The guest virtual machine is not receiving a signal to it's monitor when turning on the Virtual Machine if it's physical GPU or it's physical sound are assigned to it. Please help? 
The host's monitor seems to freeze or perhaps it's just the inputs that are freezing like the keyboard and mouse being switched to the VM, however that does not occur unless the passthrough GPU or it's sound is assigned to the Virtual Machine.
Checklist:
1. CPU supports VT-x, VT-d, ACS & EPT.
2. Motherboard supports VT-d.
3. Passthrough GPU supports UEFI.
4. The two GPU's are not identical, both are different generations, and both are NVidia.
5. The guest monitor is plugged into the GPU that will be passed through and it is turned on and set to display through said cable
6. The GPU as well as the monitor that will be assigned to the guest are not damaged in any way and if the GPU Passthrough works, they should be functioning properly.
7. VT-d is turned on in the bios.
8. CPU: "virtualization extensions available"
9. IOMMU is turned on. [ 0.000000] DMAR: IOMMU enabled [ 10.892650] DMAR: Intel(R) Virtualization Technology for Directed I/O
11. The devices I'm trying to pass through support resetting.
12. The PCI groups are valid.
13. These are installed: qemu-kvm, seabios, qemu-utils, hugepages, bridge-utils & ovmf.
14. Testing unbinding the PCI Stub from the Passthrough GPU through the terminal works properly and does not freeze the host monitor or inputs.
15. The GPU that will be passed through as well as it's High Definition Audio Controller are claimed by PCI Stub. "claimed by stub"
16. I created the /etc/modprobe.d/kvm_iommu.conf with: options kvm allow_unsafe_assigned_interrupts=1
17. The guest OS installs and run fine when using the host's GPU & monitor.
18. I don't see any errors from virt-manager.
19. I removed the default: spice server & it's associated GPU, spice channel, CD-ROM Device, Sound, Serial, VIrtio Serial, USB Directors and tablet from the virt manager setup..
20. KVM hidden state, is turned on in the xml of the VM:
<features> <acpi/> <apic/> <kvm> <hidden state='on'/> </kvm> </features> <cpu mode='host-passthrough'/> <clock offset='localtime'> <timer name='rtc' tickpolicy='catchup'/> <timer name='pit' tickpolicy='delay'/> <timer name='hpet' present='no'/> </clock>
'QEMU/KVM Connection Details'
TBD
'Virtual Machine Manager Settings:'
Overview:
Hypervisor Details:
Hypervisor: KVM
Architecture: x86_64
Emulator: /usr/bin/kvm-spice
Firmware: UEFI x86_64: /usr/share/OVMF/OVMF_CODE.fd
Chipset: i440FX
CPUs:
CPUs:
Local host CPUs: 12
Current Allocation: 8
Maximum Allocation: 8
Configuration:
Model: host-passthrough
Memory:
Memory:
Total host memory: 16010 MiB
Current allocation: 7096
Maximum allocation: 7096 MiB
Boot Options:
Boot device order:
IDE Disk 1
IDE Disk 1:
Virtual Disk:
Advanced Options:
Disk Bus: IDE
Storage Format: raw
Mouse:
Virtual Input Device:
Type: Generic PS2 Mouse
Mode: Relative Movement
'(Not able to be removed as the button is greyed out)'
Keyboard:
Virtual Input Device:
Type: Generic PS2 Keyboard
'(Not able to be removed as the button is greyed out)'
PCI '(My PCI address here)':
Physical PCI Device:
Device: '(My GPU and its address here)'
ROM BAR: Checked
PCI '(My PCI address here)':
Physical PCI Device:
Device: '(My GPUs High Definition Audio Controller and its address here)'
ROM BAR: Checked
Controller USB:
Type: USB
Model: USB 2
Controller PCI:
Type: PCI
Model: pci-root
Controller IDE:
Controller:
Type: IDE
'(Not able to be removed as the button is greyed out)'