Hi Pingfan,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[cannot apply to v5.3-rc3 next-20190807]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Pingfan-Liu/x86-mce-protect-nr_cpus-from-rebooting-by-broadcast-mce/20190806-101748
config: i386-randconfig-a004-201931 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.2-10+deb8u1) 4.9.2
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

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

All errors (new ones prefixed by >>):

   ld: arch/x86/kernel/smpboot.o: in function `do_stable_cpu':
>> arch/x86/kernel/smpboot.c:1057: undefined reference to `initial_gs'

vim +1057 arch/x86/kernel/smpboot.c

  1048	
  1049	static void __init do_stable_cpu(int cpu)
  1050	{
  1051		static char capped_tmp_stack[512];
  1052		int cpu0_nmi_registered = 0, apicid = cpuid_to_apicid[cpu];
  1053		unsigned long start_ip = real_mode_header->trampoline_start;
  1054		unsigned long timeout, boot_error = 0;
  1055	
  1056		/* invalid percpu area */
> 1057		initial_gs = 0;
  1058		/*
  1059		 * Borrow the value of cpu 0. Since capped cpu segment shadow register
  1060		 * can cache the content, and keep it unchanged.
  1061		 */
  1062		early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(0);
  1063		initial_code = (unsigned long)make_capped_cpu_stable;
  1064		initial_stack  = (unsigned long)&capped_tmp_stack;
  1065	
  1066		if (apic->wakeup_secondary_cpu)
  1067			boot_error = apic->wakeup_secondary_cpu(apicid, start_ip);
  1068		else
  1069			boot_error = wakeup_cpu_via_init_nmi(cpu, start_ip, apicid,
  1070							     &cpu0_nmi_registered);
  1071		if (cpu0_nmi_registered)
  1072			unregister_nmi_handler(NMI_LOCAL, "wake_cpu0");
  1073	
  1074		if (!boot_error) {
  1075			/* Wait 10s total for first sign of life from capped cpu */
  1076			boot_error = -1;
  1077			timeout = jiffies + 10*HZ;
  1078			while (time_before(jiffies, timeout)) {
  1079				if (cpumask_test_cpu(cpu, cpu_capped_done_mask))
  1080					break;
  1081				schedule();
  1082			}
  1083		}
  1084	}
  1085	

---
0-DAY kernel test infrastructure                Open Source Technology Center
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