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Old 08-01-2015, 04:59 PM   #1
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Registered: Aug 2015
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KVM GPU Passthrough won't work

Hey Guys!

I have been trying to get GPU passthrough to work, but cannot seem to find out where the problem lies, since I do not get any errors.

I have primarily used these guides as sources:

Lubuntu 14.04 with patched 3.18.0 kernel
i5 4690K (VT-d enabled)
Gigabyte Z97 D3H
TV with multiple outputs (VGA, HDMI)

The IGPU runs over VGA, whereas the GPU is connected via HDMI.
I use the IGPU for the host system, while attempting to pass the GTX 750TI through to the Guest.
When I run the script, a qemu window pops up saying "compat_monitor0 console Qemu 2.1.2 monitor - type help
When I switch to the HDMI output of the TV, to which the GPU is connected, nothing appears. However, my GPU usage ramps up to 25%, hence something must be going on.

When I assign one of the downloaded gpu roms in the script, the colors become fuzzy and inverted (which cannot be seen on the screen), while nothing appears on the HDMI output and the cpu usage only momentarily rises, while dropping shortly after:

.)I compiled, patched and installed kernel 3.18.0 with ACS and i915:
.)Downloaded a rom file for my GPU (GTX 750 TI):
.)Upgraded Qemu to version 2.1.2 via this ppa:jacob/virtualisation
.)Installed all necessary packages as suggested by this guide:

GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_iommu=on vfio_iommu_type1.allow_unsafe_interrupts=1 pcie_acs_override=downstream i915.enable_hd_vgaarb=1"
2.)Nvidia IDs
lspci -nn | grep NVIDIA
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM107 [GeForce GTX 750 Ti] [10de:1380] (rev a2)
01:00.1 Audio device [0403]: NVIDIA Corporation Device [10de:0fbc] (rev a1)
pci_stub ids=10de:1380,10de:0fbc
5.)Here my script (Here without a rom file assigned, this can be seen in the screen above)


vfiobind() {
        vendor=$(cat /sys/bus/pci/devices/$dev/vendor)
        device=$(cat /sys/bus/pci/devices/$dev/device)
        if [ -e /sys/bus/pci/devices/$dev/driver ]; then
                echo $dev > /sys/bus/pci/devices/$dev/driver/unbind
        echo $vendor $device > /sys/bus/pci/drivers/vfio-pci/new_id

modprobe vfio-pci

cat $configfile | while read line;do
    echo $line | grep ^# >/dev/null 2>&1 && continue
        vfiobind $line

sudo qemu-system-x86_64 -enable-kvm -M q35 -m 4096 -cpu host,kvm=off \
-smp 4,sockets=1,cores=4,threads=1 \
-bios /usr/share/qemu/bios.bin -vga none \
-device ioh3420,bus=pcie.0,addr=1c.0,multifunction=on,port=1,chassis=1,id=root.1 \
-device vfio-pci,host=01:00.0,bus=root.1,addr=00.0,multifunction=on,x-vga=on \
-device vfio-pci,host=01:00.1,bus=root.1,addr=00.1 \
-drive file=/home/jackson/windows.img,id=disk,format=raw -device ide-hd,bus=ide.0,drive=disk \
-drive file=/home/jackson/Downloads/windows.iso,id=isocd -device ide-cd,bus=ide.1,drive=isocd \
-boot menu=on

exit 0
Please help me find out what's wrong.

Thank you!

-- mod edit: read the Forum Etiquette and only post thumbnails [jwr] --
Old 08-04-2015, 05:08 PM   #2
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Registered: Jan 2008
Distribution: Arch/Manjaro, might try Slackware again
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Just a quick suggestion: have you tried following with or without OVMF? It is more up to date. Which Windows are you trying to run? What happens if you try the example in the arch thread, which I've given below?

(For testing I'd separate the vfio bind step of your script from the qemu command step.)

qemu-system-x86_64 -enable-kvm -m 1024 -cpu host,kvm=off \
-smp 4,sockets=1,cores=4,threads=1 \
-device vfio-pci,host=01:00.0,x-vga=on -device vfio-pci,host=01:00.1 \
-vga none
Or the corresponding OVMF example immediately below it?

I presume that you are manually switching the TV inputs from VGA to HDMI with a remote.


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