PCI pass trhough allows you to use a physical PCI device ( graphic card, network card ...) form your host directly on the VM (KVM only) If you "PCI passthrough" a device, the device is not available in the host anymore, only in the VM.
To enable PCI passthrough, you need to configure:
# update-grub # reboot
Then run "dmesg | grep -e DMAR -e IOMMU" from the command line. If there is no output, then something is wrong.
# vi /etc/default/grub
# update-grub # echo "options kvm allow_unsafe_assigned_interrupts=1" > /etc/modprobe.d/kvm_iommu_map_guest.conf # reboot
Determine your PCI card address, and configure your VM
Locate your card using "lspci". The address should be in the form of: 04:00.0
Manually edit the node.conf file. It can be located at: /etc/pve/nodes/proxmox3/qemu-server/vmnumber.conf.
Add this line to the end of the file: "hostpci0: 04:00.0"
Start the VM from the UI.
Enter the qm monitor. "qm monitor vmnumber"
Verify that your card is listed here: "info pci"
Then install drivers on your guest OS.
NOTE: Card support might be limited to 2 or 3 devices.
NOTE: This process will remove the card from the proxmox host OS.
Editorial Note: Using PCI passthrough to present drives direct to a ZFS (FreeNAS, Openfiler, OmniOS) virtual machine is dangerous on many levels and is not recommended for production use. Specific FreeNAS warnings can be found here: http://forums.freenas.org/threads/absolutely-must-virtualize-freenas-a-guide-to-not-completely-losing-your-data.12714/
PCI EXPRESS PASSTHROUGH
Since proxmox 3.3, it's possible to passthrough pci express device (including nvidia/amd graphic card)
you need to run pve-kernel 3.10
simple pci-express passthrough
machine: q35 hostpci0: 04:00.0,pcie=1,driver=vfio
vga pci-express passthrough
machine: q35 hostpci0: 04:00.0,x-vga=on,pcie=1,driver=vfio
multi-function pciexpress device. (like a vga card with embedded audio chipset).
Remove the .0 in pci address.
machine: q35 hostpci0: 04:00,x-vga=on,pcie=1,driver=vfio
GPU PASSTHROUGH NOTES
MD RADEON 5xxx, 6xxx, 7xxx and NVIDIA GEFORCE 7, 8, 4xx, 5xx, 6xx, 7xx have been reported working.
intel IGD'S WONT WORK currently with proxmox kernel 3.10, try with debian kernel > 3.16.
Maybe you'll need to load some specific options in grub.cfg or other tunning values,
here a good forum thread of archlinux:
AMD passthrough error
kvm: -device vfio-pci,host=01:00.0,id=hostpci0.0,bus=ich9-pcie-port-1,addr=0x0.0,x-vga=on,multifunction=on: vfio: error opening /dev/vfio/1: No such file or directory kvm: -device vfio-pci,host=01:00.0,id=hostpci0.0,bus=ich9-pcie-port-1,addr=0x0.0,x-vga=on,multifunction=on: vfio: failed to get group 1 kvm: -device vfio-pci,host=01:00.0,id=hostpci0.0,bus=ich9-pcie-port-1,addr=0x0.0,x-vga=on,multifunction=on: Device initialization failed. kvm: -device vfio-pci,host=01:00.0,id=hostpci0.0,bus=ich9-pcie-port-1,addr=0x0.0,x-vga=on,multifunction=on: Device 'vfio-pci' could not be initialized
If you have this error, you need to pass "pcie_acs_override=downstream" to grub options to get iommu group working correctly
you can also try to add this option
echo "options vfio_iommu_type1 allow_unsafe_interrupts=1" > /etc/modprobe.d/iommu_unsafe_interrupts.conf
WORKING NVIDIA SETUP
I've been able to get this working with an NVIDIA GTX 750 Ti card using driver version 344.75 (newer versions inconsistently cause Code 43 Errors) by using the following setup:
Add to /etc/modules: pci_stub vfio vfio_iommu_type1 vfio_pci kvm kvm_intel
Add the following options to /etc/default/grub on the GRUB_CMDLINE_LINUX_DEFAULT line:
intel_iommu=on vfio_iommu_type1.allow_unsafe_interrupts=1 rootdelay=10 scsi_mod.scan=sync
Add the following to /etc/initramfs-tools/modules (find the PCI stub IDs for your card by running lspci -nn | grep NVIDIA): pci_stub ids=10de:0f02,10de:0bea
Run: update-initramfs -u and then reboot into the new kernel.
Boot into the VM using the Proxmox web interface, and install the OS (I had better luck with Windows 8.1 - can't remember specifics though).
Add the following options to /etc/pve/host/qemu-server/vmid.conf (get the PCI address from lspci command, and I added the USB device address for my Avocent KVM DSRIQ USB module, you can do the same for a physical keyboard and mouse):
hostpci0: 05:00,x-vga=on,pcie=1,driver=vfio machine: q35 usb0: host=0624:0307