KVM - Enable Direct PCI Pass-Through

This example was done on Ubuntu server.

* Enable VM direct I/O in the BIOS.
* Open /etc/default/grub using an editor like nano or something.
* Find GRUB_CMDLINE_LINUX_DEFAULT and add intel_iommu=on as a parameter.  Make sure it's lowercase.  Save and exit.
* update-grub
* shutdown -r now
* dmesg | grep -e DMAR -e IOMMU and you should see a line in there stating that IOMMU is enabled.