[broonie-misc:for-kernelci 6/13] include/linux/pgtable.h:237:2: error: call to undeclared function 'arch_enter_lazy_mmu_mode'; ISO C99 and later do not support implicit function declarations

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

Hi Kevin,

FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/misc.git for-kernelci
head:   cde5afc166019bb0b077b88d78b3706ede96628a
commit: 3763e0f7bacf2669411cf2e580ca62e64eafb813 [6/13] mm: introduce generic lazy_mmu helpers
config: x86_64-allyesconfig (https://download.01.org/0day-ci/archive/20251015/202510150845.bOLBMSFb-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/20251015/202510150845.bOLBMSFb-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/202510150845.bOLBMSFb-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:31:
>> include/linux/pgtable.h:237:2: error: call to undeclared function 'arch_enter_lazy_mmu_mode'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     237 |         arch_enter_lazy_mmu_mode();
         |         ^
>> include/linux/pgtable.h:242:2: error: call to undeclared function 'arch_leave_lazy_mmu_mode'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     242 |         arch_leave_lazy_mmu_mode();
         |         ^
   include/linux/pgtable.h:247:2: error: call to undeclared function 'arch_leave_lazy_mmu_mode'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     247 |         arch_leave_lazy_mmu_mode();
         |         ^
   include/linux/pgtable.h:252:2: error: call to undeclared function 'arch_enter_lazy_mmu_mode'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     252 |         arch_enter_lazy_mmu_mode();
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:98:11: warning: array index 3 is past the end of the array (that has type 'unsigned long[1]') [-Warray-bounds]
      98 |                 return (set->sig[3] | set->sig[2] |
         |                         ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:98:25: warning: array index 2 is past the end of the array (that has type 'unsigned long[1]') [-Warray-bounds]
      98 |                 return (set->sig[3] | set->sig[2] |
         |                                       ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:99:4: warning: array index 1 is past the end of the array (that has type 'unsigned long[1]') [-Warray-bounds]
      99 |                         set->sig[1] | set->sig[0]) == 0;
         |                         ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:101:11: warning: array index 1 is past the end of the array (that has type 'unsigned long[1]') [-Warray-bounds]
     101 |                 return (set->sig[1] | set->sig[0]) == 0;
         |                         ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:114:11: warning: array index 3 is past the end of the array (that has type 'const unsigned long[1]') [-Warray-bounds]
     114 |                 return  (set1->sig[3] == set2->sig[3]) &&
         |                          ^         ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:114:27: warning: array index 3 is past the end of the array (that has type 'const unsigned long[1]') [-Warray-bounds]
     114 |                 return  (set1->sig[3] == set2->sig[3]) &&
         |                                          ^         ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:115:5: warning: array index 2 is past the end of the array (that has type 'const unsigned long[1]') [-Warray-bounds]
     115 |                         (set1->sig[2] == set2->sig[2]) &&
         |                          ^         ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:115:21: warning: array index 2 is past the end of the array (that has type 'const unsigned long[1]') [-Warray-bounds]
     115 |                         (set1->sig[2] == set2->sig[2]) &&
         |                                          ^         ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:116:5: warning: array index 1 is past the end of the array (that has type 'const unsigned long[1]') [-Warray-bounds]
     116 |                         (set1->sig[1] == set2->sig[1]) &&
         |                          ^         ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
      24 |         unsigned long sig[_NSIG_WORDS];
         |         ^
   In file included from arch/x86/boot/startup/sme.c:38:
   In file included from include/linux/mm.h:36:


vim +/arch_enter_lazy_mmu_mode +237 include/linux/pgtable.h

   214	
   215	/*
   216	 * A facility to provide lazy MMU batching.  This allows PTE updates and
   217	 * page invalidations to be delayed until a call to leave lazy MMU mode
   218	 * is issued.  Some architectures may benefit from doing this, and it is
   219	 * beneficial for both shadow and direct mode hypervisors, which may batch
   220	 * the PTE updates which happen during this window.  Note that using this
   221	 * interface requires that read hazards be removed from the code.  A read
   222	 * hazard could result in the direct mode hypervisor case, since the actual
   223	 * write to the page tables may not yet have taken place, so reads though
   224	 * a raw PTE pointer after it has been modified are not guaranteed to be
   225	 * up to date.
   226	 *
   227	 * In the general case, no lock is guaranteed to be held between entry and exit
   228	 * of the lazy mode. So the implementation must assume preemption may be enabled
   229	 * and cpu migration is possible; it must take steps to be robust against this.
   230	 * (In practice, for user PTE updates, the appropriate page table lock(s) are
   231	 * held, but for kernel PTE updates, no lock is held). Nesting is not permitted
   232	 * and the mode cannot be used in interrupt context.
   233	 */
   234	#ifdef CONFIG_ARCH_LAZY_MMU
   235	static inline void lazy_mmu_mode_enable(void)
   236	{
 > 237		arch_enter_lazy_mmu_mode();
   238	}
   239	
   240	static inline void lazy_mmu_mode_disable(void)
   241	{
 > 242		arch_leave_lazy_mmu_mode();
   243	}
   244	

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