[Intel-gfx] [RFC 6/8] drm/i915/svm: Skip vma_lookup for persistent vmas

[Niranjana Vishwanathapura]

vma_lookup is tied to segment of the object instead of section
of VA space. Hence, it do not support aliasing (ie., multiple
bindings to the same section of the object).
Hence skip vma_lookup for persistent vmas which should support
aliasing.

This needs proper solution.

Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Jon Bloomfield <jon.bloomfield at intel.com>
Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Chris P Wilson <chris.p.wilson at intel.com>
Cc: Sudeep Dutt <sudeep.dutt at intel.com>
Cc: Stuart Summers <stuart.summers at intel.com>
Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
---
 drivers/gpu/drm/i915/i915_vma.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 3e16b291f806..9e2d0dbd308c 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -181,6 +181,10 @@ vma_create(struct drm_i915_gem_object *obj,
 
 	spin_lock(&obj->vma.lock);
 
+	if (!i915_vma_is_ggtt(vma) &&
+	    (view && view->type == I915_GGTT_VIEW_PARTIAL))
+		goto skip_rb_insert;
+
 	rb = NULL;
 	p = &obj->vma.tree.rb_node;
 	while (*p) {
@@ -210,6 +214,7 @@ vma_create(struct drm_i915_gem_object *obj,
 	rb_link_node(&vma->obj_node, rb, p);
 	rb_insert_color(&vma->obj_node, &obj->vma.tree);
 
+skip_rb_insert:
 	if (i915_vma_is_ggtt(vma))
 		/*
 		 * We put the GGTT vma at the start of the vma-list, followed
@@ -274,13 +279,16 @@ i915_vma_instance(struct drm_i915_gem_object *obj,
 		  struct i915_address_space *vm,
 		  const struct i915_ggtt_view *view)
 {
-	struct i915_vma *vma;
+	struct i915_vma *vma = NULL;
 
 	GEM_BUG_ON(!atomic_read(&vm->open));
 
-	spin_lock(&obj->vma.lock);
-	vma = vma_lookup(obj, vm, view);
-	spin_unlock(&obj->vma.lock);
+	if (i915_is_ggtt(vm) || !view ||
+	    view->type != I915_GGTT_VIEW_PARTIAL) {
+		spin_lock(&obj->vma.lock);
+		vma = vma_lookup(obj, vm, view);
+		spin_unlock(&obj->vma.lock);
+	}
 
 	/* vma_create() will resolve the race if another creates the vma */
 	if (unlikely(!vma))
@@ -1046,7 +1054,10 @@ void i915_vma_release(struct kref *ref)
 
 		spin_lock(&obj->vma.lock);
 		list_del(&vma->obj_link);
-		rb_erase(&vma->obj_node, &obj->vma.tree);
+
+		if (!i915_vma_is_persistent(vma))
+			rb_erase(&vma->obj_node, &obj->vma.tree);
+
 		spin_unlock(&obj->vma.lock);
 
 		mutex_lock(&vma->vm->svm_mutex);
-- 
2.21.0.rc0.32.g243a4c7e27