Steps I have done to make NVIDIA vGPU works:

1. Install XCP-ng 8.2.1
2. Install all update yum update
3. reboot
4. Download NVIDIA vGPU drivers for XenServer 8.2 from NVIDIA site. Version NVIDIA-GRID-CitrixHypervisor-8.2-510.108.03-513.91
5. Unzip and install rpm from Host-Drivers
6. reboot again
7. Download free CitrixHypervisor-8.2.0-install-cd.iso from Citrix site
8. Open CitrixHypervisor-8.2.0-install-cd.iso with 7-zip, then unzip vgpu binary file from Packages->vgpu....rpm->vgpu....cpio->.->usr->lib64->xen->bin
9. Upload vgpu to XCP-ng host to /usr/lib64/xen/bin and made it executable chmod +x /usr/lib64/xen/bin/vgpu
10. Deployed VM with vGPU and it started without any problems

So I did not make any modifications with emu-manager.

My test server is far away from me and it will take some time to download the windows ISO to this test location. Then I will check how it works in the guest OS and report back here.

Hello!

I'm system and network engineer.
I have started work with xenserver since 2013 (I think it was opensource 6.2 version).
In 2015 I started deploing my own control panel for hosting based on xenserver.

After Citrix closed free version I started to move to XCP-ng.

Now I'm playing with xcp-ng + GPU, testing performance in different scenarios and sharing on this forum I believe that knowledge should be open so that everyone can move forward faster.

Some time later I faced with problem that VMs (Linux and Windows) can't correctly start GPU (ADM MxGPU).
In windows device manager there was error #43.
I have solved this error without host reboot by reloading gim module.

Hope this will help somebody else.

rmmod gim gim_api
modprobe gim gim_api

+1 to @Andrew setup

@wyatt-made I need few days to test it.
Will report later here

Finally after a week I found the solution!
There is no problem with emu-manager.
XCP does not contain necessary package vgpu.
I copied vgpu from Citrix ISO and now it is alive! : )

Live migration is not possible in this case, because of lack of free space.

You have to shutdown VM, then click this button and chose another host