vdpa: Define vdpa mgmt device, ops and a netlink interface

To add one or more VDPA devices, define a management device which
allows adding or removing vdpa device. A management device defines
set of callbacks to manage vdpa devices.

To begin with, it defines add and remove callbacks through which a user
defined vdpa device can be added or removed.

A unique management device is identified by its unique handle identified
by management device name and optionally the bus name.

Hence, introduce routine through which driver can register a
management device and its callback operations for adding and remove
a vdpa device.

Introduce vdpa netlink socket family so that user can query management
device and its attributes.

Example of show vdpa management device which allows creating vdpa device of
networking class (device id = 0x1) of virtio specification 1.1
section 5.1.1.

$ vdpa mgmtdev show
vdpasim_net:
  supported_classes:
    net

Example of showing vdpa management device in JSON format.

$ vdpa mgmtdev show -jp
{
    "show": {
        "vdpasim_net": {
            "supported_classes": [ "net" ]
        }
    }
}

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Eli Cohen <elic@nvidia.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210105103203.82508-4-parav@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Including a bugfix:

vpda: correctly size vdpa_nl_policy

We need to ensure last entry of vdpa_nl_policy[]
is zero, otherwise out-of-bounds access is hurting us.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Parav Pandit <parav@nvidia.com>
Cc: Eli Cohen <elic@nvidia.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20210210134911.4119555-1-eric.dumazet@gmail.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/Kconfig

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 menuconfig VDPA
 	tristate "vDPA drivers"
+	depends on NET
 	help
 	  Enable this module to support vDPA device that uses a
 	  datapath which complies with virtio specifications with

drivers/vdpa/vdpa.c

@@ -11,11 +11,17 @@
 #include <linux/idr.h>
 #include <linux/slab.h>
 #include <linux/vdpa.h>
+#include <uapi/linux/vdpa.h>
+#include <net/genetlink.h>
+#include <linux/mod_devicetable.h>
 
+static LIST_HEAD(mdev_head);
 /* A global mutex that protects vdpa management device and device level operations. */
 static DEFINE_MUTEX(vdpa_dev_mutex);
 static DEFINE_IDA(vdpa_index_ida);
 
+static struct genl_family vdpa_nl_family;
+
 static int vdpa_dev_probe(struct device *d)
 {
 	struct vdpa_device *vdev = dev_to_vdpa(d);
@@ -195,13 +201,218 @@ void vdpa_unregister_driver(struct vdpa_driver *drv)
 }
 EXPORT_SYMBOL_GPL(vdpa_unregister_driver);
 
+/**
+ * vdpa_mgmtdev_register - register a vdpa management device
+ *
+ * @mdev: Pointer to vdpa management device
+ * vdpa_mgmtdev_register() register a vdpa management device which supports
+ * vdpa device management.
+ */
+int vdpa_mgmtdev_register(struct vdpa_mgmt_dev *mdev)
+{
+	if (!mdev->device || !mdev->ops || !mdev->ops->dev_add || !mdev->ops->dev_del)
+		return -EINVAL;
+
+	INIT_LIST_HEAD(&mdev->list);
+	mutex_lock(&vdpa_dev_mutex);
+	list_add_tail(&mdev->list, &mdev_head);
+	mutex_unlock(&vdpa_dev_mutex);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vdpa_mgmtdev_register);
+
+void vdpa_mgmtdev_unregister(struct vdpa_mgmt_dev *mdev)
+{
+	mutex_lock(&vdpa_dev_mutex);
+	list_del(&mdev->list);
+	mutex_unlock(&vdpa_dev_mutex);
+}
+EXPORT_SYMBOL_GPL(vdpa_mgmtdev_unregister);
+
+static bool mgmtdev_handle_match(const struct vdpa_mgmt_dev *mdev,
+				 const char *busname, const char *devname)
+{
+	/* Bus name is optional for simulated management device, so ignore the
+	 * device with bus if bus attribute is provided.
+	 */
+	if ((busname && !mdev->device->bus) || (!busname && mdev->device->bus))
+		return false;
+
+	if (!busname && strcmp(dev_name(mdev->device), devname) == 0)
+		return true;
+
+	if (busname && (strcmp(mdev->device->bus->name, busname) == 0) &&
+	    (strcmp(dev_name(mdev->device), devname) == 0))
+		return true;
+
+	return false;
+}
+
+static struct vdpa_mgmt_dev *vdpa_mgmtdev_get_from_attr(struct nlattr **attrs)
+{
+	struct vdpa_mgmt_dev *mdev;
+	const char *busname = NULL;
+	const char *devname;
+
+	if (!attrs[VDPA_ATTR_MGMTDEV_DEV_NAME])
+		return ERR_PTR(-EINVAL);
+	devname = nla_data(attrs[VDPA_ATTR_MGMTDEV_DEV_NAME]);
+	if (attrs[VDPA_ATTR_MGMTDEV_BUS_NAME])
+		busname = nla_data(attrs[VDPA_ATTR_MGMTDEV_BUS_NAME]);
+
+	list_for_each_entry(mdev, &mdev_head, list) {
+		if (mgmtdev_handle_match(mdev, busname, devname))
+			return mdev;
+	}
+	return ERR_PTR(-ENODEV);
+}
+
+static int vdpa_nl_mgmtdev_handle_fill(struct sk_buff *msg, const struct vdpa_mgmt_dev *mdev)
+{
+	if (mdev->device->bus &&
+	    nla_put_string(msg, VDPA_ATTR_MGMTDEV_BUS_NAME, mdev->device->bus->name))
+		return -EMSGSIZE;
+	if (nla_put_string(msg, VDPA_ATTR_MGMTDEV_DEV_NAME, dev_name(mdev->device)))
+		return -EMSGSIZE;
+	return 0;
+}
+
+static int vdpa_mgmtdev_fill(const struct vdpa_mgmt_dev *mdev, struct sk_buff *msg,
+			     u32 portid, u32 seq, int flags)
+{
+	u64 supported_classes = 0;
+	void *hdr;
+	int i = 0;
+	int err;
+
+	hdr = genlmsg_put(msg, portid, seq, &vdpa_nl_family, flags, VDPA_CMD_MGMTDEV_NEW);
+	if (!hdr)
+		return -EMSGSIZE;
+	err = vdpa_nl_mgmtdev_handle_fill(msg, mdev);
+	if (err)
+		goto msg_err;
+
+	while (mdev->id_table[i].device) {
+		supported_classes |= BIT(mdev->id_table[i].device);
+		i++;
+	}
+
+	if (nla_put_u64_64bit(msg, VDPA_ATTR_MGMTDEV_SUPPORTED_CLASSES,
+			      supported_classes, VDPA_ATTR_UNSPEC)) {
+		err = -EMSGSIZE;
+		goto msg_err;
+	}
+
+	genlmsg_end(msg, hdr);
+	return 0;
+
+msg_err:
+	genlmsg_cancel(msg, hdr);
+	return err;
+}
+
+static int vdpa_nl_cmd_mgmtdev_get_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct vdpa_mgmt_dev *mdev;
+	struct sk_buff *msg;
+	int err;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	mutex_lock(&vdpa_dev_mutex);
+	mdev = vdpa_mgmtdev_get_from_attr(info->attrs);
+	if (IS_ERR(mdev)) {
+		mutex_unlock(&vdpa_dev_mutex);
+		NL_SET_ERR_MSG_MOD(info->extack, "Fail to find the specified mgmt device");
+		err = PTR_ERR(mdev);
+		goto out;
+	}
+
+	err = vdpa_mgmtdev_fill(mdev, msg, info->snd_portid, info->snd_seq, 0);
+	mutex_unlock(&vdpa_dev_mutex);
+	if (err)
+		goto out;
+	err = genlmsg_reply(msg, info);
+	return err;
+
+out:
+	nlmsg_free(msg);
+	return err;
+}
+
+static int
+vdpa_nl_cmd_mgmtdev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
+{
+	struct vdpa_mgmt_dev *mdev;
+	int start = cb->args[0];
+	int idx = 0;
+	int err;
+
+	mutex_lock(&vdpa_dev_mutex);
+	list_for_each_entry(mdev, &mdev_head, list) {
+		if (idx < start) {
+			idx++;
+			continue;
+		}
+		err = vdpa_mgmtdev_fill(mdev, msg, NETLINK_CB(cb->skb).portid,
+					cb->nlh->nlmsg_seq, NLM_F_MULTI);
+		if (err)
+			goto out;
+		idx++;
+	}
+out:
+	mutex_unlock(&vdpa_dev_mutex);
+	cb->args[0] = idx;
+	return msg->len;
+}
+
+static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
+	[VDPA_ATTR_MGMTDEV_BUS_NAME] = { .type = NLA_NUL_STRING },
+	[VDPA_ATTR_MGMTDEV_DEV_NAME] = { .type = NLA_STRING },
+};
+
+static const struct genl_ops vdpa_nl_ops[] = {
+	{
+		.cmd = VDPA_CMD_MGMTDEV_GET,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = vdpa_nl_cmd_mgmtdev_get_doit,
+		.dumpit = vdpa_nl_cmd_mgmtdev_get_dumpit,
+	},
+};
+
+static struct genl_family vdpa_nl_family __ro_after_init = {
+	.name = VDPA_GENL_NAME,
+	.version = VDPA_GENL_VERSION,
+	.maxattr = VDPA_ATTR_MAX,
+	.policy = vdpa_nl_policy,
+	.netnsok = false,
+	.module = THIS_MODULE,
+	.ops = vdpa_nl_ops,
+	.n_ops = ARRAY_SIZE(vdpa_nl_ops),
+};
+
 static int vdpa_init(void)
 {
-	return bus_register(&vdpa_bus);
+	int err;
+
+	err = bus_register(&vdpa_bus);
+	if (err)
+		return err;
+	err = genl_register_family(&vdpa_nl_family);
+	if (err)
+		goto err;
+	return 0;
+
+err:
+	bus_unregister(&vdpa_bus);
+	return err;
 }
 
 static void __exit vdpa_exit(void)
 {
+	genl_unregister_family(&vdpa_nl_family);
 	bus_unregister(&vdpa_bus);
 	ida_destroy(&vdpa_index_ida);
 }

include/linux/vdpa.h

@@ -35,6 +35,8 @@ struct vdpa_vq_state {
 	u16	avail_index;
 };
 
+struct vdpa_mgmt_dev;
+
 /**
  * vDPA device - representation of a vDPA device
  * @dev: underlying device
@@ -335,4 +337,33 @@ static inline void vdpa_get_config(struct vdpa_device *vdev, unsigned offset,
 	ops->get_config(vdev, offset, buf, len);
 }
 
+/**
+ * vdpa_mgmtdev_ops - vdpa device ops
+ * @dev_add:	Add a vdpa device using alloc and register
+ *		@mdev: parent device to use for device addition
+ *		@name: name of the new vdpa device
+ *		Driver need to add a new device using _vdpa_register_device()
+ *		after fully initializing the vdpa device. Driver must return 0
+ *		on success or appropriate error code.
+ * @dev_del:	Remove a vdpa device using unregister
+ *		@mdev: parent device to use for device removal
+ *		@dev: vdpa device to remove
+ *		Driver need to remove the specified device by calling
+ *		_vdpa_unregister_device().
+ */
+struct vdpa_mgmtdev_ops {
+	int (*dev_add)(struct vdpa_mgmt_dev *mdev, const char *name);
+	void (*dev_del)(struct vdpa_mgmt_dev *mdev, struct vdpa_device *dev);
+};
+
+struct vdpa_mgmt_dev {
+	struct device *device;
+	const struct vdpa_mgmtdev_ops *ops;
+	const struct virtio_device_id *id_table; /* supported ids */
+	struct list_head list;
+};
+
+int vdpa_mgmtdev_register(struct vdpa_mgmt_dev *mdev);
+void vdpa_mgmtdev_unregister(struct vdpa_mgmt_dev *mdev);
+
 #endif /* _LINUX_VDPA_H */

include/uapi/linux/vdpa.h

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ * vdpa device management interface
+ * Copyright (c) 2020 Mellanox Technologies Ltd. All rights reserved.
+ */
+
+#ifndef _UAPI_LINUX_VDPA_H_
+#define _UAPI_LINUX_VDPA_H_
+
+#define VDPA_GENL_NAME "vdpa"
+#define VDPA_GENL_VERSION 0x1
+
+enum vdpa_command {
+	VDPA_CMD_UNSPEC,
+	VDPA_CMD_MGMTDEV_NEW,
+	VDPA_CMD_MGMTDEV_GET,		/* can dump */
+};
+
+enum vdpa_attr {
+	VDPA_ATTR_UNSPEC,
+
+	/* bus name (optional) + dev name together make the parent device handle */
+	VDPA_ATTR_MGMTDEV_BUS_NAME,		/* string */
+	VDPA_ATTR_MGMTDEV_DEV_NAME,		/* string */
+	VDPA_ATTR_MGMTDEV_SUPPORTED_CLASSES,	/* u64 */
+
+	/* new attributes must be added above here */
+	VDPA_ATTR_MAX,
+};
+
+#endif