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

Tvrtko Ursulin
2020-09-09T09:17:08Z

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