tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/hyperv
head:   61eeb1f6d1f2648a218855d7c8d44f16df242ef3
commit: 6b48cb5f8347bc0153ff1d7b075db92e6723ffdb [1/6] X86/Hyper-V: Enlighten APIC access
config: i386-randconfig-c0-05191955 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        git checkout 6b48cb5f8347bc0153ff1d7b075db92e6723ffdb
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   arch/x86/hyperv/hv_init.o: In function `hyperv_init':
>> arch/x86/hyperv/hv_init.c:302: undefined reference to `hv_apic_init'

vim +302 arch/x86/hyperv/hv_init.c

   238	
   239	/*
   240	 * This function is to be invoked early in the boot sequence after the
   241	 * hypervisor has been detected.
   242	 *
   243	 * 1. Setup the hypercall page.
   244	 * 2. Register Hyper-V specific clocksource.
   245	 * 3. Setup Hyper-V specific APIC entry points.
   246	 */
   247	void __init hyperv_init(void)
   248	{
   249		u64 guest_id, required_msrs;
   250		union hv_x64_msr_hypercall_contents hypercall_msr;
   251		int cpuhp;
   252	
   253		if (x86_hyper_type != X86_HYPER_MS_HYPERV)
   254			return;
   255	
   256		/* Absolutely required MSRs */
   257		required_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE |
   258			HV_X64_MSR_VP_INDEX_AVAILABLE;
   259	
   260		if ((ms_hyperv.features & required_msrs) != required_msrs)
   261			return;
   262	
   263		/* Allocate percpu VP index */
   264		hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
   265					    GFP_KERNEL);
   266		if (!hv_vp_index)
   267			return;
   268	
   269		hv_vp_assist_page = kcalloc(num_possible_cpus(),
   270					    sizeof(*hv_vp_assist_page), GFP_KERNEL);
   271		if (!hv_vp_assist_page) {
   272			ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
   273			goto free_vp_index;
   274		}
   275	
   276		cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
   277					  hv_cpu_init, hv_cpu_die);
   278		if (cpuhp < 0)
   279			goto free_vp_assist_page;
   280	
   281		/*
   282		 * Setup the hypercall page and enable hypercalls.
   283		 * 1. Register the guest ID
   284		 * 2. Enable the hypercall and register the hypercall page
   285		 */
   286		guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
   287		wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);
   288	
   289		hv_hypercall_pg  = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RX);
   290		if (hv_hypercall_pg == NULL) {
   291			wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
   292			goto remove_cpuhp_state;
   293		}
   294	
   295		rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
   296		hypercall_msr.enable = 1;
   297		hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
   298		wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
   299	
   300		hyper_alloc_mmu();
   301	
 > 302		hv_apic_init();
   303	
   304		/*
   305		 * Register Hyper-V specific clocksource.
   306		 */
   307	#ifdef CONFIG_HYPERV_TSCPAGE
   308		if (ms_hyperv.features & HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
   309			union hv_x64_msr_hypercall_contents tsc_msr;
   310	
   311			tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
   312			if (!tsc_pg)
   313				goto register_msr_cs;
   314	
   315			hyperv_cs = &hyperv_cs_tsc;
   316	
   317			rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
   318	
   319			tsc_msr.enable = 1;
   320			tsc_msr.guest_physical_address = vmalloc_to_pfn(tsc_pg);
   321	
   322			wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
   323	
   324			hyperv_cs_tsc.archdata.vclock_mode = VCLOCK_HVCLOCK;
   325	
   326			clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
   327			return;
   328		}
   329	register_msr_cs:
   330	#endif
   331		/*
   332		 * For 32 bit guests just use the MSR based mechanism for reading
   333		 * the partition counter.
   334		 */
   335	
   336		hyperv_cs = &hyperv_cs_msr;
   337		if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
   338			clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
   339	
   340		return;
   341	
   342	remove_cpuhp_state:
   343		cpuhp_remove_state(cpuhp);
   344	free_vp_assist_page:
   345		kfree(hv_vp_assist_page);
   346		hv_vp_assist_page = NULL;
   347	free_vp_index:
   348		kfree(hv_vp_index);
   349		hv_vp_index = NULL;
   350	}
   351	

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