drm/i915: Add soft-pinning API for execbuffer

Userspace can pass in an offset that it presumes the object is located
at. The kernel will then do its utmost to fit the object into that
location. The assumption is that userspace is handling its own object
locations (for example along with full-ppgtt) and that the kernel will
rarely have to make space for the user's requests.

v2: Fix i915_gem_evict_range() (now evict_for_vma) to handle ordinary
and fixed objects within the same batch
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Daniel, Thomas" <thomas.daniel@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -1071,6 +1071,25 @@ static void i915_gem_record_rings(struct drm_device *dev,
 		list_for_each_entry(request, &ring->request_list, list) {
 			struct drm_i915_error_request *erq;
 
+			if (count >= error->ring[i].num_requests) {
+				/*
+				 * If the ring request list was changed in
+				 * between the point where the error request
+				 * list was created and dimensioned and this
+				 * point then just exit early to avoid crashes.
+				 *
+				 * We don't need to communicate that the
+				 * request list changed state during error
+				 * state capture and that the error state is
+				 * slightly incorrect as a consequence since we
+				 * are typically only interested in the request
+				 * list state at the point of error state
+				 * capture, not in any changes happening during
+				 * the capture.
+				 */
+				break;
+			}
+
 			erq = &error->ring[i].requests[count++];
 			erq->seqno = request->seqno;
 			erq->jiffies = request->emitted_jiffies;