Description: Playing VAC games(CS:GO) on Steam with a Win 10 VM cause issues. A known bug in Steams anti-cheat software, namely VAC, started to happen after I upgraded from unraid 6.2.4. I have been playing for months on the same hardware before this Issue occured when I updated unraid.

How to reproduce: Play Steam game like CS:GO on a Win 10 VM on Unraid [6.3.2] 

Other information: These are the suggestions steam have for fixing the problem: https://support.steampowered.com/kb_article.php?ref=2117-ILZV-2837. None works.

I'm interested in the answer, too.  That being said, I'm willing to bet the problem is more with Qemu or Steam than unRAID.  From the page you linked, it sounds like Valve wants you to disable any hypervisors.  Valve might be cracking down on people running VMs to stop some sort of undesirable behavior in-game.

What version of QEMU was 6.2.4 running vs now?  Was there a change in the command line string unRAID used to launch QEMU?   ...or did this coincide with a Steam VAC update?  Hard to tell.

 

Here's someone with a similar sounding issue... https://www.redhat.com/archives/vfio-users/2017-February/msg00097.html

Another Reddit link... https://www.reddit.com/r/VFIO/comments/5xzwp9/vac_authentication_error_on_windows10_guest_in/?sort=top&st=j0s7rmnm&sh=f1f8f118

 

Edited March 27, 20179 yr by Iguanac64
Added another link to similar issue

This is actually a really interesting find.  Apparently the issue is specific to VAC (Valve Anti Cheat) and there is actually good and reasonable reasons for why they are doing this.  Using a VM, you could, in theory, do far more nefarious cheats that you wouldn't be able to detect from within the VM.  I'll have to ping Alex Williamson on this and get his thoughts.  Perhaps QEMU/KVM could put features in that would make valve feel more comfortable with VMs.

Ok, so I did get some feedback from Alex on this but not much to go on at this point.  Basically the big things to try are isolcpus, cpu pinning, and setting up an emulator pin.  It is possible that they aren't probably detecting the presence of a hypervisor as much as the hypervisor is potentially causing some slight timing issues that is triggering VAC to cause this issue.