linux-kernel - Re: [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx

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Message-ID: <CAGXu5j+QJZk9PghXdo=3Rp-noshG-GeSKxn+nuicqpRgFiiR5w@mail.gmail.com>
Date:   Mon, 5 Dec 2016 14:18:29 -0800
From:   Kees Cook <keescook@...omium.org>
To:     David Woodhouse <dwmw2@...radead.org>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        iommu@...ts.linux-foundation.org,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        intel-gfx@...ts.freedesktop.org, Joerg Roedel <joro@...tes.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx

On Mon, Dec 5, 2016 at 2:07 PM, David Woodhouse <dwmw2@...radead.org> wrote:
> On Mon, 2016-12-05 at 13:58 -0800, Kees Cook wrote:
>> This blacklists the Q35 integrated graphics so IOMMU can be otherwise
>> enabled. Without this, a Q35 system can only enable IOMMU when booting
>> with "intel_iommu=on,igfx_off" but not "intel_iommu=on".
>
> Hm, is this definitely the same bug? Or is it something different, and
> perhaps a BIOS issue? There are many of those...

Hm, I have no idea. :) What would I look for in the BIOS?

I figured since g4 was busted, surely q35 was too, since it's even older...

-Kees

-- 
Kees Cook
Nexus Security