Re: [PATCH v3 10/10] x86/split_lock: Handle #AC exception for split lock

[kbuild test robot]

Hi Fenghua,

I love your patch! Yet something to improve:

[auto build test ERROR on tip/auto-latest]
[also build test ERROR on v5.0-rc4 next-20190204]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Fenghua-Yu/x86-split_lock-Enable-AC-exception-for-split-locked-accesses/20190204-162843
config: i386-randconfig-a2-02040849 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   ld: arch/x86/kernel/traps.o: in function `do_alignment_check':
   arch/x86/kernel/traps.c:310: undefined reference to `do_ac_split_lock'
   ld: arch/x86/kernel/setup.o: in function `setup_arch':
>> arch/x86/kernel/setup.c:965: undefined reference to `set_ac_split_lock'

vim +965 arch/x86/kernel/setup.c

   949	
   950		strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
   951		*cmdline_p = command_line;
   952	
   953		/*
   954		 * x86_configure_nx() is called before parse_early_param() to detect
   955		 * whether hardware doesn't support NX (so that the early EHCI debug
   956		 * console setup can safely call set_fixmap()). It may then be called
   957		 * again from within noexec_setup() during parsing early parameters
   958		 * to honor the respective command line option.
   959		 */
   960		x86_configure_nx();
   961	
   962		parse_early_param();
   963	
   964		/* Set up #AC for split lock at the earliest phase. */
 > 965		set_ac_split_lock();
   966	
   967		if (efi_enabled(EFI_BOOT))
   968			efi_memblock_x86_reserve_range();
   969	#ifdef CONFIG_MEMORY_HOTPLUG
   970		/*
   971		 * Memory used by the kernel cannot be hot-removed because Linux
   972		 * cannot migrate the kernel pages. When memory hotplug is
   973		 * enabled, we should prevent memblock from allocating memory
   974		 * for the kernel.
   975		 *
   976		 * ACPI SRAT records all hotpluggable memory ranges. But before
   977		 * SRAT is parsed, we don't know about it.
   978		 *
   979		 * The kernel image is loaded into memory at very early time. We
   980		 * cannot prevent this anyway. So on NUMA system, we set any
   981		 * node the kernel resides in as un-hotpluggable.
   982		 *
   983		 * Since on modern servers, one node could have double-digit
   984		 * gigabytes memory, we can assume the memory around the kernel
   985		 * image is also un-hotpluggable. So before SRAT is parsed, just
   986		 * allocate memory near the kernel image to try the best to keep
   987		 * the kernel away from hotpluggable memory.
   988		 */
   989		if (movable_node_is_enabled())
   990			memblock_set_bottom_up(true);
   991	#endif
   992	
   993		x86_report_nx();
   994	
   995		/* after early param, so could get panic from serial */
   996		memblock_x86_reserve_range_setup_data();
   997	
   998		if (acpi_mps_check()) {
   999	#ifdef CONFIG_X86_LOCAL_APIC
  1000			disable_apic = 1;
  1001	#endif
  1002			setup_clear_cpu_cap(X86_FEATURE_APIC);
  1003		}
  1004	
  1005		e820__reserve_setup_data();
  1006		e820__finish_early_params();
  1007	
  1008		if (efi_enabled(EFI_BOOT))
  1009			efi_init();
  1010	
  1011		dmi_scan_machine();
  1012		dmi_memdev_walk();
  1013		dmi_set_dump_stack_arch_desc();
  1014	
  1015		/*
  1016		 * VMware detection requires dmi to be available, so this
  1017		 * needs to be done after dmi_scan_machine(), for the boot CPU.
  1018		 */
  1019		init_hypervisor_platform();
  1020	
  1021		tsc_early_init();
  1022		x86_init.resources.probe_roms();
  1023	
  1024		/* after parse_early_param, so could debug it */
  1025		insert_resource(&iomem_resource, &code_resource);
  1026		insert_resource(&iomem_resource, &data_resource);
  1027		insert_resource(&iomem_resource, &bss_resource);
  1028	
  1029		e820_add_kernel_range();
  1030		trim_bios_range();
  1031	#ifdef CONFIG_X86_32
  1032		if (ppro_with_ram_bug()) {
  1033			e820__range_update(0x70000000ULL, 0x40000ULL, E820_TYPE_RAM,
  1034					  E820_TYPE_RESERVED);
  1035			e820__update_table(e820_table);
  1036			printk(KERN_INFO "fixed physical RAM map:\n");
  1037			e820__print_table("bad_ppro");
  1038		}
  1039	#else
  1040		early_gart_iommu_check();
  1041	#endif
  1042	
  1043		/*
  1044		 * partially used pages are not usable - thus
  1045		 * we are rounding upwards:
  1046		 */
  1047		max_pfn = e820__end_of_ram_pfn();
  1048	
  1049		/* update e820 for memory not covered by WB MTRRs */
  1050		mtrr_bp_init();
  1051		if (mtrr_trim_uncached_memory(max_pfn))
  1052			max_pfn = e820__end_of_ram_pfn();
  1053	
  1054		max_possible_pfn = max_pfn;
  1055	
  1056		/*
  1057		 * This call is required when the CPU does not support PAT. If
  1058		 * mtrr_bp_init() invoked it already via pat_init() the call has no
  1059		 * effect.
  1060		 */
  1061		init_cache_modes();
  1062	
  1063		/*
  1064		 * Define random base addresses for memory sections after max_pfn is
  1065		 * defined and before each memory section base is used.
  1066		 */
  1067		kernel_randomize_memory();
  1068	

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