Hi Baoquan, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/lee/linux.git android-3.18-preview head: 8c4eb268823e5844582318d81cd4ae69b69f5704 commit: 39972bcf660a4a878675bc794f07a860eb4de0c3 [389/772] x86/apic: Set up through-local-APIC mode on the boot CPU if 'noapic' specified config: i386-randconfig-a014-20210322 (attached as .config) compiler: gcc-5 (Ubuntu 5.5.0-12ubuntu1) 5.5.0 20171010 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/lee/linux.git/commit/?id=... git remote add lee-korg https://git.kernel.org/pub/scm/linux/kernel/git/lee/linux.git git fetch --no-tags lee-korg android-3.18-preview git checkout 39972bcf660a4a878675bc794f07a860eb4de0c3 # save the attached .config to linux build tree make W=1 ARCH=i386 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 arch/x86/include/asm/pgalloc.h:6:0, from arch/x86/kernel/apic/apic.c:42: include/linux/pagemap.h: In function 'fault_in_multipages_readable': include/linux/pagemap.h:633:16: warning: variable 'c' set but not used [-Wunused-but-set-variable] volatile char c; ^ arch/x86/kernel/apic/apic.c: At top level: arch/x86/kernel/apic/apic.c:957:28: warning: no previous prototype for 'smp_trace_apic_timer_interrupt' [-Wmissing-prototypes] __visible void __irq_entry smp_trace_apic_timer_interrupt(struct pt_regs *regs) ^ arch/x86/kernel/apic/apic.c: In function 'setup_local_APIC': if (!cpu && (pic_mode || !value || skip_ioapic_setup)) { ^ arch/x86/kernel/apic/apic.c:1471:37: note: each undeclared identifier is reported only once for each function it appears in arch/x86/kernel/apic/apic.c: At top level: arch/x86/kernel/apic/apic.c:1595:12: warning: no previous prototype for 'enable_IR' [-Wmissing-prototypes] int __init enable_IR(void) ^ arch/x86/kernel/apic/apic.c: In function 'enable_IR_x2apic': arch/x86/kernel/apic/apic.c:1617:11: warning: variable 'x2apic_enabled' set but not used [-Wunused-but-set-variable] int ret, x2apic_enabled = 0; ^ arch/x86/kernel/apic/apic.c: In function 'apic_verify': arch/x86/kernel/apic/apic.c:1706:16: warning: variable 'h' set but not used [-Wunused-but-set-variable] u32 features, h, l; ^ arch/x86/kernel/apic/apic.c: At top level: arch/x86/kernel/apic/apic.c:1980:16: warning: no previous prototype for 'smp_trace_spurious_interrupt' [-Wmissing-prototypes] __visible void smp_trace_spurious_interrupt(struct pt_regs *regs) ^ arch/x86/kernel/apic/apic.c:2036:16: warning: no previous prototype for 'smp_trace_error_interrupt' [-Wmissing-prototypes] __visible void smp_trace_error_interrupt(struct pt_regs *regs) ^ arch/x86/kernel/apic/apic.c: In function 'generic_processor_info': arch/x86/kernel/apic/apic.c:2174:43: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits] if (!boot_cpu_detected && num_processors >= nr_cpu_ids - 1 && ^ vim +/skip_ioapic_setup +1471 arch/x86/kernel/apic/apic.c 1453 1454 /* 1455 * Set spurious IRQ vector 1456 */ 1457 value |= SPURIOUS_APIC_VECTOR; 1458 apic_write(APIC_SPIV, value); 1459 1460 /* 1461 * Set up LVT0, LVT1: 1462 * 1463 * set up through-local-APIC on the BP's LINT0. This is not 1464 * strictly necessary in pure symmetric-IO mode, but sometimes 1465 * we delegate interrupts to the 8259A. 1466 */ 1467 /* 1468 * TODO: set up through-local-APIC from through-I/O-APIC? --macro 1469 */ 1470 value = apic_read(APIC_LVT0) & APIC_LVT_MASKED; 1472 value = APIC_DM_EXTINT; 1473 apic_printk(APIC_VERBOSE, "enabled ExtINT on CPU#%d\n", cpu); 1474 } else { 1475 value = APIC_DM_EXTINT | APIC_LVT_MASKED; 1476 apic_printk(APIC_VERBOSE, "masked ExtINT on CPU#%d\n", cpu); 1477 } 1478 apic_write(APIC_LVT0, value); 1479 1480 /* 1481 * only the BP should see the LINT1 NMI signal, obviously. 1482 */ 1483 if (!cpu) 1484 value = APIC_DM_NMI; 1485 else 1486 value = APIC_DM_NMI | APIC_LVT_MASKED; 1487 if (!lapic_is_integrated()) /* 82489DX */ 1488 value |= APIC_LVT_LEVEL_TRIGGER; 1489 apic_write(APIC_LVT1, value); 1490 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org