cxl: Change 'struct cxl_memdev_state' *_perf_list to single 'struct cxl_dpa_perf'

In order to address the issue with being able to expose qos_class sysfs
attributes under 'ram' and 'pmem' sub-directories, the attributes must
be defined as static attributes rather than under driver->dev_groups.
To avoid implementing locking for accessing the 'struct cxl_dpa_perf`
lists, convert the list to a single 'struct cxl_dpa_perf' entry in
preparation to move the attributes to statically defined.

While theoretically a partition may have multiple qos_class via CDAT, this
has not been encountered with testing on available hardware. The code is
simplified for now to not support the complex case until a use case is
needed to support that.

Link: https://lore.kernel.org/linux-cxl/65b200ba228f_2d43c29468@dwillia2-mobl3.amr.corp.intel.com.notmuch/Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20240206190431.1810289-2-dave.jiang@intel.comReviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/cdat.c

@@ -210,19 +210,12 @@ static int cxl_port_perf_data_calculate(struct cxl_port *port,
 	return 0;
 }
 
-static void add_perf_entry(struct device *dev, struct dsmas_entry *dent,
-			   struct list_head *list)
+static void update_perf_entry(struct device *dev, struct dsmas_entry *dent,
+			      struct cxl_dpa_perf *dpa_perf)
 {
-	struct cxl_dpa_perf *dpa_perf;
-
-	dpa_perf = kzalloc(sizeof(*dpa_perf), GFP_KERNEL);
-	if (!dpa_perf)
-		return;
-
 	dpa_perf->dpa_range = dent->dpa_range;
 	dpa_perf->coord = dent->coord;
 	dpa_perf->qos_class = dent->qos_class;
-	list_add_tail(&dpa_perf->list, list);
 	dev_dbg(dev,
 		"DSMAS: dpa: %#llx qos: %d read_bw: %d write_bw %d read_lat: %d write_lat: %d\n",
 		dent->dpa_range.start, dpa_perf->qos_class,
@@ -230,20 +223,6 @@ static void add_perf_entry(struct device *dev, struct dsmas_entry *dent,
 		dent->coord.read_latency, dent->coord.write_latency);
 }
 
-static void free_perf_ents(void *data)
-{
-	struct cxl_memdev_state *mds = data;
-	struct cxl_dpa_perf *dpa_perf, *n;
-	LIST_HEAD(discard);
-
-	list_splice_tail_init(&mds->ram_perf_list, &discard);
-	list_splice_tail_init(&mds->pmem_perf_list, &discard);
-	list_for_each_entry_safe(dpa_perf, n, &discard, list) {
-		list_del(&dpa_perf->list);
-		kfree(dpa_perf);
-	}
-}
-
 static void cxl_memdev_set_qos_class(struct cxl_dev_state *cxlds,
 				     struct xarray *dsmas_xa)
 {
@@ -263,16 +242,14 @@ static void cxl_memdev_set_qos_class(struct cxl_dev_state *cxlds,
 	xa_for_each(dsmas_xa, index, dent) {
 		if (resource_size(&cxlds->ram_res) &&
 		    range_contains(&ram_range, &dent->dpa_range))
-			add_perf_entry(dev, dent, &mds->ram_perf_list);
+			update_perf_entry(dev, dent, &mds->ram_perf);
 		else if (resource_size(&cxlds->pmem_res) &&
 			 range_contains(&pmem_range, &dent->dpa_range))
-			add_perf_entry(dev, dent, &mds->pmem_perf_list);
+			update_perf_entry(dev, dent, &mds->pmem_perf);
 		else
 			dev_dbg(dev, "no partition for dsmas dpa: %#llx\n",
 				dent->dpa_range.start);
 	}
-
-	devm_add_action_or_reset(&cxlds->cxlmd->dev, free_perf_ents, mds);
 }
 
 static int match_cxlrd_qos_class(struct device *dev, void *data)
@@ -293,24 +270,24 @@ static int match_cxlrd_qos_class(struct device *dev, void *data)
 	return 0;
 }
 
-static void cxl_qos_match(struct cxl_port *root_port,
-			  struct list_head *work_list,
-			  struct list_head *discard_list)
+static void reset_dpa_perf(struct cxl_dpa_perf *dpa_perf)
 {
-	struct cxl_dpa_perf *dpa_perf, *n;
+	*dpa_perf = (struct cxl_dpa_perf) {
+		.qos_class = CXL_QOS_CLASS_INVALID,
+	};
+}
 
-	list_for_each_entry_safe(dpa_perf, n, work_list, list) {
-		int rc;
+static bool cxl_qos_match(struct cxl_port *root_port,
+			  struct cxl_dpa_perf *dpa_perf)
+{
+	if (dpa_perf->qos_class == CXL_QOS_CLASS_INVALID)
+		return false;
 
-		if (dpa_perf->qos_class == CXL_QOS_CLASS_INVALID)
-			return;
+	if (!device_for_each_child(&root_port->dev, &dpa_perf->qos_class,
+				   match_cxlrd_qos_class))
+		return false;
 
-		rc = device_for_each_child(&root_port->dev,
-					   (void *)&dpa_perf->qos_class,
-					   match_cxlrd_qos_class);
-		if (!rc)
-			list_move_tail(&dpa_perf->list, discard_list);
-	}
+	return true;
 }
 
 static int match_cxlrd_hb(struct device *dev, void *data)
@@ -334,23 +311,10 @@ static int match_cxlrd_hb(struct device *dev, void *data)
 	return 0;
 }
 
-static void discard_dpa_perf(struct list_head *list)
-{
-	struct cxl_dpa_perf *dpa_perf, *n;
-
-	list_for_each_entry_safe(dpa_perf, n, list, list) {
-		list_del(&dpa_perf->list);
-		kfree(dpa_perf);
-	}
-}
-DEFINE_FREE(dpa_perf, struct list_head *, if (!list_empty(_T)) discard_dpa_perf(_T))
-
 static int cxl_qos_class_verify(struct cxl_memdev *cxlmd)
 {
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
-	LIST_HEAD(__discard);
-	struct list_head *discard __free(dpa_perf) = &__discard;
 	struct cxl_port *root_port;
 	int rc;
 
@@ -363,16 +327,18 @@ static int cxl_qos_class_verify(struct cxl_memdev *cxlmd)
 	root_port = &cxl_root->port;
 
 	/* Check that the QTG IDs are all sane between end device and root decoders */
-	cxl_qos_match(root_port, &mds->ram_perf_list, discard);
-	cxl_qos_match(root_port, &mds->pmem_perf_list, discard);
+	if (!cxl_qos_match(root_port, &mds->ram_perf))
+		reset_dpa_perf(&mds->ram_perf);
+	if (!cxl_qos_match(root_port, &mds->pmem_perf))
+		reset_dpa_perf(&mds->pmem_perf);
 
 	/* Check to make sure that the device's host bridge is under a root decoder */
 	rc = device_for_each_child(&root_port->dev,
 				   (void *)cxlmd->endpoint->host_bridge,
 				   match_cxlrd_hb);
 	if (!rc) {
-		list_splice_tail_init(&mds->ram_perf_list, discard);
-		list_splice_tail_init(&mds->pmem_perf_list, discard);
+		reset_dpa_perf(&mds->ram_perf);
+		reset_dpa_perf(&mds->pmem_perf);
 	}
 
 	return rc;

drivers/cxl/core/mbox.c

@@ -1391,8 +1391,8 @@ struct cxl_memdev_state *cxl_memdev_state_create(struct device *dev)
 	mds->cxlds.reg_map.host = dev;
 	mds->cxlds.reg_map.resource = CXL_RESOURCE_NONE;
 	mds->cxlds.type = CXL_DEVTYPE_CLASSMEM;
-	INIT_LIST_HEAD(&mds->ram_perf_list);
-	INIT_LIST_HEAD(&mds->pmem_perf_list);
+	mds->ram_perf.qos_class = CXL_QOS_CLASS_INVALID;
+	mds->pmem_perf.qos_class = CXL_QOS_CLASS_INVALID;
 
 	return mds;
 }

drivers/cxl/cxlmem.h

@@ -395,13 +395,11 @@ enum cxl_devtype {
 
 /**
  * struct cxl_dpa_perf - DPA performance property entry
- * @list - list entry
  * @dpa_range - range for DPA address
  * @coord - QoS performance data (i.e. latency, bandwidth)
  * @qos_class - QoS Class cookies
  */
 struct cxl_dpa_perf {
-	struct list_head list;
 	struct range dpa_range;
 	struct access_coordinate coord;
 	int qos_class;
@@ -471,8 +469,8 @@ struct cxl_dev_state {
  * @security: security driver state info
  * @fw: firmware upload / activation state
  * @mbox_send: @dev specific transport for transmitting mailbox commands
- * @ram_perf_list: performance data entries matched to RAM
- * @pmem_perf_list: performance data entries matched to PMEM
+ * @ram_perf: performance data entry matched to RAM partition
+ * @pmem_perf: performance data entry matched to PMEM partition
  *
  * See CXL 3.0 8.2.9.8.2 Capacity Configuration and Label Storage for
  * details on capacity parameters.
@@ -494,8 +492,8 @@ struct cxl_memdev_state {
 	u64 next_volatile_bytes;
 	u64 next_persistent_bytes;
 
-	struct list_head ram_perf_list;
-	struct list_head pmem_perf_list;
+	struct cxl_dpa_perf ram_perf;
+	struct cxl_dpa_perf pmem_perf;
 
 	struct cxl_event_state event;
 	struct cxl_poison_state poison;

drivers/cxl/mem.c

@@ -221,18 +221,8 @@ static ssize_t ram_qos_class_show(struct device *dev,
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
-	struct cxl_dpa_perf *dpa_perf;
 
-	if (!dev->driver)
-		return -ENOENT;
-
-	if (list_empty(&mds->ram_perf_list))
-		return -ENOENT;
-
-	dpa_perf = list_first_entry(&mds->ram_perf_list, struct cxl_dpa_perf,
-				    list);
-
-	return sysfs_emit(buf, "%d\n", dpa_perf->qos_class);
+	return sysfs_emit(buf, "%d\n", mds->ram_perf.qos_class);
 }
 
 static struct device_attribute dev_attr_ram_qos_class =
@@ -244,18 +234,8 @@ static ssize_t pmem_qos_class_show(struct device *dev,
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
-	struct cxl_dpa_perf *dpa_perf;
-
-	if (!dev->driver)
-		return -ENOENT;
-
-	if (list_empty(&mds->pmem_perf_list))
-		return -ENOENT;
-
-	dpa_perf = list_first_entry(&mds->pmem_perf_list, struct cxl_dpa_perf,
-				    list);
 
-	return sysfs_emit(buf, "%d\n", dpa_perf->qos_class);
+	return sysfs_emit(buf, "%d\n", mds->pmem_perf.qos_class);
 }
 
 static struct device_attribute dev_attr_pmem_qos_class =
@@ -273,11 +253,11 @@ static umode_t cxl_mem_visible(struct kobject *kobj, struct attribute *a, int n)
 			return 0;
 
 	if (a == &dev_attr_pmem_qos_class.attr)
-		if (list_empty(&mds->pmem_perf_list))
+		if (mds->pmem_perf.qos_class == CXL_QOS_CLASS_INVALID)
 			return 0;
 
 	if (a == &dev_attr_ram_qos_class.attr)
-		if (list_empty(&mds->ram_perf_list))
+		if (mds->ram_perf.qos_class == CXL_QOS_CLASS_INVALID)
 			return 0;
 
 	return a->mode;