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Subject: Re: [Intel-gfx] [PATCH 0/8] Convert the intel iommu driver to the
 dma-iommu api
To:     Tom Murphy <murphyt7@tcd.ie>
Cc:     Logan Gunthorpe <logang@deltatee.com>, kvm@vger.kernel.org,
        David Airlie <airlied@linux.ie>,
        dri-devel@lists.freedesktop.org,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        linux-tegra@vger.kernel.org, Julien Grall <julien.grall@arm.com>,
        Will Deacon <will@kernel.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        linux-samsung-soc@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        linux-rockchip@lists.infradead.org, Andy Gross <agross@kernel.org>,
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        linux-arm-msm@vger.kernel.org, intel-gfx@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        virtualization@lists.linux-foundation.org,
        Gerald Schaefer <gerald.schaefer@de.ibm.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Cornelia Huck <cohuck@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        iommu@lists.linux-foundation.org, Kukjin Kim <kgene@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>
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 <465815ae-9292-f37a-59b9-03949cb68460@deltatee.com>
 <20200529124523.GA11817@infradead.org>
 <CGME20200529190523eucas1p2c086133e707257c0cdc002f502d4f51d@eucas1p2.samsung.com>
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 <b27cae1f-07ff-bef2-f125-a5f0d968016d@linux.intel.com>
 <CALQxJut5c=cWdi+SVkN3JnbkhPSYmLkOyRUhduL-UJ9gyKn9Ow@mail.gmail.com>
From:   Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Organization: Intel Corporation UK Plc
Message-ID: <7106602a-9964-851e-9c4e-d8acf4033b89@linux.intel.com>
Date:   Wed, 9 Sep 2020 10:16:38 +0100
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On 08/09/2020 23:43, Tom Murphy wrote:
> On Tue, 8 Sep 2020 at 16:56, Tvrtko Ursulin
> <tvrtko.ursulin@linux.intel.com> wrote:
>>
>>
>> On 08/09/2020 16:44, Logan Gunthorpe wrote:
>>> On 2020-09-08 9:28 a.m., Tvrtko Ursulin wrote:
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h
>>>>> b/drivers/gpu/drm/i915/i915
>>>>> index b7b59328cb76..9367ac801f0c 100644
>>>>> --- a/drivers/gpu/drm/i915/i915_scatterlist.h
>>>>> +++ b/drivers/gpu/drm/i915/i915_scatterlist.h
>>>>> @@ -27,13 +27,19 @@ static __always_inline struct sgt_iter {
>>>>>     } __sgt_iter(struct scatterlist *sgl, bool dma) {
>>>>>            struct sgt_iter s = { .sgp = sgl };
>>>>>
>>>>> +       if (sgl && !sg_dma_len(s.sgp))
>>>>
>>>> I'd extend the condition to be, just to be safe:
>>>>       if (dma && sgl && !sg_dma_len(s.sgp))
>>>>
>>>
>>> Right, good catch, that's definitely necessary.
>>>
>>>>> +               s.sgp = NULL;
>>>>> +
>>>>>            if (s.sgp) {
>>>>>                    s.max = s.curr = s.sgp->offset;
>>>>> -               s.max += s.sgp->length;
>>>>> -               if (dma)
>>>>> +
>>>>> +               if (dma) {
>>>>> +                       s.max += sg_dma_len(s.sgp);
>>>>>                            s.dma = sg_dma_address(s.sgp);
>>>>> -               else
>>>>> +               } else {
>>>>> +                       s.max += s.sgp->length;
>>>>>                            s.pfn = page_to_pfn(sg_page(s.sgp));
>>>>> +               }
>>>>
>>>> Otherwise has this been tested or alternatively how to test it? (How to
>>>> repro the issue.)
>>>
>>> It has not been tested. To test it, you need Tom's patch set without the
>>> last "DO NOT MERGE" patch:
>>>
>>> https://lkml.kernel.org/lkml/20200907070035.GA25114@infradead.org/T/
>>
>> Tom, do you have a branch somewhere I could pull from? (Just being lazy
>> about downloading a bunch of messages from the archives.)
> 
> I don't unfortunately. I'm working locally with poor internet.
> 
>>
>> What GPU is in your Lenovo x1 carbon 5th generation and what
>> graphical/desktop setup I need to repro?
> 
> 
> Is this enough info?:
> 
> $ lspci -vnn | grep VGA -A 12
> 00:02.0 VGA compatible controller [0300]: Intel Corporation HD
> Graphics 620 [8086:5916] (rev 02) (prog-if 00 [VGA controller])
>      Subsystem: Lenovo ThinkPad X1 Carbon 5th Gen [17aa:224f]
>      Flags: bus master, fast devsel, latency 0, IRQ 148
>      Memory at eb000000 (64-bit, non-prefetchable) [size=16M]
>      Memory at 60000000 (64-bit, prefetchable) [size=256M]
>      I/O ports at e000 [size=64]
>      [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
>      Capabilities: [40] Vendor Specific Information: Len=0c <?>
>      Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
>      Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
>      Capabilities: [d0] Power Management version 2
>      Capabilities: [100] Process Address Space ID (PASID)
>      Capabilities: [200] Address Translation Service (ATS)

Works for a start. What about the steps to repro? Any desktop 
environment and it is just visual corruption, no hangs/stalls or such?

I've submitted a series consisting of what I understood are the patches 
needed to repro the issue to our automated CI here:

https://patchwork.freedesktop.org/series/81489/

So will see if it will catch something, or more targeted testing will be 
required. Hopefully it does trip over in which case I can add the patch 
suggested by Logan on top and see if that fixes it. Or I'll need to 
write a new test case.

If you could glance over my series to check I identified the patches 
correctly it would be appreciated.

Regards,

Tvrtko