Re: Intel IGD passthrough working intermittently

[Marco]

On Wed, Oct 2, 2024 at 2:30 PM Corvin Köhne <C.Koehne@beckhoff.com> wrote:
>
> First of all, you should make sure to pass the correct gms value to the
> guest. I've already seen issues when passing the wrong value to guests.
> That's why I've recently send a patch to qemu to always reuse the host
> value [1].

Ok thanks, I seem to understand I should use the same value that the
host uses, but how do I figure out that value?

> I assume that you're booting in UEFI mode by using OVMF?

I'm booting using SeaBios, as my understanding from reading various
sources (vfio mailing list and forums) is that it wouldn't work at all
with OVMF (in fact I even think I tried EFI at the beginning, and
never got any output).
I might try again, just in case.
One thing I didn't mention: I've tried using various machine types
from pc-q35-6.2 up to pc-q35-8.2 without any noticeable change.

> I don't know why it boots sometimes fine and sometimes not. However,
> your black screen at boot is caused by a missing GOP. It's the EFI
> graphics driver. That's why you only get graphics output when an OS
> driver like i915 or the Windows driver is available. Unfortunately,
> there're currently some constraints making it very hard to get a working
> GOP:

That's fine for my use case. I don't mind if I cannot see the initial
part of the boot, as long as the windows part works reliably (which it
doesn't at the moment, as explained).

Thanks!