Drivers: hv: vmbus: add numa_node to sysfs

Being able to find the numa_node for a device is useful for userspace
drivers (DPDK) and also for diagnosing performance issues.  This makes
vmbus similar to pci.
Signed-off-by: NStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/stable/sysfs-bus-vmbus

@@ -42,6 +42,13 @@ Contact:	K. Y. Srinivasan <kys@microsoft.com>
 Description:	The 16 bit vendor ID of the device
 Users:		tools/hv/lsvmbus and user level RDMA libraries
 
+What:		/sys/bus/vmbus/devices/<UUID>/numa_node
+Date:		Jul 2018
+KernelVersion:	4.19
+Contact:	Stephen Hemminger <sthemmin@microsoft.com>
+Description:	This NUMA node to which the VMBUS device is
+		attached, or -1 if the node is unknown.
+
 What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>
 Date:		September. 2017
 KernelVersion:	4.14

drivers/hv/vmbus_drv.c

@@ -210,6 +210,20 @@ static ssize_t modalias_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(modalias);
 
+#ifdef CONFIG_NUMA
+static ssize_t numa_node_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct hv_device *hv_dev = device_to_hv_device(dev);
+
+	if (!hv_dev->channel)
+		return -ENODEV;
+
+	return sprintf(buf, "%d\n", hv_dev->channel->numa_node);
+}
+static DEVICE_ATTR_RO(numa_node);
+#endif
+
 static ssize_t server_monitor_pending_show(struct device *dev,
 					   struct device_attribute *dev_attr,
 					   char *buf)
@@ -492,6 +506,9 @@ static struct attribute *vmbus_dev_attrs[] = {
 	&dev_attr_class_id.attr,
 	&dev_attr_device_id.attr,
 	&dev_attr_modalias.attr,
+#ifdef CONFIG_NUMA
+	&dev_attr_numa_node.attr,
+#endif
 	&dev_attr_server_monitor_pending.attr,
 	&dev_attr_client_monitor_pending.attr,
 	&dev_attr_server_monitor_latency.attr,