[vfio-users] Cannot get vfio-pci to work

[Alex Williamson]

[cc +vfio-users]

On Thu, 16 Aug 2018 18:39:18 +0200
Jes Urup <jes at urup.me> wrote:

> Okay, i thought that i should add a network card to the vm and select the
> physical nic.
> So i now tried to add the physical nic from "PCI Host Device", but i then
> get this error when i try to start it: 0000:04:00.0: no such host device:
> Permission denied.
> Hope you can help with that error or guide me to where i can get help with
> that.
> And thanks for your quick replies!

The board is sufficiently old that perhaps the processor is missing or
has broken and disabled interrupt remapping, in which case dmesg would
be telling you:

	No interrupt remapping support.  Use the module param
	"allow_unsafe_interrupts" to enable VFIO IOMMU support on this
	platform

This puts your system at risk of a malicious guest trying to exploit
interrupts via DMA.  If you opt-in to this risk, then update your
modprobe.d with:

options vfio_iommu_type1 allow_unsafe_interrupts=1

Thanks,
Alex