[SOLVED] Windows Guest Boot Hangs after Enabling Hyper-V in Windows Guest on 13th Gen Intel CPU

[brewdamaster]

Hi, I have been banging my head against the wall trying to get a working configuration for enabling Hyper-V on a 13700K intel host.

I've referenced various CPU flags & kernel versions (5.15-6.2) to try as well as Windows 10/11/Server2019/Server2022 as OS options with no joy so far. With any configuration I use the boot hangs after enabling Hyper-V on the guest.

What are the best practices when trying a setup like this? I used a 10700K as a proof of concept of this idea an was able to enable Hyper-V and utilize GPU-P to split a passed through NVIDIA GPU across the guest and nested guest within. Now on 13th gen I do not get the same result with the same VM details and BIOS options.

I only need to pass the whole GPU via VFIO and don't have issues with code 43 on the guest, so I am just trying to get nested virtualization to work on a Windows guest with hyper-v. How can I troubleshoot why the guest hangs on the boot logo in console?

Thanks! And please let me know if I can provide any more info!

 

[brewdamaster]

As a follow up, I was able to get this to work on the 13700k intel host with the following arguments in the vm conf file:

args: -cpu SandyBridge,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time,+vmx

 

[fakezeta]

Sorry for the necroposting, but I looked so hard to find a solution to this problem affecting also 12th gen that I really want to thank @brewdamaster and confirm it's working.

Performance hit anyway is huge (near 45%).
Here a Geekbench 6 comparison between host and SandyBridge options:


Using a more recent CPU model and enabling all the 12th gen supported features like below

args: -cpu Cascadelake-Server-noTSX,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time,+vmx,+pdpe1gb,+md-clear,+mds-no,+taa-no,+tsx-ctrl,+spec-ctrl,+stibp,+ssbd,+pcid

mitigate the performance hit (near 10%):

 

[brewdamaster]

Thanks @fakezeta ! I was able to get almost double single core score on 13700k with your flags. Not quite as improved on the multicore score (about 30% improved) but still a nice performance bump!

 

[fakezeta]

I'm experimenting with other CPU model.
The most recent I could get working was Icelake-Server-v4 and performance are near "host" with HVCI off:
args: -cpu Icelake-Server-v4,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time,+vmx,+pdpe1gb,+md-clear,+mds-no,+taa-no,+tsx-ctrl,+spec-ctrl,+stibp,+ssbd,+pcid


Performance with HVCI on are instead reduced of 30% but I think that we must live with performance impact on nested virtualization.

 

[p.b]

I was searching for days in order to get my WIndows 10 Pro Desktop VM back online again (while keeping the host cpu) after enabling Core Isolation (aka Virtualization-based Security) without doing a snapshot in advance. And then I luckily found this link. It turned out that getting the nested Hyper-V and WSL running on my Intel i7-13700T Proxmox VE 8.1 host was just a matter of adding

args: -cpu host,level=30

in the VM config file.

Afterwards the VM instantly booted again but still felt a bit slow and caused its assigned vcpus to constantly run at high load. After carefully reading the QEMU documentation for Hyper-V Enlightenments for the hv_* flags, I enabled everything that promised some performance gain:


From this I would recommend to use somthing like the following custom arguments for the VM config for such a processor:

args: -cpu host,level=30,hv_relaxed,hv_reset,hv_runtime,hv_time,hv_spinlocks=0x1fff,hv_vapic,hv_vpindex,hv_ipi,hv_synic,hv_stimer,hv_apicv,hv_xmm_input,hv_stimer_direct,hv_frequencies,hv_reenlightenment,hv_evmcs,hv_emsr_bitmap,hv_tlbflush,hv_tlbflush_ext,hv_tlbflush_direct

Please note that the hv_evmcs flag is Intel-only and some of the others might only be supported on AlderLake/RaptorLake processors and newer.

But using passthrough also seems to work fine and is much simpler and less error prone:

args: -cpu host,hv_passthrough,level=30

Guess this would also allow to use Credential Guard with WIndows 10 Enterprise or Windows 11 (sorry for the German screenshots):


Windows Subsystem for Linux (WSL) also works without any issues:




To get Windows 11 Pro started, it was necessary to add the -waitpkg flag (same link as above) and use the following arguments:

args: -cpu host,hv_passthrough,level=30,-waitpkg

It was also essential that MSRs are ignored according to the nested docs. Without the two adjustments, the test machine did not boot or ended up with a BSOD.

For some reason, Windows 11 works much faster than Windows 10 and gives close to bare metal results (also in WSL) with Hyper-V and VBS enabled:



For the benchmarks I was only using 6 P-cores (x2) while the other 2 P-cores were dedicated to the PVE host.
All 8 E-cores have been used exclusively for 6 background VMs (nextcloud, omv, dc, ...) that were more or less idling during the tests.

Thanks to @brewdamaster and @fakezeta for this thread for search inspirations!

Hope this is helpful.

 

[ralphte]

THANK YOU. fixed my issue just want to give my thanks!

 

[scyto]

Wow i think this just solved my automatic repair boot loop issue args: -cpu host,hv_passthrough,level=30,-waitpkg

thanks @p.b

now if only i could work out how to re-enable the vGPU passthrough and not get code 43 on the IrisXE vGPU, hope i don't need the V2 extended topology feature for that.....

 

[trey.b]

I think this resolved our issue, we just got 5th generation Xeon R760 servers and to my surprise we couldn't boot with host CPU type, which is required to run WSL/nested virtualization. Besides the fact virtualized CPUs have awful performance in some areas.

After using the suggested -cpu host,hv_pass... suggestion we can boot and "wsl --install -d Ubuntu-20.04" completes post reboot whereas before it would error about BIOS needing virtualization support.

Thank you

I don't understand why Windows is so weird about drivers.

 

[ogvirt]

Well, this was a huge find. I ignorantly installed WSL on Win11 yesterday without doing research, rebooted, and found myself in recovery mode. Attempted to search but so many false paths and old information. I managed to find this this morning and the "Win11 Args" booted me right in!

Thanks to everyone who contributed to this thread.