How to make OpenWrt running on AWS EC2?

I have tried two methods to upload openwrt x86_64 image to AWS AMI and run on EC2, but both failed.

The image I built runs ok on VirutalBox and vmware.

The first method - vm_import/export.
I tried vm_import/export tools of AWS. It failed ans said "Not found initrd in Grub" at last.
ref. https://amazonaws-china.com/cn/ec2/vm-import/

The second method - ec2-bundle-image/ec2-upgrade-image
I tried this way, and it can upload image files and metadata files to S3, and I could make a new AMI, and launch EC2 too. But EC2 instance was not be booted correctly it stop at the grub>, which I got from instance system log.
ref. https://forum.archive.openwrt.org/viewtopic.php?id=41588
ref. https://docs.aws.amazon.com/zh_cn/AWSEC2/latest/UserGuide/create-instance-store-ami.html#amazon_linux_instructions

Could any one help me? Thanks.

See here: