cxl/pmem: Export dirty shutdown count via sysfs

Similar to how the acpi_nfit driver exports Optane dirty shutdown count,
introduce:

  /sys/bus/cxl/devices/nvdimm-bridge0/ndbusX/nmemY/cxl/dirty_shutdown

Under the conditions that 1) dirty shutdown can be set, 2) Device GPF
DVSEC exists, and 3) the count itself can be retrieved.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://patch.msgid.link/20250220220235.276831-4-dave@stgolabs.net
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Author: Davidlohr Bueso

Documentation/ABI/testing/sysfs-bus-cxl

@@ -586,3 +586,15 @@ 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/nvdimm-bridge0/ndbusX/nmemY/cxl/dirty_shutdown
+Date:		Feb, 2025
+KernelVersion:	v6.15
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) The device dirty shutdown count value, which is the number
+		of times the device could have incurred in potential data loss.
+		The count is persistent across power loss and wraps back to 0
+		upon overflow. If this file is not present, the device does not
+		have the necessary support for dirty tracking.

Documentation/driver-api/cxl/maturity-map.rst

@@ -130,7 +130,7 @@ Mailbox commands
 * [0] Switch CCI
 * [3] Timestamp
 * [1] PMEM labels
-* [1] PMEM GPF / Dirty Shutdown
+* [3] PMEM GPF / Dirty Shutdown
 * [0] Scan Media
 
 PMU

drivers/cxl/core/mbox.c

@@ -1308,6 +1308,27 @@ int cxl_mem_create_range_info(struct cxl_memdev_state *mds)
 }
 EXPORT_SYMBOL_NS_GPL(cxl_mem_create_range_info, "CXL");
 
+int cxl_get_dirty_count(struct cxl_memdev_state *mds, u32 *count)
+{
+	struct cxl_mailbox *cxl_mbox = &mds->cxlds.cxl_mbox;
+	struct cxl_mbox_get_health_info_out hi;
+	struct cxl_mbox_cmd mbox_cmd;
+	int rc;
+
+	mbox_cmd = (struct cxl_mbox_cmd) {
+		.opcode = CXL_MBOX_OP_GET_HEALTH_INFO,
+		.size_out = sizeof(hi),
+		.payload_out = &hi,
+	};
+
+	rc = cxl_internal_send_cmd(cxl_mbox, &mbox_cmd);
+	if (!rc)
+		*count = le32_to_cpu(hi.dirty_shutdown_cnt);
+
+	return rc;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_get_dirty_count, "CXL");
+
 int cxl_arm_dirty_shutdown(struct cxl_memdev_state *mds)
 {
 	struct cxl_mailbox *cxl_mbox = &mds->cxlds.cxl_mbox;

drivers/cxl/cxl.h

@@ -563,6 +563,7 @@ struct cxl_nvdimm {
 	struct device dev;
 	struct cxl_memdev *cxlmd;
 	u8 dev_id[CXL_DEV_ID_LEN]; /* for nvdimm, string of 'serial' */
+	u64 dirty_shutdowns;
 };
 
 struct cxl_pmem_region_mapping {

drivers/cxl/cxlmem.h

@@ -693,6 +693,18 @@ struct cxl_mbox_set_partition_info {
 
 #define  CXL_SET_PARTITION_IMMEDIATE_FLAG	BIT(0)
 
+/* Get Health Info Output Payload CXL 3.2 Spec 8.2.10.9.3.1 Table 8-148 */
+struct cxl_mbox_get_health_info_out {
+	u8 health_status;
+	u8 media_status;
+	u8 additional_status;
+	u8 life_used;
+	__le16 device_temperature;
+	__le32 dirty_shutdown_cnt;
+	__le32 corrected_volatile_error_cnt;
+	__le32 corrected_persistent_error_cnt;
+} __packed;
+
 /* Set Shutdown State Input Payload CXL 3.2 Spec 8.2.10.9.3.5 Table 8-152 */
 struct cxl_mbox_set_shutdown_state_in {
 	u8 state;
@@ -834,6 +846,7 @@ void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
 			    enum cxl_event_log_type type,
 			    enum cxl_event_type event_type,
 			    const uuid_t *uuid, union cxl_event *evt);
+int cxl_get_dirty_count(struct cxl_memdev_state *mds, u32 *count);
 int cxl_arm_dirty_shutdown(struct cxl_memdev_state *mds);
 int cxl_set_timestamp(struct cxl_memdev_state *mds);
 int cxl_poison_state_init(struct cxl_memdev_state *mds);

drivers/cxl/pmem.c

@@ -42,22 +42,83 @@ static ssize_t id_show(struct device *dev, struct device_attribute *attr, char *
 }
 static DEVICE_ATTR_RO(id);
 
+static ssize_t dirty_shutdown_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct nvdimm *nvdimm = to_nvdimm(dev);
+	struct cxl_nvdimm *cxl_nvd = nvdimm_provider_data(nvdimm);
+
+	return sysfs_emit(buf, "%llu\n", cxl_nvd->dirty_shutdowns);
+}
+static DEVICE_ATTR_RO(dirty_shutdown);
+
 static struct attribute *cxl_dimm_attributes[] = {
 	&dev_attr_id.attr,
 	&dev_attr_provider.attr,
+	&dev_attr_dirty_shutdown.attr,
 	NULL
 };
 
+#define CXL_INVALID_DIRTY_SHUTDOWN_COUNT ULLONG_MAX
+static umode_t cxl_dimm_visible(struct kobject *kobj,
+				struct attribute *a, int n)
+{
+	if (a == &dev_attr_dirty_shutdown.attr) {
+		struct device *dev = kobj_to_dev(kobj);
+		struct nvdimm *nvdimm = to_nvdimm(dev);
+		struct cxl_nvdimm *cxl_nvd = nvdimm_provider_data(nvdimm);
+
+		if (cxl_nvd->dirty_shutdowns ==
+		    CXL_INVALID_DIRTY_SHUTDOWN_COUNT)
+			return 0;
+	}
+
+	return a->mode;
+}
+
 static const struct attribute_group cxl_dimm_attribute_group = {
 	.name = "cxl",
 	.attrs = cxl_dimm_attributes,
+	.is_visible = cxl_dimm_visible
 };
 
 static const struct attribute_group *cxl_dimm_attribute_groups[] = {
 	&cxl_dimm_attribute_group,
 	NULL
 };
 
+static void cxl_nvdimm_arm_dirty_shutdown_tracking(struct cxl_nvdimm *cxl_nvd)
+{
+	struct cxl_memdev *cxlmd = cxl_nvd->cxlmd;
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
+	struct device *dev = &cxl_nvd->dev;
+	u32 count;
+
+	/*
+	 * Dirty tracking is enabled and exposed to the user, only when:
+	 *   - dirty shutdown on the device can be set, and,
+	 *   - the device has a Device GPF DVSEC (albeit unused), and,
+	 *   - the Get Health Info cmd can retrieve the device's dirty count.
+	 */
+	cxl_nvd->dirty_shutdowns = CXL_INVALID_DIRTY_SHUTDOWN_COUNT;
+
+	if (cxl_arm_dirty_shutdown(mds)) {
+		dev_warn(dev, "GPF: could not set dirty shutdown state\n");
+		return;
+	}
+
+	if (!cxl_gpf_get_dvsec(cxlds->dev, false))
+		return;
+
+	if (cxl_get_dirty_count(mds, &count)) {
+		dev_warn(dev, "GPF: could not retrieve dirty count\n");
+		return;
+	}
+
+	cxl_nvd->dirty_shutdowns = count;
+}
+
 static int cxl_nvdimm_probe(struct device *dev)
 {
 	struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
@@ -78,20 +139,20 @@ static int cxl_nvdimm_probe(struct device *dev)
 	set_bit(ND_CMD_GET_CONFIG_SIZE, &cmd_mask);
 	set_bit(ND_CMD_GET_CONFIG_DATA, &cmd_mask);
 	set_bit(ND_CMD_SET_CONFIG_DATA, &cmd_mask);
-	nvdimm = __nvdimm_create(cxl_nvb->nvdimm_bus, cxl_nvd,
-				 cxl_dimm_attribute_groups, flags,
-				 cmd_mask, 0, NULL, cxl_nvd->dev_id,
-				 cxl_security_ops, NULL);
-	if (!nvdimm)
-		return -ENOMEM;
 
 	/*
 	 * Set dirty shutdown now, with the expectation that the device
 	 * clear it upon a successful GPF flow. The exception to this
 	 * is upon Viral detection, per CXL 3.2 section 12.4.2.
 	 */
-	if (cxl_arm_dirty_shutdown(mds))
-		dev_warn(dev, "GPF: could not dirty shutdown state\n");
+	cxl_nvdimm_arm_dirty_shutdown_tracking(cxl_nvd);
+
+	nvdimm = __nvdimm_create(cxl_nvb->nvdimm_bus, cxl_nvd,
+				 cxl_dimm_attribute_groups, flags,
+				 cmd_mask, 0, NULL, cxl_nvd->dev_id,
+				 cxl_security_ops, NULL);
+	if (!nvdimm)
+		return -ENOMEM;
 
 	dev_set_drvdata(dev, nvdimm);
 	return devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);