On bxt, we require a VT'd w/a to serialise all GGTT updates with memory
transfers, and use stop_machine() for this purpose. stop_machine() is a
global serialisation barrier and so dangerous to use from within
critical sections, as the stop_machine() will wait for all cpus to enter
the stop_machine callback, and those cpus may be waiting for the
critical section already held.
Fixes: d7085b0faac8 ("drm/i915/gem: Poison stolen pages before use")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index 4f923b8c43fb..29bffc6afcc1 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -505,6 +505,9 @@ static void dbg_poison(struct i915_ggtt *ggtt,
if (!drm_mm_node_allocated(&ggtt->error_capture))
return;
+ if (ggtt->vm.bind_async_flags & I915_VMA_GLOBAL_BIND)
+ return; /* beware stop_machine() inversion */
+
GEM_BUG_ON(!IS_ALIGNED(size, PAGE_SIZE));
mutex_lock(&ggtt->error_mutex);
--
2.20.1
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