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

[Tvrtko Ursulin]

On 08/09/2020 23:43, Tom Murphy wrote:
> On Tue, 8 Sep 2020 at 16:56, Tvrtko Ursulin
> <tvrtko.ursulin@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxx/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