Hi Daniel,

I love your patch! Yet something to improve:

[auto build test ERROR on drm-intel/for-linux-next]
[also build test ERROR on drm-tip/drm-tip drm-exynos/exynos-drm-next tegra-drm/drm/tegra/for-next linus/master v5.13-rc3 next-20210527]
[cannot apply to drm/drm-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Daniel-Vetter/shmem-helpers-for-vgem/20210527-221432
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
config: h8300-randconfig-r031-20210526 (attached as .config)
compiler: h8300-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/cd68a984a14ba7e76552f5e75ee5ab6fd0cb2d05
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Daniel-Vetter/shmem-helpers-for-vgem/20210527-221432
        git checkout cd68a984a14ba7e76552f5e75ee5ab6fd0cb2d05
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=h8300 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "vmf_insert_pfn" [drivers/gpu/drm/drm.ko] undefined!

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org