drm/i915: Track GGTT writes on the vma

As writes through the GTT and GGTT PTE updates do not share the same
path, they are not strictly ordered and so we must explicitly flush the
indirect writes prior to modifying the PTE. We do track outstanding GGTT
writes on the object itself, but since the object may have multiple GGTT
vma, that is overly coarse as we can track and flush individual vma as
required.

Whilst here, update the GGTT flushing behaviour for Cannonlake.

v2: Hard-code ring offset to allow use during unload (after RCS may have
been freed, or never existed!)

References: https://bugs.freedesktop.org/show_bug.cgi?id=104002
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171206124914.19960-2-chris@chris-wilson.co.uk

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 1013403fcfea..0ebd75693505 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -322,6 +322,7 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)
 	if (err)
 		goto err_unpin;
 
+	i915_vma_set_ggtt_write(vma);
 	return ptr;
 
 err_unpin:
@@ -330,12 +331,24 @@ err:
 	return IO_ERR_PTR(err);
 }
 
+void i915_vma_flush_writes(struct i915_vma *vma)
+{
+	if (!i915_vma_has_ggtt_write(vma))
+		return;
+
+	i915_gem_flush_ggtt_writes(vma->vm->i915);
+
+	i915_vma_unset_ggtt_write(vma);
+}
+
 void i915_vma_unpin_iomap(struct i915_vma *vma)
 {
 	lockdep_assert_held(&vma->obj->base.dev->struct_mutex);
 
 	GEM_BUG_ON(vma->iomap == NULL);
 
+	i915_vma_flush_writes(vma);
+
 	i915_vma_unpin_fence(vma);
 	i915_vma_unpin(vma);
 }
@@ -792,6 +805,15 @@ int i915_vma_unbind(struct i915_vma *vma)
 	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
 
 	if (i915_vma_is_map_and_fenceable(vma)) {
+		/*
+		 * Check that we have flushed all writes through the GGTT
+		 * before the unbind, other due to non-strict nature of those
+		 * indirect writes they may end up referencing the GGTT PTE
+		 * after the unbind.
+		 */
+		i915_vma_flush_writes(vma);
+		GEM_BUG_ON(i915_vma_has_ggtt_write(vma));
+
 		/* release the fence reg _after_ flushing */
 		ret = i915_vma_put_fence(vma);
 		if (ret)