nandflash驱动测试时，使用NFS作为根文件系统不能挂接

linux虚拟机网络配置如下：
名称：ens33；ip：192.168.1.190；网关：192.168.1.1；掩码：255.255.255.0

开发板相关参数：

设置启动参数为：
set bootargs console=ttySAC0 root=/dev/nfs nfsroot=192.168.1.190:/work/nfs_root/first_fs ip=192.168.1.17:192.168.1.190:192.168.1.1:255.255.255.0::ens33:off

串口提示消息：

IP-Config: Device `ens33' not found.
Looking up port of RPC 100003/2 on 192.168.1.190
rPCBind: server 192.168.1.190 not responding, timed out
Root-NFS: Unable to get nfsd port number from server, using default
Looking up port of RPC 100005/1 on 192.168.1.190
rpcbind: server 192.168.1.190 not responding, timed out
Root-NFS: Unable to get mountd port number from server, using default
mount: server 192.168.1.190 not responding, timed out
Root-NFS: Server returned error -5 while mounting /work/nfs_root/first_fs
VFS: Unable to mount root fs via NFS, trying floppy.
VFS: Cannot open root device "nfs" or unknown-block(2,0)
Please append a correct "root=" boot option; here are the available partitions:
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)



在保持启动参数为set bootargs console=ttySAC0 root=/dev/nfs nfsroot=192.168.1.190:/work/nfs_root/first_fs ip=192.168.1.17:192.168.1.190:192.168.1.1:255.255.255.0::ens33:off
开发板ping虚拟机是没有问题的：

但是虚拟机ping开发板有问题：


将开发板启动参数改为set bootargs noinitrd root=/dev/mtdblock3 init=/linuxrc console=ttySAC0,115200后，虚拟机ping开发板没问题：





请问这个是什么问题，需要如何解决呢？谢谢！