[CentOS-virt] PCI Passthrough not working

[George Dunlap]

On Wed, Jun 22, 2016 at 10:56 AM, Francis Greaves <francis at choughs.net> wrote:
> Further to my messages back in May I have at last got round to trying to
> get my DomU to recognise USB devices.
>
> I am using Xen 4.6 with CentOS kernel 3.18.34-20.el7.x86_64.
> I have to manually make the port available before creating the DomU by
> issuing the command:
> xl pci-assignable-add 00:1a.0
> otherwise nothing shows in:
> xl pci-assignable-list
>
> I have added this to my .cfg file as per the May Emails:
> pci=['00:1a.0,rdm_policy=relaxed']

The two-stage process for assigning pci devices (first
pci-assignible-add, then pci-add) is a "seatbelt" to make sure that an
accidental mis-type doesn't cause you to grab (say) your hard disk
controller instead of your USB controller.

You can add "seize=1" to your pci string to have xl automatically do
both steps for you.  Obviously, use this with care. :-)

More on your next post...

 -George