[NDCTL PATCH v8 3/4] ndctl: cxl: add QoS class check for CXL region creation

[Dave Jiang <dave.jiang@intel.com>]

The CFMWS provides a QTG ID. The kernel driver creates a root decoder that
represents the CFMWS. A qos_class attribute is exported via sysfs for the root
decoder.

One or more qos_class tokens are retrieved via QTG ID _DSM from the ACPI0017
device for a CXL memory device. The input for the _DSM is the read and write
latency and bandwidth for the path between the device and the CPU. The
numbers are constructed by the kernel driver for the _DSM input. When a
device is probed, QoS class tokens  are retrieved. This is useful for a
hot-plugged CXL memory device that does not have regions created.

Add a QoS check during region creation. If --enforce-qos/-Q is set and
the qos_class mismatches, the region creation will fail.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
v8:
- Add qos_class comparison in libcxl instead of user set flag. (Vishal)
- Move check into validate_decoder(). (Vishal)
---
 Documentation/cxl/cxl-create-region.txt |  6 +++
 cxl/json.c                              |  6 +++
 cxl/lib/libcxl.c                        | 29 ++++++++++++++
 cxl/lib/libcxl.sym                      |  1 +
 cxl/libcxl.h                            |  1 +
 cxl/region.c                            | 53 ++++++++++++++++++++++++-
 6 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/Documentation/cxl/cxl-create-region.txt b/Documentation/cxl/cxl-create-region.txt
index f11a412bddfe..b244af60b8a6 100644
--- a/Documentation/cxl/cxl-create-region.txt
+++ b/Documentation/cxl/cxl-create-region.txt
@@ -105,6 +105,12 @@ include::bus-option.txt[]
 	supplied, the first cross-host bridge (if available), decoder that
 	supports the largest interleave will be chosen.
 
+-Q::
+--enforce-qos::
+	Parameter to enforce qos_class mismatch failure. Region create operation
+	will fail of the qos_class of the root decoder and one of the memdev that
+	backs the region mismatches.
+
 include::human-option.txt[]
 
 include::debug-option.txt[]
diff --git a/cxl/json.c b/cxl/json.c
index c8bd8c27447a..b9ed62abe0e2 100644
--- a/cxl/json.c
+++ b/cxl/json.c
@@ -1238,6 +1238,12 @@ struct json_object *util_cxl_region_to_json(struct cxl_region *region,
 		}
 	}
 
+	if (!cxl_region_qos_class_matches(region)) {
+		jobj = json_object_new_boolean(true);
+		if (jobj)
+			json_object_object_add(jregion, "qos_class_mismatches", jobj);
+	}
+
 	json_object_set_userdata(jregion, region, NULL);
 
 
diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
index 6c293f1dfc91..3ca0dca8db52 100644
--- a/cxl/lib/libcxl.c
+++ b/cxl/lib/libcxl.c
@@ -414,6 +414,35 @@ CXL_EXPORT int cxl_region_is_enabled(struct cxl_region *region)
 	return is_enabled(path);
 }
 
+CXL_EXPORT bool cxl_region_qos_class_matches(struct cxl_region *region)
+{
+	struct cxl_decoder *root_decoder = cxl_region_get_decoder(region);
+	struct cxl_memdev_mapping *mapping;
+
+	cxl_mapping_foreach(region, mapping) {
+		struct cxl_decoder *decoder;
+		struct cxl_memdev *memdev;
+
+		decoder = cxl_mapping_get_decoder(mapping);
+		if (!decoder)
+			continue;
+
+		memdev = cxl_decoder_get_memdev(decoder);
+		if (!memdev)
+			continue;
+
+		if (region->mode == CXL_DECODER_MODE_RAM) {
+			if (root_decoder->qos_class != memdev->ram_qos_class)
+				return false;
+		} else if (region->mode == CXL_DECODER_MODE_PMEM) {
+			if (root_decoder->qos_class != memdev->pmem_qos_class)
+				return false;
+		}
+	}
+
+	return true;
+}
+
 CXL_EXPORT int cxl_region_disable(struct cxl_region *region)
 {
 	const char *devname = cxl_region_get_devname(region);
diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
index 465c78dc6c70..a203b3ce3976 100644
--- a/cxl/lib/libcxl.sym
+++ b/cxl/lib/libcxl.sym
@@ -285,4 +285,5 @@ global:
 	cxl_root_decoder_get_qos_class;
 	cxl_memdev_get_pmem_qos_class;
 	cxl_memdev_get_ram_qos_class;
+	cxl_region_qos_class_matches;
 } LIBCXL_7;
diff --git a/cxl/libcxl.h b/cxl/libcxl.h
index a180f01cb05e..bd8e924844ff 100644
--- a/cxl/libcxl.h
+++ b/cxl/libcxl.h
@@ -335,6 +335,7 @@ int cxl_region_clear_target(struct cxl_region *region, int position);
 int cxl_region_clear_all_targets(struct cxl_region *region);
 int cxl_region_decode_commit(struct cxl_region *region);
 int cxl_region_decode_reset(struct cxl_region *region);
+bool cxl_region_qos_class_matches(struct cxl_region *region);
 
 #define cxl_region_foreach(decoder, region)                                    \
 	for (region = cxl_region_get_first(decoder); region != NULL;           \
diff --git a/cxl/region.c b/cxl/region.c
index 3a762db4800e..735b3be7759b 100644
--- a/cxl/region.c
+++ b/cxl/region.c
@@ -32,6 +32,7 @@ static struct region_params {
 	bool force;
 	bool human;
 	bool debug;
+	bool qos_enforce;
 } param = {
 	.ways = INT_MAX,
 	.granularity = INT_MAX,
@@ -49,6 +50,7 @@ struct parsed_params {
 	const char **argv;
 	struct cxl_decoder *root_decoder;
 	enum cxl_decoder_mode mode;
+	bool qos_enforce;
 };
 
 enum region_actions {
@@ -81,7 +83,8 @@ OPT_STRING('U', "uuid", &param.uuid, \
 	   "region uuid", "uuid for the new region (default: autogenerate)"), \
 OPT_BOOLEAN('m', "memdevs", &param.memdevs, \
 	    "non-option arguments are memdevs"), \
-OPT_BOOLEAN('u', "human", &param.human, "use human friendly number formats")
+OPT_BOOLEAN('u', "human", &param.human, "use human friendly number formats"), \
+OPT_BOOLEAN('Q', "enforce-qos", &param.qos_enforce, "enforce of qos_class matching")
 
 static const struct option create_options[] = {
 	BASE_OPTIONS(),
@@ -360,6 +363,8 @@ static int parse_create_options(struct cxl_ctx *ctx, int count,
 		}
 	}
 
+	p->qos_enforce = param.qos_enforce;
+
 	return 0;
 
 err:
@@ -423,10 +428,52 @@ static void collect_minsize(struct cxl_ctx *ctx, struct parsed_params *p)
 	}
 }
 
+static int create_region_validate_qos_class(struct parsed_params *p)
+{
+	int root_qos_class;
+	int qos_class;
+	int i;
+
+	if (!p->qos_enforce)
+		return 0;
+
+	root_qos_class = cxl_root_decoder_get_qos_class(p->root_decoder);
+	if (root_qos_class == CXL_QOS_CLASS_NONE)
+		return 0;
+
+	for (i = 0; i < p->ways; i++) {
+		struct json_object *jobj =
+			json_object_array_get_idx(p->memdevs, i);
+		struct cxl_memdev *memdev = json_object_get_userdata(jobj);
+
+		if (p->mode == CXL_DECODER_MODE_RAM)
+			qos_class = cxl_memdev_get_ram_qos_class(memdev);
+		else
+			qos_class = cxl_memdev_get_pmem_qos_class(memdev);
+
+		/* No qos_class entries. Possibly no kernel support */
+		if (qos_class == CXL_QOS_CLASS_NONE)
+			break;
+
+		if (qos_class != root_qos_class) {
+			if (p->qos_enforce) {
+				log_err(&rl, "%s QoS Class mismatches %s\n",
+					cxl_decoder_get_devname(p->root_decoder),
+					cxl_memdev_get_devname(memdev));
+
+				return -ENXIO;
+			}
+		}
+	}
+
+	return 0;
+}
+
 static int validate_decoder(struct cxl_decoder *decoder,
 			    struct parsed_params *p)
 {
 	const char *devname = cxl_decoder_get_devname(decoder);
+	int rc;
 
 	switch(p->mode) {
 	case CXL_DECODER_MODE_RAM:
@@ -446,6 +493,10 @@ static int validate_decoder(struct cxl_decoder *decoder,
 		return -EINVAL;
 	}
 
+	rc = create_region_validate_qos_class(p);
+	if (rc)
+		return rc;
+
 	/* TODO check if the interleave config is possible under this decoder */
 
 	return 0;
-- 
2.43.0