Hi Pekka, I love your patch! Yet something to improve: [auto build test ERROR on linus/master] [also build test ERROR on v5.8-rc5 next-20200714] [cannot apply to mmotm/master] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Pekka-Enberg/mm-pgtable-Make-gen... base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 0dc589da873b58b70f4caf4b070fb0cf70fdd1dc config: arm-randconfig-r033-20200714 (attached as .config) compiler: arm-linux-gnueabi-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 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arm If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): In file included from include/linux/mm.h:32, from include/linux/scatterlist.h:8, from include/linux/dma-mapping.h:11, from drivers/gpu/drm/tilcdc/tilcdc_crtc.c:8: include/linux/pgtable.h: In function 'pgprot_modify': 834 | if (pgprot_val(oldprot) == pgprot_val(pgprot_noncached(oldprot))) | ^~ include/linux/pgtable.h:836:26: error: self-comparison always evaluates to true [-Werror=tautological-compare] 836 | if (pgprot_val(oldprot) == pgprot_val(pgprot_writecombine(oldprot))) | ^~ include/linux/pgtable.h:838:26: error: self-comparison always evaluates to true [-Werror=tautological-compare] 838 | if (pgprot_val(oldprot) == pgprot_val(pgprot_device(oldprot))) | ^~ cc1: all warnings being treated as errors vim +834 include/linux/pgtable.h 829 830 #ifndef pgprot_modify 831 #define pgprot_modify pgprot_modify 832 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) 833 { 835 newprot = pgprot_noncached(newprot); 836 if (pgprot_val(oldprot) == pgprot_val(pgprot_writecombine(oldprot))) 837 newprot = pgprot_writecombine(newprot); 838 if (pgprot_val(oldprot) == pgprot_val(pgprot_device(oldprot))) 839 newprot = pgprot_device(newprot); 840 return newprot; 841 } 842 #endif 843 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org