From mboxrd@z Thu Jan  1 00:00:00 1970
From: Darren Hart <dvhart@infradead.org>
Subject: Re: [Patch v3] apple-gmux: lock iGP IO to protect from vgaarb changes
Date: Mon, 1 Jun 2015 19:31:58 +0200
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Cc: Michael Marineau <michael.marineau@coreos.com>, Bjorn Helgaas <bhelgaas@google.com>, platform-driver-x86@vger.kernel.org, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Petri Hodju <petrihodju@yahoo.com>, Matthew Garrett <matthew.garrett@nebula.com>, "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
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On Mon, Jun 01, 2015 at 08:22:27AM +0200, Bruno Pr=E9mont wrote:
> On Fri, 29 May 2015 18:36:50 +0200 Darren Hart wrote:
> > > Making sure to lock only the intel GPU when present and especiall=
y protecting
> > > against nvidia driver will be hard if legacy-IO is being processe=
d by a hidden
> > > device!
> >=20
> > Ugh indeed. Worst case we can special case via dmi strings. Is this=
 Apple device
> > significantly different from others? Bruno, what are you testing on=
?
>=20
> I only own a pretty old MacBook Air with just NVIDIA IGP and had to
> rely on BUG reports and testing from affected users.
>=20
> Not doing anything on apple-gmux when only a single GPU is visible
> should be easy, but denying any vgaarb operation when Intel IGP is
> hidden and just discrete GPU present is much harder (if one does not
> want to risk opening the next can of worms).
>=20
> DMI based special-casing would work but will it uncover the next issu=
e
> with the same device configured differently?

No, we would need a combination. I presume "configured differently" wou=
ld mean
the Intel GPU present - which would be detectable.

DMI + Nvidia =3D do A
DMI + Intel =3D do B

--=20
Darren Hart
Intel Open Source Technology Center