Hi Nicholas,

I love your patch! Yet something to improve:

[auto build test ERROR on powerpc/next]
[also build test ERROR on linus/master v5.14-rc5 next-20210811]
[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/Nicholas-Piggin/KVM-PPC-Book3S-HV-P9-entry-exit-optimisations/20210812-000748
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc64-randconfig-r024-20210811 (attached as .config)
compiler: powerpc-linux-gcc (GCC) 10.3.0
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/b5149d8c735b6802aa0433a0cecc73e4d943e795
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Nicholas-Piggin/KVM-PPC-Book3S-HV-P9-entry-exit-optimisations/20210812-000748
        git checkout b5149d8c735b6802aa0433a0cecc73e4d943e795
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 make.cross ARCH=powerpc64 

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 >>):

>> arch/powerpc/kernel/process.c:596:6: error: no previous prototype for 'save_user_regs_kvm' [-Werror=missing-prototypes]
     596 | void save_user_regs_kvm(void)
         |      ^~~~~~~~~~~~~~~~~~
   cc1: all warnings being treated as errors


vim +/save_user_regs_kvm +596 arch/powerpc/kernel/process.c

   595	
 > 596	void save_user_regs_kvm(void)
   597	{
   598		unsigned long usermsr;
   599	
   600		if (!current->thread.regs)
   601			return;
   602	
   603		usermsr = current->thread.regs->msr;
   604	
   605		if (usermsr & MSR_FP)
   606			save_fpu(current);
   607	
   608		if (usermsr & MSR_VEC)
   609			save_altivec(current);
   610	

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