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

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Message-ID: <CAGXu5jJZhqu_o+k0MOqG3XADV5xhQM9g=H3ZCMODRkCKyisUcw@mail.gmail.com>
Date:   Mon, 5 Dec 2016 15:16:22 -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 2:47 PM, David Woodhouse <dwmw2@...radead.org> wrote:
> On Mon, 2016-12-05 at 14:18 -0800, Kees Cook wrote:
>> Hm, I have no idea. :) What would I look for in the BIOS?
>
> For a start, what is the actual failure mode?

Based on initial testing (not that I've spent tons of time with it,
since I need that machine running): at graphics init, entire system
hangs. :P

>> I figured since g4 was busted, surely q35 was too, since it's even
>> older...
>
> Oh no, they all have different failures. Intel never actually *tested*
> their graphics hardware before shipping it, but IIRC it was only Q4x
> where we concluded the hardware was just too broken to live.

Wheee!

-Kees

-- 
Kees Cook
Nexus Security