drm/i915: Fix secure dispatch with full ppgtt

Based upon a hunk from a patch from Chris Wilson, but augmented to:
- Process the batch in the full ppgtt vm so that self-relocations
  match again with userspace's expectations..
- Add a comment why plain pin for the global gtt binding is safe at
  that point.

v2: Drop local bind_vm variable (Chris).

v3: Explain why this works despite the lack of proper active tracking
for the ggtt batch vma.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 70946c5..e1eac15 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -95,7 +95,6 @@ eb_lookup_vmas(struct eb_vmas *eb,
               struct i915_address_space *vm,
               struct drm_file *file)
 {
-       struct drm_i915_private *dev_priv = vm->dev->dev_private;
        struct drm_i915_gem_object *obj;
        struct list_head objects;
        int i, ret;
@@ -130,7 +129,6 @@ eb_lookup_vmas(struct eb_vmas *eb,
        i = 0;
        while (!list_empty(&objects)) {
                struct i915_vma *vma;
-               struct i915_address_space *bind_vm = vm;
 
                if (exec[i].flags & EXEC_OBJECT_NEEDS_GTT &&
                    USES_FULL_PPGTT(vm->dev)) {
@@ -138,13 +136,6 @@ eb_lookup_vmas(struct eb_vmas *eb,
                        goto err;
                }
 
-               /* If we have secure dispatch, or the userspace assures us that
-                * they know what they're doing, use the GGTT VM.
-                */
-               if (((args->flags & I915_EXEC_SECURE) &&
-                   (i == (args->buffer_count - 1))))
-                       bind_vm = &dev_priv->gtt.base;
-
                obj = list_first_entry(&objects,
                                       struct drm_i915_gem_object,
                                       obj_exec_link);
@@ -157,7 +148,7 @@ eb_lookup_vmas(struct eb_vmas *eb,
                 * from the (obj, vm) we don't run the risk of creating
                 * duplicated vmas for the same vm.
                 */
-               vma = i915_gem_obj_lookup_or_create_vma(obj, bind_vm);
+               vma = i915_gem_obj_lookup_or_create_vma(obj, vm);
                if (IS_ERR(vma)) {
                        DRM_DEBUG("Failed to lookup VMA\n");
                        ret = PTR_ERR(vma);
@@ -1391,25 +1382,36 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
        /* snb/ivb/vlv conflate the "batch in ppgtt" bit with the "non-secure
         * batch" bit. Hence we need to pin secure batches into the global gtt.
         * hsw should have this fixed, but bdw mucks it up again. */
-       if (flags & I915_DISPATCH_SECURE &&
-           !batch_obj->has_global_gtt_mapping) {
-               /* When we have multiple VMs, we'll need to make sure that we
-                * allocate space first */
-               struct i915_vma *vma = i915_gem_obj_to_ggtt(batch_obj);
-               BUG_ON(!vma);
-               vma->bind_vma(vma, batch_obj->cache_level, GLOBAL_BIND);
-       }
+       if (flags & I915_DISPATCH_SECURE) {
+               /*
+                * So on first glance it looks freaky that we pin the batch here
+                * outside of the reservation loop. But:
+                * - The batch is already pinned into the relevant ppgtt, so we
+                *   already have the backing storage fully allocated.
+                * - No other BO uses the global gtt (well contexts, but meh),
+                *   so we don't really have issues with mutliple objects not
+                *   fitting due to fragmentation.
+                * So this is actually safe.
+                */
+               ret = i915_gem_obj_ggtt_pin(batch_obj, 0, 0);
+               if (ret)
+                       goto err;
 
-       if (flags & I915_DISPATCH_SECURE)
                exec_start += i915_gem_obj_ggtt_offset(batch_obj);
-       else
+       } else
                exec_start += i915_gem_obj_offset(batch_obj, vm);
 
        ret = legacy_ringbuffer_submission(dev, file, ring, ctx,
-                       args, &eb->vmas, batch_obj, exec_start, flags);
-       if (ret)
-               goto err;
+                                          args, &eb->vmas, batch_obj, exec_start, flags);
 
+       /*
+        * FIXME: We crucially rely upon the active tracking for the (ppgtt)
+        * batch vma for correctness. For less ugly and less fragility this
+        * needs to be adjusted to also track the ggtt batch vma properly as
+        * active.
+        */
+       if (flags & I915_DISPATCH_SECURE)
+               i915_gem_object_ggtt_unpin(batch_obj);
 err:
        /* the request owns the ref now */
        i915_gem_context_unreference(ctx);