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/[email protected]/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/[email protected]/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 <[email protected]>
> | Closes:
> https://lore.kernel.org/oe-kbuild-all/[email protected]/
>
> 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)
