VGA Passthrough
Requirements
For intel:
CPU that supports Vt-d and Vt-x
Motherboard that supports Vt-d
Vt-d and Vt-x must be enabled in BIOS or UEFI
For AMD
CPU that supports IOMMU and VMX
Motherboard that supports IOMMU
IOMMU and VMX must be enabled in BIOS or UEFI
Video Card
Most Radeon HD cards support vga passthrough
Only the Quatro Nvidia cards support vga passthrough
Some Intel graphics work with vga passthrough
Software Requirements
Examples
Example XEN passthrough config
# nut sure if really needed
kernel="/usr/lib/xen-default/boot/hvmloader"
builder = "hvm"
name = "win7x64-hvm"
# RAM size in MB
memory = "4096"
# number CPU cores
vcpus = 2
vif = ['type=ioemu']
# boot from cd and hdd
disk = ['phy:/dev/virtual-machines/win7x64,hda,w','file:/home/user/images/WIN_7_PROFESSIONAL.iso,hdc:cdrom,r']
boot="dc"
# boot from hdd
#disk = ['phy:/dev/virtual-machines/win7x64,hda,w']
#boot="c"
# enable remote vnc access until video card driver is installed
vnc = 1
acpi=1
sdl=0
serial='pty'
# list your pci devices (HD7950,HD7950,USB)
pci=['01:00.0','01:00.1','00:1a.0']
Sound and USB
Since the physical video output of the passed video card is used there will be no SDL/VNC screen this means that a sound card must also be passed for the vm to have sound
For that same reason as above you will want to pass one USB controller for input
Sources