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Subject: Re: [PATCH V2 5/5] DO NOT MERGE: iommu: disable list appending in
 dma-iommu
To:     Christoph Hellwig <hch@infradead.org>, Tom Murphy <murphyt7@tcd.ie>
References: <20200903201839.7327-1-murphyt7@tcd.ie>
 <20200903201839.7327-6-murphyt7@tcd.ie>
 <20200907070035.GA25114@infradead.org>
 <CALQxJute8_y=JsW4UV1awSccOjxT_1OyPdymq=R_PurVQzENeQ@mail.gmail.com>
 <20200908053619.GA15418@infradead.org> <20200908055510.GA19078@infradead.org>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Message-ID: <9655fdc9-6ea0-e4c1-e104-a9a8981ecb1e@linux.intel.com>
Date:   Tue, 8 Sep 2020 14:04:53 +0800
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Hi Christoph,

On 9/8/20 1:55 PM, Christoph Hellwig wrote:
> On Tue, Sep 08, 2020 at 06:36:19AM +0100, Christoph Hellwig wrote:
>> On Mon, Sep 07, 2020 at 09:18:50PM +0100, Tom Murphy wrote:
>>> Yeah we talked about passing an attr to map_sg to disable merging at
>>> the following microconfernce:
>>> https://linuxplumbersconf.org/event/7/contributions/846/
>>> As far as I can remember everyone seemed happy with that solution. I
>>> won't be working on this though as I don't have any more time to
>>> dedicate to this. It seems Lu Baolu will take over this.
>>
>> I'm absolutely again passing a flag.  Tha just invites further
>> abuse.  We need a PCI ID based quirk or something else that can't
>> be as easily abused.
> 
> Also, I looked at i915 and there are just three dma_map_sg callers.
> The two dmabuf related ones are fixed by Marek in his series, leaving

Do you mind telling where can I find Marek's series?

Best regards,
baolu

> just the one in i915_gem_gtt_prepare_pages, which does indeed look
> very fishy.  But if that one is so hard to fix it can just be replaced
> by an open coded for_each_sg loop that contains manual dma_map_page
> calls.
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