Try unsynchronized userptr if regular one fails.
https://github.com/FreeBSDDesktop/kms-drm/issues/197

--- media_driver/linux/common/os/i915/mos_bufmgr.c.orig	2019-12-10 08:54:00 UTC
+++ media_driver/linux/common/os/i915/mos_bufmgr.c
@@ -945,10 +945,15 @@ mos_gem_bo_alloc_userptr(struct mos_bufmgr *bufmgr,
     userptr.user_size = size;
     userptr.flags = 0;
 
+retry:
     ret = drmIoctl(bufmgr_gem->fd,
             DRM_IOCTL_I915_GEM_USERPTR,
             &userptr);
     if (ret != 0) {
+        if (errno == ENODEV && userptr.flags == 0) {
+            userptr.flags = I915_USERPTR_UNSYNCHRONIZED;
+            goto retry;
+        }
         MOS_DBG("bo_create_userptr: "
             "ioctl failed with user ptr %p size 0x%lx, "
             "user flags 0x%lx\n", addr, size, flags);
@@ -1021,6 +1026,9 @@ retry:
         if (errno == ENODEV && userptr.flags == 0) {
             userptr.flags = I915_USERPTR_UNSYNCHRONIZED;
             goto retry;
+        }
+        if (geteuid() != 0) {
+            fprintf(stderr, "%s", "ioctl(I915_GEM_USERPTR) failed. Try running as root but expect poor stability.\n");
         }
         free(ptr);
         return false;