AMD EPYC Nested Virtualization problems (not working)

[joe2]

Few questions about AMD EPYC processor support.

Does Proxmox VE support hardware accelerated nested virtualization for EPYC?

Are there any configuration tweaks that are recommended for EPYC system?

 

[wolfgang]

Does Proxmox VE support hardware accelerated nested virtualization for EPYC?

Yes

Are there any configuration tweaks that are recommended for EPYC system?

For which case? EPYC is a normal CPU and supported in the current kernel.

 

[joe2]

That's great! I was checking because it's a new CPU architecture and I know MS Hyper-V does not support it yet!

Thank you @wolfgang for the quick reply, it's much appreciated.

 

[joe2]

After installing Windows as a guest VM and enabling hyper-v the guest fails to load. It hangs here in the boot process (see attached image).

Guest CPU options set to 'host' and NUMA is enabled.

Also the following was set:

root@pve:~# cat /sys/module/kvm_amd/parameters/nested
1
root@pve:~# cat /etc/modprobe.d/kvm-amd.conf
options kvm-amd nested=1

 

[wolfgang]

AFIK Windows 2016 can only run nested on a Windows 2016.

http://events17.linuxfoundation.org/sites/events/files/slides/HyperV-KVM.pdf

 

[joe2]

Here is more info on the issue (by the same author as the slides @wolfgang found)
https://ladipro.wordpress.com/2017/07/21/hyperv-in-kvm-known-issues/

I also added "args: -cpu host,+svm" to the VM configuration as described in https://pve.proxmox.com/wiki/Nested_Virtualization#PVE_as_nested_Hypervisor

It's still not working, I will be investigating further.

 

[joe2]

Hyper-V Nested virtualization works well with 1 vCPU but crashes with more cores enabled on the L1 (hyper-v host)