[Qemu-discuss] GPU passthrough not working

[Jan Schermer]

Hi,
hoping someone can help with this.

I ran into several snags trying to setup GPU passthrough on my box. It is the 
only GPU, thus primary.
efifb claims mem region on the GPU so it has to be blacklisted completely, even 
disabling it with video=efifb:off is not enough, the console would no longer 
work but qemu would complain about “BAR 0 unable to reserve….
Not sure if I can somehow get a pure text console when booting in EFI mode, but 
that’s not the main problem.

Once I disabled efifb I was able to start QEMU and pass the GPU to the VM 
(clean Windows 10 install) but only got a black screen. I installed the latest 
AMD Radeon drivers which at some point crashed the VM and only displayed black 
screen on both the physical and virtual GPU.
The VM actually does something with it because it turns back while previously 
it would show the rEFInd boot screen. Now after installing drivers the VM 
starts consuming 100% cpu shortlly after boot  and does not respond to 
anything. If I leave the virtual spice graphics in there it doesn’t work either 
and never displays anything beyong the OVMF splash screen.

Here’s the log from libvirt, the last few lines about irqfd look fishy but I 
have no clue what it is. Can I get some guidance on what to try next? 
Reinstalling in legacy mode? Different drivers? Something wrong with the 
platform itself?

Thank

Jan


2019-06-16 10:30:52.853+0000: starting up libvirt version: 5.2.0, qemu version: 
4.0.0, kernel: 5.1.10-gentoo, hostname: something
LC_ALL=C \
PATH=/bin:/sbin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:/usr/lib/llvm/8/bin:/opt/bin
 \
HOME=/var/lib/libvirt/qemu/domain-1-win10 \
USER=root \
XDG_DATA_HOME=/var/lib/libvirt/qemu/domain-1-win10/.local/share \
XDG_CACHE_HOME=/var/lib/libvirt/qemu/domain-1-win10/.cache \
XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain-1-win10/.config \
QEMU_AUDIO_DRV=none \
/usr/bin/qemu-system-x86_64 \
-name guest=win10,debug-threads=on \
-S \
-object 
secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-1-win10/master-key.aes
 \
-machine pc-q35-4.0,accel=kvm,usb=off,vmport=off,dump-guest-core=off \
-cpu host,hv_relaxed,hv_vapic,hv_spinlocks=0x1fff \
-drive 
file=/usr/share/edk2-ovmf/OVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on \
-drive 
file=/var/lib/libvirt/qemu/nvram/win10_VARS.fd,if=pflash,format=raw,unit=1 \
-m 8192 \
-realtime mlock=off \
-smp 4,sockets=4,cores=1,threads=1 \
-uuid 23b2b99c-acd1-4f51-a49c-60e845a78e77 \
-display none \
-no-user-config \
-nodefaults \
-chardev socket,id=charmonitor,fd=22,server,nowait \
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=localtime,driftfix=slew \
-global kvm-pit.lost_tick_policy=delay \
-no-shutdown \
-global ICH9-LPC.disable_s3=1 \
-global ICH9-LPC.disable_s4=1 \
-boot strict=on \
-device 
pcie-root-port,port=0x10,chassis=1,id=pci.1,bus=pcie.0,multifunction=on,addr=0x2
 \
-device pcie-root-port,port=0x11,chassis=2,id=pci.2,bus=pcie.0,addr=0x2.0x1 \
-device pcie-root-port,port=0x12,chassis=3,id=pci.3,bus=pcie.0,addr=0x2.0x2 \
-device pcie-root-port,port=0x13,chassis=4,id=pci.4,bus=pcie.0,addr=0x2.0x3 \
-device pcie-root-port,port=0x14,chassis=5,id=pci.5,bus=pcie.0,addr=0x2.0x4 \
-device qemu-xhci,p2=15,p3=15,id=usb,bus=pci.2,addr=0x0 \
-drive 
file=/var/lib/libvirt/images/win10.img,format=raw,if=none,id=drive-sata0-0-0,cache=writeback
 \
-device 
ide-hd,bus=ide.0,drive=drive-sata0-0-0,id=sata0-0-0,bootindex=1,write-cache=on \
-drive 
file=/var/lib/libvirt/images/Win10_1903_V1_EnglishInternational_x64.iso,format=raw,if=none,id=drive-sata0-0-1,readonly=on
 \
-device ide-cd,bus=ide.1,drive=drive-sata0-0-1,id=sata0-0-1 \
-netdev tap,fd=24,id=hostnet0 \
-device e1000e,netdev=hostnet0,id=net0,mac=52:54:00:f7:29:d3,bus=pci.1,addr=0x0 
\
-chardev pty,id=charserial0 \
-device isa-serial,chardev=charserial0,id=serial0 \
-device 
vfio-pci,host=25:00.0,id=hostdev0,bus=pci.4,multifunction=on,addr=0x0,rombar=1,romfile=/etc/libvirt/rom/Sapphire.RXVega64.8192.180125_1.rom
 \
-device vfio-pci,host=25:00.1,id=hostdev1,bus=pci.4,addr=0x0.0x1 \
-device virtio-balloon-pci,id=balloon0,bus=pci.3,addr=0x0 \
-sandbox 
on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
-msg timestamp=on
2019-06-16 10:30:52.853+0000: Domain id=1 is tainted: host-cpu
2019-06-16 10:30:52.853+0000: Domain id=1 is tainted: shell-scripts
char device redirected to /dev/pts/2 (label charserial0)
2019-06-16T10:30:54.178752Z qemu-system-x86_64: -device 
vfio-pci,host=25:00.0,id=hostdev0,bus=pci.4,multifunction=on,addr=0x0,rombar=1,romfile=/etc/libvirt/rom/Sapphire.RXVega64.8192.180125_1.rom:
 warning: vfio 0000:25
:00.0: failed to setup resample irqfd: Invalid argument
2019-06-16T10:30:54.213972Z qemu-system-x86_64: -device 
vfio-pci,host=25:00.1,id=hostdev1,bus=pci.4,addr=0x0.0x1: warning: vfio 
0000:25:00.1: failed to setup resample irqfd: Invalid argument
2019-06-16T10:30:55.253317Z qemu-system-x86_64: warning: vfio 0000:25:00.0: 
failed to setup resample irqfd: Invalid argument
2019-06-16T10:30:55.253369Z qemu-system-x86_64: warning: vfio 0000:25:00.1: 
failed to setup resample irqfd: Invalid argument
2019-06-16T10:30:55.253463Z qemu-system-x86_64: warning: vfio 0000:25:00.1: 
failed to setup resample irqfd: Invalid argument
2019-06-16T10:30:55.253523Z qemu-system-x86_64: warning: vfio 0000:25:00.0: 
failed to setup resample irqfd: Invalid argument