[Intel-gfx] [PATCH] drm/i915: don't do allocate_va_range again on pin update

[Chris Wilson]

From: Matthew Auld <matthew.auld at intel.com>

If a vma is already bound to a ppgtt, we incorrectly call
allocate_va_range again when doing a PIN_UPDATE, which will result in
over accounting within our paging structures, such that when we do
unbind something we don't actually destroy the structures and end up
inadvertently recycling them. In reality this probably isn't too bad,
but once we start touching PDEs and PDPEs for 64K/2M/1G pages this
apparent recycling will manifest into lots of really, really subtle
bugs.

v2: Fix the testing of vma->flags for aliasing_ppgtt_bind_vma

Fixes: ff685975d97f ("drm/i915: Move allocate_va_range to GTT")
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 62871cd50605..6354fe78238f 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -193,9 +193,12 @@ static int ppgtt_bind_vma(struct i915_vma *vma,
 	u32 pte_flags;
 	int ret;
 
-	ret = vma->vm->allocate_va_range(vma->vm, vma->node.start, vma->size);
-	if (ret)
-		return ret;
+	if (!(vma->flags & I915_VMA_LOCAL_BIND)) {
+		ret = vma->vm->allocate_va_range(vma->vm, vma->node.start,
+						 vma->size);
+		if (ret)
+			return ret;
+	}
 
 	vma->pages = vma->obj->mm.pages;
 
@@ -2304,7 +2307,8 @@ static int aliasing_gtt_bind_vma(struct i915_vma *vma,
 	if (flags & I915_VMA_LOCAL_BIND) {
 		struct i915_hw_ppgtt *appgtt = i915->mm.aliasing_ppgtt;
 
-		if (appgtt->base.allocate_va_range) {
+		if (!(vma->flags & I915_VMA_LOCAL_BIND) &&
+		    appgtt->base.allocate_va_range) {
 			ret = appgtt->base.allocate_va_range(&appgtt->base,
 							     vma->node.start,
 							     vma->node.size);
-- 
2.11.0