vdpa: Introduce query of device config layout

Introduce a command to query a device config layout.

An example query of network vdpa device:

$ vdpa dev add name bar mgmtdev vdpasim_net

$ vdpa dev config show
bar: mac 00:35:09:19:48:05 link up link_announce false mtu 1500

$ vdpa dev config show -jp
{
    "config": {
        "bar": {
            "mac": "00:35:09:19:48:05",
            "link ": "up",
            "link_announce ": false,
            "mtu": 1500,
        }
    }
}
Signed-off-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20211026175519.87795-3-parav@nvidia.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa.c

@@ -14,6 +14,8 @@
 #include <uapi/linux/vdpa.h>
 #include <net/genetlink.h>
 #include <linux/mod_devicetable.h>
+#include <linux/virtio_net.h>
+#include <linux/virtio_ids.h>
 
 static LIST_HEAD(mdev_head);
 /* A global mutex that protects vdpa management device and device level operations. */
@@ -66,6 +68,7 @@ static void vdpa_release_dev(struct device *d)
 		ops->free(vdev);
 
 	ida_simple_remove(&vdpa_index_ida, vdev->index);
+	mutex_destroy(&vdev->cf_mutex);
 	kfree(vdev);
 }
 
@@ -127,6 +130,7 @@ struct vdpa_device *__vdpa_alloc_device(struct device *parent,
 	if (err)
 		goto err_name;
 
+	mutex_init(&vdev->cf_mutex);
 	device_initialize(&vdev->dev);
 
 	return vdev;
@@ -309,6 +313,7 @@ void vdpa_get_config(struct vdpa_device *vdev, unsigned int offset,
 {
 	const struct vdpa_config_ops *ops = vdev->config;
 
+	mutex_lock(&vdev->cf_mutex);
 	/*
 	 * Config accesses aren't supposed to trigger before features are set.
 	 * If it does happen we assume a legacy guest.
@@ -316,6 +321,7 @@ void vdpa_get_config(struct vdpa_device *vdev, unsigned int offset,
 	if (!vdev->features_valid)
 		vdpa_set_features(vdev, 0);
 	ops->get_config(vdev, offset, buf, len);
+	mutex_unlock(&vdev->cf_mutex);
 }
 EXPORT_SYMBOL_GPL(vdpa_get_config);
 
@@ -329,7 +335,9 @@ EXPORT_SYMBOL_GPL(vdpa_get_config);
 void vdpa_set_config(struct vdpa_device *vdev, unsigned int offset,
 		     const void *buf, unsigned int length)
 {
+	mutex_lock(&vdev->cf_mutex);
 	vdev->config->set_config(vdev, offset, buf, length);
+	mutex_unlock(&vdev->cf_mutex);
 }
 EXPORT_SYMBOL_GPL(vdpa_set_config);
 
@@ -661,6 +669,168 @@ static int vdpa_nl_cmd_dev_get_dumpit(struct sk_buff *msg, struct netlink_callba
 	return msg->len;
 }
 
+static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
+				       struct sk_buff *msg, u64 features,
+				       const struct virtio_net_config *config)
+{
+	u16 val_u16;
+
+	if ((features & (1ULL << VIRTIO_NET_F_MQ)) == 0)
+		return 0;
+
+	val_u16 = le16_to_cpu(config->max_virtqueue_pairs);
+	return nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MAX_VQP, val_u16);
+}
+
+static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg)
+{
+	struct virtio_net_config config = {};
+	u64 features;
+	u16 val_u16;
+
+	vdpa_get_config(vdev, 0, &config, sizeof(config));
+
+	if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac),
+		    config.mac))
+		return -EMSGSIZE;
+
+	val_u16 = le16_to_cpu(config.status);
+	if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_STATUS, val_u16))
+		return -EMSGSIZE;
+
+	val_u16 = le16_to_cpu(config.mtu);
+	if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
+		return -EMSGSIZE;
+
+	features = vdev->config->get_features(vdev);
+
+	return vdpa_dev_net_mq_config_fill(vdev, msg, features, &config);
+}
+
+static int
+vdpa_dev_config_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq,
+		     int flags, struct netlink_ext_ack *extack)
+{
+	u32 device_id;
+	void *hdr;
+	int err;
+
+	hdr = genlmsg_put(msg, portid, seq, &vdpa_nl_family, flags,
+			  VDPA_CMD_DEV_CONFIG_GET);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (nla_put_string(msg, VDPA_ATTR_DEV_NAME, dev_name(&vdev->dev))) {
+		err = -EMSGSIZE;
+		goto msg_err;
+	}
+
+	device_id = vdev->config->get_device_id(vdev);
+	if (nla_put_u32(msg, VDPA_ATTR_DEV_ID, device_id)) {
+		err = -EMSGSIZE;
+		goto msg_err;
+	}
+
+	switch (device_id) {
+	case VIRTIO_ID_NET:
+		err = vdpa_dev_net_config_fill(vdev, msg);
+		break;
+	default:
+		err = -EOPNOTSUPP;
+		break;
+	}
+	if (err)
+		goto msg_err;
+
+	genlmsg_end(msg, hdr);
+	return 0;
+
+msg_err:
+	genlmsg_cancel(msg, hdr);
+	return err;
+}
+
+static int vdpa_nl_cmd_dev_config_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 dev_err;
+	}
+	vdev = container_of(dev, struct vdpa_device, dev);
+	if (!vdev->mdev) {
+		NL_SET_ERR_MSG_MOD(info->extack, "unmanaged vdpa device");
+		err = -EINVAL;
+		goto mdev_err;
+	}
+	err = vdpa_dev_config_fill(vdev, msg, info->snd_portid, info->snd_seq,
+				   0, info->extack);
+	if (!err)
+		err = genlmsg_reply(msg, info);
+
+mdev_err:
+	put_device(dev);
+dev_err:
+	mutex_unlock(&vdpa_dev_mutex);
+	if (err)
+		nlmsg_free(msg);
+	return err;
+}
+
+static int vdpa_dev_config_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_config_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_config_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_config_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 },
@@ -692,6 +862,12 @@ static const struct genl_ops vdpa_nl_ops[] = {
 		.doit = vdpa_nl_cmd_dev_get_doit,
 		.dumpit = vdpa_nl_cmd_dev_get_dumpit,
 	},
+	{
+		.cmd = VDPA_CMD_DEV_CONFIG_GET,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = vdpa_nl_cmd_dev_config_get_doit,
+		.dumpit = vdpa_nl_cmd_dev_config_get_dumpit,
+	},
 };
 
 static struct genl_family vdpa_nl_family __ro_after_init = {

include/linux/vdpa.h

@@ -63,6 +63,7 @@ struct vdpa_mgmt_dev;
  * @dev: underlying device
  * @dma_dev: the actual device that is performing DMA
  * @config: the configuration ops for this device.
+ * @cf_mutex: Protects get and set access to configuration layout.
  * @index: device index
  * @features_valid: were features initialized? for legacy guests
  * @use_va: indicate whether virtual address must be used by this device
@@ -74,6 +75,7 @@ struct vdpa_device {
 	struct device dev;
 	struct device *dma_dev;
 	const struct vdpa_config_ops *config;
+	struct mutex cf_mutex; /* Protects get/set config */
 	unsigned int index;
 	bool features_valid;
 	bool use_va;

include/uapi/linux/vdpa.h

@@ -17,6 +17,7 @@ enum vdpa_command {
 	VDPA_CMD_DEV_NEW,
 	VDPA_CMD_DEV_DEL,
 	VDPA_CMD_DEV_GET,		/* can dump */
+	VDPA_CMD_DEV_CONFIG_GET,	/* can dump */
 };
 
 enum vdpa_attr {
@@ -34,6 +35,11 @@ enum vdpa_attr {
 	VDPA_ATTR_DEV_MAX_VQ_SIZE,		/* u16 */
 	VDPA_ATTR_DEV_MIN_VQ_SIZE,		/* u16 */
 
+	VDPA_ATTR_DEV_NET_CFG_MACADDR,		/* binary */
+	VDPA_ATTR_DEV_NET_STATUS,		/* u8 */
+	VDPA_ATTR_DEV_NET_CFG_MAX_VQP,		/* u16 */
+	VDPA_ATTR_DEV_NET_CFG_MTU,		/* u16 */
+
 	/* new attributes must be added above here */
 	VDPA_ATTR_MAX,
 };