Re: [RFC Patch 1/7] kexec: Introduce multikernel support via kexec

[kernel test robot <lkp@intel.com>]

Hi Cong,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on linus/master v6.17-rc6 next-20250919]
[cannot apply to tip/x86/core powerpc/next powerpc/fixes]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Cong-Wang/kexec-Introduce-multikernel-support-via-kexec/20250919-062852
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250918222607.186488-2-xiyou.wangcong%40gmail.com
patch subject: [RFC Patch 1/7] kexec: Introduce multikernel support via kexec
config: x86_64-buildonly-randconfig-002-20250920 (https://download.01.org/0day-ci/archive/20250920/202509201300.onsuDJUN-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250920/202509201300.onsuDJUN-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509201300.onsuDJUN-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/kexec_core.c:1352:7: error: call to undeclared function 'multikernel_kick_ap'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    1352 |         rc = multikernel_kick_ap(cpu, kexec_image->start);
         |              ^
   kernel/kexec_core.c:1352:7: note: did you mean 'multikernel_kexec'?
   kernel/kexec_core.c:1333:5: note: 'multikernel_kexec' declared here
    1333 | int multikernel_kexec(int cpu)
         |     ^
   1 error generated.


vim +/multikernel_kick_ap +1352 kernel/kexec_core.c

  1332	
  1333	int multikernel_kexec(int cpu)
  1334	{
  1335		int rc;
  1336	
  1337		pr_info("multikernel kexec: cpu %d\n", cpu);
  1338	
  1339		if (cpu_online(cpu)) {
  1340			pr_err("The CPU is currently running with this kernel instance.");
  1341			return -EBUSY;
  1342		}
  1343	
  1344		if (!kexec_trylock())
  1345			return -EBUSY;
  1346		if (!kexec_image) {
  1347			rc = -EINVAL;
  1348			goto unlock;
  1349		}
  1350	
  1351		cpus_read_lock();
> 1352		rc = multikernel_kick_ap(cpu, kexec_image->start);

-- 
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https://github.com/intel/lkp-tests/wiki