[Intel-gfx] [PATCH] drm/i915: Differentiate between aliasing-ppgtt and ggtt pinning

[Chris Wilson]

Userptr causes lockdep to complain when we are using the aliasing-ppgtt
(and ggtt, but for that it is rightfully so to complain about) in that
when we revoke the userptr we take a mutex which we also use to revoke
the mmaps. However, we only revoke mmaps for GGTT bindings and we never
allow userptr to create a GGTT binding so the warning should be false
and is simply caused by our conflation of the aliasing-ppgtt with the
ggtt. So lets try treating the binding into the aliasing-ppgtt as a
separate lockclass from the ggtt. The downside is that we are
deliberately suppressing lockdep;s ability to warn us of cycles.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/478
---
 drivers/gpu/drm/i915/i915_vma.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 191577a98390..9f4a31cd54ac 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -914,7 +914,8 @@ int i915_vma_pin(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 		wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm);
 
 	/* No more allocations allowed once we hold vm->mutex */
-	err = mutex_lock_interruptible(&vma->vm->mutex);
+	err = mutex_lock_interruptible_nested(&vma->vm->mutex,
+					      !(flags & PIN_GLOBAL));
 	if (err)
 		goto err_fence;
 
@@ -1320,7 +1321,7 @@ int i915_vma_unbind(struct i915_vma *vma)
 	if (err)
 		goto out_rpm;
 
-	err = mutex_lock_interruptible(&vm->mutex);
+	err = mutex_lock_interruptible_nested(&vma->vm->mutex, !wakeref);
 	if (err)
 		goto out_rpm;
 
-- 
2.20.1