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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [PNV Bisected]igt/gem_exec_big fails"
href="https://bugs.freedesktop.org/show_bug.cgi?id=88191#c4">Comment # 4</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [PNV Bisected]igt/gem_exec_big fails"
href="https://bugs.freedesktop.org/show_bug.cgi?id=88191">bug 88191</a>
from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
<pre>My hypothesis is that we need a mb() to serialise updating the GTT and
accessing the PTE via the CPU.
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c
b/drivers/gpu/drm/i915/i915_gem
index bdfd44c..c8932b3 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -1444,6 +1444,7 @@ static int i915_ggtt_bind_vma(struct i915_vma *vma,
BUG_ON(!i915_is_ggtt(vma->vm));
intel_gtt_insert_sg_entries(vma->obj->pages, entry, flags);
+ wmb();
vma->bound = GLOBAL_BIND;
vma->vm->dirty = true;
is sufficient, but intel_gtt_insert_sg_entries() already ends with a readl()!</pre>
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