[RFC PATCH v4 25/27] cxl/core: Add private node support to cxl_sysram

[Gregory Price <gourry@gourry.net>]

Extend the cxl_sysram region to support N_MEMORY_PRIVATE hotplug
via add_private_memory_driver_managed(). When a caller passes
private=true to devm_cxl_add_sysram(), the memory is registered
as a private node, isolating it from normal allocations and reclaim.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
 drivers/cxl/core/core.h          |  2 +-
 drivers/cxl/core/region_sysram.c | 50 +++++++++++++++++++++++++-------
 drivers/cxl/cxl.h                |  9 ++++--
 3 files changed, 48 insertions(+), 13 deletions(-)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 973bbcae43f7..8ca3d6d41fe4 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -56,7 +56,7 @@ u64 cxl_dpa_to_hpa(struct cxl_region *cxlr, const struct cxl_memdev *cxlmd,
 		   u64 dpa);
 int devm_cxl_add_dax_region(struct cxl_region *cxlr, enum dax_driver_type);
 int devm_cxl_add_pmem_region(struct cxl_region *cxlr);
-int devm_cxl_add_sysram(struct cxl_region *cxlr, enum mmop online_type);
+int devm_cxl_add_sysram(struct cxl_region *cxlr, bool private, enum mmop online_type);
 
 #else
 static inline u64 cxl_dpa_to_hpa(struct cxl_region *cxlr,
diff --git a/drivers/cxl/core/region_sysram.c b/drivers/cxl/core/region_sysram.c
index 47a415deb352..77aaa52e7332 100644
--- a/drivers/cxl/core/region_sysram.c
+++ b/drivers/cxl/core/region_sysram.c
@@ -85,12 +85,23 @@ static int sysram_hotplug_add(struct cxl_sysram *sysram, enum mmop online_type)
 	/*
 	 * Ensure that future kexec'd kernels will not treat
 	 * this as RAM automatically.
+	 *
+	 * For private regions, use add_private_memory_driver_managed()
+	 * to register as N_MEMORY_PRIVATE which isolates the memory from
+	 * normal allocations and reclaim.
 	 */
-	rc = __add_memory_driver_managed(sysram->mgid,
-					 sysram->hpa_range.start,
-					 range_len(&sysram->hpa_range),
-					 sysram_res_name, mhp_flags,
-					 online_type);
+	if (sysram->private)
+		rc = add_private_memory_driver_managed(sysram->mgid,
+						       sysram->hpa_range.start,
+						       range_len(&sysram->hpa_range),
+						       sysram_res_name, mhp_flags,
+						       online_type, &sysram->np);
+	else
+		rc = __add_memory_driver_managed(sysram->mgid,
+						 sysram->hpa_range.start,
+						 range_len(&sysram->hpa_range),
+						 sysram_res_name, mhp_flags,
+						 online_type);
 	if (rc) {
 		remove_resource(res);
 		kfree(res);
@@ -108,10 +119,23 @@ static int sysram_hotplug_remove(struct cxl_sysram *sysram)
 	if (!sysram->res)
 		return 0;
 
-	rc = offline_and_remove_memory(sysram->hpa_range.start,
-				       range_len(&sysram->hpa_range));
-	if (rc)
-		return rc;
+	if (sysram->private) {
+		rc = offline_and_remove_private_memory(sysram->numa_node,
+						       sysram->hpa_range.start,
+						       range_len(&sysram->hpa_range));
+		/*
+		 * -EBUSY means memory was removed but node_private_unregister()
+		 * could not complete because other regions share the node.
+		 * Continue to resource cleanup since the memory is gone.
+		 */
+		if (rc && rc != -EBUSY)
+			return rc;
+	} else {
+		rc = offline_and_remove_memory(sysram->hpa_range.start,
+					       range_len(&sysram->hpa_range));
+		if (rc)
+			return rc;
+	}
 
 	if (sysram->res) {
 		remove_resource(sysram->res);
@@ -257,7 +281,8 @@ static void sysram_unregister(void *_sysram)
 	device_unregister(&sysram->dev);
 }
 
-int devm_cxl_add_sysram(struct cxl_region *cxlr, enum mmop online_type)
+int devm_cxl_add_sysram(struct cxl_region *cxlr, bool private,
+			enum mmop online_type)
 {
 	struct cxl_sysram *sysram __free(put_cxl_sysram) = NULL;
 	struct memory_dev_type *mtype;
@@ -291,6 +316,11 @@ int devm_cxl_add_sysram(struct cxl_region *cxlr, enum mmop online_type)
 	if (online_type >= 0)
 		sysram->online_type = online_type;
 
+	/* Set up private node registration if requested */
+	sysram->private = private;
+	if (private)
+		sysram->np.owner = sysram;
+
 	dev = &sysram->dev;
 
 	rc = dev_set_name(dev, "sysram_region%d", cxlr->id);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 8e8342fd4fde..54e5f9ac59dc 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -10,6 +10,7 @@
 #include <linux/bitops.h>
 #include <linux/log2.h>
 #include <linux/node.h>
+#include <linux/node_private.h>
 #include <linux/io.h>
 #include <linux/range.h>
 #include <linux/dax.h>
@@ -619,6 +620,8 @@ struct cxl_dax_region {
  * @mgid: Memory group id
  * @mtype: Memory tier type
  * @numa_node: NUMA node for this memory
+ * @private: true if this region uses N_MEMORY_PRIVATE hotplug
+ * @np: private node registration state (valid when @private is true)
  *
  * Device that directly performs memory hotplug for CXL RAM regions.
  */
@@ -633,6 +636,8 @@ struct cxl_sysram {
 	int mgid;
 	struct memory_dev_type *mtype;
 	int numa_node;
+	bool private;
+	struct node_private np;
 };
 
 /**
@@ -987,7 +992,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled);
 struct cxl_dax_region *to_cxl_dax_region(struct device *dev);
 struct cxl_sysram *to_cxl_sysram(struct device *dev);
 struct device *cxl_sysram_dev(struct cxl_sysram *sysram);
-int devm_cxl_add_sysram(struct cxl_region *cxlr, enum mmop online_type);
+int devm_cxl_add_sysram(struct cxl_region *cxlr, bool private, enum mmop online_type);
 int cxl_sysram_offline_and_remove(struct cxl_sysram *sysram);
 u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint, u64 spa);
 #else
@@ -1011,7 +1016,7 @@ static inline struct cxl_sysram *to_cxl_sysram(struct device *dev)
 {
 	return NULL;
 }
-static inline int devm_cxl_add_sysram(struct cxl_region *cxlr,
+static inline int devm_cxl_add_sysram(struct cxl_region *cxlr, bool private,
 				      enum mmop online_type)
 {
 	return -ENXIO;
-- 
2.53.0