drm/i915: Allow relocation deltas outside of target bo

Userspace has a legitimate requirement to use a delta that points to
outside of the target bo, and so we need to enable this. (As this is an
abi break, albeit a relaxation of the current restrictions, mark the change
with a new flag.)
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_dma.c

@@ -772,6 +772,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
 	case I915_PARAM_HAS_EXEC_CONSTANTS:
 		value = INTEL_INFO(dev)->gen >= 4;
 		break;
+	case I915_PARAM_HAS_RELAXED_DELTA:
+		value = 1;
+		break;
 	default:
 		DRM_DEBUG_DRIVER("Unknown parameter %d\n",
 				 param->param);

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -350,16 +350,6 @@ i915_gem_execbuffer_relocate_entry(struct drm_i915_gem_object *obj,
 		return ret;
 	}
 
-	/* and points to somewhere within the target object. */
-	if (unlikely(reloc->delta >= target_obj->size)) {
-		DRM_ERROR("Relocation beyond target object bounds: "
-			  "obj %p target %d delta %d size %d.\n",
-			  obj, reloc->target_handle,
-			  (int) reloc->delta,
-			  (int) target_obj->size);
-		return ret;
-	}
-
 	reloc->delta += target_offset;
 	if (obj->base.write_domain == I915_GEM_DOMAIN_CPU) {
 		uint32_t page_offset = reloc->offset & ~PAGE_MASK;

include/drm/i915_drm.h

@@ -290,6 +290,7 @@ typedef struct drm_i915_irq_wait {
 #define I915_PARAM_HAS_RELAXED_FENCING	 12
 #define I915_PARAM_HAS_COHERENT_RINGS	 13
 #define I915_PARAM_HAS_EXEC_CONSTANTS	 14
+#define I915_PARAM_HAS_RELAXED_DELTA	 15
 
 typedef struct drm_i915_getparam {
 	int param;