Re: [PATCH 1/3] x86/x2apic: disable x2apic on resume if the kernel expects so

Re: [PATCH 1/3] x86/x2apic: disable x2apic on resume if the kernel expects so

[kernel test robot]

Hi Shashank,

kernel test robot noticed the following build errors:

[auto build test ERROR on 18f7fcd5e69a04df57b563360b88be72471d6b62]

url:    https://github.com/intel-lab-lkp/linux/commits/Shashank-Balaji/x86-x2apic-disable-x2apic-on-resume-if-the-kernel-expects-so/20260202-181147
base:   18f7fcd5e69a04df57b563360b88be72471d6b62
patch link:    https://lore.kernel.org/r/20260202-x2apic-fix-v1-1-71c8f488a88b%40sony.com
patch subject: [PATCH 1/3] x86/x2apic: disable x2apic on resume if the kernel expects so
config: i386-randconfig-001-20260202 (https://download.01.org/0day-ci/archive/20260203/202602030600.jFhsJyEC-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/20260203/202602030600.jFhsJyEC-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/202602030600.jFhsJyEC-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/x86/kernel/apic/apic.c:2463:3: error: call to undeclared function '__x2apic_disable'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    2463 |                 __x2apic_disable();
         |                 ^
   arch/x86/kernel/apic/apic.c:2463:3: note: did you mean '__x2apic_enable'?
   arch/x86/kernel/apic/apic.c:1896:20: note: '__x2apic_enable' declared here
    1896 | static inline void __x2apic_enable(void) { }
         |                    ^
   1 error generated.


vim +/__x2apic_disable +2463 arch/x86/kernel/apic/apic.c

  2435	
  2436	static void lapic_resume(void *data)
  2437	{
  2438		unsigned int l, h;
  2439		unsigned long flags;
  2440		int maxlvt;
  2441	
  2442		if (!apic_pm_state.active)
  2443			return;
  2444	
  2445		local_irq_save(flags);
  2446	
  2447		/*
  2448		 * IO-APIC and PIC have their own resume routines.
  2449		 * We just mask them here to make sure the interrupt
  2450		 * subsystem is completely quiet while we enable x2apic
  2451		 * and interrupt-remapping.
  2452		 */
  2453		mask_ioapic_entries();
  2454		legacy_pic->mask_all();
  2455	
  2456		if (x2apic_mode) {
  2457			__x2apic_enable();
  2458		} else {
  2459			/*
  2460			 * x2apic may have been re-enabled by the
  2461			 * firmware on resuming from s2ram
  2462			 */
> 2463			__x2apic_disable();
  2464	
  2465			/*
  2466			 * Make sure the APICBASE points to the right address
  2467			 *
  2468			 * FIXME! This will be wrong if we ever support suspend on
  2469			 * SMP! We'll need to do this as part of the CPU restore!
  2470			 */
  2471			if (boot_cpu_data.x86 >= 6) {
  2472				rdmsr(MSR_IA32_APICBASE, l, h);
  2473				l &= ~MSR_IA32_APICBASE_BASE;
  2474				l |= MSR_IA32_APICBASE_ENABLE | mp_lapic_addr;
  2475				wrmsr(MSR_IA32_APICBASE, l, h);
  2476			}
  2477		}
  2478	
  2479		maxlvt = lapic_get_maxlvt();
  2480		apic_write(APIC_LVTERR, ERROR_APIC_VECTOR | APIC_LVT_MASKED);
  2481		apic_write(APIC_ID, apic_pm_state.apic_id);
  2482		apic_write(APIC_DFR, apic_pm_state.apic_dfr);
  2483		apic_write(APIC_LDR, apic_pm_state.apic_ldr);
  2484		apic_write(APIC_TASKPRI, apic_pm_state.apic_taskpri);
  2485		apic_write(APIC_SPIV, apic_pm_state.apic_spiv);
  2486		apic_write(APIC_LVT0, apic_pm_state.apic_lvt0);
  2487		apic_write(APIC_LVT1, apic_pm_state.apic_lvt1);
  2488	#ifdef CONFIG_X86_THERMAL_VECTOR
  2489		if (maxlvt >= 5)
  2490			apic_write(APIC_LVTTHMR, apic_pm_state.apic_thmr);
  2491	#endif
  2492	#ifdef CONFIG_X86_MCE_INTEL
  2493		if (maxlvt >= 6)
  2494			apic_write(APIC_LVTCMCI, apic_pm_state.apic_cmci);
  2495	#endif
  2496		if (maxlvt >= 4)
  2497			apic_write(APIC_LVTPC, apic_pm_state.apic_lvtpc);
  2498		apic_write(APIC_LVTT, apic_pm_state.apic_lvtt);
  2499		apic_write(APIC_TDCR, apic_pm_state.apic_tdcr);
  2500		apic_write(APIC_TMICT, apic_pm_state.apic_tmict);
  2501		apic_write(APIC_ESR, 0);
  2502		apic_read(APIC_ESR);
  2503		apic_write(APIC_LVTERR, apic_pm_state.apic_lvterr);
  2504		apic_write(APIC_ESR, 0);
  2505		apic_read(APIC_ESR);
  2506	
  2507		irq_remapping_reenable(x2apic_mode);
  2508	
  2509		local_irq_restore(flags);
  2510	}
  2511	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 1/3] x86/x2apic: disable x2apic on resume if the kernel expects so

[Shashank Balaji]

On Tue, Feb 03, 2026 at 06:31:40AM +0800, kernel test robot wrote:
> Hi Shashank,
> 
> kernel test robot noticed the following build errors:
> 
> [auto build test ERROR on 18f7fcd5e69a04df57b563360b88be72471d6b62]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Shashank-Balaji/x86-x2apic-disable-x2apic-on-resume-if-the-kernel-expects-so/20260202-181147
> base:   18f7fcd5e69a04df57b563360b88be72471d6b62
> patch link:    https://lore.kernel.org/r/20260202-x2apic-fix-v1-1-71c8f488a88b%40sony.com
> patch subject: [PATCH 1/3] x86/x2apic: disable x2apic on resume if the kernel expects so
> config: i386-randconfig-001-20260202 (https://download.01.org/0day-ci/archive/20260203/202602030600.jFhsJyEC-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/20260203/202602030600.jFhsJyEC-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/202602030600.jFhsJyEC-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
> >> arch/x86/kernel/apic/apic.c:2463:3: error: call to undeclared function '__x2apic_disable'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>     2463 |                 __x2apic_disable();
>          |                 ^
>    arch/x86/kernel/apic/apic.c:2463:3: note: did you mean '__x2apic_enable'?
>    arch/x86/kernel/apic/apic.c:1896:20: note: '__x2apic_enable' declared here
>     1896 | static inline void __x2apic_enable(void) { }
>          |                    ^
>    1 error generated.

This happens when CONFIG_X86_X2APIC is disabled. This patch fixes it,
which I'll include in v2:

diff --git i/arch/x86/kernel/apic/apic.c w/arch/x86/kernel/apic/apic.c
index 8820b631f8a2..06cce23b89c1 100644
--- i/arch/x86/kernel/apic/apic.c
+++ w/arch/x86/kernel/apic/apic.c
@@ -1894,6 +1894,7 @@ void __init check_x2apic(void)

 static inline void try_to_enable_x2apic(int remap_mode) { }
 static inline void __x2apic_enable(void) { }
+static inline void __x2apic_disable(void) {}
 #endif /* !CONFIG_X86_X2APIC */

 void __init enable_IR_x2apic(void)