Merge branch 'for-6.19/cxl-elc' into cxl-for-next

- Add extended linear cache size sysfs attribute.
- Adjust failure emission of extended linear cache detection in cxl_acpi.

Author: davejiang

Documentation/ABI/testing/sysfs-bus-cxl

@@ -496,8 +496,17 @@ Description:
 		changed, only freed by writing 0. The kernel makes no guarantees
 		that data is maintained over an address space freeing event, and
 		there is no guarantee that a free followed by an allocate
-		results in the same address being allocated.
+		results in the same address being allocated. If extended linear
+		cache is present, the size indicates extended linear cache size
+		plus the CXL region size.
 
+What:		/sys/bus/cxl/devices/regionZ/extended_linear_cache_size
+Date:		October, 2025
+KernelVersion:	v6.19
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) The size of extended linear cache, if there is an extended
+		linear cache. Otherwise the attribute will not be visible.
 
 What:		/sys/bus/cxl/devices/regionZ/mode
 Date:		January, 2023

drivers/cxl/acpi.c

@@ -372,7 +372,7 @@ static int cxl_acpi_set_cache_size(struct cxl_root_decoder *cxlrd)
 
 	rc = hmat_get_extended_linear_cache_size(&res, nid, &cache_size);
 	if (rc)
-		return rc;
+		return 0;
 
 	/*
 	 * The cache range is expected to be within the CFMWS.
@@ -397,21 +397,18 @@ static void cxl_setup_extended_linear_cache(struct cxl_root_decoder *cxlrd)
 	int rc;
 
 	rc = cxl_acpi_set_cache_size(cxlrd);
-	if (!rc)
-		return;
-
-	if (rc != -EOPNOTSUPP) {
+	if (rc) {
 		/*
-		 * Failing to support extended linear cache region resize does not
+		 * Failing to retrieve extended linear cache region resize does not
 		 * prevent the region from functioning. Only causes cxl list showing
 		 * incorrect region size.
 		 */
 		dev_warn(cxlrd->cxlsd.cxld.dev.parent,
-			 "Extended linear cache calculation failed rc:%d\n", rc);
-	}
+			 "Extended linear cache retrieval failed rc:%d\n", rc);
 
-	/* Ignoring return code */
-	cxlrd->cache_size = 0;
+		/* Ignoring return code */
+		cxlrd->cache_size = 0;
+	}
 }
 
 DEFINE_FREE(put_cxlrd, struct cxl_root_decoder *,

drivers/cxl/core/region.c

@@ -467,21 +467,6 @@ static ssize_t commit_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(commit);
 
-static umode_t cxl_region_visible(struct kobject *kobj, struct attribute *a,
-				  int n)
-{
-	struct device *dev = kobj_to_dev(kobj);
-	struct cxl_region *cxlr = to_cxl_region(dev);
-
-	/*
-	 * Support tooling that expects to find a 'uuid' attribute for all
-	 * regions regardless of mode.
-	 */
-	if (a == &dev_attr_uuid.attr && cxlr->mode != CXL_PARTMODE_PMEM)
-		return 0444;
-	return a->mode;
-}
-
 static ssize_t interleave_ways_show(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
@@ -760,6 +745,21 @@ static ssize_t size_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(size);
 
+static ssize_t extended_linear_cache_size_show(struct device *dev,
+					       struct device_attribute *attr,
+					       char *buf)
+{
+	struct cxl_region *cxlr = to_cxl_region(dev);
+	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, "%#llx\n", p->cache_size);
+}
+static DEVICE_ATTR_RO(extended_linear_cache_size);
+
 static struct attribute *cxl_region_attrs[] = {
 	&dev_attr_uuid.attr,
 	&dev_attr_commit.attr,
@@ -768,9 +768,34 @@ static struct attribute *cxl_region_attrs[] = {
 	&dev_attr_resource.attr,
 	&dev_attr_size.attr,
 	&dev_attr_mode.attr,
+	&dev_attr_extended_linear_cache_size.attr,
 	NULL,
 };
 
+static umode_t cxl_region_visible(struct kobject *kobj, struct attribute *a,
+				  int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct cxl_region *cxlr = to_cxl_region(dev);
+
+	/*
+	 * Support tooling that expects to find a 'uuid' attribute for all
+	 * regions regardless of mode.
+	 */
+	if (a == &dev_attr_uuid.attr && cxlr->mode != CXL_PARTMODE_PMEM)
+		return 0444;
+
+	/*
+	 * Don't display extended linear cache attribute if there is no
+	 * extended linear cache.
+	 */
+	if (a == &dev_attr_extended_linear_cache_size.attr &&
+	    cxlr->params.cache_size == 0)
+		return 0;
+
+	return a->mode;
+}
+
 static const struct attribute_group cxl_region_group = {
 	.attrs = cxl_region_attrs,
 	.is_visible = cxl_region_visible,
@@ -3580,6 +3605,10 @@ static int __construct_region(struct cxl_region *cxlr,
 			 "Extended linear cache calculation failed rc:%d\n", rc);
 	}
 
+	rc = sysfs_update_group(&cxlr->dev.kobj, &cxl_region_group);
+	if (rc)
+		return rc;
+
 	rc = insert_resource(cxlrd->res, res);
 	if (rc) {
 		/*