Hayley Hughes <[email protected]> writes:

Hi Yuchen,
I have some experience with running windows using vfio gpu passthrough so might be able to help.

What are the problems you've encountered as well as the distro of the host?

The host distro is also Debian. I was following tutorials on single GPU passthrough using libvirt hooks[1][2].

[1] https://github.com/joeknock90/Single-GPU-Passthrough
[2] https://yewtu.be/watch?v=eTX10QlFJ6c

The problem is black screen upon starting the vm.

I managed to set the kernel parameters related to iommu and confirmed that the GPU with its sound card are an iommu group. I also edited the /etc/modprobe.d/vfio.conf[3] as well as adding the gpu and its sound card to the vm. I tested the startup script[4] separately which (as expected) turned off the display. When I enable the hook and start the vm, the display goes black without the vm display showing up. I tested this with and without extra graphics and video field (usually spice + virgl) in the vm xml and in both situations the display goes dark. With the extra graphics and video field I could access the spice graphical console. Without the extra graphical console, I could not even ssh into the vm to debug. The logs at /var/log/libvirt/qemu/<domain-name>.log did not contain any useful info.

[3]: /etc/modprobe.d/vfio.conf:
options vfio-pci ids=10de:13bb,10de:0fbc
options vfio-pci disable_vga=1

[4]: the start script:
#!/bin/bash
# Helpful to read output when debugging
set -x

# Stop X server
killall X

# Unbind VTconsoles
echo 0 > /sys/class/vtconsole/vtcon0/bind
echo 0 > /sys/class/vtconsole/vtcon1/bind

# Unbind EFI-Framebuffer. This only works with nomodeset kernel parameter
# set, otherwise I get segfault
echo efi-framebuffer.0 > /sys/bus/platform/drivers/efi-framebuffer/unbind

modprobe -r nouveau

# Avoid a Race condition by waiting 5 seconds. This can be calibrated to be shorter or longer if required for your system
sleep 5

# Unbind the GPU from display driver
virsh nodedev-detach pci_0000_03_00_0
virsh nodedev-detach pci_0000_03_00_1

# Load VFIO Kernel Module modprobe vfio-pci



Regards,
Hayley

On 25 Oct 2021, at 23:13, Yuchen Pei via luv-main <[email protected]> wrote:

Hello,

I wonder if anyone here has done GPU passthrough with libvirt?

I've been trying to do it with an nvidia quadro k620 into a Debian guest system, without success.

--
Best,
Yuchen

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Best,
Yuchen

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