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Date:   Mon, 7 Sep 2020 08:00:35 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Tom Murphy <murphyt7@tcd.ie>
Cc:     iommu@lists.linux-foundation.org,
        David Woodhouse <dwmw2@infradead.org>,
        linux-kernel@vger.kernel.org,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH V2 5/5] DO NOT MERGE: iommu: disable list appending in
 dma-iommu
Message-ID: <20200907070035.GA25114@infradead.org>
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 <20200903201839.7327-6-murphyt7@tcd.ie>
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On Thu, Sep 03, 2020 at 09:18:37PM +0100, Tom Murphy wrote:
> Disable combining sg segments in the dma-iommu api.
> Combining the sg segments exposes a bug in the intel i915 driver which
> causes visual artifacts and the screen to freeze. This is most likely
> because of how the i915 handles the returned list. It probably doesn't
> respect the returned value specifying the number of elements in the list
> and instead depends on the previous behaviour of the intel iommu driver
> which would return the same number of elements in the output list as in
> the input list.

So what is the state of addressing this properly in i915?  IF we can't
get it done ASAP I wonder if we need a runtime quirk to disable
merging instead of blocking this conversion..