RDMA: Add NLDEV_GET_CHARDEV to allow char dev discovery and autoload

Allow userspace to issue a netlink query against the ib_device for
something like "uverbs" and get back the char dev name, inode major/minor,
and interface ABI information for "uverbs0".

Since we are now in netlink this can also trigger a module autoload to
make the uverbs device come into existence.

Largely this will let us replace searching and reading inside sysfs to
setup devices, and provides an alternative (using driver_id) to device
name based provider binding for things like rxe.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/core_priv.h

@@ -88,6 +88,15 @@ typedef int (*nldev_callback)(struct ib_device *device,
 int ib_enum_all_devs(nldev_callback nldev_cb, struct sk_buff *skb,
 		     struct netlink_callback *cb);
 
+struct ib_client_nl_info {
+	struct sk_buff *nl_msg;
+	struct device *cdev;
+	unsigned int port;
+	u64 abi;
+};
+int ib_get_client_nl_info(struct ib_device *ibdev, const char *client_name,
+			  struct ib_client_nl_info *res);
+
 enum ib_cache_gid_default_mode {
 	IB_CACHE_GID_DEFAULT_MODE_SET,
 	IB_CACHE_GID_DEFAULT_MODE_DELETE

drivers/infiniband/core/device.c

@@ -1726,6 +1726,104 @@ void ib_unregister_client(struct ib_client *client)
 }
 EXPORT_SYMBOL(ib_unregister_client);
 
+static int __ib_get_global_client_nl_info(const char *client_name,
+					  struct ib_client_nl_info *res)
+{
+	struct ib_client *client;
+	unsigned long index;
+	int ret = -ENOENT;
+
+	down_read(&clients_rwsem);
+	xa_for_each_marked (&clients, index, client, CLIENT_REGISTERED) {
+		if (strcmp(client->name, client_name) != 0)
+			continue;
+		if (!client->get_global_nl_info) {
+			ret = -EOPNOTSUPP;
+			break;
+		}
+		ret = client->get_global_nl_info(res);
+		if (WARN_ON(ret == -ENOENT))
+			ret = -EINVAL;
+		if (!ret && res->cdev)
+			get_device(res->cdev);
+		break;
+	}
+	up_read(&clients_rwsem);
+	return ret;
+}
+
+static int __ib_get_client_nl_info(struct ib_device *ibdev,
+				   const char *client_name,
+				   struct ib_client_nl_info *res)
+{
+	unsigned long index;
+	void *client_data;
+	int ret = -ENOENT;
+
+	down_read(&ibdev->client_data_rwsem);
+	xan_for_each_marked (&ibdev->client_data, index, client_data,
+			     CLIENT_DATA_REGISTERED) {
+		struct ib_client *client = xa_load(&clients, index);
+
+		if (!client || strcmp(client->name, client_name) != 0)
+			continue;
+		if (!client->get_nl_info) {
+			ret = -EOPNOTSUPP;
+			break;
+		}
+		ret = client->get_nl_info(ibdev, client_data, res);
+		if (WARN_ON(ret == -ENOENT))
+			ret = -EINVAL;
+
+		/*
+		 * The cdev is guaranteed valid as long as we are inside the
+		 * client_data_rwsem as remove_one can't be called. Keep it
+		 * valid for the caller.
+		 */
+		if (!ret && res->cdev)
+			get_device(res->cdev);
+		break;
+	}
+	up_read(&ibdev->client_data_rwsem);
+
+	return ret;
+}
+
+/**
+ * ib_get_client_nl_info - Fetch the nl_info from a client
+ * @device - IB device
+ * @client_name - Name of the client
+ * @res - Result of the query
+ */
+int ib_get_client_nl_info(struct ib_device *ibdev, const char *client_name,
+			  struct ib_client_nl_info *res)
+{
+	int ret;
+
+	if (ibdev)
+		ret = __ib_get_client_nl_info(ibdev, client_name, res);
+	else
+		ret = __ib_get_global_client_nl_info(client_name, res);
+#ifdef CONFIG_MODULES
+	if (ret == -ENOENT) {
+		request_module("rdma-client-%s", client_name);
+		if (ibdev)
+			ret = __ib_get_client_nl_info(ibdev, client_name, res);
+		else
+			ret = __ib_get_global_client_nl_info(client_name, res);
+	}
+#endif
+	if (ret) {
+		if (ret == -ENOENT)
+			return -EOPNOTSUPP;
+		return ret;
+	}
+
+	if (WARN_ON(!res->cdev))
+		return -EINVAL;
+	return 0;
+}
+
 /**
  * ib_set_client_data - Set IB client context
  * @device:Device to set context for

drivers/infiniband/core/nldev.c

@@ -120,6 +120,12 @@ static const struct nla_policy nldev_policy[RDMA_NLDEV_ATTR_MAX] = {
 	[RDMA_NLDEV_ATTR_DEV_PROTOCOL]		= { .type = NLA_NUL_STRING,
 				    .len = RDMA_NLDEV_ATTR_ENTRY_STRLEN },
 	[RDMA_NLDEV_NET_NS_FD]			= { .type = NLA_U32 },
+	[RDMA_NLDEV_ATTR_CHARDEV]		= { .type = NLA_U64 },
+	[RDMA_NLDEV_ATTR_CHARDEV_ABI]		= { .type = NLA_U64 },
+	[RDMA_NLDEV_ATTR_CHARDEV_TYPE]		= { .type = NLA_NUL_STRING,
+				    .len = 128 },
+	[RDMA_NLDEV_ATTR_CHARDEV_NAME]		= { .type = NLA_NUL_STRING,
+				    .len = RDMA_NLDEV_ATTR_ENTRY_STRLEN },
 };
 
 static int put_driver_name_print_type(struct sk_buff *msg, const char *name,
@@ -1347,6 +1353,91 @@ static int nldev_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return 0;
 }
 
+static int nldev_get_chardev(struct sk_buff *skb, struct nlmsghdr *nlh,
+			     struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[RDMA_NLDEV_ATTR_MAX];
+	char client_name[IB_DEVICE_NAME_MAX];
+	struct ib_client_nl_info data = {};
+	struct ib_device *ibdev = NULL;
+	struct sk_buff *msg;
+	u32 index;
+	int err;
+
+	err = nlmsg_parse(nlh, 0, tb, RDMA_NLDEV_ATTR_MAX - 1, nldev_policy,
+			  extack);
+	if (err || !tb[RDMA_NLDEV_ATTR_CHARDEV_TYPE])
+		return -EINVAL;
+
+	if (nla_strlcpy(client_name, tb[RDMA_NLDEV_ATTR_CHARDEV_TYPE],
+			sizeof(client_name)) >= sizeof(client_name))
+		return -EINVAL;
+
+	if (tb[RDMA_NLDEV_ATTR_DEV_INDEX]) {
+		index = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
+		ibdev = ib_device_get_by_index(sock_net(skb->sk), index);
+		if (!ibdev)
+			return -EINVAL;
+
+		if (tb[RDMA_NLDEV_ATTR_PORT_INDEX]) {
+			data.port = nla_get_u32(tb[RDMA_NLDEV_ATTR_PORT_INDEX]);
+			if (!rdma_is_port_valid(ibdev, data.port)) {
+				err = -EINVAL;
+				goto out_put;
+			}
+		} else {
+			data.port = -1;
+		}
+	} else if (tb[RDMA_NLDEV_ATTR_PORT_INDEX]) {
+		return -EINVAL;
+	}
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		err = -ENOMEM;
+		goto out_put;
+	}
+	nlh = nlmsg_put(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq,
+			RDMA_NL_GET_TYPE(RDMA_NL_NLDEV,
+					 RDMA_NLDEV_CMD_GET_CHARDEV),
+			0, 0);
+
+	data.nl_msg = msg;
+	err = ib_get_client_nl_info(ibdev, client_name, &data);
+	if (err)
+		goto out_nlmsg;
+
+	err = nla_put_u64_64bit(msg, RDMA_NLDEV_ATTR_CHARDEV,
+				huge_encode_dev(data.cdev->devt),
+				RDMA_NLDEV_ATTR_PAD);
+	if (err)
+		goto out_data;
+	err = nla_put_u64_64bit(msg, RDMA_NLDEV_ATTR_CHARDEV_ABI, data.abi,
+				RDMA_NLDEV_ATTR_PAD);
+	if (err)
+		goto out_data;
+	if (nla_put_string(msg, RDMA_NLDEV_ATTR_CHARDEV_NAME,
+			   dev_name(data.cdev))) {
+		err = -EMSGSIZE;
+		goto out_data;
+	}
+
+	nlmsg_end(msg, nlh);
+	put_device(data.cdev);
+	if (ibdev)
+		ib_device_put(ibdev);
+	return rdma_nl_unicast(msg, NETLINK_CB(skb).portid);
+
+out_data:
+	put_device(data.cdev);
+out_nlmsg:
+	nlmsg_free(msg);
+out_put:
+	if (ibdev)
+		ib_device_put(ibdev);
+	return err;
+}
+
 static int nldev_sys_get_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
 			      struct netlink_ext_ack *extack)
 {
@@ -1404,6 +1495,9 @@ static const struct rdma_nl_cbs nldev_cb_table[RDMA_NLDEV_NUM_OPS] = {
 		.doit = nldev_get_doit,
 		.dump = nldev_get_dumpit,
 	},
+	[RDMA_NLDEV_CMD_GET_CHARDEV] = {
+		.doit = nldev_get_chardev,
+	},
 	[RDMA_NLDEV_CMD_SET] = {
 		.doit = nldev_set_doit,
 		.flags = RDMA_NL_ADMIN_PERM,

include/rdma/ib_verbs.h

@@ -2684,10 +2684,14 @@ struct ib_device {
 	u32 iw_driver_flags;
 };
 
+struct ib_client_nl_info;
 struct ib_client {
 	const char *name;
 	void (*add)   (struct ib_device *);
 	void (*remove)(struct ib_device *, void *client_data);
+	int (*get_nl_info)(struct ib_device *ibdev, void *client_data,
+			   struct ib_client_nl_info *res);
+	int (*get_global_nl_info)(struct ib_client_nl_info *res);
 
 	/* Returns the net_dev belonging to this ib_client and matching the
 	 * given parameters.

include/rdma/rdma_netlink.h

@@ -110,4 +110,6 @@ void rdma_link_register(struct rdma_link_ops *ops);
 void rdma_link_unregister(struct rdma_link_ops *ops);
 
 #define MODULE_ALIAS_RDMA_LINK(type) MODULE_ALIAS("rdma-link-" type)
+#define MODULE_ALIAS_RDMA_CLIENT(type) MODULE_ALIAS("rdma-client-" type)
+
 #endif /* _RDMA_NETLINK_H */

include/uapi/rdma/rdma_netlink.h

@@ -279,6 +279,8 @@ enum rdma_nldev_command {
 
 	RDMA_NLDEV_CMD_RES_PD_GET, /* can dump */
 
+	RDMA_NLDEV_CMD_GET_CHARDEV,
+
 	RDMA_NLDEV_NUM_OPS
 };
 
@@ -491,6 +493,18 @@ enum rdma_nldev_attr {
 	 */
 	RDMA_NLDEV_NET_NS_FD,			/* u32 */
 
+	/*
+	 * Information about a chardev.
+	 * CHARDEV_TYPE is the name of the chardev ABI (ie uverbs, umad, etc)
+	 * CHARDEV_ABI signals the ABI revision (historical)
+	 * CHARDEV_NAME is the kernel name for the /dev/ file (no directory)
+	 * CHARDEV is the 64 bit dev_t for the inode
+	 */
+	RDMA_NLDEV_ATTR_CHARDEV_TYPE,		/* string */
+	RDMA_NLDEV_ATTR_CHARDEV_NAME,		/* string */
+	RDMA_NLDEV_ATTR_CHARDEV_ABI,		/* u64 */
+	RDMA_NLDEV_ATTR_CHARDEV,		/* u64 */
+
 	/*
 	 * Always the end
 	 */