linux-kernel - Re: [PATCH] iommu/intel: quirk to disable DMAR for QM57 igfx

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Message-ID: <20190123164959.GF32526@8bytes.org>
Date:   Wed, 23 Jan 2019 17:49:59 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc:     Daniel Vetter <daniel@...ll.ch>, Eric Wong <e@...24.org>,
        David Woodhouse <dwmw2@...radead.org>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>, " <iommu@...ts.linux-foundation.org>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/intel: quirk to disable DMAR for QM57 igfx

On Wed, Jan 23, 2019 at 05:02:38PM +0200, Joonas Lahtinen wrote:
> We have many reports where just having intel_iommu=on (and using the
> system normally, without any virtualization stuff going on) will cause
> unexplained GPU hangs. For those users, simply switching to
> intel_iommu=igfx_off solves the problems, and the debug often ends
> there.

If you can reproduce problems on your side, then you can try to enable
CONFIG_INTEL_IOMMU_BROKEN_GFX_WA to force the GFX devices into the
identity mapping. We can also add a boot-parameter and workarounds if it
turns out that this is sufficient to make the GFX devices work with
IOMMU enabled.


Regards,

	Joerg