VFIO Windows 11 VM broke after new RAM install

Operating Systems & Open Source Virtualization
1

Hi all,

Last night I installed new RAM into my PC (32Gb > 64Gb, same speed) and this caused my Windows 11 VM (VFIO, KVM, Qemu, libvirt) to not display any output from the passed through GPU (6900xt reference).

My setup had been working flawlessly for weeks, so I’m confident It’s something to do with the RAM.

In terms of troubleshooting I had to go to the extent of starting fresh on my Guest and Host OS’s, following the same instructions I used to get the setup working multiple times before this, however the same issue occurs, no video when connecting into GPU DP port.

The VM installs fine, and I can install the AMD drivers on Windows without issue, however It’s when I change over to the physical port is when the GPU outputs no signal.

Am I missing something here?

Do I have to pop the CMOS battery or something? Because I’m at the point where I wouldn’t be surprised if that worked, lol.

For reference, I use this guide:

Thanks in advance!

2

Its probably not stable? Have you done memtest for 3 passes? Dont use XMP and do a manual overclock?

Are you using a lower end AMD CPU? 5600X perhaps?

3

I will try a memtest after work, however the Fedora host runs perfectly fine, I’ve even put the old RAM kit back in and the same issue is there.

Is XMP a known issue with VFIO?

4

My CPU is a 13900k.

5

Not really a specific issue/concern but more along the lines of a general instability issues with overclocking. Try disabling the XMP to see if it helps.

Since you are on Intel IIRC the memory controller would be on the motherboard (vs on the CPU in the case of AMD). Are you on the latest mobo firmware? Sometimes updating helps?

Also I just realized the way you worded your post, did you replace it with new RAM or did you just add new modules and retained the old ones? If you retained the old, did you properly stagger it in its slot?

A1 - old RAM
B1 - new RAM
A2 - old RAM
B2 - new RAM

6

The new RAM is a complete new kit (4x16gb) and was installed properly. Will try disabling XMP.

Yes, I am on the latest Mobo firmware

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7

FIXED

Pulling the CMOS battery fixed it.

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