vdpa: Enable user to query vdpa device info

Enable user to query vdpa device information.

$ vdpa dev add mgmtdev vdpasim_net name foo2

Show the newly created vdpa device by its name:
$ vdpa dev show foo2
foo2: type network mgmtdev vdpasim_net vendor_id 0 max_vqs 2 max_vq_size 256

$ vdpa dev show foo2 -jp
{
    "dev": {
        "foo2": {
            "type": "network",
            "mgmtdev": "vdpasim_net",
            "vendor_id": 0,
            "max_vqs": 2,
            "max_vq_size": 256
        }
    }
}

Signed-off-by: Parav Pandit <[email protected]>
Reviewed-by: Eli Cohen <[email protected]>
Reviewed-by: Jason Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Including a memory leak fix:

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Michael S. Tsirkin <[email protected]>

drivers/vdpa/vdpa.c

@@ -478,6 +478,131 @@ static int vdpa_nl_cmd_dev_del_set_doit(struct sk_buff *skb, struct genl_info *i
 	return err;
 }
 
+static int
+vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq,
+	      int flags, struct netlink_ext_ack *extack)
+{
+	u16 max_vq_size;
+	u32 device_id;
+	u32 vendor_id;
+	void *hdr;
+	int err;
+
+	hdr = genlmsg_put(msg, portid, seq, &vdpa_nl_family, flags, VDPA_CMD_DEV_NEW);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	err = vdpa_nl_mgmtdev_handle_fill(msg, vdev->mdev);
+	if (err)
+		goto msg_err;
+
+	device_id = vdev->config->get_device_id(vdev);
+	vendor_id = vdev->config->get_vendor_id(vdev);
+	max_vq_size = vdev->config->get_vq_num_max(vdev);
+
+	err = -EMSGSIZE;
+	if (nla_put_string(msg, VDPA_ATTR_DEV_NAME, dev_name(&vdev->dev)))
+		goto msg_err;
+	if (nla_put_u32(msg, VDPA_ATTR_DEV_ID, device_id))
+		goto msg_err;
+	if (nla_put_u32(msg, VDPA_ATTR_DEV_VENDOR_ID, vendor_id))
+		goto msg_err;
+	if (nla_put_u32(msg, VDPA_ATTR_DEV_MAX_VQS, vdev->nvqs))
+		goto msg_err;
+	if (nla_put_u16(msg, VDPA_ATTR_DEV_MAX_VQ_SIZE, max_vq_size))
+		goto msg_err;
+
+	genlmsg_end(msg, hdr);
+	return 0;
+
+msg_err:
+	genlmsg_cancel(msg, hdr);
+	return err;
+}
+
+static int vdpa_nl_cmd_dev_get_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct vdpa_device *vdev;
+	struct sk_buff *msg;
+	const char *devname;
+	struct device *dev;
+	int err;
+
+	if (!info->attrs[VDPA_ATTR_DEV_NAME])
+		return -EINVAL;
+	devname = nla_data(info->attrs[VDPA_ATTR_DEV_NAME]);
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	mutex_lock(&vdpa_dev_mutex);
+	dev = bus_find_device(&vdpa_bus, NULL, devname, vdpa_name_match);
+	if (!dev) {
+		NL_SET_ERR_MSG_MOD(info->extack, "device not found");
+		err = -ENODEV;
+		goto err;
+	}
+	vdev = container_of(dev, struct vdpa_device, dev);
+	if (!vdev->mdev) {
+		err = -EINVAL;
+		goto mdev_err;
+	}
+	err = vdpa_dev_fill(vdev, msg, info->snd_portid, info->snd_seq, 0, info->extack);
+	if (!err)
+		err = genlmsg_reply(msg, info);
+mdev_err:
+	put_device(dev);
+err:
+	mutex_unlock(&vdpa_dev_mutex);
+	if (err)
+		nlmsg_free(msg);
+	return err;
+}
+
+struct vdpa_dev_dump_info {
+	struct sk_buff *msg;
+	struct netlink_callback *cb;
+	int start_idx;
+	int idx;
+};
+
+static int vdpa_dev_dump(struct device *dev, void *data)
+{
+	struct vdpa_device *vdev = container_of(dev, struct vdpa_device, dev);
+	struct vdpa_dev_dump_info *info = data;
+	int err;
+
+	if (!vdev->mdev)
+		return 0;
+	if (info->idx < info->start_idx) {
+		info->idx++;
+		return 0;
+	}
+	err = vdpa_dev_fill(vdev, info->msg, NETLINK_CB(info->cb->skb).portid,
+			    info->cb->nlh->nlmsg_seq, NLM_F_MULTI, info->cb->extack);
+	if (err)
+		return err;
+
+	info->idx++;
+	return 0;
+}
+
+static int vdpa_nl_cmd_dev_get_dumpit(struct sk_buff *msg, struct netlink_callback *cb)
+{
+	struct vdpa_dev_dump_info info;
+
+	info.msg = msg;
+	info.cb = cb;
+	info.start_idx = cb->args[0];
+	info.idx = 0;
+
+	mutex_lock(&vdpa_dev_mutex);
+	bus_for_each_dev(&vdpa_bus, NULL, &info, vdpa_dev_dump);
+	mutex_unlock(&vdpa_dev_mutex);
+	cb->args[0] = info.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 },
@@ -503,6 +628,12 @@ static const struct genl_ops vdpa_nl_ops[] = {
 		.doit = vdpa_nl_cmd_dev_del_set_doit,
 		.flags = GENL_ADMIN_PERM,
 	},
+	{
+		.cmd = VDPA_CMD_DEV_GET,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = vdpa_nl_cmd_dev_get_doit,
+		.dumpit = vdpa_nl_cmd_dev_get_dumpit,
+	},
 };
 
 static struct genl_family vdpa_nl_family __ro_after_init = {

include/uapi/linux/vdpa.h

@@ -16,6 +16,7 @@ enum vdpa_command {
 	VDPA_CMD_MGMTDEV_GET,		/* can dump */
 	VDPA_CMD_DEV_NEW,
 	VDPA_CMD_DEV_DEL,
+	VDPA_CMD_DEV_GET,		/* can dump */
 };
 
 enum vdpa_attr {
@@ -27,6 +28,10 @@ enum vdpa_attr {
 	VDPA_ATTR_MGMTDEV_SUPPORTED_CLASSES,	/* u64 */
 
 	VDPA_ATTR_DEV_NAME,			/* string */
+	VDPA_ATTR_DEV_ID,			/* u32 */
+	VDPA_ATTR_DEV_VENDOR_ID,		/* u32 */
+	VDPA_ATTR_DEV_MAX_VQS,			/* u32 */
+	VDPA_ATTR_DEV_MAX_VQ_SIZE,		/* u16 */
 
 	/* new attributes must be added above here */
 	VDPA_ATTR_MAX,