, "%#llx\n", region_extent->hpa_range.start);
+}
+static DEVICE_ATTR_RO(offset);
+
+static ssize_t length_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct region_extent *region_extent = to_region_extent(dev);
+ u64 length = range_len(&region_extent->hpa_range);
+
+ return sysfs_emit(buf, "%#llx\n", length);
+}
+static DEVICE_ATTR_RO(length);
+
+static ssize_t tag_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct region_extent *region_extent = to_region_extent(dev);
+
+ return sysfs_emit(buf, "%pUb\n", &region_extent->tag);
+}
+static DEVICE_ATTR_RO(tag);
+
+static struct attribute *region_extent_attrs[] = {
+ &dev_attr_offset.attr,
+ &dev_attr_length.attr,
+ &dev_attr_tag.attr,
+ NULL,
+};
+
+static uuid_t empty_tag = { 0 };
+
+static umode_t region_extent_visible(struct kobject *kobj,
+ struct attribute *a, int n)
+{
+ struct device *dev = kobj_to_dev(kobj);
+ struct region_extent *region_extent = to_region_extent(dev);
+
+ if (a == &dev_attr_tag.attr &&
+ uuid_equal(&region_extent->tag, &empty_tag))
+ return 0;
+
+ return a->mode;
+}
+
+static const struct attribute_group region_extent_attribute_group = {
+ .attrs = region_extent_attrs,
+ .is_visible = region_extent_visible,
+};
+
+__ATTRIBUTE_GROUPS(region_extent_attribute);
+
static void cxled_release_extent(struct cxl_endpoint_decoder *cxled,
struct cxled_extent *ed_extent)
{
@@ -44,6 +101,7 @@ static void region_extent_release(struct device *dev)
static const struct device_type region_extent_type = {
.name = "extent",
.release = region_extent_release,
+ .groups = region_extent_attribute_groups,
};

bool is_region_extent(struct device *dev)

--
2.46.0