After the new CachyOS update, all my Virtual Machines crash or give black screens

Hello,

First of all, thank you for CachyOS. It’s rapidly becoming my favorite OS.

However, since yesterday I encountered a serious issue and I am completely stuck.

I have PCI-e passthrough (IOMMU) configured for my Nvidia RTX 4090 and my iGPU set as primary. My setup for the past 1.5 years (also before CachyOS, when I used Manjaro) has been to use a host OS (CachyOS) and a guest OS (CachyOS, Windows, etc.) configured via virt-manager & QEMU/KVM. This worked like a dream, I could code in one virtual machine, game in another, etc. My virtual machines were like virtual rooms of a virtual house.

That all came crashing (literally) down yesterday. Since a unknown update (I suspect the kernel) my VMs stopped working. I either get black screens or the VM crashes (usually it’s a crash).

I have since tried, nothing installed except:

  • CachyOS X11 or Wayland
  • CachyOS nvidia-open or nvidia (closed)
  • CachyOS linux hardered kernel
  • A older version of CachyOS
  • A different distro (latest Manjaro)
  • Windows (but this might be unrelated, as I haven’t started that VM in 2 months)
  • My RTX 4090 not attached to a VM, which indeed makes it work. But I need it (for coding to run local AI via ollama) and for gaming (I game in CachyOS VM).

Nothing worked.

Any help would be hugely appreciated. Thanks so much!

P.s. I have not yet and have considered re-installing my host OS (CachyOS), however since PCI-e passthrough is quite a bit of work to set up right, I rather avoid it if possible. Both my CachyOS host OS and Linux guest OSes (virtual machines) are up-to-date.

It can’t be the kernel then if you tried linux-cachyos-hardened. You can view /var/log/pacman.log to see which packages were recently updated and make an educated guess or bisect one by one until you’ve found the problematic update.

It seems to be a hardware issue. Thank you for putting me on the right track.

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