linux-kernel - Re: [PATCH 2/2] vfio/pci: Remove console drivers

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Date:   Sat, 3 Dec 2022 17:12:38 -0700
From:   "mb@....how" <mb@....how>
To:     alex.williamson@...hat.com
Cc:     airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        kraxel@...hat.com, kvm@...r.kernel.org, lersek@...hat.com,
        linux-kernel@...r.kernel.org, tzimmermann@...e.de
Subject: Re: [PATCH 2/2] vfio/pci: Remove console drivers

Hi,

I hope it is ok to reply to this old thread. Unfortunately, I found a
problem only now after upgrading to 6.0.

My setup has multiple GPUs (2), and I depend on EFIFB to have a working console.
pre-patch behavior, when I bind the vfio-pci to my secondary GPU both
the passthrough and the EFIFB keep working fine.
post-patch behavior, when I bind the vfio-pci to the secondary GPU,
the EFIFB disappears from the system, binding the console to the
"dummy console".
Whenever you try to access the terminal, you have the screen stuck in
whatever was the last buffer content, which gives the impression of
"freezing," but I can still type.
Everything else works, including the passthrough.

I can only think about a few options:

- Is there a way to have EFIFB show up again? After all it looks like
the kernel has just abandoned it, but the buffer is still there. I
can't find a single message about the secondary card and EFIFB in
dmesg, but there's a message for the primary card and EFIFB.
- Can we have a boolean controlling the behavior of vfio-pci
altogether or at least controlling the behavior of vfio-pci for that
specific ID? I know there's already some option for vfio-pci and VGA
cards, would it be appropriate to attach this behavior to that option?

Thanks,

Carlos Augusto