Invalid PCI ROM header signature when attempting GPU passthrough

Hello,

I am trying to passthrough a GTX 760 to my Ubuntu Server VM, using an ASRock X99 Extreme4 motherboard, E5-2683 V3 and an NVS 440 for console output.

The VM will boot to GRUB, and after selecting Ubuntu, it will display a black screen.

Here is the system log:

May 4 17:52:05 unraid-srv kernel: vgaarb: device changed decodes: PCI:0000:06:00.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
May 4 17:52:06 unraid-srv kernel: br0: port 2(vnet0) entered blocking state
May 4 17:52:06 unraid-srv kernel: br0: port 2(vnet0) entered disabled state
May 4 17:52:06 unraid-srv kernel: device vnet0 entered promiscuous mode
May 4 17:52:06 unraid-srv kernel: br0: port 2(vnet0) entered blocking state
May 4 17:52:06 unraid-srv kernel: br0: port 2(vnet0) entered forwarding state
May 4 17:52:08 unraid-srv kernel: vfio_ecap_init: 0000:06:00.0 hiding ecap 0x19@0x900
May 4 17:52:08 unraid-srv kernel: pmd_set_huge: Cannot satisfy [mem 0xc8000000-0xc8200000] with a huge-page mapping due to MTRR override.
May 4 17:52:15 unraid-srv kernel: vfio-pci 0000:06:00.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0xffff
May 4 17:52:15 unraid-srv kernel: vfio-pci 0000:06:00.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0xffff
May 4 17:52:27 unraid-srv kernel: kvm: zapping shadow pages for mmio generation wraparound
May 4 17:52:27 unraid-srv kernel: kvm: zapping shadow pages for mmio generation wraparound
May 4 17:52:42 unraid-srv kernel: kvm [24235]: vcpu0, guest rIP: 0xffffffff810644b6 unhandled rdmsr: 0x1c9
May 4 17:52:42 unraid-srv kernel: kvm [24235]: vcpu0, guest rIP: 0xffffffff810644b6 unhandled rdmsr: 0x1a6
May 4 17:52:42 unraid-srv kernel: kvm [24235]: vcpu0, guest rIP: 0xffffffff810644b6 unhandled rdmsr: 0x1a7
May 4 17:52:42 unraid-srv kernel: kvm [24235]: vcpu0, guest rIP: 0xffffffff810644b6 unhandled rdmsr: 0x3f6
May 4 17:52:42 unraid-srv kernel: hrtimer: interrupt took 2867278 ns
May 4 17:52:43 unraid-srv kernel: perf: interrupt took too long (2969 > 2500), lowering kernel.perf_event_max_sample_rate to 67000
May 4 17:52:44 unraid-srv kernel: perf: interrupt took too long (5154 > 3711), lowering kernel.perf_event_max_sample_rate to 38000
May 4 17:52:45 unraid-srv kernel: perf: interrupt took too long (6565 > 6442), lowering kernel.perf_event_max_sample_rate to 30000
May 4 17:52:46 unraid-srv kernel: perf: interrupt took too long (9287 > 8206), lowering kernel.perf_event_max_sample_rate to 21000
May 4 17:52:48 unraid-srv kernel: perf: interrupt took too long (13681 > 11608), lowering kernel.perf_event_max_sample_rate to 14000
May 4 17:52:50 unraid-srv kernel: perf: interrupt took too long (18558 > 17101), lowering kernel.perf_event_max_sample_rate to 10000
May 4 17:52:53 unraid-srv kernel: perf: interrupt took too long (23775 > 23197), lowering kernel.perf_event_max_sample_rate to 8000
May 4 17:52:57 unraid-srv kernel: perf: interrupt took too long (32332 > 29718), lowering kernel.perf_event_max_sample_rate to 6000

And the VM log:

2017-05-04 16:52:06.088+0000: starting up libvirt version: 2.4.0, qemu version: 2.7.1, hostname: unraid-srv
LC_ALL=C PATH=/bin:/sbin:/usr/bin:/usr/sbin HOME=/ QEMU_AUDIO_DRV=none /usr/local/sbin/qemu -name 'guest=Ubuntu Server,debug-threads=on' -S -object 'secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-1-Ubuntu Server/master-key.aes' -machine pc-q35-2.7,accel=kvm,usb=off,dump-guest-core=off,mem-merge=off -cpu host -drive file=/usr/share/qemu/ovmf-x64/OVMF_CODE-pure-efi.fd,if=pflash,format=raw,unit=0,readonly=on -drive file=/etc/libvirt/qemu/nvram/e3c32728-a5c6-2ea2-78bf-0ac7fbdb0d91_VARS-pure-efi.fd,if=pflash,format=raw,unit=1 -m 16384 -realtime mlock=off -smp 24,sockets=1,cores=12,threads=2 -uuid e3c32728-a5c6-2ea2-78bf-0ac7fbdb0d91 -no-user-config -nodefaults -chardev 'socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-1-Ubuntu Server/monitor.sock,server,nowait' -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=discard -no-hpet -no-shutdown -boot strict=on -device i82801b11-bridge,id=pci.1,,bus=usb.0,port=1 -vnc 0.0.0.0:0,websocket=5700 -k en-us -device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vram64_size_mb=0,vgamem_mb=16,max_outputs=1,bus=pcie.0,addr=0x1 -device vfio-pci,host=06:00.0,id=hostdev0,bus=pci.2,addr=0x5 -device virtio-balloon-pci,id=balloon0,bus=pci.2,addr=0x6 -msg timestamp=on
Domain id=1 is tainted: high-privileges
Domain id=1 is tainted: host-cpu
char device redirected to /dev/pts/1 (label charserial0)

Any advice or help would be greatly appreciated.

Thanks!