[PATCH 3/3] cxl/core: Add sysfs attribute get_poison for list retrieval

[alison.schofield@intel.com]

From: Alison Schofield <alison.schofield@intel.com>

The sysfs attribute, get_poison, allows user space to request the
retrieval of a CXL devices poison list for its persistent memory.

From Documentation/ABI/.../sysfs-bus-cxl
        (WO) When a '1' is written to this attribute the memdev
        driver retrieves the poison list from the device. The list
        includes addresses that are poisoned or would result in
        poison if accessed, and the source of the poison. This
        attribute is only visible for devices supporting the
        capability. The retrieved errors are logged as kernel
        trace events with the label: cxl_poison_list.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 Documentation/ABI/testing/sysfs-bus-cxl | 13 ++++++++++
 drivers/cxl/core/memdev.c               | 32 +++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 7c2b846521f3..9d0c3988fdd2 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -163,3 +163,16 @@ Description:
 		memory (type-3). The 'target_type' attribute indicates the
 		current setting which may dynamically change based on what
 		memory regions are activated in this decode hierarchy.
+
+What:		/sys/bus/cxl/devices/memX/get_poison
+Date:		June, 2022
+KernelVersion:	v5.20
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(WO) When a '1' is written to this attribute the memdev
+		driver retrieves the poison list from the device. The list
+		includes addresses that are poisoned or would result in
+		poison if accessed, and the source of the poison. This
+		attribute is only visible for devices supporting the
+		capability. The retrieved errors are logged as kernel
+		trace events with the label: cxl_poison_list.
diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index f7cdcd33504a..5ef9ffaa934a 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -106,12 +106,34 @@ static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(numa_node);
 
+static ssize_t get_poison_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t len)
+
+{
+	int rc;
+
+	if (!sysfs_streq(buf, "1")) {
+		dev_err(dev, "%s: unknown value: %s\n", attr->attr.name, buf);
+		return -EINVAL;
+	}
+
+	rc = cxl_mem_get_poison_list(dev);
+	if (rc) {
+		dev_err(dev, "Failed to retrieve poison list %d\n", rc);
+		return rc;
+	}
+	return len;
+}
+static DEVICE_ATTR_WO(get_poison);
+
 static struct attribute *cxl_memdev_attributes[] = {
 	&dev_attr_serial.attr,
 	&dev_attr_firmware_version.attr,
 	&dev_attr_payload_max.attr,
 	&dev_attr_label_storage_size.attr,
 	&dev_attr_numa_node.attr,
+	&dev_attr_get_poison.attr,
 	NULL,
 };
 
@@ -130,6 +152,16 @@ static umode_t cxl_memdev_visible(struct kobject *kobj, struct attribute *a,
 {
 	if (!IS_ENABLED(CONFIG_NUMA) && a == &dev_attr_numa_node.attr)
 		return 0;
+
+	if (a == &dev_attr_get_poison.attr) {
+		struct device *dev = container_of(kobj, struct device, kobj);
+		struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+		struct cxl_dev_state *cxlds = cxlmd->cxlds;
+
+		if (!test_bit(CXL_MEM_COMMAND_ID_GET_POISON,
+			      cxlds->enabled_cmds))
+			return 0;
+	}
 	return a->mode;
 }
 
-- 
2.31.1