GPU Passthrough resulting in high CPU load - Ideas?

[longshot902]

I have been working on an attempt to pass my gpu to a vm running on my proxmox system.
I'm running version 4.0-48

I have followed the Proxmox document for PCI-E setup.
This includes changing Grub entries.

I have enabled IOMMU on my motherboard as well as virtualization.
My motherboard calls the feature "SVM Mode" and that has been enabled.
*I'm running an AMD CPU.

I have the following lines in my vm.conf file:
machine: q35
hostpci0: 01:00.0,x-vga=on,pcie=1
*My GPU is registered to BUS 01.

The vm is a Windows 7 image with the QEMU drivers + chipset installed.
If I remove the hostpci0 line from my vm config, the vm runs great. Adding the line reduced system performance and the CPU load is always near 100%.

I assume what is happening is my CPU is drawing the window frames instead of my GPU doing the work. Even though the system recognizes I have a GPU installed and the OS can detect the model, yet it somehow doesn't pass full control to it.
Initially, I had thought the issue related to maybe the CPU/motherboard didn't fully support visualization. But since I can just remove the "hostpci0" option from the vm.conf, it works great no CPU issues.

Does anyone have ideas on what I could try to resolve this problem? Or hit a similar wall?

 

[manu]

Hi
The IOMMU feature for PCI passthough you need is called AMD-vi, this is an extra feature that you need to add additionally to SVM.

 

[longshot902]

Thanks for the reply,

I've reached out to my motherboard manufacturer to see about clarification on this as the manual states that "IOMMU" is what they call "AMD-VI".
If you lookup "x86 virtualization" on Wikipedia, there is a section regarding AMD-VI and Intel VT. (I cannot post the link due to my account age.)
So based on that, as long as IOMMU and SVM are enabled on my board, it should work.

I am using an MSI 970 Gaming motherboard (Its the only board I have on hand at the moment.)

To make sure i'm not missing anything - i'm going to try another system running the same version of ProxmoxVE and see if results continue.

 

[longshot902]

I tried this with VMWare 6.0 Update 1 and my results were far worse than before. (I will try 5.5 tonight as it appears 6+ has some features disabled and only available if purchasing a vcenter license.)
This could be an issue with the motherboard chipset not supporting all the correct features; I ordered a new board today that other people have confirmed working and we'll see if that yields better results.

 

[longshot902]

I have tested with a completely new set of motherboard + memory and the problem continues. However, reading through new topics posted yesterday, I found this one here:http://forum.proxmox.com/threads/24178-Proxmox-4-0-PCI-passthrough-broken-in-several-waysSymptom #1 is identical to what I'm experiencing.The bug in the kernel for this problem is being tracked here:https://bugzilla.kernel.org/show_bug.cgi?id=107561I will update again once a new patch has been released.