drm/i915: Perform execbuffer object locking as a separate step

To help avoid evicting already resident buffers from the batch we're
processing, perform locking as a separate step.
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210615113600.30660-1-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -922,21 +922,38 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
 	return err;
 }
 
-static int eb_validate_vmas(struct i915_execbuffer *eb)
+static int eb_lock_vmas(struct i915_execbuffer *eb)
 {
 	unsigned int i;
 	int err;
 
-	INIT_LIST_HEAD(&eb->unbound);
-
 	for (i = 0; i < eb->buffer_count; i++) {
-		struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];
 		struct eb_vma *ev = &eb->vma[i];
 		struct i915_vma *vma = ev->vma;
 
 		err = i915_gem_object_lock(vma->obj, &eb->ww);
 		if (err)
 			return err;
+	}
+
+	return 0;
+}
+
+static int eb_validate_vmas(struct i915_execbuffer *eb)
+{
+	unsigned int i;
+	int err;
+
+	INIT_LIST_HEAD(&eb->unbound);
+
+	err = eb_lock_vmas(eb);
+	if (err)
+		return err;
+
+	for (i = 0; i < eb->buffer_count; i++) {
+		struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];
+		struct eb_vma *ev = &eb->vma[i];
+		struct i915_vma *vma = ev->vma;
 
 		err = eb_pin_vma(eb, entry, ev);
 		if (err == -EDEADLK)