On Tue, 8 Sep 2020 at 16:56, Tvrtko Ursulin
[off-list ref] wrote:

On 08/09/2020 16:44, Logan Gunthorpe wrote:

quoted

On 2020-09-08 9:28 a.m., Tvrtko Ursulin wrote:

quoted

quoted

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.

quoted

quoted

+               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)

Regards,

Tvrtko

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