Can't boot from grubx64.efi (xen.efi is ok)

I can't boot from grubx64 on my Intel NUC6i5syh.

 menuentry 'XenGT 4.3.0' --class ubuntu --class gnu-linux --class gnu --class os {
            insmod part_gpt
            insmod ext2
            set root='hd0,gpt3'
            search --no-floppy --fs-uuid --set=root e31d4a0a-3acf-46fe-a0eb-9c4fdfeffee0
echo '1'
            multiboot   /boot/xen-vgt.gz dom0_mem=2048M loglvl=all guest_loglvl=all conring_size=4M noreboot
echo '2'
            module  /boot/vmlinuz-4.3.0 root=UUID=e31d4a0a-3acf-46fe-a0eb-9c4fdfeffee0 rw rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM ignore_loglevel console=tty0 console=hvc0 consoleblank=0 log_buf_len=4M i915.hvm_boot_foreground=1
#i915.enable_cmd_parser=0
echo '3'
            module  /boot/initrd.img
echo '4'
        }

the screen only prompt:

1
WARNING: no console will be avaiilable to OS
2
3
4

But I can boot from xen.efi:

compile kernel with ssd +ext4 support
copy vmlinuz and initrd.img into efi partition
create xen.cfg:

[global]
default=xen

[xen]
options=dom0_mem=2048M loglvl=all guest_loglvl=all conring_size=4M noreboot
kernel=vmlinuz-4.3.0 root=UUID=e31d4a0a-3acf-46fe-a0eb-9c4fdfeffee0 rw rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM ignore_loglevel console=tty0 console=hvc0 consoleblank=0 log_buf_len=4M i915.hvm_boot_foreground=0
ramdisk=initrd.img

So, I can boot ubuntu 16.04 desktop on dom-0

fox@nuc5:~$ sudo xl info
host                   : nuc5
release                : 4.3.0-rc6-vgt
version                : #6 SMP Mon Aug 1 01:33:51 CST 2016
machine                : x86_64
nr_cpus                : 4
max_cpu_id             : 3
nr_nodes               : 1
cores_per_socket       : 2
threads_per_core       : 2
cpu_mhz                : 1800
hw_caps                : bfebfbff:2c100800:00000000:00007f00:77fafbbf:00000000:00000121:029c67af
virt_caps              : hvm hvm_directio
total_memory           : 15313
free_memory            : 13048
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 6
xen_extra              : .0
xen_version            : 4.6.0
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          :
xen_commandline        : dom0_mem=2048M loglvl=all guest_loglvl=all conring_size=4M noreboot
cc_compiler            : gcc (Ubuntu 5.4.0-6ubuntu1~16.04.1) 5.4.0 20160609
cc_compile_by          : fox
cc_compile_domain      :
cc_compile_date        : Sun Jul 31 20:44:55 CST 2016
xend_config_format     : 4

Why the iGVT-g_Setup_Guide.txt writes: 'Note: for UEFI environment, use grubx64.efi instead of xen.efi to load system'?

intel / Igvtg-kernel

Can't boot from grubx64.efi (xen.efi is ok) #14