cxl/memdev: Add numa_node attribute

While CXL memory targets will have their own memory target node,
individual memory devices may be affinitized like other PCI devices.
Emit that attribute for memdevs.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/164298428430.3018233.16409089892707993289.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

Documentation/ABI/testing/sysfs-bus-cxl

@@ -34,6 +34,15 @@ Description:
 		capability. Mandatory for CXL devices, see CXL 2.0 8.1.12.2
 		Memory Device PCIe Capabilities and Extended Capabilities.
 
+What:		/sys/bus/cxl/devices/memX/numa_node
+Date:		January, 2022
+KernelVersion:	v5.18
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) If NUMA is enabled and the platform has affinitized the
+		host PCI device for this memory device, emit the CPU node
+		affinity for this device.
+
 What:		/sys/bus/cxl/devices/*/devtype
 Date:		June, 2021
 KernelVersion:	v5.14

drivers/cxl/core/memdev.c

@@ -99,11 +99,19 @@ static ssize_t serial_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(serial);
 
+static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	return sprintf(buf, "%d\n", dev_to_node(dev));
+}
+static DEVICE_ATTR_RO(numa_node);
+
 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,
 	NULL,
 };
 
@@ -117,8 +125,17 @@ static struct attribute *cxl_memdev_ram_attributes[] = {
 	NULL,
 };
 
+static umode_t cxl_memdev_visible(struct kobject *kobj, struct attribute *a,
+				  int n)
+{
+	if (!IS_ENABLED(CONFIG_NUMA) && a == &dev_attr_numa_node.attr)
+		return 0;
+	return a->mode;
+}
+
 static struct attribute_group cxl_memdev_attribute_group = {
 	.attrs = cxl_memdev_attributes,
+	.is_visible = cxl_memdev_visible,
 };
 
 static struct attribute_group cxl_memdev_ram_attribute_group = {

tools/testing/cxl/test/cxl.c

@@ -583,6 +583,7 @@ static __init int cxl_test_init(void)
 		if (!pdev)
 			goto err_mem;
 		pdev->dev.parent = &port->dev;
+		set_dev_node(&pdev->dev, i % 2);
 
 		rc = platform_device_add(pdev);
 		if (rc) {