[vfio-users] Igd passthrough not working on w10, works with ubuntu

[Alex Williamson]

[re-adding vfio-users]

On Mon, 11 Mar 2019 18:23:14 +0100
Cor Saelmans <c.saelmans at gmail.com> wrote:

> Thank you Alex for your reply.
> 
> I tested earlier today with a fresh install of my ubuntu host in legacy
> mode and this worked directly without any further customization.
> 
> Just reinstalled my host back to EFI and tried your suggestion, but without
> any result.
> 
> I did not know display output is not supported with upt.
> 
> I reinstalled my host again in legacy mode.

The legacy mode I'm referring to is specifically for the VM, not the
host, see:

https://git.qemu.org/?p=qemu.git;a=blob;f=docs/igd-assign.txt;hb=HEAD

The host can make a difference though, but it's usually in the
availability of the vBIOS.  For instance since we really only support
SeaBIOS in the guest with physical IGD assignment, it may be necessary
to boot the host in legacy mode to dump a legacy compatible ROM image
for the device.  The ROM image file can then be used for the VM
regardless of the host booting via legacy or EFI.  The entire idea of
"support" with physical IGD assignment is a bit of a misnomer, Intel
seems to have mostly abandoned the idea of Universal Passthrough Mode
and IGD legacy mode is barely supportable by it's very nature and lack
of standards within the hardware.  Intel vGPU is closer to supported,
but does not currently have an option for controlling the physical
display output.  There is QEMU "display" support though, which can make
local graphics fairly efficient, but the output is still controlled by
the host drivers.  Thanks,

Alex