Re: [Intel-gfx] [PATCH 0/8] Convert the intel iommu driver to the dma-iommu api

From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Tom Murphy <murphyt7@tcd.ie>
Cc: kvm@vger.kernel.org, David Airlie <airlied@linux.ie>,
	dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org,
	Julien Grall <julien.grall@arm.com>,
	Will Deacon <will@kernel.org>,
	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>,
	linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org,
	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>,
	Logan Gunthorpe <logang@deltatee.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>
Subject: Re: [Intel-gfx] [PATCH 0/8] Convert the intel iommu driver to the dma-iommu api
Date: Wed, 9 Sep 2020 13:55:49 +0100	[thread overview]
Message-ID: <ea24e077-5aa6-dd8e-69a7-d186b606703f@linux.intel.com> (raw)
In-Reply-To: <7106602a-9964-851e-9c4e-d8acf4033b89@linux.intel.com>

On 09/09/2020 10:16, Tvrtko Ursulin wrote:
> 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.

Our CI was more than capable at catching the breakage so I've copied you 
on a patch (https://patchwork.freedesktop.org/series/81497/) which has a 
good potential to fix this. (Or improve the robustness of our sg walks, 
depends how you look at it.)

Would you be able to test it in your environment by any chance? If it 
works I understand it unblocks your IOMMU work, right?

Regards,

Tvrtko
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