Hi Peter, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on cb0e52b7748737b2cf6481fdd9b920ce7e1ebbdf] url: https://github.com/0day-ci/linux/commits/Peter-Oskolkov/sched-mm-x86-uacc... base: cb0e52b7748737b2cf6481fdd9b920ce7e1ebbdf config: m68k-randconfig-r026-20211121 (attached as .config) compiler: m68k-linux-gcc (GCC) 11.2.0 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/439d26d60c10ac8de229f859297b3cb8d... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Peter-Oskolkov/sched-mm-x86-uaccess-implement-User-Managed-Concurrency-Groups/20211122-052209 git checkout 439d26d60c10ac8de229f859297b3cb8df029a9a # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=m68k If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): vim +491 mm/maccess.c 474 475 /** 476 * xchg_user_[32|64][_nofault|]() - exchange 32/64-bit values 477 * @uaddr: Destination address, in user space; 478 * @val: Source address, in kernel space. 479 * 480 * This is the standard atomic xchg: exchange values pointed to by @uaddr and @val. 481 * 482 * The _nofault versions don't fault and can be used in 483 * atomic/preempt-disabled contexts. 484 * 485 * Return: 486 * 0 : OK/success; 487 * -EINVAL: @uaddr is not properly aligned ('may fault' versions only); 488 * -EFAULT: memory access error (including mis-aligned @uaddr in _nofault). 489 */ 490 int xchg_user_32_nofault(u32 __user *uaddr, u32 *val) 492 int ret; 493 494 if (unlikely(!access_ok(uaddr, sizeof(*uaddr)))) 495 return -EFAULT; 496 497 pagefault_disable(); 498 499 if (!user_access_begin(uaddr, sizeof(*uaddr))) { 500 pagefault_enable(); 501 return -EFAULT; 502 } 503 504 ret = __try_xchg_user_32(val, uaddr, *val); 505 user_access_end(); 506 507 pagefault_enable(); 508 509 return ret; 510 } 511 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org