Hi Alexandre, [FYI, it's a private test report for your RFC patch.] [auto build test WARNING on tip/x86/mm] [also build test WARNING on v5.10-rc4] [cannot apply to tip/x86/core tip/x86/asm next-20201116] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Alexandre-Chartre/x86-pti-Defer-... base: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 1fcd009102ee02e217f2e7635ab65517d785da8e config: i386-randconfig-a012-20201115 (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce (this is a W=1 build): # https://github.com/0day-ci/linux/commit/8fa40c99f8d79767c2e49a4899ccf6bd1... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Alexandre-Chartre/x86-pti-Defer-CR3-switch-to-C-code/20201116-225620 git checkout 8fa40c99f8d79767c2e49a4899ccf6bd11f65532 # 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 warnings (new ones prefixed by >>): In file included from arch/x86/include/asm/cpufeature.h:5, from arch/x86/include/asm/thread_info.h:53, from include/linux/thread_info.h:38, from arch/x86/include/asm/preempt.h:7, from include/linux/preempt.h:78, from include/linux/rcupdate.h:27, from include/linux/rculist.h:11, from include/linux/pid.h:5, from include/linux/sched.h:14, from include/linux/context_tracking.h:5, from arch/x86/kernel/traps.c:15: arch/x86/include/asm/idtentry.h: In function 'pti_kernel_stack': arch/x86/include/asm/processor.h:773:53: error: 'KERNEL_STACK_SIZE' undeclared (first use in this function); did you mean 'KERNEL_IMAGE_SIZE'? 773 | ((void *)(((unsigned long)task_stack_page(task)) + KERNEL_STACK_SIZE)) | ^~~~~~~~~~~~~~~~~ arch/x86/include/asm/idtentry.h:52:26: note: in expansion of macro 'task_top_of_kernel_stack' 52 | stack = (unsigned long)task_top_of_kernel_stack(current); | ^~~~~~~~~~~~~~~~~~~~~~~~ arch/x86/include/asm/processor.h:773:53: note: each undeclared identifier is reported only once for each function it appears in 773 | ((void *)(((unsigned long)task_stack_page(task)) + KERNEL_STACK_SIZE)) | ^~~~~~~~~~~~~~~~~ arch/x86/include/asm/idtentry.h:52:26: note: in expansion of macro 'task_top_of_kernel_stack' 52 | stack = (unsigned long)task_top_of_kernel_stack(current); | ^~~~~~~~~~~~~~~~~~~~~~~~ In file included from arch/x86/include/asm/traps.h:9, from arch/x86/kernel/traps.c:49: arch/x86/include/asm/idtentry.h: In function 'run_idt': arch/x86/include/asm/idtentry.h:24:3: error: implicit declaration of function 'asm_call_on_stack_1' [-Werror=implicit-function-declaration] 24 | asm_call_on_stack_1(stack, \ | ^~~~~~~~~~~~~~~~~~~ arch/x86/include/asm/idtentry.h:66:2: note: in expansion of macro 'CALL_ON_STACK_1' 66 | CALL_ON_STACK_1(pti_kernel_stack(regs), func, regs); | ^~~~~~~~~~~~~~~ arch/x86/include/asm/idtentry.h: In function 'run_idt_errcode': arch/x86/include/asm/idtentry.h:30:3: error: implicit declaration of function 'asm_call_on_stack_2' [-Werror=implicit-function-declaration] 30 | asm_call_on_stack_2(stack, \ | ^~~~~~~~~~~~~~~~~~~ arch/x86/include/asm/idtentry.h:73:2: note: in expansion of macro 'CALL_ON_STACK_2' 73 | CALL_ON_STACK_2(pti_kernel_stack(regs), func, regs, error_code); | ^~~~~~~~~~~~~~~ arch/x86/include/asm/idtentry.h: In function 'run_idt_pagefault': arch/x86/include/asm/idtentry.h:36:3: error: implicit declaration of function 'asm_call_on_stack_3' [-Werror=implicit-function-declaration] 36 | asm_call_on_stack_3(stack, \ | ^~~~~~~~~~~~~~~~~~~ arch/x86/include/asm/idtentry.h:82:2: note: in expansion of macro 'CALL_ON_STACK_3' 82 | CALL_ON_STACK_3(pti_kernel_stack(regs), | ^~~~~~~~~~~~~~~ arch/x86/kernel/traps.c: In function 'exc_double_fault': 348 | unsigned long saved_cr3; | ^~~~~~~~~ cc1: some warnings being treated as errors vim +/saved_cr3 +348 arch/x86/kernel/traps.c 324 325 /* 326 * Runs on an IST stack for x86_64 and on a special task stack for x86_32. 327 * 328 * On x86_64, this is more or less a normal kernel entry. Notwithstanding the 329 * SDM's warnings about double faults being unrecoverable, returning works as 330 * expected. Presumably what the SDM actually means is that the CPU may get 331 * the register state wrong on entry, so returning could be a bad idea. 332 * 333 * Various CPU engineers have promised that double faults due to an IRET fault 334 * while the stack is read-only are, in fact, recoverable. 335 * 336 * On x86_32, this is entered through a task gate, and regs are synthesized 337 * from the TSS. Returning is, in principle, okay, but changes to regs will 338 * be lost. If, for some reason, we need to return to a context with modified 339 * regs, the shim code could be adjusted to synchronize the registers. 340 * 341 * The 32bit #DF shim provides CR2 already as an argument. On 64bit it needs 342 * to be read before doing anything else. 343 */ 344 DEFINE_IDTENTRY_DF(exc_double_fault) 345 { 346 static const char str[] = "double fault"; 347 struct task_struct *tsk; 349 #ifdef CONFIG_VMAP_STACK 350 unsigned long address; 351 #endif 352 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org